Official PDF , 164 pages

December 2014

FHM – Technical review and support Jakarta Flood Management System Including Sunter, Cakung, Marunda and upper Cideng

Ciliwung diversions and Cisadane

Final Report – phase 2

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WB406484

Typewritten Text

95806

Technical review and support Jakarta

Flood Management System

Final Report - phase 2

© Deltares, 2014

December 2014, Final Report - Phase 2

Technical review and support Jakarta Flood Management System

i

Contents

1 Introduction 1 1.1 Background 1 1.2 Introduction to the project 2 1.3 Polder systems 2 1.4 Project Tasks 4 1.5 Report outline 5

2 Kamal / Tanjungan polder 7 2.1 Description of the area 7 2.2 Pump scheme alternatives 8

2.2.1 A1 – Kamal and Tanjungan as separate systems, no additional storage 9 2.2.2 A2 – Combined Kamal and Tanjungan system, storage reservoir 45 ha 12 2.2.3 A3 – Kamal-Tanjungan with 90 ha storage 14

2.3 Verification with the hydraulic model and JEDI Synchronization 15 2.3.1 Introduction 15 2.3.2 Results 16 2.3.3 Impact of creation of western lake NCICD 18

2.4 Synchronization with other hydraulic infrastructure 19

3 Lower Angke / Karang polder 20 3.1 Description of the area 20 3.2 Pump scheme alternatives 21

3.2.1 B1 – Lower Angke/Karang, no additional storage 22 3.2.2 B2A – Lower Angke/Karang, new reservoir at Lower Angke 23 3.2.3 B2B – Lower Angke/Karang, 30 ha waduk and 12 ha emergency storage 25 3.2.4 B3 – as B2B, but with all possible green area as emergency storage 27 3.2.5 B4 –Splitting the polder in two parts, no additional storage 29 3.2.6 B5 –Splitting the polder area in two parts, additional storage 33 3.2.7 Other possible options 37

3.3 Verification with the hydraulic model and JEDI Synchronization 37 3.3.1 Introduction 37 3.3.2 Results 38 3.3.3 Impact of creation of western lake NCICD 40

3.4 Synchronization with other hydraulic infrastructure 41

4 Marina/Sentiong polder 42 4.1 Description of the area 42 4.2 Pump scheme alternatives 44

4.2.1 C1 – Marina/Sentiong, no additional storage 45 4.2.2 C2 – Marina/Sentiong and Sunter Utara, no additional storage 47 4.2.3 C3 – Marina/Sentiong and Sunter Utara extra open space 49 4.2.4 C4 – Marina/Sentiong, including Sunter Utara and a Marina retention 51 4.2.5 C5 – Marina/Sentiong, as C2 plus continuous 70 m

3/s Ciliwung Lama 53

4.2.6 C6 – Marina/Sentiong, as C5, but inflow Ciliwung Lama after local rainfall 55 4.3 Verification with the hydraulic model and JEDI Synchronization 57

4.3.1 Introduction 57 4.3.2 Results 59

ii



4.3.3 Impact of creation of western lake NCICD 60 4.4 Synchronization with other hydraulic infrastructure 60

5 Sunter polder 63 5.1 Description of the area 63

5.1.1 Introduction 63 5.2 Pump scheme alternatives 64

5.2.1 Sunter drain outlet 64 5.2.2 Sunter drain design 64

5.3 Verification with the hydraulic model and JEDI synchronisation 65 5.3.1 Introduction and results 65 5.3.2 NCICD developments 65 5.3.3 Catchment boundaries and connections 66

6 Cakung polder 67 6.1 Description of the area 67 6.2 Pump scheme alternatives 69

6.2.1 Cakung drain outlet 69 6.2.2 Cakung drain design 69

6.3 Verification with the hydraulic model and JEDI synchronisation 70 6.3.1 Introduction and results 70 6.3.2 Cakung Lama system 71 6.3.3 Secondary systems 71

6.4 Alternatives for further development under future scenarios, including NCICD 72 6.4.1 No plan integration: increasing pump-capacity to 250m

3/s 72

6.4.2 Using 445ha retention pond to extend retention volume 72 6.4.3 Integrate pump scheme in NCICD phase 3 72

7 Marunda polder 74 7.1 Description of the area 74 7.2 Pump scheme alternatives 75

8 Upper Cideng - Setiabudi 76 8.1 Introduction 76 8.2 Modelling 79 8.3 Conclusions 81

9 Review of the proposed Ciliwung-BKT and Cisadane diversions 82 9.1 Diverting flow from the Ciliwung 82

9.1.1 Ciliwung – BKT diversion 83 9.1.2 New flood strategy for the Ciliwung – BKB system 84 9.1.3 Katu Lampa – Cisadane diversion 84

9.2 Ciliwung-BKT diversion 84 9.2.1 Introduction 84 9.2.2 Improvements required at the BKT and Cipinang 85 9.2.3 Diversion capacities 87 9.2.4 Effect of diversions on Ciliwung and Banjir Kanal Timur water levels 88 9.2.5 Towards “equal distribution” 92 9.2.6 Prefer ability of alternative 93

9.3 Alternatif Diversion Channel (Sudetan) Ciliwung - BKT 94



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9.3.1 Ciliwung (Jembatan Kampung Melayu) – Banjir Kanal Timur (Jl. Basuki

Rachmad) 94 9.3.2 Opsi Pembuatan Sudetan Ciliwung-Banjir Kanal Timur 97 9.3.3 Opsi Alternatif Outlet Diversion 99 9.3.4 Pengaruh sudetan alternatif 1 pada muka air Ciliwung dan Banjir Kanal Timur

103 9.4 Preliminary review Ciliwung – Cisadane diversion 107

9.4.1 Diversion Katu Lampa-BKT, Nikken 1997 107 9.4.2 Diversion Katu Lampa-Cisadane, Deltares 2014 110

10 Extension of the Jakarta FHM modelling framework 116 10.1 History of Jakarta FHM modelling framework 2007 – 2013 116 10.2 The Jakarta SOBEK modelling system 118 10.3 The Jakarta FHM- modelling framework 118

10.3.1 Overview 118 10.3.2 The rainfall-runoff model 119 10.3.3 The 1D-2D Flow schematization 120

10.4 Extension with Cisadane and Bekasi river systems 121 10.4.1 First overview of the Cisadane and surrounding catchment 121 10.5.1 Model setup 123 10.5.2 Model calibration 123 10.5.3 First overview of the Bekasi and surrounding catchment 125 10.5.4 Model setup 126 10.5.5 Model calibration 126

11 Updating JFM and FMIS databases 128 11.1 Processing of Digital Elevation Map 128 11.2 Description of Lidar based DEM 128

11.2.1 Origin of retrieve data 128 11.2.2 Projection and datum 128 11.2.3 Review on filtering 129

11.3 Comparison of Lidar with 1D geometry 131 11.4 Lidar derivatives 131

11.4.1 Streamlines for sub-catchment delineation 131 11.4.2 Updating the FHM framework databases 132

Appendix A – Methodology 134

Appendix B – Sobek and the Jakarta FHM framework 149



1

1 Introduction

1.1 Background

Greater Jakarta is the political and economic centre of Indonesia. With an estimated

population of over 28 million, it accounts for a quarter of the nation’s non-oil GDP. The

Province of Jakarta (Daerah Khusus Ibukota or DKI) lies in the delta of the Ciliwung River and

has a population of about 10 million. About 40% of the city is below sea level and large areas

are flooded during the rainy season each year.

Especially severe floods occurred in February 2002, February 2007, and again in January

2013 and 2014, when more than 25% of Jakarta was inundated, flooding up to a depth of 5

meters in places, causing deaths and displacing of more than 100,000 inhabitants. The

economic costs were significantly higher considering loss of life, health costs, and disruption

to trade and industry.

The severity of floods in the capital has become a national issue given the huge financial

losses and the impacts on communities in the greater Jakarta area. For this reason, the

Ministry of Public Works and the provincial government of DKI Jakarta are jointly embarking

on an extensive flood management initiatives.

DKI and the Ministry of Public Works has designed and prepared a program to normalize and

improve the existing canal system by returning it to original design through Central

Government and DKI Jakarta own sources as well as Bank’s financing through Jakarta

Urgent Flood Mitigation Project/Jakarta Emergency Dredging Initiatives Project (JUFMP/JEDI

Project). The dredging initiatives will transcend beyond structural works to ensure that there

are proper additional measures to build capacity through programs, studies, and technical

assistance in order to address the problems comprehensively, especially in terms of

sustainability for ensuring long-lasting flood management systems known as non-structural

measures.

The sustainable effort of flood mitigation in Jakarta require substantial financing for

investment, rehabilitation, operation and maintenance (O&M), and non-structural measures

including capacity building, programing, improvement of technology and institutional

arrangement. Especially on construction and O&M, sufficient financing strategy and

availability will be the key for flood mitigation effort in Jakarta.

The ongoing subsidence of Jakarta is causing problems for the water system of Jakarta. The

plans for sea defence developed in JCDS (Jakarta Coastal Defence Study) are now being

worked out in the NCICD (National Capital Integrated Coastal Development) project.

However, the sea defence is not the only problem related to subsidence. The subsidence also

poses problems for the drainage system of large parts of northern Jakarta. The drainage is at

present mostly by gravity, but this is getting more and more difficult due to the sinking of the

land. Therefore large parts of Jakarta need to become polder systems like the existing Pluit

polder. The water level will be controlled by pumps which pump the drainage water to the

Java Sea. This study is focussing on the design of the layout of these new polder systems.



2

1.2 Introduction to the project

Currently there are many plans and substantial activities prepared and undertaken by many

different organizations and projects regarding the countermeasures to reduce floods in

Jakarta. It includes activities in the main and primary water system such as normalization,

rehabilitation and dredging through JUFMP/JEDI, improved operation of Eastern Banjir (flood)

Canal (EBC), shortcuts of Ciliwung to EBC and Cisadane, Sunter, Pesanggrahan and Angke

rehabilitation. Many retention lakes (waduks) are being restored and new retentions lakes will

be implemented. To guide and optimize these works a new flood strategy is being discussed

to minimize the upstream flows to the Western Banjir (flood) Canal (WBC) and to maximize

these flows towards the newly built EBC, including adjusted operation of Manggarai and

Karet.

The new Ciliwung diversion strategy also supports the phasing of the implementation of the

coastal defence/development works which are currently being designed through the National

Capital Integrated Coastal Development (NCICD) project. Urgent upgrade of the current

Jakarta Coastal Defence is currently under preparation through Phase A of NCICD and will

be implemented over the next three years. Under the phase A implementation the current

coastal defence (the coastal sea dike) will be heightened and strengthened. The larger

drainage channels like Cengkareng Drain, Cakung Drain, West and East Flood Channels will

most probably stay open through strengthening and heightening of their inland dikes, the

smaller channels like Kamal Drain, Lower Angke, Muara Karang, Marina and Sentiong Drains

will be closed off from the sea as no space is available to increase and heighten the inner

dikes. These closures require new pump/polder schemes to be able to manage and pump out

the local rainfall in the areas.

To counteract the effects of ongoing subsidence and implement the NCICD phase A

infrastructure, DKI is currently preparing the implementation of 5 new pumping/polder

schemes to improve critical flood conditions in the western and central low-lying Northern

parts of Jakarta. Similar pumping schemes will soon be develop to cover and protect also the

eastern areas of northern Jakarta.

This project concentrates on developing the outlines of the 5 new pumping/polder schemes

and their possible impact on proposed JEDI designs. The new pumping schemes are

overlapping with part of the JUFMP/JEDI and thus synchronization synchronisation is

required.

These new pumping schemes will close of the northern parts of Jakarta from the sea,

lowering the water levels inside the polder schemes such that the local drainage systems can

be restored and floods from local and from sea intrusion be lowered. The creation of these

polders is in line with / part of the Phase A requirements of NCICD. In the rest of the report it

is assumed that Phase A of NCICD will be implement as scheduled (completion before 2018).

1.3 Polder systems

Large parts of Jakarta, previously draining under gravity to the Java Sea (Laut Java),

currently need to be transformed to pumped/polder systems to counteract subsidence and

match the requirements for NCICD Phase A; systems draining to downstream water bodies

by pumps. Polders can be flooded in three ways (see Figure 1-1):



3

1. Local rainfall in the polder catchment. Designs to deal with local rainfall are discussed in

this study.

2. Flooding by overflowing from upstream and crossing rivers and drains, e.g. Cengkareng,

Angke, Pesanggrahan and Ciliwung. Possible weak points will be discussed in this study.

3. Flooding from the sea, covered in the National Capital Integrated Coastal Development

(NCICD) project.

The design of the polder systems in this study is focussing on the first type of flooding, i.e.

flooding due to local rainfall.

Figure 1-1 Jakarta polders have to be designed for local rainfall (1), safety from upstream rivers (2) and protection

from the sea (3)

The new pumps investigated in this study are part of large polder systems, which should be

developed simultaneously (see Figure 1-2). From west to east these polder systems are:

1. Kamal polder system (14.1 km2), serviced by the Kamal pump (PMP006). This area could

be combined with the Tanjungan polder (5.4 km2), serviced by the Tanjungan pump

(PMP0028)

2. Lower Angke/Karang polder systems, serviced by the Lower Angke pump (PMP003) and

Karang pump (PMP004). The systems are connected via the Tobagus Angke and Grogol

gates. Total catchment area is 56.1 km2

3. Marina/Sentiong polder system, serviced by the Marina pump (PMP002) and Sentiong

pump (PMP001 or PMP001A). For Sentiong pump, two alternative locations exist. One

(PMP001) only includes the Sentiong drain, the other (PMP001A) also includes the

service area of Sunter Utara pump (PMP005, hardly visible but very close to the

alternative location of Sentiong pump PMP001A in Figure 1-2). Depending on the location

of the Sentiong pump, the catchment is either 43.6 km2 or 55.2 km

2.

4. Sunter, Cakung and Marunda polder system. This system has been added in the second

phase of the JFMO study. The total catchment of Sunter, Cakung and Marunda systems

north and west of BKT is 49.44, 77.7 and 16.5 km2 respectively. The area is proposed to

be served by pumps at Sunter mouth, Cakung and Marunda. Some local drainage pumps

for internal drainage areas are already present.

This second progress report adds the layout designs for the Sunter, Cakung and Marunda

systems, the Upper Cideng area and the Ciliwung-BKT. The layout designs of the Kamal,

Lower Angke/Karang and Marina/Sentiong (KAKMS) schemes were earlier published in the

final report (April 2014) of the first JFMO phase.

Laut JavaUpstream rivers Polder

1

23



4

Figure 1-2 – Polder systems

1.4 Project Tasks

Component 1:

Provide expert technical advice to DKI by:

o Reviewing the technical aspects for the 5 new pump schemes in North

Jakarta, and advising possible options for optimizing scheme operation

o Carry out the evaluation in two additional schemes (Sunter-Cakung and upper

Cideng-Setiabudi systems), and advising possible options for optimizing

scheme operation

o Carry out a review of the proposed Ciliwung-BKT diversion, including advising

possible options to accelerate development

o Updating the Jakarta Flood Map (JFM) and FMIS databases

Further review and recommend on potential synchronization impacts between

JUFMP/JEDI and DKI’s new proposed flood operation changes and measures

Component 2:

Carry out a preliminary reviewed of a proposed Ciliwung – Cisadane diversion

scheme

Conduct a first overview of the Kali Bekasi and surrounding catchment on the east of

Jakarta



5

Figure 1-3 – JEDI work packages

1.5 Report outline

The methodology used in this report is summarised in explained in detail in Annex A. Chapter

2 until chapter 4 will discuss the layout designs of the Kamal, Lower Angke/Karang and

Marina/Sentiong (KAKMS) pumping/polder schemes which were earlier published the final

report (April 2014) of the first JFMO phase. Chapters 5 to 7 discuss the layout designs of the

Sunter, Cakung and Marunda polder systems. Chapter 8 contains the characteristics of the

upper Cideng have been collected to provide a basis for future interventions In chapter 9

gives further insight into the possibilities for expansion/accelaration of the Ciliwung – BKT

connection and presents the road survey and the relation with the planned city roads,

especially the Kampong Malayu flyover – Cawang / Priok. Chapter 9 also provides the results

of the field evaluation for the Ciliwung-Cisadane diversion. The additional extension of the

Jakarta FHM modelling framework with the Cisadane and Bekasi river systems and

improvements of the overflow module are presented in chapters 10 and 11.

The cross-reference between project tasks and chapters are as follows:

Reviewing the technical aspects for the 5 new pump schemes in North Jakarta, and

advising possible options for optimizing scheme operation (Chapters 2 - 4)

Carry out the evaluation in two additional schemes Sunter-Cakung (Chapters 5 - 7)

and upper Cideng-Setiabudi (chapter 8) systems), and advising possible options for

optimizing scheme operation

Carry out a review of the proposed Ciliwung-BKT diversion, including advising

possible options to accelerate development (Chapter 9)

Updating the Jakarta Flood Map (JFM) and FMIS databases (Chapters 2-8, 10 and

11)



6

Further review and recommend on potential synchronization impacts between

JUFMP/JEDI and DKI’s new proposed flood operation changes and measures

(Chapters 2-8)

Carry out a preliminary reviewed of a proposed Ciliwung – Cisadane diversion

scheme (Chapter 9)

Conduct a first overview of the Kali Bekasi and surrounding catchment on the east of

Jakarta (Chapter 10)



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2 Kamal / Tanjungan polder

2.1 Description of the area

The Kamal-Tanjungan area is located in the north-western edge of DKI, close to Sukarno-

Hatta airport and Tangerang. The Kamal catchment is estimated at 14.1 km2. The kali Kamal

is draining by gravity to the sea at the moment. During high tide the sea water comes in and

overflows the river banks, causing some flooding. Construction is ongoing near Kamal

Stadium to create a wide discharge channel and using sheet piles to protect the area. A

pumping station is planned near the stadium to drain the area.

Based on the available processed Lidar information, the Tanjungan catchment area is

estimated at 5.4 km2. Tanjungan is equipped with a gate (usually closed) and a pumping

station with 3 pumps of each 4 m3/s. The present pumping capacity is not sufficient for a T=25

event, but flooding in the catchment mostly occurs due to limited discharge capacity of the

drainage system to the pumping station.

Figure 2-1 – Tanjungan pumping station

The total catchment area of Kamal and Tanjungan is 19.6 km2

(see Figure 2-2), which is

approximately the same as used in the first phase. However, using the more detailed

processed Lidar digital elevation data, the distribution of the catchments is different.

Tanjungan catchment is now estimated at 5.4 km2 (before: 2.72 km

2), and Kamal catchment

is now estimated at 14.1 km2 (before: 16.7 km

2). This has an impact on the results when the

catchments are treated as two independent separate catchments. However, the results for



8

the cases with a common reservoir (waduk) are almost the same as the results of the first

phase.

Figure 2-2 – Kamal and Tanjungan catchment (area within the black lines)

The Kamal Muara area north of the toll road to the airport, between Tanjungan pumping

station and the road to Kamal stadium, is mainly in use for aquaculture (tambaks) and only

sparsely inhabited. The city is at the moment busy implementing the policy to create more

green space and water retention areas. It seems very well possible and it is very much in line

with this policy to create water retention area north of the airport toll road.

2.2 Pump scheme alternatives

Different pump schemes (varying in storage) will be discussed in this chapter:

A1. Kamal and Tanjungan as separate polder systems with pumps, no additional storage

(In the next table, this is indicated as A1-K for Kamal and A1-T for Tanjungan)

A2. Kamal-Tanjungan as a combined system, with a common storage of 45 ha

A3. Kamal-Tanjungan as a combined system, with a common storage of 90 ha

These options are schematised using the following schematisation, which already contains

the storage area. Depending on the alternative, the storage area is closed (option A1) or set

at a size of 45 or 90 ha.

The estimated required pump capacities using the water balance under different return

periods for all alternatives is shown in the table below.



9

Figure 2-3 – Sobek schematisation and location of potential reservoir in light blue (45 or 90 ha)

T=25 T=100 T=25 T=100

System Combined Combined Kamal Tanjungan Kamal Tanjungan

A1-T Tanjungan stand alone, no additional storage

27 33

A1-K Kamal - stand alone, no additional storage

70 90

A2 Kamal+Tanjungan plus storage pond 45 ha

42 62 30 12 50 12

A3 Kamal+Tanjungan plus storage pond 90 ha

24 30 12 12 18 12

Table 2-1 – Required pump capacities for different scenarios under different return periods

Due to the different distribution of the catchment over Tanjungan and Kamal polder systems,

the pumping capacities of case A1 are different from the phase 1 results of this study. The

cases A2 and A3 are still very similar.

2.2.1 A1 – Kamal and Tanjungan as separate systems, no additional storage

This alternative explores the possibilities under current open water storage availability

(approximately 0.7% of the catchment area). Even when water level is allowed to increase

2m, large pumps are required. In the present situation Tanjungan pump is not sufficient to

meet a T25 or T100 standard. However, it is not only the pumping capacity that is not

sufficient. At present the problems are also (or mainly) caused by insufficient conveyance

capacity from the catchment to the pumping station: the drainage canals are small. For

Kamal, to meet the T25 or T100 standards, a large pump is required. During field inspection it

is concluded that additional improvement of the drainage system is needed as well. Figure



10

2-4 shows the functioning of the Kamal polder scheme, and Figure 2-5 shows a similar graph

for the Tanjungan scheme.

Figure 2-4 –Functioning polder Kamal alternative A1-K, no additional storage

The characteristics of Kamal system are summarised in Table 2-2.

The table includes the pumping capacity required for T25 and T100 return periods, the

catchment area and retention area, and the retention storage and pump capacity expressed

in mm over the total catchment area. These values are defining the polder capacity line in

Figure 2-4: the retention storage is the off-set at the Y-axis, while the pump capacity is the

slope of the polder capacity line. The emptying time of the system is also included in the

summary. This is the time needed by the pumps to empty the retention storage (without

additional inflow). The emptying time of a river/canal system will be short, but for a system

with reservoirs it can be a number of hours. The emptying time of a system with reservoir

should also not be too long, as the system needs to be ready for moderate events (e.g. the

T1 event) the next day.



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Table 2-2 – Characteristics of Kamal system, alternative A1-K (no additional storage, big pump)

Figure 2-5 –Functioning polder Tanjungan alternative A1-T, no additional storage

Alternative A1-K

Kamal, stand alone system

T100 T25

Pump capacity Kamal 90 70 m3/s

Retention area 9.4 ha

Total catchment 14.1 km2

Max. retention volume 0.19 Mm3

In mm over total catchment area: T100 T25

retention storage 13 13 mm

pump capacity 22.98 17.87 mm/hour

Storage emptying time 0.6 0.7 hours



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Table 2-3 – Characteristics of Tanjungan system, alternative A1-T (no additional storage, bigger pump)

2.2.2 A2 – Combined Kamal and Tanjungan system, storage reservoir 45 ha

In this alternative an extra reservoir of 45 ha is included at the Kamal Muara (see Figure 2-3).

Note that this reservoir also increases the catchment area of the pumping stations with this

amount. The allowed level fluctuation in the reservoir is about 2 m, but with proper alignments

up to 3 m could be allowed. Both Kamal pumping station and Tanjungan pumping station will

be connected to this reservoir of 45 ha. Tanjungan already has an existing pumping station

(capacity 12 m3/s), so the additional pumping capacity can be created at Kamal pumping

station. The required total pumping capacity is 42 (T25) or 62 m3/s (T100). Figure 2-6 shows

the capacity of the combined Kamal-Tanjungan polder system. Table 2-4 summarises the

results.

Alternative A1-T

Tanjungan, stand alone system

T100 T25

Pump capacity Tanjungan 33 27 m3/s










13

Figure 2-6 – Functioning Kamal-Tanjungan polder, alternative A2 with storage reservoir 45 ha

Table 2-4 – Characteristics of Kamal + Tanjungan system, alternative A2 (45 ha reservoir storage)

Alternative A2

Kamal Tanjungan, combined additional storage reservoir 45 ha

T100 T25

Pump capacity Total 62 42 m3/s

Kamal 50 30 m3/s

Tanjungan 12 12 m3/s










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The required pumping capacities are much lower than in case A1 (stand-alone Kamal and

Tanjungan). The emptying time of the reservoir is between 7 and 11 hours, which is

acceptable.

2.2.3 A3 – Kamal-Tanjungan with 90 ha storage

In this alternative, a storage reservoir of 90 ha in Kamal Muara area is connected to Kamal

and Tanjungan pumping stations. The total pumping capacity required to meet T25 or T100

protection levels is 24 and 30 m3/s respectively. Figure 2-7 shows the capacity and Table 2-5

summarises the characteristics of this case. The required pumping capacities are again lower

than both case A1 and A2. The emptying time of the reservoir is more than 1 day.

Figure 2-7 – Functioning polder Kamal-Tanjungan, alternative A3 with 90 ha storage reservoir



15

Table 2-5 – Characteristics of Kamal + Tanjungan system, alternative A3 (90 ha reservoir storage)

2.3 Verification with the hydraulic model and JEDI Synchronization

2.3.1 Introduction

The polder scheme designs as described in the previous paragraphs have been simulated

with the hydraulic model. The hydraulic model can take into account more operational details,

hydraulic bottlenecks and the detailed lay-out of the system (including the location of storage

in the catchment area), and it can indicate remaining potential problem locations (local

flooding).

At this moment it is advised to operate the Kamal/Tanjungan system on -2 m PP*, which is a

little higher than the Pluit polder system (waduk Pluit is operated at -3 m PP*, typical polder

levels in Pluit polder are -2 m PP*). To prevent soil and sediment from drying out in the dry

season and for water quality purposes it is advised to dredge the bottom of the long storage

drains and in the reservoir to -3 m PP* or lower. The JEDI designs typically use a higher

bottom level. There are JEDI design drawings available for Kamal area, but at the moment

JEDI is not planned to be active in Kamal. Also for Tanjungan area, we assumed to bottom

level of the drainage channel to the pumps and storage area is put at -3 m PP*. Furthermore,

we assumed that below the target level the cross-sections will be less wide than above the

target level. This is done with the idea of a double purpose operation: in the dry season,

flushing (if possible) in this way requires less water, while above target level the cross-

sections are wide enough to allow high flow discharges. A typical cross section for Kamal is

shown in the next figure.

Alternative A3

Kamal Tanjungan, combined storage 90 ha

(start pumping 0.5 hour after rain starts)

T100 T25


Kamal 18 12 m3/s

Tanjungan 12 12 m3/s


Total catchment area 20.5 km2








16

Figure 2-8 –Typical double purpose cross-section

The calculations with the hydraulic model have been made using JEDI design cross-sections,

and using improved cross-sections (deeper double purpose canals) which reduce the

maximum water levels and increase the discharge capacity to the pumps.

2.3.2 Results

The calculations with the JEDI design cross sections show that the Kamal pump system

without storage and with designed pump capacity according to the water balance, will still

face large-scale flooding. The calculation with improved cross-sections (deeper than the

original cross-section, and only downstream a little wider) shows that the design pumping

capacity is in principle indeed sufficient to control the water level, but shows that additionally

improvement of cross-sections on top of the JEDI design is really necessary.

Figure 2-9 shows the bottom levels according to JEDI-design and as proposed by this study

for Kamal. Also the maximum water levels from cases A1 and A3 are shown. Figure 2-9

shows the bottom levels together with the computed maximum water levels for the T25 and

T100 return period for Kamal and Tanjungan system. The results show a number of things:

The maximum water level rise computed by the hydraulic model is more than 2 m. In

the calculations a lowest pump operation level of –1.8 m PP* has been used, while

the maximum computed water level upstream of Kamal pumping station with

improved cross-sections is 0.5 to 0.6 m PP* depending on the return period. The

maximum water level rise is thus 2.5 m, while the water balance used allowed 2 m

rise only.

The difference in water level between the JEDI design and improved cross-sections is

quite large.

Still, also with the improved cross-sections, in the upstream area some local flooding

will occur due to limited discharge capacity.



17

Figure 2-9 –Bottom levels (JEDI and improved) and T100 water levels, Kamal

The computed water levels in the storage reservoir Kamal-Tanjungan for the cases with a

storage reservoir of 45 or 90 ha are shown in the next figure for both the T25 and T100

events. The graph shows that the water level is rising from -1.8 m PP* up to a maximum level

of about +0.5 m PP*. The emptying time of the reservoir is much larger for the 90 ha reservoir

than for the 45 ha reservoir.

Figure 2-10 –Water levels in the storage reservoir for cases A2 (45 ha) and A3 (90 ha)

In the graph, the water levels for the 45 ha reservoir are in red (T100) and blue (T25), while

the water levels for the 90 ha reservoir are in grey (T25) and green (T100).

C50 F15:W.level up mean 1-TanjunganPump C51 F15:W.level up mean 1-TanjunganPump C53 F15:W.level up mean 1-TanjunganPump

C54 F15:W.level up mean 1-TanjunganPump

06-01-2013

00:00:00

05-01-2013

12:00:00

05-01-2013

00:00:00

04-01-2013

12:00:00

04-01-2013

00:00:00

03-01-2013

12:00:00

03-01-2013

00:00:00

02-01-2013

12:00:00

02-01-2013

00:00:00

01-01-2013

12:00:00

01-01-2013

00:00:00

C50 F

15:W

.level up m

ean [

m A

D]

0.8

0.6

0.4

0.2

0

-0.2

-0.4

-0.6

-0.8

-1

-1.2

-1.4

-1.6

-1.8

-2

*



18

The next figure shows locations where the computed water level rises above the

embankments for case A1, return period T100. Problem locations are in orange, red and

purple. The freeboard value is shown, which is positive if the water level is still below street

level, and becomes negative if the computed 1D water level is higher than the street level.

The colour scale is from dark blue (freeboard 1 m or more, so no problem) via light blue,

yellow (freeboard between 0.5 and 0) to problem locations indicated in orange (freeboard

between 0 and -0.1 m), red (between -0.1 and -0.5 m) and purple (more than -0.5 m). Note

that the values are only indicative, so purple indicates a more severe problem than red. But

since no 2D calculation is performed, and the 1D cross-sections are extended like vertical

walls, the negative freeboard numbers (e.g. -0.50 m) do not mean an inundation of the same

value (0.50), but less. The problem locations are mostly in the middle part of Kamal

catchment, where the river/canal is quite narrow, and in the far upstream area. Other

locations where the water level rises above the embankments are downstream of the pumps,

where the embankments are regularly flooded by the sea at high tide.

Figure 2-11 –Locations with water level rise above the 1D embankments (in red/purple), alternative A1, T100 event.

2.3.3 Impact of creation of western lake NCICD

All cases described above have been checked with the hydraulic model using the spring tide

plus 0.60 m anomaly for the 2014 situation. Using a mean sea level of 1.80 m PP* and a tidal

range of +- 0.50 m, this means the tidal boundary conditions vary within 1.3 and 2.3 m PP*.

For 2030, assuming a land subsidence of 7.5 cm per year, the same tidal boundary

conditions are equivalent to levels between 2.43 and 3.43 m PP*. The present calculations

indicate that using the spring tide conditions of 2014 hardly any use can be made of the

gates, since the water levels upstream of the pumps are for all cases below 0.9 m PP*. In

2030, the NCICD western lake is expected to be developed. Preliminary proposed target

levels are -0.9m +LWS2012 (NCICD, 2014A). Keeping cross-section levels the same and

translating the subsidence in increased boundary water levels, this results in a downstream

boundary of 0.98m +PP* in 2030, which is higher than the water levels in Kamal and



19

Tanjungan system. This means the pumps will still be needed after the western lake is

created.

2.4 Synchronization with other hydraulic infrastructure

The other relevant development for Kamal and Tanjungan area is the planning of Cengkareng

II drain. It is said that one of the possible alignments for Cengkareng II is on the boundary of

DKI and Tangerang, where Cengkareng II ends up in Kamal area. This could interfere with

the Kamal drainage system. However, at the moment of writing of this report no further details

about the status of Cengkareng II designs are available yet.

An important sensitivity is the distribution of catchment area over Kamal and Tanjungan

catchments. In the present report the distribution is different from the phase 1 report, based

on extracting local drain directions from the detailed DEM data. The catchment subdivision

according to the 2m DEM sometimes crosses some main drains (according to the available

shape file of DKI channels). Additional field work is useful to check the catchment area and

flow direction in drains. But for now, the present estimates are the best available. For case

A1, where Tanjungan and Kamal serve separate catchments, this other subdivision has an

impact on the computed required pumping capacities. Since Kamal catchment is reduced,

and Tanjungan catchment increased, pumping capacity at Kamal can be smaller, and should

be larger at Tanjungan. For cases A2 and A3, with a combined reservoir of 45 or 90 ha, the

pumping capacity is hardly influenced by the distribution of the catchments.



20

3 Lower Angke / Karang polder


The area to be converted into the Lower Angke / Karang polder will be 56.1 km2 in total (see

Figure 3-1). In the south, the upstream boundary is defined by the Grogol – Pesanggrahan

diversion (sudetan), bypassing the upper Grogol and most upstream part of the Sekretaris

(not in figure below; see Figure 1-2). The lower Grogol and the part of the Sekretaris

downstream of the sudetan currently drain via the Grogol-Sekretaris interceptor (GroSec in

Figure 3-1) towards the Lower Angke, where it enters the Muara Angke. At this location, the

Lower Angke pump is planned.

The Grogol-Sekretaris interceptor and Lower Angke can be separated from the Karang

system with the Tobagus Angke (TA) and Grogol gates. In that case, the area East of the TA

gate and North of the Grogol gate will discharge via a siphon under the BKB and the kali

Karang to Java Bay. Kali Karang is separated from Pluit polder (an area serviced by Pompa

Duri), with the Karang gate. Also the idea of a pump at Mookervaart (into Cengkareng drain)

came up.

Figure 3-1 – Lower Angke/Karang polder



21


In all alternatives it is assumed that the operation of Pompa Lower Angke, Pompa Karang

and the Tobagus Angke and Grogol gates is optimized for optimal use of storage in the

surface water systems. The capacity of the siphon in the Grogol under passing the West

Banjir Canal (BKB) poses a limitation in the maximum pump capacity of the Karang pump.

According to Nedeco (1973) the capacity of the siphon is 60 m3/s. It is not known whether the

capacity is upgraded after 1973. We therefore assume the 60 m3/s capacity still holds for the

design conditions.

Different pump schemes (varying in storage) will be discussed in this chapter:

B1. Lower Angke/Muara Karang, using the main system only for storage

B2A. Lower Angke/Muara Karang system with additional 30 ha reservoir in Lower Angke

B2B. Lower Angke/Muara Karang system with 30 ha reservoir and 12 ha emergency space

B3. Lower Angke/Muara Karang

B4 As B1, but split the area into two separate polders, both without additional storage:

B4N Northern part of Lower Angke/Muara Karang polder

B4S Southern part of polder: GroSec, Mookervaart.

B5 As B4, split the area into two separate polders, both with additional storage:

B4N Northern part of polder, with waduk Lower Angke 30 ha

B4N-G Northern part of polder, with green open space emergency storage

B4S-G Southern part of polder: GroSec, Mookervaart with emergency storage.

Finally, also the option of an emergency connection with the upgraded Pluit polder system is

discussed.

The estimated required pump capacities by the water balance under different return periods

for all alternatives are shown in the table below.

T=25 T=100 T=25 T=100

System Combined Combined Lower Angke Karang Lower Angke Karang

B1 Lower Angke Muara Karang, no additional storage

155 205 95 60 145 60

B2A Lower Angke Muara Karang, plus local waduk 30 ha

125 180 65 60 120 60

B2B Lower Angke Muara Karang, plus local waduk + open space emergency storage

120 170 60 60 110 60

B3 Lower Angke Muara Karang, plus additional available storage

100 150 40 60 90 60

B4N Northern LA polder, no additional storage

29 47 9 20 22 25



22

T=25 T=100 T=25 T=100

System Combined Combined Lower Angke Karang Lower Angke Karang

B4S Southern LA polder (GroSec, Mookervaart), no additional storage, pump at Mookervaart

145 190

B5N as B4N, with waduk Lower Angke 30 ha

14 29 4 10 9 20

B5N-G as B4N, with green storage 41 ha

18 33 8 10 13 20

B5S-G As B4S, with green storage 9 ha, pump at Mookervaart

140 185


3.2.1 B1 – Lower Angke/Karang, no additional storage

This alternative explores the possibilities under current open water availability (1.6% of the

catchment area). Even when the water level is allowed to increase 3 m, very large pumps

area required to meet the T25 and T100 flood protection level. The total required pump

capacity is 155 or 205 m3/s respectively; these numbers are a bit smaller than in the progress

report, because of some river and canal storage which was not yet taken into account at that

time. With a maximum capacity of 60 m3/s at the Karang pump and syphon, the pump at

Lower Angke should have a capacity of 95 or 145 m3/s depending on the chosen return

period. Figure 3-2 and Figure 3-3 show the polder scheme and capacity. Table 3-2 gives an

overview of the characteristics of the polder system of this alternative.

Figure 3-2 – Lower Angke/Karang polder, alternative B1, no additional storage



23

Figure 3-3 –Functioning polder Lower Angke/Karang, alternative B1, no additional storage

Alternative B1

Lower Angke/Karang system, no additional storage

(but in comparison with first version: upstream storage included)

T100 T25


Lower Angke 145 95 m3/s

Karang 60 60 m3/s






pump capacity 13.57

10.26

mm/hour


Table 3-2 – Characteristics of Lower Angke/Karang sytem, alternative B1 (no additional storage)

3.2.2 B2A – Lower Angke/Karang, new reservoir at Lower Angke

In this alternative an extra storage reservoir (waduk) at the lower Angke of 30 ha is included

(see Figure 3-4). The assumed allowable level fluctuation is 2 m. With a maximum capacity

of 60 m3/s at the Muara Karang, a pump of 65 m

3/s or 120 m

3/s should be installed at the

Lower Angke to meet the T25 or T100 protection. Figure 3-4 and Figure 3-5 show the polder

SCS runoff and polder capacity

0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]

T25 T10 T50 T100 Polder capacity T025 Polder capacity T100



24

scheme and the capacity of the polder. Table 3-3 summarises the characteristics of the

polder in this alternative.

Figure 3-4 – Location of 30 ha storage reservoir at Lower Angke, alternative B2A

Figure 3-5 – Functioning polder Lower Angke/Karang, alternative B2A, 30 ha reservoir at Lower Angke


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]


Storage



25

Table 3-3 – Characteristics of Lower Angke/Karang sytem, alternative B2A (30 ha additional reservoir)

Alternative B2A

Lower Angke/Karang system

Additional storage 30 ha Lower Ange waduk

T100 T25

Pump capacity Total 180.0 125 m3/s


Karang 60 60 m3/s








3.2.3 B2B – Lower Angke/Karang, 30 ha waduk and 12 ha emergency storage

In comparison to B2A, not only a 30 ha reservoir with 2 m level variation is included, but this

reservoir is connected with additionally 12 ha open space. On this open space we assume 1

m depth of water is allowed in emergency conditions. The additional 12 ha emergency space

reduces the required pump capacity with about 5 m3/s. Figure 3-6 shows the location of the

30 ha reservoir at Lower Angke and the 12 ha emergency storage. Figure 3-7 shows the

polder scheme and capacity. The characteristics of the system in this alternative are

summarised in the next table.

Figure 3-6 – 30 ha reservoir at Lower Angke, and 12 ha emergency storage



26

Figure 3-7 – Functioning polder – 30 ha storage at Lower Angke pump and emergency storage

Alternative B2B

Lower Angke/Karang system with waduk 30 ha as B2A

Additionally 12 ha emergency storage (1m)

T100 T25



Karang 60 60 m3/s








Table 3-4 –Lower Angke/Karang system, alternative B2B (=B2A + 12 ha open emergency storage)


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]




27

3.2.4 B3 – as B2B, but with all possible green area as emergency storage

A number of other green space emergency storage areas has been identified. It will be a

challenge to realise all these storages, but the calculation was made to check how much

pumping capacity this would save. The allowed water depth is set at 1 m. The additional 50

ha emergency space reduces the required pump capacity with about 20 m3/s.

Figure 3-8 shows the additional retention areas. Figure 3-9 shows the polder scheme and

capacity. Table 3-5 shows the characteristics of the Lower Angke/Karang polder for this

alternative.

Figure 3-8 – Additional retention areas in Lower Angke, alternative B3



28

Figure 3-9 – Functioning polder Lower Angke, alternative B3 = B2B plus 50 ha additional emergency storage

Alternative B3

Lower Angke/Karang system as B2B, plus all other green emergency storage (1m)

T100 T25



Karang 60 60 m3/s








Table 3-5 – Characteristics of Lower Angke/Karang system, alternative B3 (B2B + 50 ha extra emergency storage)


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]




29

3.2.5 B4 –Splitting the polder in two parts, no additional storage

Without additional storage or separation of catchments, this is similar to option B1, but only

with another spatial distribution of pumping capacities since a pumping station at Mookervaart

into Cengkareng drain is included. So the water balance would require the same pumping

capacity as case B1, but the division over the pumping stations would be different based on

hydraulic considerations.

The case only becomes a different case when the whole catchment is separated by gates

such that the Mookervaart-Cengkareng connection is closed (at present the gate is always

open), and that a pumping station at Mookervaart is constructed to pump to drainage of the

southern part of the catchment (consisting of Grogol till Sudetan GroSec, Sekretaris,

Mookervaart and Lower Angke area until the confluences with GroSec and Mookervaart) to

Cengkareng drain. So we in fact get two separate polders west of the West Banjir Canal

(BKB) instead of one Lower Angke / Karang polder:

the southern Grogol/Sekretaris/ Mookervaart area, drained by pumping at the

Mookervaart into Cengkareng drain, and

the northern Lower Angke / Karang polder

Figure 3-10 – Separation of Lower Angke/Karang polder (west of BKB) into two subareas



30

The southern part is the area indicated by yellow lines. It includes the area south of the

Mookervaart and south of the GroSec connection. The pump station at Trisakti (capacity 1.5

m3/s) near Grogol gate pumps is located just downstream of the Grogol gate according to the

FMIS schematisation, so this part of the catchment still drains to lower Angke/Muara Karang.

The south-western polder is estimated at 37.2 km2, and the northern polder at 17.2 km

2. The

northern part has relatively more storage than the southern part. So, the required pump

capacity will be mostly located in the south, at the Mookervaart-Cengkareng drain location.

The pumps at northern Lower Angke and Muara Karang can be much smaller. However, by

splitting up the catchment into two independent parts, the runoff from the southern part

cannot use the available storage in retention areas in the northern polder. So the sum of the

required pumping capacity for the south and north is larger than required in alternative B1

(one large polder).

The summary results for the northern and southern polder are given in Table 3-6 and Table 3-7. Figure 3-11 and Figure 3-12 give an overview of the polder capacity for the northern and southern subarea.

Figure 3-11 – Functioning northern polder Lower Angke, alternative B4-North (split polder, no additional storage)


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]




31

Alternative B4-north

Lower Angke/Karang system

Northern part only, no additional storage

T100 T25



Karang 25 20 m3/s








Table 3-6 – Characteristics of Lower Angke/Karang sytem, alternative B4-North (split polder, no additional storage)

Figure 3-12 – Functioning southern polder Lower Angke, alternative B4-South (split polder, no additional storage)


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

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mm

]




32

Alternative B4-south

Lower Angke/Karang system south (Grosec, Mookervaart)

No additional storage, Pump from Mookervaart to Cengkareng

T100 T25


Mookervaart 190 145 m3/s








Table 3-7 – Characteristics of Lower Angke/Karang sytem, alternative B4-South (split polder, no additional storage)

Another question which remains to be answered is whether the Cengkareng drain can handle

the additional amount of water coming from the southern polder through the pumping stations

at the Mookervaart.

At present, the gate from Mookervaart to Cengkareng drain is open and cannot be closed.

This means that during high tide Cengkareng water may flow into the Mookervaart, while

during low tide Mookervaart already drains to Cengkareng. According to maps of PU,

Cengkareng drain design flow (Q50) is 566 m3/s, while the present maximum flow is about

300-340 m3/s. However, FMIS simulations in cases without tide and without inflow from the

Mookervaart to Cengkareng show a much lower flow at Cengkareng gate (150-180 m3/s) and

already a very full Cengkareng drain, with some local flooding. So it is doubtful whether

Cengkareng can handle such big additional flows from the GroSec-Mookervaart system. This

requires further analysis.



33

Figure 3-13 – Information on Cengkareng drain from PU map

If Cengkareng drain cannot handle the additional flow, an option would be the future

Cengkareng II drain, taking the upstream Angke flow which at present flows through

Cengkareng drain. However, this option will take several years to be realised since there are

no solid and agreed plans for Cengkareng II yet.

3.2.6 B5 –Splitting the polder area in two parts, additional storage

This option is similar to option B4, but now with additional storage. For the northern polder,

the options are the identified reservoir area of 30 ha or a smaller version of this reservoir, or

some green space emergency storage areas (41 ha). To see the maximum effect on the

required pumping capacity, the 30 ha size reservoir is selected. For the southern polder, there

is one additional green space emergency storage area (9 ha). The emergency storage areas

are already indicated in Figure 3-8 for alternative B3. The results are given in Figure 3-14 to

Figure 3-16 and in Table 3-8 to Table 3-10.



34

Figure 3-14 – Functioning northern polder Lower Angke, alternative B5-North A (split polder, reservoir 30 ha)

Alternative B5N-A

as B4-North, with additional waduk 30 ha (2 m)

T100 T25



Karang 20 10 m3/s








Table 3-8 – Characteristics of Lower Angke/Karang sytem, alternative B5-North A (split polder, reservoir 30 ha)


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]




35

Figure 3-15 – Functioning northern polder Lower Angke, alternative B5-North G (split polder, green emergency

storage 41 ha)

Table 3-9 – Northern polder Lower Angke, alternative B5-North G (split polder, green emergency storage 41 ha)

Alternative B5N-G

as B4-North, no additional waduk, 42 ha emergency space (1 m)

T100 T25



Karang 20 10 m3/s









0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]




36

Figure 3-16 – Functioning southern polder Lower Angke, alternative B5-South G (split polder, 9 ha green

emergency storage)

Table 3-10 – Southern polder, alternative B5-South G (split polder, 9 ha green emergency storage)

Alternative B5-south

Lower Angke/Karang system south (Grosec, Mookervaart)

Additional green storage 9 ha (1 m)

T100 T25


Mookervaart 185 140 m3/s








So for option B5 similar observations as for option B4 hold: the pumping capacity at the

Mookervaart required for the southern subarea is very large, due to the very limited number of

identified possibilities for retention storage so far. It needs to be checked whether the

Cengkareng drain can handle such a big additional flow.


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]




37

3.2.7 Other possible options

The standard operation of the polder systems (Lower Angke/Muara Karang, Marina/Sentiong)

would be to have the polders work as separate polder systems. It would however be possible

to connect neighbouring polders with the already existing Pluit polder, to be more flexible in

case of emergencies. The polders could be connected by having a (movable) gate in

between. Making such a connection is possible since the operational levels of the new

polders are all put at the same levels as Pluit operational levels. The most obvious connection

is at the Muara Karang area, since this is immediately adjacent to Pluit.

Currently DKI is installing new pumps in Pluit polder (at Pasar Ikan, Melati, and Pluit), thus

extending the Pluit pumping capacity considerably. After installing these additional pumps the

capacity of the Pluit polder should be sufficient, assuming proper maintenance of the pumps,

hydraulic infrastructure, sea defence and BKB levees. Especially the large pump capacity at

Pluit reservoir could be easily connected to the Muara Karang, connecting both systems. In

this way the systems can assist each other, since the probability of having a design event at

the same time in both catchments is less than the return period of the design event. So this

connection could work in two directions:

When the Pluit system is overloaded (heavy rainfall or emergency), the Karang pump

can be used to help draining the Pluit system;

When the Lower Angke/Karang system is overloaded and storage is available in the

Pluit system, water can be discharged to Pluit reservoir and the excess pump

capacity at Pluit can be used to drain the Lower Angke/Karang system.

The connection of different systems could be already taken into account in the design of the

pump capacities, and would reduce the overall total pumping capacity to be installed. We

therefore recommend to further analyse the option to connect the polder systems.


3.3.1 Introduction

At this moment it is advised to operate the Lower Angke/Karang system on -2 m PP*. To

prevent soil and sediment from drying out in the dry season and for water quality purposes it

is advised to dredge the bottom of the long storage drains to at least -3 m PP*, where the

JEDI designs use a higher bottom level. Figure 3-17 shows bottom levels according as

designed and as required.

When looking at the Lower Angke drain in alternative B1 (no additional storage), the water

balance calculations indicate a very high required pumping capacity required in T100 at

Lower Angke. As explained in Appendix A, the discharge capacity of a canal can be

estimated using the Manning equation. When using the bottom level of -3 m PP*, a Manning

roughness coefficient of 0.04 s.m-1/3

and a slope of 10 cm/km, a discharge capacity of 160

m3/s requires a rectangular canal of 40 m and depth of 6 m, or a canal of 50 m and a depth of

5 m. The Lower Angke width is about 40 m, so with a bottom level at -3 m PP* this would

require sheet piles (with capping of 1 m) up to +4 m PP*. So, when assuming no additional

storage in the system, the discharge capacity is barely enough and already needs very deep

canals (or high sheet piles) just to be able to convey the design flow.

In the hydraulic model we used both a pump and a gate at Lower Angke and Muara Karang.

The gate will allow additional discharge when the water levels in the polder are very high,



38

becoming only active when the water level before the pump already exceeds the allowed

maximum water level rise.

Figure 3-17 –Bottom levels designed (des) and required (req) for the Lower Angke, GroSec and Karang

The Sobek calculations have been made using the improved cross-sections (deeper canals)

for GroSec interceptor, Mookervaart and downstream lower Angke and Karang and putting

the bottom level at -3 m PP*, assuming a width of 40 m. For the other areas, existing cross-

sections from the FMIS schematisation have been used. Note that GroSec interceptor,

Karang and downstream Lower Angke are in JEDI, but the Mookervaart is not (see Figure

1-3).

3.3.2 Results

The capacities computed by the water balance are more or less confirmed by the hydraulic

model, although the water level rise computed by the hydraulic model is higher. This is

explained by the fact that the hydraulic model takes into account location of storages,

hydraulic bottlenecks, pump operation aspects (switch-on and off levels), which are all not

considered in the water balance. At Muara Karang, the gate is not able to discharge water to

the sea, since the upstream water levels are lower than the tidal level and the pump does the

job. The limiting capacity of the syphon under BKB explains the difference with the water level

at Lower Angke gate and pumping station: there the water levels rise higher, and in many

cases the water level rise is such that the gate can help to discharge the water.



39

Figure 3-18 –Discharges of Lower Angke gate (red) and pump (green), alternative B1, T100

Figure 3-19 shows locations where the water level computed with the hydraulic model rises

above the embankments. Problem locations are in orange, red and purple. The freeboard

value is positive if the water level is still below street level, and becomes negative if the

computed water level is higher than the street level. The colour scale is from dark blue

(freeboard 1 m or more, so no problem) via light blue, yellow (freeboard between 0.5 and 0)

to problem locations indicated in orange (freeboard between 0 and -0.1 m), red (between -0.1

and -0.5 m) and purple (more than -0.5 m). Note that the values are only indications, so

purple indicates a more severe problem than red. Since no 2D calculation is performed, and

the 1D cross-sections are vertically extended, the negative freeboard numbers (e.g. -0.50 m)

do not mean an inundation of the same value (0.50), but less.

The most vulnerable locations are in the GroSec interceptor and the lower parts of Sekretaris

and Grogol rivers. The part of Lower Angke upstream of the Mookervaart has unchanged

cross-sections but needs to be improved, it also experiences inundations.. In the Grosec

interceptor the water levels in the computation rise a little more 10 cm above the assumed

sheet pile capping. The Lower Angke water levels remain below embankments, because the

Lower Angke gate discharges during the peak water level situations. But the water level just

before the pump rises above 2 m PP* (so more than 4 m rise from the target level of -2 m

PP*).

The results show that on the lower Grogol (downstream of the Grogol gate near Trisakti) and

Karang system the water levels can be maintained below the embankments. The Jelembar

area faces inundations due to insufficient local pump capacity.

Also it can be concluded from the graph that the storage in the whole system is not used in an

optimal way. For instance, the Kali Sekretaris overtops the embankments, while the maximum

level in Tomang reservoir (in dark blue) is still 1 m or more below the maximum level and



40

Tomang is pumping at full capacity. In case the Kali Sekretaris is full it might be better to store

water first in Tomang temporarily, while storage is still available.

The results of the hydraulic model show that alternative B1 (no additional storage) requires

deep canals and high sheet piles, but also indicates that the operation of the structures like

Grogol gate, Tobagus Angke gate, and the distribution of Jelembar area drainage (by pump

or gravity) needs to be further optimised.

An option to alleviate the high required discharge capacity at the Lower Angke could be to

install part of the pumping capacity at the Mookervaart–Cengkareng junction. In that situation

part of the flow will be through the Mookervaart to Cengkareng, thus reducing the required

discharge capacity at the Lower Angke. The details of this option require further analysis with

the hydraulic model

The assumed 60 m3/s capacity of the siphon of Lower Karang under the West Banjir Canal

(BKB) is confirmed by the hydraulic model. The hydraulic model also shows a large head loss

of up to 2 m over the siphon during the flood peak.

Figure 3-19 –Locations where water level rises above the 1D embankments, alternative B1, T100 event.







indicate that using the spring tide conditions of 2014 at Muara Karang no use can be made of

the gates, since the water levels upstream of the pumps are for all cases below 0 m PP*.

However, at Lower Angke pump and gate the water levels rise much higher (and more than

desired) and the gate can still be used using the 2014 tidal boundary conditions during peak

water levels. This difference is because of the syphon before the pumping station at Muara



41

Karang with limited discharge capacity, causing the water levels at Muara Karang to be lower

than at Lower Angke pumping station. In 2030, the NCICD western lake is expected to be

developed. Preliminary proposed target levels are -0.9m +LWS2012 (NCICD, 2014A). This

translates to a downstream boundary of 0.98m +PP* in 2030, which is higher than the water

levels at Muara Karang, but still lower than peak water levels at lower Angke. This means the

pumps will still be needed after the western lake is created, but the gate at lower Angke can

still be used after creation of the western lake.


As mentioned in a previous paragraph, connecting the Lower Angke/Muara Karang polder

system to the Pluit polder system is an option which needs further analysis. The operational

levels used in the Lower Angke/Muara Karang system are higher than the operational water

levels of Pluit reservoir. This means that if Lower Angke / Muara Karang system experiences

flood conditions while Pluit does not, Pluit could help alleviate flood conditions in the Muara

Karang area. For the Lower Angke / Muara Karang system alternatives B4 and B5 a further

analysis of Cengkareng drain capacity is important, as well as possible plans for

implementing Cengkareng II.

From the Sobek hydraulic calculations it is concluded that the required high discharge

capacity at the Lower Angke, especially in the B1 alternative, results in high required

maximum depths. Installing part of the pumping capacity at the Mookervaart will reduce the

required downstream depths, but this is only possible if Cengkareng drain capacity allows

this.

The siphon at the crossing of Karang with BKB forms a hydraulic bottle-neck with a large

head loss during flood peaks.

Another conclusion is that some use of local storage may be optimised, since the Karang

system seemed ok, while in the Lower Angke system the water level rises much higher.. It is

therefore advised to check the operation of the gates in the system (Grogol gate, Tobagus

Angke gate), and to check the operation of local pumps (Jelembar, Trisakti and others) and

check if a smart operation of the local pumps can reduce the pressure on the Lower Angke

system.

During normal conditions, due to the operational level of about -2 m PP*, some area which is

now pumped may be drained by gravity. However, in flood conditions the local pumps will be

needed.

An important structure is on the upstream boundary of the polder in Pondok Indah, where the

upper Grogol is flowing via the sudetan to Pesanggrahan river. It is absolutely necessary for

the Lower Angke/Karang system that the flood waters from upper Grogol are diverted to

Pesanggrahan and Cengkareng drain (as assumed in the polder design), since the Lower

Angke/Karang system cannot handle additional inflow from the upper Grogol during flood

conditions.



42

4 Marina/Sentiong polder


The area to be converted into the Marina/Sentiong polder will be 43.6 km2 in total (see Figure

4-1). As will be discussed in the following section, configurations are possible in which also

the Sunter Utara polder (11.7 km2). On request of PU-DKI also the option of allowing a 70

m3/s flow from Ciliwung Lama into the Marina-Sentiong polder is included. In section 4.2,

different alternative pump schemes will be discussed using the water balance described in

the appendix.

Figure 4-1 – Marina/Sentiong and Sunter Utara polder

In the analyses and as indicated by the catchment area in Figure 4-1, we have assumed that

the Ciliwung Gajah Mada up to Tangki gate is not included in this catchment. At present, the

Ciliwung Lama at Istiqlal turns right, passes Pintu Air Istiqlal and flows into Gunung Sahari

drain. However, there is also a left branch going to Ciliwung Gajah Mada and Tangki. There is

no gate to control the flow, but at the bifurcation that branch is completely full with sediment

(see Figure 4-2). Gajah Mada is not considered a main drain, since it is also not part of JEDI.

It has zero flow in medium to dry conditions, but most likely will get some flow in case 70 m3/s

is coming from upstream Ciliwung Lama. Given the present extension of pumping capacity at

Pasar Ikan and Pluit, the question is what operation policy PU-DKI has planned. If DPU plans

to allow flow from Ciliwung into Gajah Mada, dredging is certainly required.

Marina/Sentiong polder

Sunter Utara polder

Sunter Utara pump

Koya pump

Marina pump

Sentiong pump

Ancol gate



43

Another related issue is the announced river restoration of Ciliwung Lama at Istiqlal, see

Figure 4-3. This project seems conflicting with the idea to use Ciliwung Lama and Gunung

Sahari for emergency releases (70 m3/s) from Manggarai.

To avoid underestimation an important choice we made is to include the whole Kali Item

catchment, including Cempaka Putih (also known as Saluran Utan Kayu) in the Marina

Sentiong polder, as the future operation of the Cempaka Putih area is not yet decided upon.

At the moment, Cempaka Putih flows into Sunter through Kali Item just downstream of Sunter

gate. By closing the most eastern gates at Kali Item the flow of Cempaka Putih will join the

other Kali Item flows to Sentiong.

Figure 4-2 – Ciliwung Lama at bifurcation upstream Istiqlal, left branch to Gajah Mada (April 2014)

Figure 4-3 – Announcement of river restoration at Istiqlal just upstream of Pintu Air Istiqlal.



44


For all pump schemes, we propose Marina/Sentiong systems to be combined in one system,

connected via the Ancol gate. Different pump schemes will be discussed in this chapter:

C1. Marina/Sentiong, using the main system only for storage

C2. Marina/Sentiong as C1, but including the Sunter Utara catchment in one system

C3. Marina/Sentiong/Sunter Utara, as C2, but using open space as extra retention

C4. Marina/Sentiong/Sunter Utara, as C3, but with a 400ha near shore retention lake between

planned land-reclamations, including some extra additional coastal catchments and part

of the land reclamation area draining into the retention lake

C5. Marina/Sentiong/Sunter Utara as C2, continuous additional inflow 70 m3/s from Ciliwung

Lama

C6. Marina/Sentiong/Sunter Utara as C2, inflow 70 m3/s from Ciliwung Lama only AFTER

local rainfall event.

The estimated required pump capacities for different return periods for all alternatives are

shown in the table below.

T=25 T=100 T=25 T=100

System M+S M+S Sentiong Marina Sentiong Marina pm Koja

C1 Marina Sentiong, no additional storage

95 140 63 32 80 60

C2 Marina Sentiong, including Sunter Utara

100 150 60 40 90 60 10

C3 Marina Sentiong, incl. Sunter Utara, plus open space retention

85 135 57 28 85 50 10

C4 Marina Sentiong, outside additional storage 400 ha lagoon + additional 500 ha coastal catchments

50 50 30 20 30 20 10

C5 C2 + 70 cms Ciliwung Lama continuously

170 220 90 80 110 110 10

C6 C2 + 70 cms Ciliwung Lama but only AFTER the runoff of the local rainfall event is pumped out (12 hours after start of design rainfall)

100 150 60 40 90 60 10




45

4.2.1 C1 – Marina/Sentiong, no additional storage

In this alternative the Sentiong pump is proposed downstream the Sentiong outflow to the

Ancol drain. Ancol pumping station is removed. The Marina and Sentiong pumps serve the

connected Gunung Sahari/Marina/Ancol/Sentiong system. The Sunter Utara system (pump

and polder) are not connected to the Marina and Sentiong system. We propose the Kampung

Bandan, Ancol Drain, Gunung Sahari, Sentiong and Sunter Selatan reservoirs to be operated

as long storage, with a bottom level of -3 m +PP. The operational level of both pumps should

be -2 m+PP.

In this alternative about 63 mm of rainfall can be retained in the open water system. Pump

capacities of 95 and 140 m3/s respectively are required to meet a T25 and T100 recurrence

flood protection level assuming a proper functioning drainage system (see Figure 4-5). The

characteristics of the system are summarised in Table 4-2.

Figure 4-4 – Alternative C1: Marina and Sentiong pump, no additional storage



46

Figure 4-5 – C1: Polder designs to meet T25 and T100 requirements

Alternative C1

Marina Sentiong, only present storage, additional pumps

T100 T25


Marina 60 32 m3/s

Sentiong 80 63 m3/s








Table 4-2 – Characteristics of Marina/Sentiong alternative C1 (no additional storage)

The distribution of the pumping capacity over Marina and Sentiong is flexible, since they are

connected by a wide (improved) Ancol drain. Looking at the catchment sizes, it is most logical

to have Sentiong pump larger than Marina pump (say ratio 2:1). However, there is already a

plan available for a pump at Marina of 60 m3/s. So for the T100 return period, Marina is put at

this capacity. The emptying time of the full retention storage in the canals is a few hours.


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

TIME [hours]

Vo

lum

e [

mm

]

T100 T50 T25T10 Polder capacity T100 Polder capacity T025



47

4.2.2 C2 – Marina/Sentiong and Sunter Utara, no additional storage

In this alternative, Sentiong pump is placed at the coastline defined by NCICD (Figure 4-6)

and will – also in the future – discharge to the sea (whereas Marina pump will discharge into

the western lake). In this way the Sunter Utara polder, including the Sunter Utara reservoir,

will be included with Marina/Sentiong into one large polder of 55.3 km2. Pump capacities of

Marina/Sentiong of 100 m3/s and 150 m

3/s are required to meet a T25 and T100 recurrence

flood protection level, assuming a proper functioning drainage system. The Sunter Utara

polder and reservoir are in this case drained by Sentiong pump, together with Koja pump in

the north-eastern corner of Sunter Utara. Koja pump is planned to be increased from the

present capacity of 3 m3/s to 10 m

3/s. The latter value is taken into account in the

computations.

Figure 4-6 – Alternative C2, Marina/Sentiong and Sunter Utara system combined



48

Figure 4-7 – Alternative C2, more detailed view of location of Sentiong and Sunter Utara; in alternative C2, Sentiong

pump is put at the location mentioned as Option 2.

Figure 4-8 – C2: Marina-Sentiong polder designs to meet T25 and T100 requirements

Including the Sunter Utara catchment means an additional inflow to the Marina Sentiong

system, so it is expected that the water balance will indicate that a higher capacity of the

Marina/Sentiong pumps is needed. The increase is however relatively small, 5 to 10 m3/s


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

TIME [hours]

Vo

lum

e [

mm

]




49

depending on the return period selected. It seems logical to put most of the additional

capacity at the Sentiong pumping station.

Alternative C2

Marina Sentiong including Sunter Utara

Only present storage, additional pumps

T100 T25


Marina 60 40 m3/s

Sentiong 90 60 m3/s

Koja 10 10 m3/s








Table 4-3 – Characteristics of Marina/Sentiong alternative C2 (including Sunter Utara)

4.2.3 C3 – Marina/Sentiong and Sunter Utara extra open space

Additionally 30 ha of open space has been identified for extra retention. However, 10 ha of

this is actually already open water drainage canal. Therefore only 20 ha of open space is

added for extra retention in this alternative (see Figure 4-9). Total pump capacities of

Marina/Sentiong of 85 and 135 m3/s respectively are required to meet a T25 and T100

recurrence flood protection level, assuming a proper functioning drainage system Additionally

10 m3/s at Koja is assumed.



50

Figure 4-9 – Alternative C3, Marina/Sentiong and Sunter Utara system combined

Figure 4-10 – Alternative C3, Marina/Sentiong and Sunter Utara system combined, additional open space storage



51

Alternative C3


Additional open space retention and pumps

T100 T25


Marina 50 28 m3/s

Sentiong 85 57 m3/s

Koja 10 10 m3/s








Table 4-4 – Characteristics of Marina/Sentiong alternative C3 (including Sunter Utara and additional open space)

4.2.4 C4 – Marina/Sentiong, including Sunter Utara and a Marina retention

When land reclamations of Jakarta can be combined with pump storage, a large retention can

be created (400ha), referred to as “Marina retention” (see Figure 4-11). The catchment of the

retention includes the Marina/Sentiong polder, the lagoon itself (400 ha), some coastal areas

which are outside Martina/Sentiong polder in the previous cases, and one small land

reclamation area (total 500 ha). It is assumed the three large land reclamation areas indicated

in Figure 4-11 do not pump into the Marina retention, but to outside. Even with the larger

catchment area, smaller pumping capacities are needed which result in smaller water level

variations compared to the previous alternatives. Pumps at Marina/Sentiong of 50 m3/s could

service the entire Marina/Sentiong/Sunter Utara polder plus the additional 900 ha under a

T100 protection level, together with a Koja pump of 10 m3/s. Smaller pump capacities do not

seem feasible, since the rainfall mass-duration follow a slope of around 3.3 mm/h

(corresponding with 59 m3/s) after duration of 24 hours (see Figure 4-12) and a very long

emptying time of the system. The characteristics of the system are given in Table 4-5.



52

Figure 4-11 – Alternative C4, “Marina lagoon retention”

Figure 4-12 –C4: Alternative “Marina lagoon retention”

Pompa Marina



53

Table 4-5 – Characteristics of Marina/Sentiong alternative C4 with ‘Marina lagoon retention’

4.2.5 C5 – Marina/Sentiong, as C2 plus continuous 70 m3/s Ciliwung Lama

As mentioned in chapter 1, the general design principle of the polders is to cut off inflow from

upstream rivers completely and to design the polder storages and pumping capacity for the

polder as a separate system. However, for the Marina/Sentiong system PU-DKI asked to also

include the possibility of handling a 70 m3/s inflow from the Ciliwung Lama which is desired

during flood conditions on the Ciliwung river.

Designing the polder storage and pump capacity such that both a local 1:100 year event can

be handled at the same time as an inflow of 70 m3/s from the Ciliwung Lama of course

means that the polder system is designed for a much more severe event than the 1:100 year

local rainfall event.

Another option would be to optimize the gate operation of the Ciliwung Lama gate. This would

mean that in periods without local rainfall in Marina/Sentiong polder, but with a Ciliwung flood,

the Ciliwung Lama gate is opened to alleviate floods on the Ciliwung. And the gate should be

closed as soon as heavy rain is expected on the local polder catchment, and can be opened

when the water levels due to the local rainfall event are back to normal. With the available

Jakarta FEWS system and forecasts such operational management seems to be already

possible.

In case C5 we indicate the consequences of designing the Marina-Sentiong polder (including

Sunter Utara) such that it can also handle an additional continuous 70 m3/s inflow from the

Ciliwung Lama gate.

Not surprisingly, it is found that in this case basically the required capacities of the C2 case

are increased with an amount of 70 m3/s.

To allow a flow of 70 m3/s through Ciliwung Lama without local flooding still requires some

improvement of cross-sections on Ciliwung Lama.

Alternative C4

Marina Sentiong&SunterUtara, outside additional storage 400 ha lagoon

T100 T25


Marina 20 20 m3/s

Sentiong 30 30 m3/s

Koja 10 10 m3/s










54

Figure 4-13 – Alternative C5, “C2 + Ciliwung Lama continuous 70 m3/s”

Alternative C5


Additionally 70 cms Ciliwung Lama Gate continuously

(so also during local rainfall event)

T100 T25


Marina 110 80 m3/s

Sentiong 110 90 m3/s

Koja 10 10 m3/s








Table 4-6 – Characteristics of Marina/Sentiong alternative C5 with Ciliwung Lama gate continously open

For the T100 case, and even distribution of the pumping capacities over Marina (110) and

Sentiong (110) gives a maximum water level of about +1.30 m PP*. In view of NCICD coastal

developments with the future lagoon one might consider not having a pumping station

(Sentiong) pumping to the sea, but concentrate all at Marina (which can be assisted by a gate

in case of the western lake). In this case, the water level at Sentiong which be higher. During


0

100

200

300

400

500

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

TIME [hours]

Vo

lum

e [

mm

]




55

the T100 the maximum water level at Sentiong is +1.60 m PP*, which is 30 cm higher than

the maximum water level at Marina (+1.30 m PP*), as shown by the following graph.

Figure 4-14 – Water levels at Sentiong (blue) and Marina (red), in case all pump capacity put at Marina

4.2.6 C6 – Marina/Sentiong, as C5, but inflow Ciliwung Lama after local rainfall

As mentioned in the discussion of alternative C5, another option is to operate the

Marina/Sentiong system such that it can handle a 1:25 or 1:100 local rainfall event, but not at

simultaneously with a flow from Ciliwung Lama gate during the design event (only sufficient

time before or after the local rainfall event). In case C6 we therefore design the polder system

such that it can handle a 70 m3/s inflow over Ciliwung Lama, but only a number of hours after

the design event. We chose to allow the Ciliwung inflow to start only 12 hours after the start of

the design rainfall event.

W.level up mean MarinaPump W.level up mean SentiongPump

04-01-2013

00:00:00

03-01-2013

18:00:00

03-01-2013

12:00:00

03-01-2013

06:00:00

03-01-2013

00:00:00

02-01-2013

18:00:00

02-01-2013

12:00:00

02-01-2013

06:00:00

02-01-2013

00:00:00

01-01-2013

18:00:00

01-01-2013

12:00:00

01-01-2013

06:00:00

01-01-2013

00:00:00

W.level up m

ean [

m A

D]

1.6

1.4

1.2

1

0.8

0.6

0.4

0.2

0

-0.2

-0.4

-0.6

-0.8

-1

-1.2

-1.4

-1.6

-1.8

-2

-2.2

-2.4

-2.6



56

Figure 4-15 – Alternative C6, “C2 + Ciliwung Lama only open after the design rainfall is largely pumped out ”

Alternative C6


70 cms Ciliwung Lama Gate, 12 hours AFTER start local rainfall event

T100 T25


Marina 60 40 m3/s

Sentiong 90 60 m3/s

Koja 10 10 m3/s








Table 4-7 – Characteristics of Marina/Sentiong alternative C6 with Ciliwung Lama gate open only after local rainfall

Comparison of C2 and C6 shows that using the design events, opening the Ciliwung Lama

gate after 12 hours of the start of the rainfall event does not impact the required pumping

capacity at all. This is because the 1:25 or 1:100 year rainfall already requires a pump

capacity larger than the allowed inflow from Ciliwung Lama gate, and because 12 hours is

long enough to get rid of most of the runoff of the design rainfall event. So case C6 does not

require any additional pumping station compared to case C2.


0

100

200

300

400

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

TIME [hours]

Vo

lum

e [

mm

]




57

On the other hand case C5, which allows the gate to be opened during the entire rainfall

event, requires a 70 m3/s increase of the pumping capacity. The shorter after a rainfall event

the gate is opened, the more pumping capacity will be needed.

Designing Marina/Sentiong such that it can handle the emergency flow through Ciliwung

Lama at the same time as a T100 local rainfall event requires an additional pumping capacity

of 70 m3/s and creates a system which is very secure (higher than T100). On the other hand,

smart operation of Ciliwung Lama gate does not require any additional pumping capacity at

all compared with the T100 polder design. In making a decision on this issue, PU-DKI should

also consider the ongoing extension of capacity of the Western Banjir Canal (BKB) at

Manggarai and Karet by adding an additional gate. Also work is in preparation to connect the

Ciliwung to the Eastern Banjir Canal (BKT) in order to reduce the Ciliwung flows at

Manggarai. After the extension of capacities of BKB and the connection to BKT are

completed and working as designed, the future need for emergency flow through Ciliwung

Lama is reduced and smart operation using the robust system of BKB, BKT and CIliwung

Lama is possible. Such a robust system with and smart operation can save the costs of an

additional 70 m3/s pumping station at Marina/Sentiong to handle the emergency flow through

Ciliwung Lama.


4.3.1 Introduction

At this moment it is advised to operate the Marina/Sentiong system on -2 m PP*. To prevent

soil and sediment from drying out in the dry season and for water quality purposes it is

advised to dredge the bottom of the long storage drains to -3 m PP*, where the JEDI designs

at present use a higher bottom level. For the Gunung Sahari, this is proposed from Marina

pump up to Capitol. For the Sentiong from the outlet to Ancol drain up to waduk Sunter

Selatan. Figure 4-16 shows bottom levels according as designed and as required. Just like for

the other catchment, the cross-sections in the hydraulic model have been assumed to be

wide when the water level is above the target level of -2 m PP* to create enough discharge

capacity. For water levels below the target, it is assumed that the cross-section width is less

in order to reduce flushing requirements.



58

Figure 4-16 –Bottom levels designed (des) and required (req) for the Gunung Sahari, Ancol and Sentiong

Figure 4-17 and Figure 4-18 show the effect of installation of pumps and the dredging of

Ciliwung Gunung Sahari together with the bottom level of the drain and the pump operational

level. Dredging the canal 1 meter roughly has the same effect in lowering the water levels.

This will result in a much better operation of local drainage systems under extreme rainfall.

Figure 4-17 - T25 water levels from Marina to Capitol, test calculation with/without dredging, with/without pump

T025 water level Gunung Sahari

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

100.

276

300.

829

501.

381

701.

933

995.

886

1189

.56

1383

.24

1576

.92

1770

.59

1963

.36

2156

.12

2450

.47

2653

.62

2856

.78

3059

.93

3263

.09

3466

.24

3669

.4

3872

.55

4092

.53

4312

.51

Distance (m)

Ele

vati

on

(m

+P

.P.)

Sheet Piles Bottom Improved bottom T25 JEDI - no pump T25 JEDI - 60m3/s T25 improved XS - 60m3/s Operational level



59

Figure 4-18 – T100 water levels from Marina to Capitol, test calculation with/without dredging, with/without pumps

The Sobek calculations have been made using JEDI design cross-sections, and using

improved cross-sections (deeper canals) which reduce the maximum water levels and

increase the discharge capacity to the pumps. Just like in the other calculations, the cross-

sections below the target level are assumed to be less wide than the cross sections above

target level. In this way, flushing flows in the dry season are smaller because of the smaller

width of the channel at target level, while above target level the full width is available and

allows sufficient discharge capacity.

4.3.2 Results

Structures like Jembatan Merah, Pintu Air Istiqlal cause water level drops at the structure

when the emergency flow from Ciliwung Lama is simulated (case C5, see Figure 4-19). Also

some very low bridges may be obstructing high flows. The calculations provide more insight

in the hydraulic bottlenecks of the system and required additional dredging, to make sure the

system has enough discharge capacity to bring the water to the pumping stations. The water

level rise in the Marina/Sentiong system is more than allowed in the water balance design

calculations. Operational aspects like different switch-on and –off levels explain part of this,

but another important explanation is that the storage in the system is not evenly distributed

and not available for the entire catchment area. In the hydraulic model the Sunter Selatan

reservoirs were only available for storing local runoff, and the pump at Sunter Selatan Barat

reservoir is operated only based on the level of the reservoir. The model calculations show

that in that case the water levels in the Sentiong rise much higher than the levels of the

Sunter Selatan reservoir. This is also confirmed by a field visit and talk with the operator. The

field visit also showed a connection from Sentiong to Sunter Selatan with a gate allowing flow

in both directions, so also allowing water from Sentiong to enter the reservoir during floods.

T100 water level Gunung Sahari

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

100.

276

300.

829

501.

381

701.

933

995.

886

1189

.56

1383

.24

1576

.92

1770

.59

1963

.36

2156

.12

2450

.47

2653

.62

2856

.78

3059

.93

3263

.09

3466

.24

3669

.4

3872

.55

4092

.53

4312

.51

Distance (m)

Ele

vati

on

(m

+P

.P.)

Sheet Piles Bottom Improved bottom T100 JEDI - no pump

T100 improved XS - 60m3/s T100 improved XS - 60m3/s Operational level



60

Figure 4-19 – C5 T100 water levels from Manggarai to Marina, with Pintu Air Istiqlal, Jembatan Merah and Marina







indicate that using the spring tide conditions of 2014 no use can be made of the gates, since

the water levels upstream of the pumps are for all cases below the lowest tidal level of 1.3 m.

In 2030, the NCICD western lake is expected to be developed. Preliminary proposed target

levels are -0.9m +LWS2012 (NCICD, 2014A). This translates to a downstream boundary of

0.98m +PP in 2030, which is just below the computed peak upstream water levels at the

Marina and Sentiong pumps, which vary between 1.1 and 1.8 m for the T100 situation for

cases C1, C2, C3, and C5. This means the pumps will still be needed also after the western

lake is created, but that the gates can help discharging water during flood conditions

(assuming the target level of the western lake can be well maintained in flood conditions!).


From a hydraulic point of view, there are some things to take into account, while

implementing the Marina/Sentiong Polder system. The relevant locations are indicated in

The following list of issues has to be taken into account:

The Ancol drain should be deepened to -3 m PP*. So far, it is not part of JEDI.

The Ancol gate should be large enough to convey water from the Ancol drain to the

Marina Pump. For case C4, the case with Marina lagoon storage, calculations of the

hydraulic model show that even with an Ancol drain deepened to -3 m PP* and a

width of 50 m, the drain and/or the gate apparently form a hydraulic bottleneck:

maximum water levels just upstream Sentiong pumping station are much higher than

water levels in the 400 ha lagoon upstream of the Marina pumping station.

Calculations for case C5 (with continuous flow from Ciliwung Lama) show that when

all pump capacity is put at Marina, the difference between Sentiong maximum water

level (at pumping station) and Marina is 30 cm, while when using an equal distribution

of pumping capacities, the maximum water levels are the same.



61

The operation of Sunter Selatan Barat pump (Pompa Sunter Selatan) needs to be

optimised in the future polder system. In the present hydraulic calculations the pump

is still operated as it is now, but that results in a higher water level rise in the Sentiong

river system than in the Sunter Selatan reservoirs. By a smart pump operation more

water can be stored in the Sunter Selatan reservoirs, and the pressure on the

downstream Marina/Sentiong system gets less. An extreme case could be to have the

Sunter Selatan reservoirs also store excess water from upper Sentiong (as is

presently assumed in water balance). In normal situations with the new low

operational levels, the reservoirs could even discharge by gravity to Sentiong.

At the southern side of the catchment there are the Ciliwung river and Kali Baru

Timur. The polder is designed as a separate system, without inflow from the upstream

Ciliwung and Kali Baru Timur to reduce flood risk (see Figure 1-1), flood mechanism

2). For the Ciliwung Lama, an option to include up to 70 m3/s was included in two

alternatives. For the Kali Baru Timur however, we assume that the complete flow will

not flow into Marina-Sentiong polder. That is possible either by improving the present

gate diverting Kali Baru Timur water to Ciliwung, or by diverting the Kali Baru water to

the East Banjir Canal (BKT) together with the diversion of Ciliwung water to the BKT.

In case of revitalising the Ciliwung Lama and allow a flow of 70 m3/s at all times

without flooding, it is also advised to improve the cross-sections of Ciliwung Lama

(this is not part of JEDI).

Kampung Bandan pump will become totally obsolete as the area can be directly

serviced by the Marina pump.

The operation of secondary and tertiary Pompa Kartini and other pumps along the

Ciliwung Gunung Sahari should be optimised (just as the Sunter Selatan pump in

Sentiong system) in order to allow both good local drainage and to retain water when

possible to reduce the peak discharge into the Gunung Sahari long storage.

Kali Item can also be operated much more frequent via de Kali Item Sentiong gates.

Even at Sumur Batu pump it might be possible to operate under gravity more

frequently.

The layout of the Sunter Utara system to Koja pumping station is not studied in detail.

In the calculations for C2, C3, C4, C5, C6 we assumed the planned extension of the

pumping station from 3 to 10 m3/s will be realised. If not, the capacity at Sentiong

pumping station (which is also serving Sunter Utara area in these cases) needs to be

enlarged with this amount.

At Jl. Yos Sudarso there are two small pumping stations which pump water from

Marina/Sentiong polder into kali Sunter. The capacities are very small (total 1.25 m3/s)

and this has therefore not been considered in designing the desired pumping capacity

at Marina/Sentiong.

The analyses have been carried out assuming Ciliwung Gajah Mada is not part of the

catchment and that there is zero flow from Ciliwung Lama to Ciliwung Gajah Mada. If

70 m3/s emergency release from Manggarai to Ciliwung Lama is active, this

assumption is doubtful and would require a Ciliwung Gajah Mada gate to be realised.

Giving the installation of pumps at Pasar Ikan (and extension of pumps at Pluit) the

question has to be answered what the present or planned operation policy of PU-DKI

is: does PU-DKI want to reconnect Gajah Mada to Ciliwung Lama again? In that case

upgrading of Gajah Mada is necessary (and at the moment not included in JEDI).

Another related issue is the proposed river restoration project of Ciliwung Lama at

Istiqlal. This idea is conflicting with an emergency release through Ciliwung Lama,

passing Istiqlal to Gunung Sahari.



62

In general it is advised to make an inventory of small service pumps under control by DKI or

districts and review their operation. Pumps discharging to the long storage of Gunung Sahari,

Ancol and Sentiong can be equipped with gates for normal operation. Under extreme

conditions the pumps can be used as backup when gravity flow to the long storages from the

secondary drainage system is not possible.

Figure 4-20 Important locations in Marina-Sentiong catchment



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5 Sunter polder


5.1.1 Introduction

The area to be converted into the Sunter polder is 39.44 km2 in total (see Figure 5-1). An area

of 15.5km2 can discharge under gravity to the upper reach of the Sunter drain. Remaining

watersheds have to be drained via small service pumps. Two watersheds between Cakung

and Sunter drain (total area 10.25 km2, see Figure 5-1) can be diverted to one of the two

polders, as the area is heavily under development. In this analysis we assume the area is

serviced via the Cakung polder. Furthermore, at present the Cempaka Putih (also known as

Saluran Utan Kayu) flows via the Kali Item gate near Jl. Yos Sudarso into the Sunter river just

downstream of Sunter gate at km 7.1. In the previous chapter this area has been included

with Kali Item in the Marina Sentiong polder.

Figure 5-1 - Sunter polder



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5.2.1 Sunter drain outlet The outlet of the Sunter polder is designed with a gate and pump. The pump allows to operate the Sunter polder at a low water level and to create sufficient storage. A number of small existing storage ponds are included in the analysis. Because the Sunter polder is largely urbanised, no additional reservoirs or retention areas have been identified. The design discharge for a pump at the Sunter outlet is 120m

3/s (T100) or 90m

3/s (T025).

These discharges are estimated using the water balance approach (described in Annex A) and verified using the Sobek hydraulic model. The target level at the Sunter outlet is put at -2.4m +PP*, which is similar to the Pluit polder level. At the location of the pump (marked as Pompa Sunter in Figure 5-1) an emergency gate should be installed to allow outflow in extreme conditions.

5.2.2 Sunter drain design

The Sunter drain is designed as a double purpose canal to accommodate low flow and peak

discharges. The lowest part of the cross-section is small, to allow flushing with a minimal

required discharge. The upper part of the cross-section (above target level) is wide in order to

maximize discharge capacity. Figure 5-2 shows typical cross-sections applied in the analysis.

The locations are indicated in Figure 5-1.

Figure 5-2 - Typical cross-sections in Sunter drain at locations KM upstream of outlet

In Figure 5-3 the maximum water levels under different rainfall and water level boundary

conditions are shown. Due to the high bottom level, embankments of the Sunter will overtop if

the JEDI designs are applied (see red line in figure). With the profiles shown in Figure 5-2,

combined with the outlet structures proposed in section 5.2.1, the freeboard will be larger

than 0.6m along the Sunter Drain, even if a T100 rainfall occurs under spring-tide conditions

with +0.6m anomaly (extreme sea water level conditions).



65

5.3 Verification with the hydraulic model and JEDI synchronisation

5.3.1 Introduction and results

The cross-section design is adjusted to allow for low flushing requirements and high

discharge capacity during floods. In comparison with JEDI designs, also the last 7.1 km (from

Sunter gate till the river mouth) has been given a lower bed level than in the JEDI designs.

The bed level has been put at 1 m below target level, so at -3.4 m PP*. From Sunter gate in

upstream direction, a typical slope of 1 m per km has been used in the hydraulic model.

The lower bed level of course results in lower maximum water levels compared with

calculations using the JEDI design.

Figure 5-3 - Water levels under different boundary conditions. JFO profiles (‘bottom’ and ‘street level’) withT025

and T100 rainfall. Red line shows water-levels under T100 rainfall with JEDI design

5.3.2 NCICD developments

The case described above has been checked with the hydraulic model using the spring tide



The maximum water level at the river mouth, just before the pump and gate, is 0 m PP* as

shown in Figure 5-3. This means the water level is still far below the tidal low water level.


conditions are equivalent to levels between 2.43 and 3.43 m PP*, so the gate cannot be used

in normal conditions. At the moment it is foreseen that Sunter river will also in the future

discharge to the sea, and not into one of the NCICD coastal lakes. But even if that would be

the case, the proposed operational level of -0.9m +LWS2012 (NCICD, 2014A) corresponds

with a level of 0.98m +PP* in 2030, which would be higher than the water levels in the Sunter



66

system. This means the pumps will still be needed, also if Sunter is to be discharging into a

coastal lake.

5.3.3 Catchment boundaries and connections As mentioned in the description of Sunter polder, there is an area, indicated in grey in Figure 5-1, which at present drains into Sunter or Cakung drain. In the analyses is has been assumed this area drains to Cakung drain. This assumption has some influence on the distribution of the pumping capacities over Sunter and Cakung area, but does not change the total required capacity. The realisation of low target levels in the Cakung area will facilitate drainage of this area to Cakung. Another advantage is that for the Cakung drain there is a future option to drain into a large coastal retention lake, which can reduce the required pumping capacity considerably (see next chapter). The catchment of Saluran Utan Kayu (Cempaka Putih) which is at present flowing to Kali Sunter has been included in the Kali Item – Kali Sentiong catchment (see chapter 5). This catchment is 802 ha. This change requires another operation of the two gates in the eastern end of Kali Item: the eastern gate should be always closed, and the western gate of the two should be always open. Including this 802 ha always in Kali Sunter instead of Kali Sentiong will change the distribution of pump capacity over Sentiong and Sunter. Including it in Marina-Sentiong polder has the advantage that future use of a coastal retention lake is possible. For both areas, the catchment boundary may not be as strict as used for the present analysis. A well-functioning Jakarta FEWS system makes it possible to create a flexible connection between the polders at these locations, and to decide which connection to use depending on the actual situation.



67

6 Cakung polder


In NCICD (2014A, p68) the Cakung drain is presented as a gravity canal to Jakarta Bay, at

least until 2030. We strongly advise the construction of a tidal gate at the mouth of the

Cakung drain. This will effectively reduce the coastline and the risk of a coastal flood via a

breach in the levees of the Cakung drain. If the levee is breached at the western-side, large

parts of dike ring ‘DKI-D’, as presented in NCICD 2014B p21, are at risk. In Figure 6-1, the

potential flood-area caused by a breach in the Cakung Drain at Marunda is given for 2012

and 2030 under different tidal conditions. The construction of a tidal date (and pump),

converts the Cakung water system to a polder.

Figure 6-1 - Areas below a certain level and connected to the Cakung drain breach.

The area to be converted into the Cakung polder is 77.6 km2 in total (see Figure 6-2), of

which 63.4 km2 can discharge under gravity to main drains. Low lying parts of this area (south

of the Marunda drain) are currently heightened by landfills, required to allow gravity

discharge. Remaining areas can be serviced with gates under low-flow conditions and

(existing) pumps under extreme conditions. Two watersheds between Cakung and Sunter

drain with a total area of 10.25 km2, can be largely diverted to one of the two polders, as the

area is heavily under development.



68

Figure 6-2 Cakung and Marunda polder



69


The design discharge at the Cakung drain outlet is 250 m3/s (T100) or 200m

3/s (T025). These

discharges are estimated using the water balance (described in annex A) and verified by

calculations with the Sobek hydraulic model.

The pump strategy for the Cakung differs from other polder systems, due to the high design-

discharges at the Cakung drain outlet. Installing a 250 m3/s pump at the outlet is regarded

undesirable and should therefore be postponed as long as possible. The scheme for current

system conditions includes:

• A tidal gate, discharging the main flow during peak conditions. A pump to drain the

Cakung drain below mean sea level, providing retention storage (see section 6.2.1).

• A redesigned Cakung drain, to meet required storage and maximum discharge capacity

(see 6.2.2).

• Design principles for the Cakung Lama (see 6.3.2).

• Design principles for upstream watersheds (see 6.3.3).

The discharge capacity of the tidal gate will decrease as subsidence continues. The

combined structure (gate and pump), can therefore be developed in alternative strategies:

1 AS1: Increasing the pump capacity to 250m3/s, by increasing the amount of installed

pumps over time at the location of gates as the latter will become less effective over

time (see section 6.4.1).

2 AS2: The retention volume can be increased by construction of a 445 ha retention area

in combination with the current harbour expansion of Tanjung Priok (IPC, 2013) (see

section 6.4.2).

3 AS3: Cakung drain can become a gravity canal if NCICD phase C is completed (NCICD

2014A) (see section 6.4.3).

6.2.1 Cakung drain outlet

The location of the combined pump and gate can be found in Figure 6-2 (marked as ‘Pompa

Cakung’). The primary function of the pump is to meet the target level in the Cakung Drain:

-3.4m +PP*. Under these conditions (low flow), the entire Cakung polder can be serviced by a

pump with a maximum capacity of 20m3/s. The part of the Cakung drain between the planned

pump and Marunda drain should be converted to a pump-storage (see Figure 6-2). Under

peak-flow conditions, the systems main outlet can be a gate with a crest-width of 30m (6x5m).

The crest level is now assumed on -2.5m +PP*, the loss coefficient on 0.8.

6.2.2 Cakung drain design

The Cakung drain should be designed as a double purpose canal to accommodate low flow,

and peak discharges. The lowest part of the cross-section is small, to allow flushing with a

minimal required discharge. The upper part of the cross-section is wide, to maximize

discharge capacity. Figure 6-3 shows some typical cross-sections applied in the analysis for

the locations indicated in

The lowest part, between the pump and Marunda drain (cross sections 0KM till 3.9KM in

Figure 6-2) is flat and should serve as retention for the polder system. The bed level is lower

than proposed in JEDI, and the levee elevation is higher than proposed in JEDI. From

Marunda to Cakung Gate, both the bottom and levee elevations gradually change to meet the

JEDI design levels at the Cakung Gate. At the Cakung gate (9.4KM in Figure 6-2), the profile

bottom and levee elevation meet the elevations used in JEDI.



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Figure 6-3 - Typical cross-sections in Cakung drain drain at locations KM upstream of outlet

6.3 Verification with the hydraulic model and JEDI synchronisation

6.3.1 Introduction and results

In Figure 6-4, maximum water levels under different rainfall and water level boundary

conditions are shown. Due to the high bottom level, embankments of the Cakung drain will

overtop if the JEDI designs are applied (see red line in figure). With the profiles shown in

Figure 6-3, combined with the outlet structures proposed in section 6.2.1, the freeboard will

be higher than 0.6m along the Cakung Drain, even if a T100 rainfall occurs under spring-tide

conditions and +0.6m anomaly.



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Figure 6-4 - Water levels under different boundary conditions. JFO profiles (‘bottom’ and ‘street level’) withT025

and T100 rainfall, average tide (AVG) spring tide + anomaly (STA). Red line shows water-levels under T100

rainfall and STA conditions with JEDI design

6.3.2 Cakung Lama system

Water levels at the Cakung drain will be lower than the polder level under normal conditions,

but higher under extreme conditions. The following subjects should be investigated in

development of the Cakung drainage system: The Cakung Lama Gate should work together with a new ‘Cakung Lama Pump’ (PMP046 in Figure 6-2) for draining the Cakung Lama under low flow and high flow conditions. At the location originally suggested by NEDECO (1973), a plot of 25 up to 50 ha is available, which should be converted into a waduk.

- Table 6-1 shows estimated required pumping capacities for Cakung Lama Pump, as a

function of available reservoir storage.

- For the Petukangan gate a standard operation procedure should be developed for high

and low flows. Preferably the gate should only serve for flushing of the Kali Petukangan,

diverting upstream water to the Cakung Drain under flood conditions.

Table 6-1 - Estimated pump capacities for Cakung lama, depending on waduk-storage

Waduk reservoir storage

Pump capacity [m

3/s]

[ha] T100 T025

25 55 40

50 40 27

6.3.3 Secondary systems

For small service-pumps as PMP033, PMP034, PMP035 and PMP045 in Figure 6-2 and

other small service pumps, the functioning should be re-evaluated. Since water levels at the

Cakung Lama and Cakung Drain will be significantly lower, some systems may be operated

by gates. For others, gates may be installed to discharge water under normal conditions.



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6.4 Alternatives for further development under future scenarios, including NCICD

The design presented in paragraph 6.2 needs improvement to cope with the subsidence rates of Jakarta. If nothing is adjusted, the proposed gate will become less effective over time. Therefore extra measures are required. Three alternative development scenarios are developed depending on the possibility to integrate with the current extension of Tanjung Priok (IPC, 2013), or NCICD phase C (NCICD, 2014A). The T100 water level under the condition of spring tide and +0.6m anomaly are shown for all alternatives in Figure 6-6.

Note: subsidence between present and 2030 is estimated to be 1.13m (0.075m * 15years).

This is incorporated in analysis by heightening the downstream boundary rather than lowering

canal geometry.

6.4.1 No plan integration: increasing pump-capacity to 250m3/s

If no alternative development strategies can be found, the pump capacity can be gradually

increased from 20m3/s to 250m

3/s. This can be done at the expense of gates, of which the

capacity will reduce over time. Two gates of 5m are assumed to be present in 2030 to

discharge under low tidal conditions.

6.4.2 Using 445ha retention pond to extend retention volume

Currently Tanjung Priok harbour is extended (IPC, 2013). Part of the extension is a road

connecting the new harbour to the west-bank of Banjir Kanal Timur. Currently this road is

elevated to connect the Cakung drain with Jakarta Bay. If the road is built on a dike instead, a

waduk will be created of 445ha. A new pump of 80m3/s (target level 0.8 m+PP*) can be

installed. On the outlet of the Cakung, no adjustments are required on the description of

paragraph 6.2.

Figure 6-5 - New waduk space integrated in Tanjung Priok development

6.4.3 Integrate pump scheme in NCICD phase 3

If NCICD phase C is constructed target levels in Jakarta Bay will be -0.9m +LWS2012

(NCICD, 2014A). This translates to a downstream boundary at the Cakung outlet of 0.98 m

+PP* in 2030. If NCICD phase C will be constructed, no additional measures are required on

the design presented in paragraph 6.2. To bridge the time between present and construction

of phase C, additional measures may be required.



73

Figure 6-6 - Water levels under T100 rainfall and spring tide + anomaly (STA) boundary conditions for different

alternative scenarios.



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7 Marunda polder


The area to be converted into the Marunda polder is 16.48 km2. Conversion to a polder was

already proposed by NEDECO (1973), though for a larger area (30km2, see stippled area in

Figure 7-1). A detailed drainage network is not yet available for this area, as it is heavily

under development.

Figure 7-1 - Marunda polder, original NEDECO (1973) plan indicated by stippled area in background layer



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7.2 Pump scheme alternatives The pump capacity is estimated using the water balance with the assumption that a reservoir (waduk) of 40 ha can be created and that 1.5% of the total catchment area is converted to a drainage system. When a total retention area of 64.7 ha is constructed and a fluctuation in water levels of 3 m is allowed, a service pump with a capacity of 25 m

3/s (T100) or 15 m

3/s

(T025) is sufficient (see Figure 7-2). Note, these estimations should be verified with a hydraulic model during the design-phase of the Marunda-polder.

Figure 7-2 - Runoff-duration versus polder design for the Marunda polder

Since Marunda area is not part of JEDI, no synchronisation with JEDI is needed. The area is in development now. Possibilities still exist to create a polder with sufficient open water storage and a pumping capacity which does not need to be extremely large. It is strongly advised to create sufficient storage including a storage reservoir (waduk) as mentioned above.



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8 Upper Cideng - Setiabudi

8.1 Introduction

The upper Cideng catchment is the catchment of Cideng upstream the West Banjir Canal

(BKB). The total catchment size is estimated at 1034 hectares and shown in Figure 8-1. The

area is for large parts already completely urbanised, although near Kuningan there is some

green space and just upstream Jl. Casablanca there is a relatively open space at a higher

elevation which is used for all kinds of activities by local people. The upper Cideng discharges

into BKB near the Setia Budi reservoirs. There is also a syphon from Upper Cideng to lower

Cideng, to be able to flush the lower Cideng. However, the syphon is closed by a gate and

hardly ever opened.

Figure 8-1 – Upper Cideng catchment and schematisation

The reason for studying the Upper Cideng is mainly because of the problems near the outflow

of Upper Cideng into BKB. There are problems during flood conditions on the Ciliwung river

and BKB (backwater flow from BKB into Upper Cideng). Bank stability of the western

embankment of Setia Budi Timur reservoir is an issue. Besides these problems at the

downstream end of Upper Cideng, there are frequent flooding problems in Upper Cideng

catchment mainly upstream Jl. Gatot Subroto.



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Figure 8-2 – Upper Cideng upstream Jl. Gatot Subroto

Figure 8-3 – Upper Cideng downstream Jl. Gatot Subroto



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Figure 8-4 – Upper Cideng near Setia Budi, sand bags on embankment to Seti Budi Timur

Near Epicentrum, the Cideng passes under a set of structures with a small clean water lake

on top, while the upper Cideng flows below during normal situations. However, during high

rainfall conditions, the Cideng will also flow over the structure. The structure will create

significant backwater effect during high flow conditions.

Figure 8-5 – Structures near Epicentrum (left: North side, right: south side)



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8.2 Modelling

The Upper Cideng area has been modelled in Sobek. For rainfall-runoff modelling the SCS

approach is applied. Given the present conditions and expected further densification, a curve

number of 95 has been used (same value as for the polders in Northern Jakarta). The rainfall

event with return period T100 has been used for analysis.

The water levels on BKB have been determined based on calculations with the full FMIS

2012 hydraulic model of Jakarta for the 2007 event, so without the Ciliwung-BKT connection,

but already with upgrading of BKB (dredging).

Figure 8-6 – Water levels at Latuharhari for the 2007 event using FMIS 2012 model

Based on this result, a downstream water level boundary condition of 7 m has been chosen

for the Upper Cideng model. A first reason is that the return period of a combined event of a

flood on the Ciliwung-BKB and a local rainfall event T100 is far more than 100 years.

Secondly, ongoing discussions on allowing an emergency flow from Manggarai through

CIliwung Lama, and making the connection of Ciliwung to the Eastern Banjir Canal (BKT) will

have a reducing effect on water levels at BKB. On the other hand, extending the discharge

capacity at Manggarai may increase the flow and water levels on BKB. All in all, a

downstream water level of 7 m at BKB is quite a high value.

The problems related to the stability of Setia Budi Timur embankments were observed with

very high water levels in BKB early this year. In order to prevent flow from BKB into the Upper

Cideng, a closable gate at the outlet of Upper Cideng to BKB is a simple option. Another

option is to raise en strengthen the embankments of the lower Upper Cideng for say 1-1.5 km

(the area influenced by backwater from BKB).

Several cross-section data were available from earlier projects. However, the exact data on

crest levels, width, opening height of the structures near Epicentrum was not available.

Calculations have been made without the structures and with these structures using



80

estimated dimensions based on field observation. The following graphs give an indication of

the impact of these structures, and a general impression on the location of flooding problems

in Upper Cideng.

Figure 8-7 – Maximum water levels on Upper Cideng, without structures near Epicentrum

Figure 8-8 – Maximum water levels on Upper Cideng, with structures Epicentrum (between x=5500 and x=6000)

The structures do have an impact on upstream water levels, but since the upper Cideng has

quite high embankments in this area, this does not lead to additional flooding in the

calculations.

Furthermore, the model results indicate water above street level in the area upstream of Jl.

Gatot Subroto, but also till 1 km downstream of Jl. Gatot Subroto (at x=4200 m in the above

figures). The latter part is not inundating according to persons we talked to during the field

visit. The model would require the 2D component included to reproduce that. Now the 1D

model overestimates upstream water levels because it assumes no embankment overflow

and vertical walls above the highest cross-section level, getting very high water levels, while



81

in reality there are large inundations, and water flows much slower to downstream of Jl. Gatot

Subroto.

The model also computes local inundations upstream of Jl. Casablanca (near x=4800), which

is in line with the field visit observations.

And, even with high downstream water level of 7 m in BKB, and a considerable head loss at

the outflow structure from Upper Cideng to BKB, the water levels in the lower reach of upper

Cideng hardly overflow when the embankments are raised to 8.0 m PP* or higher.

8.3 Conclusions

Based on the field visit and modelling of upper Cideng area the following conclusions can be

made:

• Local flooding problems occur in upper Cideng catchment especially upstream of Jl.

Gatot Subroto. The explanation is that the local drainage channels are quite narrow in

the upstream area, so the river has very little storage. Downstream of Jl. Gatot Subroto,

the river is much wider and only little flooding problems occur.

• The structures in upper Cideng river near Epicentrum cause significant backwater

effect. However, preliminary model calculations with estimated data (no actual data on

dimensions of the structures was available) show that the structures do not lead to

additional flooding since the river bed is relatively deep compared with the surface level

in that area.

• The upper Cideng area near Setia Budi reservoirs is influenced by high water levels in

the Western Banjir Canal (BKB). January 2014 this has led to stability problems of the

embankment of Setia Budi Timur reservoir. The embankments of the Setia Budi

reservoirs and Upper Cideng river need to be stabilised.

• Future development of the Ciliwung-BKT connection and the use of Ciliwung Lama

gate to divert part of Ciliwung floods will reduce BKB water levels. On the other hand,

the construction of an additional gate at Manggarai and Karet may increase the flows in

this stretch of BKB. Constructing a gate at the outlet of Upper Cideng to BKB can

prevent inflows from BKB into Cideng. Preliminary model calculations using a high water

level of +7 m PP* at BKB Latuharhari show that the discharge capacity of Upper Cideng

is large enough to handle a 1:100 year rainfall event, assuming the embankment levels

of the last 1.5 km of the upper Cideng are at least between 8.0 and 8.5 m PP*.



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9 Review of the proposed Ciliwung-BKT and Cisadane diversions

9.1 Diverting flow from the Ciliwung

The evaluation of the January 2013 and 2014 floods clearly showed that diversion of water

from the Ciliwung away from BKB to other systems would most probably had prevented the

floods. A very effective diversion between the Ciliwung and the newly built BKT was identified

for the first time during the FHM project in 2007: the Ciliwung – BKT diversion. Another

potentially effective diversion was identified in the 90s (Nikken 1997): the Katu Lampa –

Cisadane diversion.

Figure 9-1 gives an indication of the location of both the Ciliwung – BKT and Katu Lampa –

Cisadane diversions in the Jakarta catchment area. When both diversions would be

implemented up to at least 400 m3/s can be diverted away from the Ciliwung before the peak

flows reach BKB, which will very significantly reduce the chance on flooding in the

downstream Ciliwung – BKB system, effectively improving the safety of people and

properties.

Figure 9-1, Overview of prosed Ciliwung diversions



83

9.1.1 Ciliwung – BKT diversion

Figure 9-2 shows part of the no regret measures proposed by FHM in 2007, including the

implementation of the East Banjir Channel (EBC or BKT) in combination with a connection to

BKT from Ciliwung. To allow for this connection the capacity of Cipinang – Sunter BKT stretch

had to be enlarged, to allow not only the high flows from the Cipinang, but also from the

Ciliwung. During the construction of BKT it was decided to follow the advice of FHM to

increase the capacity of the Cipinang – Sunter stretch to allow for a possible future

connection from Ciliwung. The BKT was completed in 2010 and is very effective in reducing

the floods in the eastern parts of Jakarta.

Figure 9-2, Proposed 'no regret' measures, FHM 2007

Due to the different hydrological characteristics of the Ciliwung and BKT catchments, it can

be shown that during high flow conditions on the Ciliwung, nearly always BKT is capable to

receive considerable flows from the Ciliwung. Also during the January 2013 floods, the BKT

system was virtually empty and most probably the floods would have been prevented with the

diversion from Ciliwung to BKT. For that reason the Government decided to immediately start

the preparation by re-evaluation of the hydraulics for the diversion.

In chapter 9.2 the evaluation and effectiveness of the Ciliwung – BKT diversion is presented.

It clearly shows that the diversion would bring great relieve to the BKT system without

compromising the drainage task of BKT. The construction of the diversion would immediate

optimize the investments of the BKT.

• Stepwise approach:

A. Cipinang-Sunter-Buaran-Cakung

(With increased Cipinang-Sunter capacity)

B. Finish EBC-NE stretch

C. Optimize Manggarai gate

D. Connect with Ciliwung

WBC EBC

Cakung

Sunter

Cipinang

Manggarai

Ciliwung



84

9.1.2 New flood strategy for the Ciliwung – BKB system

With the diversion also the flood strategy can/should be optimized and changed. So far, the

flood strategy included the further widening of BKB to allow more flood waters from the

Ciliwung to pass through the inner city. However, BKB is a very old channel, with many

bottlenecks located in the dense urban areas of Jakarta. It is very difficult to keep BKB safe

as was shown by the revetment collapse during January 2013. By including the BKT in the

flood management strategy of the Ciliwung – BKB system, immediately the safety levels

increase, as BKT is a brand new channel, flowing around the urban areas for most part and

enough space along BKT is available and already reserved to allow for future capacity

increase of BKT. It is therefore proposed to change the current flood strategy to:

Minimize the flow to BKB (instead of maximize the flow to BKB)

Optimize the flow to BKT

An ‘Equal BKB-BKT distribution’ principle is therefore proposed for the future flood

management strategy.

9.1.3 Katu Lampa – Cisadane diversion

With the implementation of the Jakarta Flood Early Warning System (JFEWS) also another

possibility to divert water from the Ciliwung: from Kata Lampa – to the Cisadane. This

connection was earlier proposed in the 90s, but could not be implemented because of

increased risk on flooding in Tanggerang. The Katu Lampa – Cisadane diversion requires a

flood prediction and operational management to avoid increase of flood hazards in

Tanggerang. With the implementation of JFEWS such an operational system comes available

to properly manage the Katu Lampa – Cisadane connection.

The location and characteristics of the Katu Lampa – Cisadane connection is presented in

chapter 9.3. A detailed design of the Katu Lampa – Cisadane diversion has already been

made, but it is advised to reconsider the detailed design as a better alignment seems to be

available with the entrance closer to Katu Lampa, which makes the operation of the diversion

easier and more effective.

9.2 Ciliwung-BKT diversion

9.2.1 Introduction

The main reason to divert water from the Ciliwung to the Banjir Kanal Timur (BKT) is that

discharges higher than 400m3/s on the Banjir Kanal Barat (BKB) can be considered unsafe.

This statement is supported by the fact that the BKB overtopped January 2013 with upstream

discharges of 300-400 m3/s. Model simulations show that with a proper functioning Manggarai

and Karet gate discharges of >400 m3/s will limit the freeboard downstream of Karet gate to

40cm (see Figure 9-3). It must be noted that an assumption of 400 m3/s as maximum

discharge depends on assumptions of bed friction (m=0.03), downstream water levels

(MSL=1.2m). Taken into account uncertainties, 400m3/s is considered to be a “likely

assumption” for the maximum discharge on the BKB with an uncertainty of +/- 100 m3/s.

Since a discharge of 400 m3/s or higher occurred in 2007 as well as in 2013, access water

needs to be diverted elsewhere. A diversion option is to discharge excess water to the Banjir

Kanal Timur (BKT).



85

Figure 9-3 – Water levels at the Banjir Kanal Barat (BKB) under 390 m3/s discharge at the Ciliwung and Krukut

From January 21st 2013 onward, Deltares is assisting PU with the analysis of four alternatives

(see Figure 9-4):

1. Alternative BBWSCC: Connects Ciliwung at Otista tiga, underpasses Kali Baru Timur and Cipinang and connects to the Banjir Kanal Timur (BKT) downstream the dropstructure at the Cipinang

2. Alternative Otista tiga (OT3): Connects to the Ciliwung at the same location as alternative BBWSCC. However, it connects directly to the Cipinang, shortening the trajectory with +/- 1km, but making it necessary to replace the Cipinang drop structure.

3. Alternative Casablanca: Connects to the Ciliwung at Jl Casablanca. It connects to the BKT at the same location as alternative BBWSCC. Jl Casablanca also overpasses the water supply line to Pejompongan.

4. Alternative Tarum Kanal Barat (TKB). It connects the Ciliwung and BKT at the Tarum Kanal Barat.

9.2.2 Improvements required at the BKT and Cipinang

Depending on the alternative improvements are necessary or suggested to the Banjir Kanal

Barat (BKT), see Figure 9-5:

- BKT improvement: For a stretch of +/- 1km the canal should be deepened with +/- 1 meter. This is only suggested for alternatives all alternatives and only when significant bypass discharges are reached (>50m

3/s)

- Removal of drop structure. If the diversion diverts from the Ciliwung to the Cipinang, the drop structure at the connection between the Cipinang and BKT should be removed. Note: the removal of the drop structure possibly requires an extra gate downstream of the lower Cipinang confluence if BKT water is used to flush the lower Cipinang. Removing the drop structure is required for alternatives OT3 and TKB

- Cipinang improvements. For alternatives OT3 and TKB the Cipinang should also be improved until the outlet of the diversion. Upstream the slope of the Cipinang should be gradually changed to meet bed levels, or a weir can be constructed similarly to present currently at the drop structure.



86

Figure 9-4 – Alternatives BBWSCC (up left), Otista tiga (up right), Casablanca (down left), Tarum Kanal Barat

(down right)

For all alternatives a side-spill is purposed at the Ciliwung. From the formula of submerged

weir flow, the discharge can be calculated (see eq1). If the width of the side spill is 50 meters,

the loss over the structure will be only 0.1 in most extreme cases. Such losses are

acceptable.

1/2

2e w s up crst dwn upQ c c W h h g h h (eq1)

with: Q = discharge (m3/s)

ce, cw = loss and contraction coefficients (both assumed 1)

Ws = width (m)

hup,hdwn,hcrst = upstream, downstream and crest width elevation (m)

g = gravity coefficient (9.81 m/s2)

The crest level of the inlet structure should be constructed at a safe level. The current

perception of such a level is a Q5. However, at Q5, the floodplain of the Ciliwung is already

flooded.



87

Figure 9-5 – Modifications BKT required for different alternatives

9.2.3 Diversion capacities

To divert water, three strategies have been discussed:

- Open cut; an open canal between the Ciliwung and BKT. Early studies (JFM1) already have shown that capacity of such a diversion is easily sufficient. Further analysis has not been conducted at this point, since space for constructing such diversion is generally considered too limited

- Tunnelling; an underground tunnel between Ciliwung and BKT. Depending the diameter required, the tunnel has to be dug several meters to 30 meters below the surface. Therefore it will always function as a siphon. Neglecting negative aspects such as sedimentation and captivation of air and trash inside the tunnel, a sufficient discharge capacity requires pipe diameters of (roughly) 2x6meters or 1x8 meters in diameter (see Figure 9-6).

- Box culverts; a concrete culvert placed in segments directly below the street surface. Such diversion will function similar to an open cut, until the water levels in the Ciliwung and BKT are higher than the top of the culverts. When water levels at Ciliwung and BKT are higher than the top of the culverts, the capacity is similar to that of a siphon. Assuming culvert diameters of 5X6 (width X height), two till three box culverts are required depending on the trajectory (see Table 9-1).

Weir 1 drop

Cipinang

BKT

Proposed

Outlet BBWSCC and Outlet

Outlet



88

Figure 9-6 – Discharge versus diameter for different alternatives

Table 9-1 – discharge capacity (m3/s) of tunnel diversions using box culverts under T=100 design. 1 Culvert is 5X6

meters.

The nature of the Ciliwung water system, high sedimentation rates and trash accumulation,

limit the possibilities of constructing diversions with siphons. Discharges plotted in Figure 9-4

are based on the assumption that there are no obstructions in the siphon. Siphons are very

sensitive to obstructions by captivation of air, accumulation of sediments and accumulation of

trash.

9.2.4 Effect of diversions on Ciliwung and Banjir Kanal Timur water levels

To significantly reduce the water levels at the Ciliwung a diversion with a capacity of

>150m3/s should be constructed. To underpin this number, system behaviour has been

analyzed using two eventas:

- The T100 design event. In this event, rainfall occurs in the entire catchment at the same

time. Figure 9-7 shows the relation between rainfall, peak discharge at the Ciliwung at MT

Haryono (just upstream of the diversion inlets) and the BKT.

- The 2007 event. This event represents the rainfall which led to the flooding of Jakarta city

in February 2007. This event is characterised by high rainfall intensities in the city prior to

extreme rainfall in the upper Ciliwung catchment.

Maximum tunnel discharge capacity under T=100 design

0

50

100

150

200

250

300

0 1 2 3 4 5 6 7 8 9 10Diameter (meter)

Dis

charg

e c

apacity (

m3/s

)

Capacity (BBWSCC alternative)

Capacity (Otista Tiga alternative)

Parameters:

Head difference: 3

Inlet loss coefficient: 1

Outlet loss coefficient: 1

Bend loss coefficient: 2

Under current situation Ciliwung

1 culvert 2 culverts 3 culverts

BBWSCC 70 140 210

OT3 77 153 230

TKB 79 158 237

Casablanca 64 129 193



89

Figure 9-7 – Relation between rainfall and discharge peaks on the Ciliwung and BKT

Effects on maximum water levels at the Ciliwung under T=100 design conditions, are given in

Figure 9-8. Analysis shows that for this particular event, the water level of the Ciliwung drops

with more than a meter when >140 m3/s is diverted from the Ciliwung to the BKT.

Effects of the diversion on maximum water levels on the Ciliwung are less, but in the same

order of magnitude, as shown in Figure 9-9. However, when maximum water levels are

compared with the canal embankment, it is clear that BKT capacity is sufficient to handle the

amount of discharge diverted in this particular event.

Figure 9-8 – Effect diversions on water levels of the Ciliwung (T=100)



90

Figure 9-9 – Effect diversion on water levels on the Banjir Kanal Timur (BKT) (=100)

In Figure 9-10 the effect of a diversion at Casablanca with three box culverts is plotted. It

must be noted that such diversion will divert around 200 m3/s in a T=100 case, such diversion

will discharge +/- 195 m3/s. Figure 9-10 shows that effects are significant, +/- 1.75m upstream

Manggarai and +/- 1.5m downstream Manggarai.

Figure 9-11 shows the effect on water levels of the BKT for the same event. Effects on

maximum water levels on the BKT are zero, since discharge trough the diversion under peak

discharge conditions in the BKT is zero.

Figure 9-10 – Effect diversions on water levels of the Ciliwung (2007 event)



91

Figure 9-11 – Effect diversion on water levels on the Banjir Kanal Timur (BKT) (2007 event)

The effects on the Ciliwung and BKT discharges are shown in Figure 9-12 and Figure 9-13.

Peak discharge trough the Cilwiung lasts for a period of 2-3 days. Even before the peaks are

reached water is diverted to the BKT. The first peak of the Ciliwung coincides with a peak on

the BKT, which reduces the discharge to the diversion to zero. Therefore, the peak discharge

and corresponding water levels at the BKT are determined by discharge to the BKT from its

tributary rivers only. After the discharge peak at the BKT, with a duration of a few hours, has

passed, sufficient capacity is available to reduce the rest of the discharge peak at the

Ciliwung.

Figure 9-12 – Discharge distribution on Ciliwung (2007 event)

Discharge distribution Ciliwung at diversion outlet (2007 simulation)

Ciliwung discharge us diversion Ciliwung discharge ds divesion Diversion Discharge

9-2-20077-2-20075-2-20073-2-20071-2-200730-1-200728-1-200726-1-2007

Dis

cha

rge

(m

³/s)

460

440

420

400

380

360

340

320

300

280

260

240

220

200

180

160

140

120

100

80

60

40

20

0



92

Figure 9-13 – Discharge distribution BKT (2007 event)

From analysis the conclusion is drawn (based on available data), that diverting water from the

Ciliwung to the BKT must be possible in most cases. Discharge waves at the Ciliwung near

the possible locations for inlets are diffusive. In extreme cases multiple rainfall events build up

one discharge peak which causes high water levels for multiple days. This is caused by the

relatively long travel time of a wave trough the Ciliwung. At the BKT, travel times are

significantly less, in the order of a few hours. In between discharge peaks at the BKT a large

capacity is available to discharge excess water from the Ciliwung.

9.2.5 Towards “equal distribution”

Based on the alternative trajectories and discharge capacities of different diversion strategies,

a concept for redistribution is defined henceforward referred to as “equal distribution”. Figure

9-14 shows how water redistributes when the Casablanca alternative in combination with

three box culverts is constructed. In this fictive design event, water from the Ciliwung is about

equally redistributed over the Banjir Kanal Barat and Banjir Kanal Timur.

Redistribution gives flexibility. If discharge at the Ciliwung is low and discharge at the BKT is

high, a significant amount (around 50% until 400 m3/s upstream MT Haryono is reached) can

be diverted from the Ciliwung to the BKT. If peak discharges at the BKT is high, the diversion

volume can be limited. As explained in section 9.2.4, it is likely that such occurrence only

takes place during a limited amount of time.

Discharge distribution BKT at diversion outlet (2007 simulation)

BKT discharge (downstream inlet) Cipinang discharge (upstream inlet) Diversion Discharge

9-2-20077-2-20075-2-20073-2-20071-2-200730-1-200728-1-200726-1-2007

Dis

cha

rge

(m

3/s

)

380

360

340

320

300

280

260

240

220

200

180

160

140

120

100

80

60

40

20

0



93

Figure 9-14 – Equal distribution concept using Casablanca and three box-culverts (T=100 event).

9.2.6 Prefer ability of alternative

Table 9-2 shows different aspects for every alternative. The value in every cell indicates how

this aspect can be met under the given alternative, the colour indicates its prefer ability,

scaled green till red from preferable till non-preferable.

- Achievable capacity: Indicates how much water can be diverted from every alternative

under the diversion strategy. Only for Casablanca a box culvert strategy has been

discussed and seems achievable. For all other alternatives tunnelling is assumed to be

the diversion strategy.

- Length: Length of the diversion

- Type of tunnelling: Indicating which tunnelling strategy seems to be possible.

- Deepening of BKT: Indicating the length over which the BKT has to be deepened (see

Figure 9-5)

- Improvement of Cipinang: Indicating the length over which the Cipinang has to bee

improved (see Figure 9-5)

- Removal of weir at Cipinang: Indicating if weir at Cipinang, the drop structure which

connects the Cipinang to the BKT, has to be removed (see Figure 9-5)

- Constructing flushing gate at BKT: Indicating if a new flushing gate has to be constructed

at the BKT. This gate is necessary if water should be diverted to the lower Cipinang in the

dry season and the weir at the Cipinang is removed. Note: at the moment no water is

diverted to the lower Cipinang. Before a diversion gate is constructed the necessity of

flushing of the lower Cipinang should be discussed

- Inlet structure at Ciliwung: The structure at the Ciliwung (side spill) which allows water to

flow from the Ciliwung to the diversion

- Inlet gate at Ciliwung: gate at the inlet structure at Ciliwung, which allows a closure of the

diversion for maintenance purposes and in case diversion is undesired

- Outlet structure at BKT/Cipinang: structure at the BKT which connects the diversion to the

BKT.

Table 9-2 – Different aspects (“features”) per alternative



94

Based the analysis in this report, in our point of view the Casablanca alternative should be the preferable alternative. Main reason is the type of tunnelling deemed possible and the fact that no modifications to the Cipinang river profile are necessary. Feasibility of this alternative should be studied further on (at least) the following aspects: - Mapping of conflicts with the Casablanca diversion and existing “underground”

infrastructure, such as electricity lines, water pipes, etc. - Traffic impacts of constructing box culverts under jl. Casablanca - Further detailing of the diversion itself, including detailed design of the inlet structure, gate

and outlet structure

9.3 Alternatif Diversion Channel (Sudetan) Ciliwung - BKT

9.3.1 Ciliwung (Jembatan Kampung Melayu) – Banjir Kanal Timur (Jl. Basuki Rachmad)

9.3.1.1 Deskripsi Umum

Permasalahan banjir Jakarta menjadi perhatian nasional terutama permasalahan banjir yang

diakibatkan oleh sungai Ciliwung dengan Banjir Kanal baratnya(BKB).

Pengembangan pembangunan Banjir Kanal barat selesai tahun 2009 dengan kapasitas

400m3/det di bagian Manggarai-Karet, 450m3/det di bagian Karet-muara Angke, 500m3/det

di bagian muara Angke-Laut, sedangkan pengembangan Pembangunan sungai Ciliwung

masih dalam taraf Perencanaan detail tahun 2013 mulai dari Manggarai sampai jalan Tol

Simatupang dan pelaksanaan fisiknya sedang dilaksanakan 2014 sampai 2016 dengan

kapasitas 400m3/det.

Dengan terbangunnya Banjir Kanal Timur(BKT) tahun 2011, memberikan pemikiran

pemanfaatan kapasitas BKT yang ada untuk dimanfaatkan menyalurkan debit banjir sungai

Ciliwung melalui potensi BKT dengan pembuatan sudetan berupa terowongan atau gorong-

gorong dari sungai Ciliwung ke BKT, hal ini sudah diantisipasi dengan satu opsi koneksi

Ciliwung-BKT dalam studi FHM Jakarta tahun 2007 oleh Deltares.

Secara umum Pembangunan Infrastruktur Penanggulangan Banjir Jakarta masih terfokus

dalam penanganan di bagian hilir yang menjadi prioritas di daerah pusat kota yang terletak di

bagian utara, sedangkan penanganan di bagian tengah dan hulu masih baru di mulai dengan

penanganan sungai Angke, sungai Pesanggrahan, sungai Sunter dan Ciliwung, yang tidak

diimbangi dengan penanganan drainasenya.



95

9.3.1.2 Sistem Penanggulangan Banjir Jakarta

Sistem Penanggulangan banjir Jakarta secara umum dapat dibagi menjadi dua bagian yaitu

dengan pengembangan sistem Flood Control dan sistem Drainase perkotaan. Sistem Flood

Control atau penanganan sungai-sungai utama mulai dari sungai Angke sampai sungai

Cakung, yang secara global dapat dibagi menjadi :

a. Sistem Cengkareng drain

b. Sistem Ciliwung dengan Banjir Kanal Barat

c. Sistem Banjir Kanal Timur

d. Sistem Cakung drain

e. Sistem Sunter bawah

f. Sistem Ciliwung bawah

g. Sistem Angke bawah

h. Sistem Sentiong

i. Sistem Polder seperti Pluit dll.

Secara umum sistem-sistem tersebut diatas berdiri sendiri dapat dilihat dalam Gambar 1.

Gamabar 1

Permasalahan yang terjadi untuk sungai Ciliwung dengan kejadian banjir yang relatif sering

disebabkan kapasitas sungai Ciliwung dengan BKB sudah tidak mampu menampung debit

banjir yang ada sehingga perlu penanganan dengan beberapa opsi seperti pembuatan

normalisasi sungai Ciliwung, Sudetan Ciliwung-BKT di Jakarta seperti di Otista 3 dengan

terowongan dengan kapasitas 60m3/det oleh BBWSCC atau Box culvert dengan kapasitas

150m3/det di Jembatan Kp.Melayu-BKT dan sudetan Ciliwung- Cisadane di Bogor berupa

terowongan dengan kapasitas 400m3/det, dapat dilihat dalam Gambar 2.

Gambar 2



96

9.3.1.3 Kondisi Banjir Kanal Timur

Setelah dibangunnya BKT tahun 2011 dengan kapasitas 270m3/det dibagian hulu,

350m3/det dibagian hilir, kejadian banjir yang terjadi akibat sungai Cipinang,sungai Sunter,

sungai Jatikramat, sungai Buaran dan sungai Cakung telah menyelesaikan masalah banjir di

bagian hilir BKT, tetapi masih menyisakan masalah banjir di bagian hulu BKT sungai-sungai

tersebut, karena masih dalam taraf pembangunan.

Dari aspek hidrologi, catchment area BKT relatif lebih hilir dan kecil (dapat dilihat dalam

Gambar 1), menyebabkan waktu konsentrasi relatif lebih cepat sehingga debit puncak BKT

sudah terlewati dan sungai Ciliwung dengan waktu konsentrasi yang lebih lama

menyebabkan kondisi debit BKT relatif sudah kecil diperkirakan 60m3/det. Dengan kapasitas

270m3/det dibagian hulu BKT cukup untuk menampung debit puncak sungai Ciliwung yang

datang kemudian dengan memanfaatkan kapasitas yang tersisa diperkirakan sebesar

210m3/det dengan 60m3/det dari sudetan Otista 3 dan 150m3/det dari sudetan Jembatan

Kp.Melayu-BKT dibawah jalan Abdullah Syafei-Kp.Melayu besar-Basuki Rachmat, dapat

ditingkatkan dari 210m3/det menjadi 320m3/det dengan memperbesar kapasitas BKT dari

Cipinang ke Jatikramat menjadi 320m3/det, dengan menghilangkan drop structure I dan II di

bagian hulu BKT, 1 m di drop structure I dan 2.2 m di drop structure II.

Dari kejadian banjir BKT setelah terbangunnya BKT pada kejadian tahun 2011-Januari 2014

lebih kurang lima kali kejadian banjir besar BKT dan sungai Ciliwung, dari data telemetri

menunjukan Banjir di BKT selalu lebih awal sehingga pada saat Banjir puncak Ciliwung

datang BKT dalam keadaan debit rendah sehingga dapat dimanfaatkan untuk menampung

sebagian debit puncak banjir sungai Ciliwung yang datang kemudian.



97

9.3.2 Opsi Pembuatan Sudetan Ciliwung-Banjir Kanal Timur

Meninjau kondisi Banjir Kanal Timur yang masih cukup potensial untuk dioptimalkan, dari

segi kapasitasnya yang masih mampu menampung tambahan sebesar 210 m3/det, dan yang

secara langsung akan mengurangi beban debit aliran ke Sungai Ciliwung dan Banjir Kanal

Barat, telah diusulkan tiga jalur alternatif untuk mengalihkan sebagian debit aliran dari Sungai

Ciliwung ke Banjir Kanal Timur. Ketiga jalur alternatif tersebut dapat dilihat dalam gambar 3

adalah sebagai berikut:



98

Gambar 3

Alternatif I

Ciliwung - Jembatan Kampung Melayu Banjir Kanal Timur (Jl. Basuki Rachmad)

Alternatif pertama yaitu mengalihkan debit aliran dari Sungai Ciliwung pada titik lokasi inlet

bermula di Jembatan Kampung Melayu dengan memanfaatkan jalur di bawah jalan raya

sekunder dari Jl. Abdullah Syafe’i ke Kp. Melayu Besar hingga Jl. Basuki Rachmad. Ada tiga

titik lokasi outlet yang memungkinkan dengan memanfaatkan Sungai Cipinang ke BKT atau

langsung menuju ke BKT. Peninjauan secara teknis dibahas lebih detail kemudian.

Alternatif II

Ciliwung - Jl. Otista Tiga Banjir Kanal Timur (Jl. Basuki Rachmad)

Ciliwung - Jl. Otista Tiga Cipinang - Banjir Kanal Timur (Jl. Basuki Rachmad)

Alternatif kedua yaitu mengalirkan debit aliran dari Sungai Ciliwung pada titik lokasi inlet

bermula di garis lurus perpotongan dari Sungai Ciliwung ke Jl. Otista 3 hingga menuju ke

Sungai Cipinang (melalui Jl. Pulomas Cawang hingga Jl. Kebon Nanas). Ada dua alternatif

lokasi outlet yaitu: (i) Jl. Otista Tiga dialirkan terlebih dahulu ke Sungai Cipinang lalu Banjir

Kanal Timur, dan (i) Jl. Otista Tiga langsung dialirkan ke Banjir Kanal Timur. Alternatif kedua

didesain dengan terowongan berupa pipa berdiameter 2x3.5 m dan kapasitas debit rencana

Q = 60 m3/detik.

Alternatif III

Ciliwung-West Tarum Canal Cipinang – Banjir Kanal Timur (Jl. Basuki Rachmad)

Alternatif ketiga sudetan adalah dengan memanfaatkan existing West Tarum Canal yang

pada rencana awalnya dibangun sebagai supply channel berasal dari Sungai Citarum (Jawa

Barat) ke WTP Pejompongan di Jakarta Pusat. Jadi, sebesar 80 % suplai air bersih untuk

Jakarta berasal dari Jatiluhur sementara 20 % dari air baku ditambahkan dari Sungai



99

Ciliwung. Sehingga sebagian aliran suplai air bersih dari Kali Malang (West Tarum Canal) ke

Cipinang disalurkan melalui pipa ke Sungai Ciliwung hingga ke Pejompongan di Jakarta

Pusat. Namun, saat ini pipa tersebut tidak lagi digunakan sebagai suplai air bersih sehingga

prasarana pipa Kali Malang-Cipinang-Ciliwung yang telah ada ini bisa dimanfaatkan dengan

alih fungsi untuk mengalirkan debit banjir sebaliknya dari Ciliwung ke Cipinang yang

diteruskan hingga ke Banjir Kanal Timur. Namun kapasitas pipa terbatas pada suplai air 20%

untuk wilayah Jakarta dari total kebutuhan sehingga diperkirakan kapasitas yang ada berkisar

19 m3/detik dan masih bisa ditingkatkan lagi.

Dari ketiga alternatif jalur Sudetan Ciliwung - Banjir Kanal Timur, alternatif II

(Ciliwung-Otista 3) menggunakan tunneltelah dimulai pelaksanaannya dan hingga kini

masih berjalan dengan pelaksana BBWSCC. Alternatif III melalui gorong-gorong

ujung kalimalang juga dapat membantu mengalihkan debit aliran Ciliwung namun

hingga saat ini masih sebatas kajian. Dengan additional inflow 60m3/det ke BKT

sementara kapasitas hulu BKT adalah 270 m3/detik, maka BKT masih dapat

menampung tambahan debit air masuk sebesar 210 m3/det.

Setelah melaksanakan beberapa kajian studi singkat, alternatif I (Ciliwung-

Kp.Melayu-BKT) denganbox-culvert diusulkan sebagai alternatif yang efektif dan

efisien untuk mengalihkan debit aliran Ciliwung dalam jumlah yang lebih besar (150-

200m3/detik).

9.3.3 Opsi Alternatif Outlet Diversion

Opsi alternative I memiliki lokasi inlet diversion yang cukup jelas yaitu di sebelah hulu

Jembatan Ciliwung di Kampung Melayu. Diusulkan tiga alternatif lokasi outlet point melihat

dari aspek ruang jalan dan pemanfaatan sungai Cipinang. Alternatif lokasi outlet point berikut

tinjauannya adalah sebagai berikut (Gambar 4):

(i) Alternatif-1: Jl. Abdullah Syafe’i – Jl. Basuki Rachmad – Drop Structure I

BKT

Ruas Jl.Basuki Rachmad yang bersebelahan BKT memiliki ruang jalan cukup tersedia untuk

pelaksanaan box-culvert dengan lebar sekitar 12 – 16 meter, jarak dari bawah Jl.Tol Cawang-

Priuk hingga S.Cipinang (Jl.Basuki Rachmad) sekitar 220 meter, jarak memanjang box-

culvert dari Sungai Cipinang (Jl.Basuki Rachmad) hingga drop structure I sekitar 800 meter.

(ii) Alternatif-2: Jl. Abdullah Syafe’i –Sungai Cipinang (Jl.Basuki Rachmad) –

BKT

Bagian awal ruas Jl.Basuki Rachmad masih cukup tersedia 12 meter dengan panjang 220

meter dari bawah Jl.Tol Cawang-Priuk hingga Sungai Cipinang (Jl.Basuki Rachmad),

kemudian box-culvert dihubungkan ke existing channel Sungai Cipinang ke Selatan hingga

BKT, penghematan konstruksi memanjang diversion, namun diperlukan sedikit penyesuaian

alur sungai di Sungai Cipinang.

(iii) Alternatif-3: Jl. Tol Cawang-Priuk – Jl. Basuki Rachmad –Drop Structure II

BKT

Ruas Jl.Basuki Rachmad yang bersebelahan BKT memiliki ruang jalan cukup tersedia untuk

pelaksanaan diversion (box-culvert) dengan lebar sekitar 12 – 16 meter, jarak dari bawah

Jl.Tol Cawang-Priuk hingga S.Cipinang (Jl.Basuki Rachmad) sekitar 220 meter, jarak



100

memanjang box-culvert dari Sungai Cipinang (Jl.Basuki Rachmad) hingga drop structure II

sekitar 1,5 kilometer.

Gambar 4

panjang box culvert keseluruhan tiap alternatif Alt 1=2.3km, Alt 2=2.1km, Alt 3=3.1km

Tinjauan Lapangan dan Hidraulik

Dalam kajian studi ini, telah dilakukan beberapa tahap investigasi:

Tinjauan Lapangan

Survey lapangan dilaksanakan dengan koordinasi Dinas Pekerjaan Umum DKI Jakarta

antara Sub-Dinas Bina Marga dan Sub-Dinas SDA untuk meninjau apakah lokasi dan akses

jalan pada wilayah tersebut memungkinkan untuk konstruksi box-culvert. Mengingat teknis

pelaksanaan akan dilakukan di bawah tanah, maka perlu diperhatikan lebar jalan sepanjang

lokasi Sudetan, jarak antara fondasi pilar (footing/pile cap)serta utilitas yang ada di bawah

tanah jalan layang Jl.KH.Abdullah Syafe’i (terutama transmisi pipeline air baku Cawang-

Pejompongan diameter 2x2m dan utilitas yang lain). DPU DKI sepakat pada kesimpulan

bersama bahwa konstruksi box-culvertalternative I Kp.Melayu (Ciliwung) – BKT

sudetanmemungkinkan untuk diimplementasikan, dapat dilihat dalam gambar 5

Inlet point

3 Alternatif outlet point

Alt 1 Alt 2

Alt 3



101

Gambar 5

Meskipun demikian, terdapat 5 titik utama tinjauan dari Kp.Melayu ke arah Jl. Basuki

Rachmad yang penting untuk diperhatikan dalam detail perencanaan teknis:

1. Penyempitan Kampung - Jalan sebelum Jl. Tol Cawang-Priuk

2. Persilangan pipa air baku (Pejompongan) di sebelah timur sungai Kalibaru

3. Persilangan jalur box-culvert dengan Jl. Tol Cawang-Priuk

4. Pertemuan jalur box-culvert dengan Sungai Kalibaru

5. Integrasi titik tumpu Pilar rencana Fly Over Tol baru yaitu ruas Kp.Melayu-Duri

pulo, Melayu-Sunter dan Bekasi-Cawang-Kp.Melayu, dapat dilihat dalam

gambar 6 berikut:

Gambar 6



102

Tinjauan Hidraulik

BKB dikategorikan tidak aman apabila debit alirannya melebihi 400 m3/det. Bulan Januari

2013 BKB meluap ketika debit di hulu mencapai 300-400 m3/det. Simulasi model (SOBEK

model-Deltares) menunjukkan bahwa apabila pintu air Manggarai dan Karet berfungsi baik,

dan debit air lebih dari 400 m3/det akan membatasi freeboard BKB setelah pintu Karet

sebesar 40 cm (Gambar xx) dengan asumsi kekasaran dasar sungai m=0.03 dan muka air

hilir MSL= +1.2m.

Diakibatkan oleh terjadinya debit 400 m3/det atau lebih pada tahun 2007, 2013 dan juga

diperkirakan terjadi pada tahun 2014, urgensi semakin nyata bahwa diperlukannya

pengalihan aliran air dari Ciliwung-BKB ke sungai lain. Opsi pengalihan adalah dengan

mengalirkan kelebihan air ke BKT.

Gambar 7

– Water levels at the Banjir Kanal Barat (BKB) under 390 m

3/s discharge at the Ciliwung and

Krukut

Dengan kapasitas sisa BKT yang masih bisa dimanfaatkan sebesar 210 m3/det, sudetan

harus didesain dengan kapasitas >150 m3/det. Hal ini didukung dengan analisa pemodelan

hidraulik menggunakan kejadian desain hujan T100 yang menunjukan adanya pola debit

dimana di Sungai Ciliwung MT Haryono debit puncak lebih tinggi dibandingkan yang terjadi di

Cipinang.



103

Gambar 8

– Relation between rainfall and discharge peaks on the Ciliwung (MT Haryono) and

Cipinang-BKT

9.3.4 Pengaruh sudetan alternatif 1 pada muka air Ciliwung dan Banjir Kanal Timur

Pengaruh muka air maksimum di sungai Ciliwung pada kondisi desain kala ulang T=100

tahun ditunjukkan pada Gambar xx. Muka air Ciliwung turun lebih dari 1 meter ketika

dialihkan debit > 140 m3/det dari Ciliwung ke BKT.

Dampak dari sudetan terhadap muka air maksimum di BKT tidak tampak terlalu signifikan.

Meskipun demikian, muka air maksimum di BKT masih jauh dari tinggi tanggul BKT. Hal ini

membuktikan bahwa kapasitas BKT cukup memadai untuk menampung sejumlah debit aliran

yang dialihkan dari Ciliwung-BKT pada contoh kejadian simulasi ini.



104

Gambar 9

– Effect diversions on water levels of the Ciliwung (T=100)

Gambar 10

– Effect diversion on water levels on the Banjir Kanal Timur (BKT) (=100)

**untuk mencapai kapasitas 150 m3/s 2 x (5 x 6) meter



105

Untuk ketiga alternatif tersebut, pengalihan debit aliran sungai Ciliwung akan digunakan

desain struktur hydraulic Box-Culvert dengan ukuran 5 x 6 meter.

Perkiraan kapasitas sudetan menggunakan Box Culvert dalam konteks kala ulang kejadian

T=100 tahunan untuk semua alternatif apabila terpasang 1, 2 atau 3 buah box adalah sbb:

Tabel 1

Pada Gambar 4 berikut dapat dilihat dampak sudetan alternatif 1 menggunakan 3 buah box-

culvert bahwa terjadi penurunan signifikan + 1.75m di hulu Manggarai dan + 1.5 m hilir

Manggarai. Gambar selanjutnya mengindikasikan bahwa muka air maksimum di BKT akan

sama tingginya dengan muka air maksimum ketika terjadi debit puncak hujan yang

mengalirkan aliran dari Sungai-sungai hulu ke BKT (Cipinang, Sunter, Buaran, Jati Kramat

dan Cakung).

6m

5m

Desain Debit Aliran

(m3/dtk) Lebar (m) Tinggi (m)

1 box culvert 64 5 6

2 box culverts 129 12 6

3 box culverts 193 18 6

Diversion-

Channel

Dimensi



106

Gambar 11,

Pengaruh Desain Box Culvert dalam mereduksi debit aliran dari Ciliwung hulu ke pintu air

Manggarai dan Banjir Kanal Barat

Aliran Sungai Ciliwung tereduksi hingga1.5 meter, akan terjadi penurunan tinggi muka

air perlahan dimulai dari inlet di sekitar Jembatan Kampung Melayu, yang kemudian

menjadi semakin signifikan di bagian hilir hingga 1.5 meter dikarenakan pengalihan

debit secara kontinyu sebesar 100-210 m3/detik.

Gambar 12



107

Pengaruh Desain Diversion – terhadap kondisi Banjir Kanal Timur apabila aliran terlah

dialihkan

Berdasarkan hasil simulasi model, kondisi kapasitas Banjir Kanal Timur setelah

mendapatkan tambahan debit aliran sebesar + 210 m3/detik masih cukup memadai.

Hanya ada satu lokasi weakpoint yang masih perlu dipertimbangkan.

9.4 Preliminary review Ciliwung – Cisadane diversion

9.4.1 Diversion Katu Lampa-BKT, Nikken 1997

With the implementation of the Jakarta Flood Early Warning System (JFEWS) also another

possibility to divert water from the Ciliwung: from Kata Lampa – to the Cisadane. This

connection was earlier proposed in the 90s (Nikken 1997), but could not be implemented

because of increased risk on flooding in Tanggerang.

A feasibility design of the Katu Lampa – Cisadane diversion was formulated by Nikken in

1997. But after intense discussions between 1997 – 2000, it was finally decided not to

construct the diversion because of:

Possible increased flood risk in Tangerang

The complex social conditions around inlet and outlet,

Large construction in and under the city center

However, further analysis by Deltares after the severe flooding in January 2013 and again

after the high water early 2014, showed the Ciliwung – Cisadane diversion is a very effective

flood measure for Jakarta and that increased flood risk can be avoided.

It was therefore concluded to reconsider the earlier designs as a better, more effective

alignment was identified. This new alignment is the described in the next chapter.

In March 2014 the Ciliwung – Cisadane was discussed again between Jakarta – Tangerang

and PU. It was decided to first carry out the urgently required maintenance program for the

Cisadane and after completion of the rehabilitation to reconsider the proposed diversion.

The original Nikken1997 is presented in Figure 9-15 - Figure 9-19. to be available with the

entrance closer to Katu Lampa, which makes the operation of the diversion easier and more

effective.



108

Figure 9-15, Proposed alignment for the Katu Lampa - Cisadane diversion, Nikken 1997




109


Figure 9-18, Proposed Inlet for the Katu Lampa - Cisadane diversion, Nikken 1997



110

Figure 9-19, Local impression of the inlet for the Katu Lampa - Cisadane diversion, Nikken 1997

9.4.2 Diversion Katu Lampa-Cisadane, Deltares 2014

With the implementation of the Jakarta Flood Early Warning System (JFEWS) the Ciliwung

diversion from Kata Lampa – to the Cisadane can be operated in such a way that increased

flood risk on the Cisadane and in Tangerang can easily be avoided. The Katu Lampa –

Cisadane diversion requires a flood prediction and operational management to avoid increase

of flood hazards in Tanggerang. With the implementation of JFEWS the basis for such an

operational system is available to properly manage the Katu Lampa – Cisadane connection.

To avoid the difficulties along the Nikken alignment regarding the complex social conditions

around inlet and outlet, avoid large construction in and under the city center additional field

work was carried out to see if an alternative alignment would be possible. An alternative

alignment was identified (Deltares 2013) and was further investigated and discussed. The first

findings were confirmed and although the tunnel length increases, a new, effective diversion

seems certainly possible:

No social or land acquisition issues at inlet and outlet

Increased head (from 11 to 40m) and therefore reduced tunnel diameter

Tunnelling under nearly uninhabited area (e.g. parks and cemetery)

The proposed alignment is shown in Figure 9-20 - Figure 9-25. The length of the diversion is

approximately 3 km and the level difference between entrance and outflow point over 40 m,

which provides easy diversion of at least 200 m3/s, which is a significant reduction of the

peak-flows from Katu Lampa. As can be seen from Figure 9-28 the diversion requires a bored

tunnel, which is similar to the earlier designs from the 90s. But where for the Ciliwung – BKT

soft soil ground works are required, the Katu Lampa – Cisadane diversions is located on hard

rock.



111

Figure 9-20, Proposed alignment for the Katu Lampa - Cisadane diversion, Deltares 2014

Figure 9-21, Proposed entrance for the Katu Lampa - Cisadane diversion



112

Figure 9-22, Local impression Katu Lampa weir downstream

Figure 9-23, Local impression proposed entrance location A for the Katu Lampa - Cisadane diversion



113

Figure 9-24, Local impression proposed entrance location B for the Katu Lampa - Cisadane diversion

Figure 9-25, Proposed outflow point for the Katu Lampa - Cisadane diversion

Outflow

Cisadane



114

Figure 9-26, Overview outflow point for the Katu Lampa - Cisadane diversion

Figure 9-27, Local impression outflow point for the Katu Lampa - Cisadane diversion



115

Figure 9-28, 3D - view of the Katu Lampa - Cisadane diversion



116

10 Extension of the Jakarta FHM modelling framework

Together with the Ciliwung-Cisadane diversion, also a maintenance/rehabilitation program is

proposed for the Cisadane river, to allow for the possible increased flow and also to restore

the design capacity (2000 m3/s) of the Cisadane and especially the Pasar Baru weir. Hereto,

the Cisadane is to be analysed for flood mitigation and operational purposes. Therefore it is

proposed to extent the Jakarta FHM framework with a hydrological\hydraulic model of the

Cisadane (see Figure 10-4). The following paragraphs first describe the development and

content of the Jakarta FHM modelling framework, followed by the approach to add the

Cisadane and Bekasi rivers.

10.1 History of Jakarta FHM modelling framework 2007 – 2013

After the severe floods of February 2007, as part of the non-structural Dutch Assistance

Jakarta Flood Management initiative (DA JFM), a new successful approach to assist Jakarta

in understanding and counteracting the floods was introduced. An important part of the

approach was developed through the "Flood Hazard Mapping (FHM)" projects (2007-2009)

During the three consecutive FHM projects a unique FHM modelling framework was

developed and further updated including the 13 crossing rivers and the complete major

drainage system of Jakarta.

The developed GIS based FHM modelling framework starts in the upper Panggrango - Gede

area and runs to the northern coastal area of Jakarta. It includes complete hydrology, land-

use, major river and drainage system and is capable to simulate floods in the complete DKI

area. During the Situ Situ Safety Inspection (S3I) study (2009), the FHM modelling framework

was further expanded to include all major Situ Situ upstream and in Jakarta. The FHM

modelling framework was further used and updated during the Jakarta Flood Readiness Scan

(JFRS) in 2011, the Flood Management Information System (FMIS) in 2012 and during the

evaluation of the January 2013 floods. As the FHM modelling framework was setup for use as

part of an online monitoring / flood early warning system (FEWS), the FHM modelling

framework was connected to the Jakarta Flood Early Warning System (JFEWS) during the

Joint Cooperation Program (JCP 2011-2012). In the FMIS project JFEWS was further

enhanced and implemented at the flood operation and disaster centres in Jakarta.

Many different parts of the Jakarta have been analysed and evaluated with the FHM

modelling framework since 2007. An overview of the projects and related reports is presented

in Table 10-1 in which the Jakarta FHM modelling framework was developed, maintained,

updated and extended.

Table 10-1, Overview of FHM and Hydraulic activities in Jakarta 2007 - 2013

Jakarta - FHM and Hydraulic Activities 2007 - 2013

Project Report nr

Project Title Relevant Report Title

FHM1

Flood Hazard Mapping 1 (2007)

1 Overview 16122007.pdf

2 Main Report 151207.pdf

3 Flood extent and Bottlenecks 151207.pdf



117


Project Report nr


4 Hydraulics 151207.pdf

5 Hydrology and Sea Water Levels 15122007.pdf

6 Annex A, Sea Water Levels 15122007.pdf

7 Annex B, Discharge Measuring Stations 15122007.pdf

FHM2



2 FHM modelling framework 230309.pdf

3 HU database and FEMapping 230309.pdf

4 Jakarta Flood Early Warning System, Main 230309.pdf

5 Jakarta Flood Early Warning System, Appendix A 230309.pdf

6 Jakarta Flood Early Warning System, Appendix B 230309.pdf

7 Jakarta Flood Early Warning System, Appendix C 230309.pdf

FHM3


1 01 Final Report.pdf

2 03 Evaluation Dredging in Jakarta.pdf

3 06 Evaluation Training Planning Unit with FHM Model.pdf

4 07 Long Term Rehabilitation & Maintenance Program.pdf

5 08 Inventory of Urban Drainage Systems in Pademangan Barat and Thamrin Monas.pdf

6 09 Performance Analysis Drainage System Sub catchment Jalan Thamrin Jakarta.pdf

7 10 Analysis Capacity Drainage System Pademangan Barat.pdf

8 14 GPS Based Flood Extent Mapping.pdf

S3I

Situ Situ Safety Inspection (2009)

1 Field inspection and investigation 270709.pdf

2 Safety inspection manual 270709.pdf

3 Short-term Action Plan 240709.pdf

4 Soil Investigation 270709.pdf

JFRS

Jakarta Flood Readiness Scan (2011 - 2012)

1 Jakarta Disaster Preparation December 2011.pdf

FMIS

Flood Management Information System (2012)

1 FMIS Main report 10022013.pdf

2 FMIS Annex A, FHM framework and measures 10022013.pdf

3 FMIS Annex B, Hydro-meteorological monitoring network Jakarta 10022013.pdf

4 FMIS Annex C, FMIS institutional framework 10022013.pdf

EA2013 FHM - Emergency Assistance Floods January 2013 (2013)



118


Project Report nr


1 Jakarta Floods January 2013 - Emergency assistance - April 2013.pdf

10.2 The Jakarta SOBEK modelling system

SOBEK is the main hydrologic and hydraulic modelling software used for analyzing the

propagation of water through the Ciliwung catchment. It consists of modules that can be used

separately or combined. The available Sobek-modules cover a wide range of processes, from

rainfall-runoff, to 1D/2D hydrodynamics, to water quality processes and emissions. SOBEK is

developed in close co-operation with several organizations in the water sector, based on a

long history of developments of flow modelling in systems.

The first release, SOBEK-RE, was launched in the early nineties. Next, SOBEK-Urban was

developed as a tool for integral studies of the effects of precipitation and waste water

management in urban areas. Subsequently, SOBEK-Rural was developed for drainage and

irrigation studies in low lying areas and the associated water management. Finally, SOBEK-

RIVER was launched a few years ago, focusing entirely on the modelling of river systems.

Both the 1D- and 2D flow modules solve the full set of the de Saint-Venant equations. This

makes SOBEK ideally suited for difficult-to-model systems, as it can handle flow conditions

that other packages cannot: super-critical flow, transition from super- to sub-critical flow

(hydraulic jumps), and both wetting and drying of grid-cells. It comes equipped with a variety

of boundary conditions, wind effects, hydraulic structure descriptions, lateral flows and cross-

section descriptions.

10.3 The Jakarta FHM- modelling framework

10.3.1 Overview

In the Jakarta FHM modelling framework the following three SOBEK modules are used:

1. The hydrological rainfall runoff module (RR) that simulates the transformation of rainfall

to runoff for each river catchment, and thus computes the inflows into the one

dimensional hydraulic river module.

2. The one-dimensional hydraulic module (1D) that simulates the one-dimensional flow

(water levels and discharges) though the main rivers and the main drainage system.

3. The 2-dimensional hydraulic module (2D) that simulates the inundation pattern over the

project area from the locations where the one dimensional water courses are

overtopped. The results from this module are used to construct the flood hazard maps.



119

Figure 10-1 Overview of used Sobek Modules

10.3.2 The rainfall-runoff model

The rainfall-runoff model provides the 1D-flow model with runoff from the sub-catchments

using the following steps:

Step one simulates runoff from +/- 450 sub-catchments

(see Figure 10-2), based on rainfall data and sub-

catchment characteristics. The well-known Sacramento

model concept has been used for this purpose. The

Sacramento model can be used for both event-based and

year-round continuous simulations. For each sub-

catchment, main characteristics as surface area, land use,

slope, flow path length have been determined.

The second step in the modelling process is to connect the

computed runoff from the various sub-catchments to the 1D

river schematisation. For the upstream small rivers which

are not modelled in the 1D river model, the computed

runoff is routed in SOBEK-RR using the Muskingum

method to the outlet points of the catchments. At the outlet

1) simulation of runoff

using Sacramento

model (SOBEK-RR)

2) Hydrologic routing of

runoff towards main river

system using Muskingum

method (SOBEK-RR)

3) Hydraulic routing

through river

system towards sea

(SOBEK-1D)



120

points of the catchments, the computed runoff enters the 1D-river model as a lateral

discharge. From there onwards, the water is routed through the river system using the

hydraulic SOBEK-1D flow module.

The rainfall-runoff model has been calibrated during the JFM1 and JFM2 projects (Deltares,

2007-2009). During the FMIS project (Deltares, 2012), the parameters of the Sacramento

model have been adjusted for land-use changes in the Jabotabek area.

Figure 10-2 Sub-catchments in the Jakarta basin

10.3.3 The 1D-2D Flow schematization

Figure B.11-10 shows the hydraulic model of the drainage system as it was developed for the

Flood Management Information System (FMIS) December 2012. It contains all major rivers

and channels in the Jakarta area. Some aspects worth mentioning are:

• The 1D model consists of nodes and branches. The branches follow the alignment of

the drainage system. The nodes are objects that are placed on top of the branches.

They can represent for example surveyed cross-sections or structures (weirs, gates,

etc.).

• The hydraulic model simulates water levels/depths and discharges/velocities at grid

points. These grid points are defined by the computational grid. In the 1D model, the

user can manually specify the average distance between successive grid points. In the

2D model, this distance is set by the size of the grid elements.

• The 2D model consists of a rectangular DEM grid cells. The elevation in every grid cell

represents the average surface-level. The Jakarta model consists of two overlapping

grids: one with 100x100m grid cells, representing the entire flood-prone area, and one

nested grid with 50x50m cells, representing part of the Ciliwung River upstream of

Manggarai gate.

• SOBEK automatically connects the 1D and 2D grid points. This way, water will start to

flow from the 1D to the 2D domain as soon as the water level overtops the

embankments. Reverse flow is also possible: when 2D overland flow reaches a drain

modelled in 1D, it will enter that drain if the water level exceeds the embankment.

• The 1D model includes cross-sections, defining the river geometry. The data from these

cross-sections comes from a large number of different sources, using different survey

methods. Cross-sections are the most important data for 1D models, as they determine

the conveyance capacity of the system.

• Along the main river several large structures are used to regulate water during low and

peak flow conditions (e.g. Manggarai and Karet gate at the Banjir Kanal Barat). Most of

these structures are incorporated in the modelling framework.



121

• Most of the low-lying areas in Jakarta cannot drain into the sea by gravity as a result of

the continuous subsidence caused by compacting of the soils because of deep

groundwater abstractions. These low-lying areas usually drain into reservoirs (waduks),

from where the water is pumped to the main river system. Waduks and pumps are

included in the model.

• The combined schematization

was calibrated for the

January/February 2007 flood

event, and validated for the

January/February 2008 flood

event in the FHM1 and FHM2

studies (Deltares, 2007-2009).

• After the FHM1 and FHM2

studies the Banjir Kanal Timur

(BKT) was included in the

schematization for the Java

Flood Insurance studies

(Deltares, 2011), being the

flood mitigating measure with

the largest impact on the flood

patterns in the east of Jakarta.

• During the FMIS project

(Deltares, 2012), the major part

of the FHM framework has

been updated (as far as

possible) to the system state of

2012.

Figure 10-3 - Overview the FMIS hydraulic 1D & 2D flow model

10.4 Extension with Cisadane and Bekasi river systems

10.4.1 First overview of the Cisadane and surrounding catchment



122

Figure 10-4 Ciliwung-Cisadane diversion

Pasar Baru

Batu Beula

Diversion



123

10.5.1 Model setup

10.5.1.1 Hydrological model

It is proposed to develop a WFLOW-SBM hydrological model, which can be calibrated on the

discharge series of Batu Beula and Pasar Baru. For parameterization, WFLOW requires a:

- DEM, to be derived from SRTM (open data)

- Landuse, to be optained from BIG or open data

- Soil type, to be optained via FAO or Indonesian sources

WFLOW-SBM will provide discharge to be used in hydrological simulations of the Cisadane

river.

10.5.1.2 Hydraulic model

It is proposed to extent the Sobek 1D (possibly 2D) hydraulic model to the Cisadane river. For

that 1D geometry is required downstream of the Ciliwung-Cisadane diversion until the Java

sea. This geometry, together with the geometry of Pasar Baru gate should be projected in the

same X,Y,Z coordinate system as the FHM framework. Currently, TM3 zone 48.2 is used as

XY projection. As Z datum, the PP (peil priok) value of Pasar Rabo (BMPP60) is used.

10.5.2 Model calibration

The meteorological model requires meteorological data as boundary condition. These data

can sub-subsequently be derived from:

- AWS and manual rainfall gauges from BBWSCC and BMKG

- BMKG radar

- TRMM rainfall satellite

Most accurate rainfall products can be obtained by a combination of radar and rainfall

gauges, where gauged data is assimilated with radar to get the most accurate spatial-

temporal representation of rainfall events.

10.5.2.1 Batu Beula

Batu Beula can be used as an upstream calibration and validation location for the

hydrological and hydraulic model. PusAir (yearbook, 2009) published a discharge series for

Batu Beula found in Figure 10-4. For this year book water level recordings at the gauge was

converted to discharge using the rating curve:

Q=19.652(h+0.939)2.152

For this study we require the original water level (h) from BBWSCC and data from which the

rating curve is derived. Also, some extreme peaks and suspicious trends after 1985 should be

clarified. Preferably, the water level should also be referenced to the pp value of BMPP60 to

align with the FHM framework.



124

Figure 10-5 Batu Beula discharge series

10.5.2.2 Pasar Baru

This location (see Figure 10-6) should be used to calibrate the downstream part of the

hydrological-hydraulic model. At Pasar Baru reports are available with water level recordings

(upstream and downstream) and gate operations. These reports contain weir formula to

convert these water levels to discharges under gate operations. All these data should be

digitized to produce a series of water levels and discharges.

An automatic water level recorder (AWLR) is available from BBWSCC (see left side of Figure

10-6). These data should be obtained from BBWSCC together with its rating curve if

available. The crest level of the gate and staff gauges should be referenced to the pp value of

BMPP60.

Figure 10-6 Pasar Baru

Suspicious trends



125

10.5.3 First overview of the Bekasi and surrounding catchment

The Kali Bekasi is the first river on the East-side of the Ciliwung. For flood mitigation

purposes, it is proposed to extent the FHM framework including this river. By this, the

effectiveness of flood mitigation measures can be analysed. It is also possible to setup an

operational system dedicated to Bekasi flood operation.

Figure 10.7 Jakarta FHM modelling framework and the Bekasi

Pondok Mitra Lestari

Kali Bekasi

K. Bekasi

K. Cikeas

Bendung Bekasi



126

10.5.4 Model setup

10.5.4.1 Hydrological model

It is proposed to develop a WFLOW-SBM hydrological model, which can be calibrated at

Bendung Bekasi and Pondok Mitra Lestari. For parameterization, WFLOW requires a:

- DEM, to be derived from SRTM (open data)

- Landuse, to be optained from BIG or open data

- Soil type, to be optained via FAO or Indonesian sources

WFLOW-SBM will provide discharge to be used in hydrological simulations of the Bekasi river

catchment.

10.5.4.2 Hydraulic model

It is proposed to extent the Sobek 1D (possibly 2D) hydraulic model to the Bekasi river. For

that 1D geometries are required for all areas where floods should be analysed. This

geometry, together with the geometry of Pasar Baru gate should be projected in the same

X,Y,Z coordinate system as the FHM framework. Currently, TM3 zone 48.2 is used as XY

projection. As Z datum, the PP (peil priok) value of Pasar Rabo (BMPP60) is used.

10.5.5 Model calibration

The meteorological model requires meteorological data as boundary condition. These data

can sub-subsequently be derived from:

- AWS and manual rainfall gauges from BBWSCC and BMKG

- BMKG radar

- TRMM rainfall satellite

Most accurate rainfall products can be obtained by a combination of radar and rainfall

gauges, where gauged data is assimilated with radar to get the most accurate spatial-

temporal representation of rainfall events.

10.5.5.1 Pondok Mitra Lestari

This gauge is under authority of the province. It is not clear if it is automatic or a manual

gauge. It is downstream so most likely under tidal influence

10.5.5.2 Bendung Bekasi

This AWLR is under authority of BBWSCC, placed upstream a weir near upstream the West

Tarum Canal. From the 6Cis project a discharge series is available from 1972 to 1985.

Probably this series can be extended. Currently the AWLR is offline. The discharge series is

converted from water level to discharge using a rating curve, which needs to be obtained.



127

Figure 10.8 Bendung Bekasi series (6Cis)



128

11 Updating JFM and FMIS databases

11.1 Processing of Digital Elevation Map

The supplied Lidar DEM has the following characteristics:

Fileformat: GeoTiff

Projection: TM3 48.2S (EPSG:23834)

Gridsize: 2X2m

Vertical datum: -1.2m + MSL (PP*); estimation, see section 11.2.2

Vertical accuracy: +/- 0.75m (90%), +/- 0.3m (50%); estimation based on visual

inspection, see section 11.2.3 and paragraph 0.

In paragraph 11.2, the details of the DEM are described in detail. In paragraph 0 a

comparison between the DEM and the 1D FHM geometry is given. In paragraph 11.4 Lidar

derived products are described.

11.2 Description of Lidar based DEM

11.2.1 Origin of retrieve data The raw Lidar data is under police custody and could not be retrieved. The Lidar data have

been processed by Tata Ruang to a 2x2m product. This product is retrieved.

11.2.2 Projection and datum

The 2x2m DEM is supplied in the TM3 48.2S projection, generally used in Jakarta

(EPSG:23834). It is assumed that the recorded ellipsoid data have been converted to geoid-

height by the Earth Gravitational Model, EGM96.

Peil Priok (PP) relates to the NWP reference system of Jakarta established in 1926 (from:

NEDECO 1973). Levels measured from NWP benchmarks in 1926 related to low water spring

tide (LWS). Mean Sea Level (MSL) in 1926 was estimated to be at 0.6m to the NWP

benchmarks.

Today, the constant between all benchmarks and MSL is lost due to subsidence. Most

credible land surveys (JEDI and JICA) take the level from benchmark BMNWP60, also

referred to as BMPP.60 or “benchmark Pasar Rebo”. The Lidar data is referenced to the

same benchmark.

Although, BMNWP60 is considered to be stable in present conditions, it is assumed that field

surveys taken from the benchmark relate to MSL by +1.2m. This number is estimated in

2005. The 0.6m difference between the original value in 1926 and the current value is due to

0.2m consolidation and 0.4m sea level rise (see Figure 11.1).



129

Figure 11.1 – Estimation of BMNWP60/BMPP.60 to MSL (2005)

11.2.3 Review on filtering

For flood hazard mapping, a ground-DEM is required. The accuracy of such a DEM is

influenced by (1) noise in the sensor (Lidar), (2) conversion from WGS84 ellipsoid height to

geoid height and (3) filtering of the DEM.

Since there is no process description available from the produced DEM, a visual inspection

has been applied at first. These are the main conclusions:

- It is clear that buildings have been removed. Large buildings are filtered out to their

footprints. An example is shown of the commercial centre at Plaza Indonesia in Figure

11.2. At small buildings (slums) results are a little less satisfactory

- Other man-made features, like Trans Jakarta overpasses are filtered out; a “noise”

estimated of roughly +/- 0.2m

- Toll road overpasses, crossing waterways are filtered out; a “noise” estimated of roughly

+/- 0.3m (see e.g. Figure 11.3)

- Green areas (e.g. Sudirman park) are clearly filtered; a “noise” estimated of roughly +/-

0.3m

- Noise at roads is estimated less than +/- 0.1m (see Figure 11.4)

- Some “pits” are found in the DEM, which cannot be found on areal images. These will be

removed (see section 11.4.2)

Based on our visual inspection we estimate that roughly 90% of the DEM has a vertical

accuracy of +/- 0.75m, 50% of the DEM has a vertical accuracy of +/- 0.3m. Elevation at

roads, the most important infrastructure for flood computations, is assumed to be accurate +/-

0.1m.



130

Figure 11.2 – Buildings (left taken from Google Earth) removed in DEM to building footprint (right)

Figure 11.3 – Removal of overpasses upstream Manggarai (left) and near Karet (right)

Figure 11.4 – Elevation graph (left) over jl.Sudirman South of Banjir Kanal Barat (see green line, right)



131

11.3 Comparison of Lidar with 1D geometry

As mentioned in 11.2.2, the benchmark system in Jakarta is instable due to subsidence. A

validation of the “vertical fit” between 1D river geometry (river profiles), 2D topography (DEM)

and water levels is key for obtaining a good hydrodynamic model.

In this project, the fit between the Lidar and the 1D geometry has been validated and

improved where necessary. By (1) comparison of the Lidar-profile and geometry sets which

are known to be referenced to the same benchmark (BMNWP60), the vertical datum of the

DEM is validated. All river geometries measured by JEDI and JICA use the BMNWP60

benchmark. The vertical datum of these geometries and the Lidar matched.

By (2) comparison of geometry sets referenced to a different or unknown benchmark and

Lidar, the vertical datum of these geometry sets are validated (see e.g. Figure 11.5). Based

on this comparison vertical shifts have been applied to the following sets:

- Kali Pertukangan/Cakung lama; profiles 1m too high

- Krukut lama; many profiles have a poor fit in the topography

- Kali Bandengan; road and walls included in profiles

- Lower Angke between Cakung drain and Mookervart; many profiles have a poor fit in the

topography

Figure 11.5 – Comparison (left) of 1D geometry (blue profile) with Lidar DEM (purple line) for BBWSCC BKT cross

section (right). In this case there is a nearly perfect match.

11.4 Lidar derivatives

11.4.1 Streamlines for sub-catchment delineation

From the Lidar DEM a streamline map is generated. This map, together with the DEM itself, a

road map, an aerial image and (most importantly) a field inspection is used to update the sub-

catchment layer in the FHM framework. Below two streamline products are shown, one

produced with ArcHydro (ArcGIS) and one produced with PCRaster (see Figure 11.6). Both

methods give different results, but are equally useable for generating streamlines.



132

Figure 11.6 – Streamline maps derived with ArcHydro (left) and PCRaster (right)

11.4.2 Updating the FHM framework databases

In the FHM framework a 1D hydraulic model is coupled to a 2D overland flow model. The 2D

model uses a 100m resolution DEM, with a more detailed 50m DEM around the Ciliwung, an

area of interest. With this setup it is not only important that the overland flow model DEM is

accurate, but also that it connects well to the profile elevations in the 1D hydraulic model. A

number of steps have been taken to arrive at the 2D model DEM based on the 2m Lidar

DEM.

1. Removal of errors in 2m DEM

o At locations where clear errors or undesired features are seen, they are marked

with polygons. The elevation inside these polygons is then corrected to a suitable

environmental value. An example of such a correction is a deep construction pit.

These deep features would affect the coarser aggregated DEM, as it would have

a large effect on the average elevation. However they are of a temporary nature

and do not represent the surface elevation, thus they are removed.

2. Aggregating 2m DEM to 50/100m based on average values

o The corrected 2m DEM from the previous step is used as the basis of the

aggregation. Since the 2m DEM is already filtered, the aggregation is based on

the average of the smaller cells inside the coarser cells. This step yields two DEM

files of the extent and resolution necessary for the model. However testing made

it apparent that further adaptation of both the DEM and the 1D hydraulic model is

necessary to take full advantage of the availability of the Lidar DEM for the FHM

framework.

3. Elevating 100m DEM at reaches to maximum of current value and 2.1m +PP* (coastal

flood level) and lowest embankment in 1D geometry.

o Water is exchanged between the 1D and 2D model at nodes, situated along

reaches. Special care must be taken to ensure the DEM elevation at these

exchange points is reasonable. It was found that in some canals near the sea the

100m DEM had values below the coastal flood level. Whether this is an

aggregation artefact or due to the DEM only measuring water level, a reasonable

minimum DEM elevation at these points is the coastal flood level. Therefore these

points were elevated. At locations where reliable lowest embankment levels are

known from nearby cross sections, and the DEM gave elevations below these

levels, the DEM was also elevated to these lowest embankment levels. The

magnitude and location of the changes in the elevation are illustrated in Figure

11.7.



133

Figure 11.7 – Resulting elevation difference from step 3 in 11.4.2



134

A Appendix A - Methodology

A.1 Introduction

This chapter describes the methodology used in Jakarta Flood Overview (JFO) to analyse

and design the pumping systems of the polders in northern Jakarta to handle local rainfall. In

analysis, the following components are used

Hydrology: design rainfall is translated to runoff serving as a boundary condition for

analysis

Water levels: frequently used reference levels are related and typical boundary

conditions for Jakarta Bay are derived

Water Balance: first estimates of sensible pump-schemes can be made by a water

balance: of storage and pump-capacity are derived by making a water balance

Hydraulics: improvements, using the FHM framework (Sobek).

A.2 Hydrology

A.2.1 General

For the hydrology the following steps are taken:

1. First, the design rainfall amounts used for analysis have to be determined. For that, a

comparison of NEDECO (1973), FHM (2007), S3I and FMIS is made.

2. Design rainfall has to be averaged over the catchment using Areal Reduction Factors

3. Average catchment rainfall has to be transformed to catchment runoff, which is the input

used for the design of pump capacity and storage.

A.2.2 Design rainfall

The hydrology used for designing the pumping schemes is based on the hydrology used in NEDECO, FHM, S3I

and FMIS. The station design rainfall with various duration and return periods is given in Table A 1 - Daily

and 24-hour rainfall according to different studies

. For the conversion between daily rainfall and 24 hour rainfall a factor of 1.12 is applied

(NEDECO, 1973).

T (years) Daily rainfall

24 hour rainfall NEDECO [1973] JICA [1996] FHM [2007]

2 100 98 108 111-122

10 159

25 189 192 184 208-217

50 212

100 234 238 231 261-269

Table A 1 - Daily and 24-hour rainfall according to different studies

From all studies, NEDECO 1973 still had the most comprehensive database of hourly and

daily rainfall. To derive rainfall-mass curves (see Figure A 1), 34 stations where available with

10 years of validated rainfall. It seems NEDECO is conservative, regarding the 24 hour

rainfall estimates (265 mm at T100 return period). When comparing the FHM mass-curve



135

(derived from the DKI3-10 hyetograph) with the mass-curve of NEDECO, the latter is also the

most conservative regarding peak intensities (see Figure A 1 ).

Since NEDECO uses higher rainfall amounts and higher intensities, its mass curves are used

in this stage of the study. As design return period, both T25 and T100 are considered. T25 is

currently the official return period on which water systems should be designed. The T100

return period is the ambition of DPU.

Figure A 1 – Rainfall mass curves according to NEDECO (1973) and DKI3-10

A.2.3 Areal reduction factors

The station rainfall amount is transformed to catchment rainfall amount using an areal

reduction factor (ARF), depending on the rainfall duration and catchment size. The ARF

relation is derived from data collected by Boerema (1925) as reported in Nedeco (1973), see

Table A 1).

duration Area (km2)

hours 5 10 30 50 70 90 100 150 200

1/6 0.94 0.91 0.81 0.74 0.69 0.65 0.63 0.56 0.5

0.5 0.95 0.92 0.83 0.77 0.73 0.69 0.67 0.6 0.55

1.0 0.96 0.93 0.86 0.81 0.76 0.73 0.71 0.64 0.59

2.0 0.96 0.94 0.88 0.82 0.79 0.75 0.74 0.67 0.62

3.0 0.96 0.94 0.87 0.83 0.79 0.75 0.74 0.68 0.63

4.0 0.96 0.94 0.88 0.83 0.79 0.76 0.74 0.68 0.63

5.0 0.97 0.94 0.88 0.84 0.8 0.77 0.75 0.69 0.64

12.0 0.98 0.97 0.92 0.89 0.87 0.84 0.83 0.79 0.75

24.0 0.99 0.98 0.96 0.94 0.93 0.91 0.9 0.87 0.85

Table A 2 – Area reduction factors according to Boerema (1925) reported in Nedeco (1973)

0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50

TIME [H]

RA

INF

AL

L V

OL

. [m

m]

T100

T050

T025

T010

FHM mass-curve



136

For computational purposes, the numbers of Table A 1 are fitted in continuous exponential

functions in the form of equation 1 (eq. 1). For every duration, a relation between the ARF

and catchment area (A) is obtained by choosing the correct fitting parameters α and β, given

in Table A 2)

1ARF A (eq. 1)

duration α Β

10 min 0.035 0.51

1/2h 0.03 0.52

1h 0.025 0.57

2-5h 0.015 0.61

12h 0.01 0.61

24h 0.004 0.69

Table A 3 – Fitting parameters for eq.1 depending on duration

Figure A 2 shows the result of the application of eq.1 and Table A 3. Areal reduction factors

for durations not included in Boerema (1925) are obtained by linear interpolation between

known ARF values if the duration is less than 24h. For durations of more than 24 hours,

values between 12 and 24 hours are linearly extrapolated till a maximum ARF of 1 is reached.

Figure A 2 – Rainfall mass curves according to NEDECO (1973) and DKI3-10

A.2.4 From rainfall to runoff

The FMIS Sobek framework is using the Sacramento rainfall-runoff model. Within the Sobek

framework also other rainfall-runoff methods are available. For a quick first assessment using

a water balance we selected the SCS model which is also available in Sobek. Like

Sacramento, the SCS method is commonly known and applied in Indonesia and around the

world for single high intensity rainfall events in urban areas. Note that for year-round

Areal reduction factors

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

0.90

0.95

1.00

0 10 20 30 40 50 60 70 80 90 100

Area [km2]

AR

F [

-]

10min

0.5h

1h

2-5h

12h

24h



137

application, dealing with both dry and wet situations, it is important to use a rainfall-runoff

concept which takes into account groundwater storage. For this purpose, Sacramento is a

more logical choice than SCS.

SCS only needs three parameters, i.e. the curve number (CN), the average flow path length

to the catchment outlet, and the average slope. For the densely urbanised areas in Jakarta,

CN is assumed to be 95. The flow path length and slopes are based on FHM. However,

several sub-catchments are now merged into 1 polder. Based on the FHM data on catchment

characteristics initial estimates of 2500 m for the flow path length to sub-catchment outlet,

and slope of 1 m per km are assumed as conservative estimates. For each return period and

rainfall duration, the total runoff is determined from the SCS equations:

100254 1 ( )

S mm

CN (eq. 2)

The initial abstraction is taken as 20% of S. The excess rainfall is determined from:

2( )

0

0.2

ae a

a

e a

a

P IP for P I

P I S

P for P I

I S

(eq. 3)

where:

Q = Catchment runoff [mm]

P = Catchment average precipitation [mm] Pe = Excess precipitation (mm) which is transformed into runoff

Ia = Initial abstraction before runoff begins

S = Potential retention after rainfall begins (mm)

CN = Curve Number, ranging from 30 to 100.

A curve number of 100 results in no retention and no losses, while a curve number of 30

results in large storage and losses. For strongly urbanized catchments like Jakarta, values of

90-95 are used (USDA, 1986). We adopted CN=95

The SCS runoff (Pe, the excess precipitation) is routed using a unit hydrograph, which uses

estimation of tp (time to peak) and qp (peak flow value per mm excess rainfall). The time to

peak follows from the lag time tL which is about 0.6 times the time of concentration tc. The lag

time is derived as a function of the basin length and slope and the Curve Number. The

following formula applies:

0.70.8

0.7 0.5

2,540 22.86(min) 60

14,104

L

L CNt

CN Y (eq. 4)

where:

tL = time lag (minutes)

L = flow path (m)

CN = SCS Curve Number

Y = average sub-basin slope (m/m)

Then the time to peak and the peak discharge per mm excess rain follow from:



138

23

( )2

( )0.208 ( / ) /

( )

p L

p

p

Dt t hr

A kmq m s mm excess rain

t hr

(eq. 5)

where:

D = rainfall duration in computational procedure (hr)

tp = time to peak (hr)

The hydrograph will delay the runoff and reduce the peak runoff. Figure A 3 illustrates the

principle. First the station rainfall amount (black line) is converted to areal rainfall (purple line)

using the area reduction factor. Next, the reduced rainfall is converted to runoff (light blue) by

applying the SCS losses. Finally, the total runoff is routed using the unit hydrograph to

produce the routed runoff (dark blue).

Note: in this first estimation, we put the most intensive rainfall at the beginning. So the most

intensive rainfall falls within the first hour. Nedeco did not derive any hyetographs, giving the

distribution of rainfall mass during the day.

Figure A 3 – Transformation from rainfall to runoff, for an area of 25 km2.

Using the method described in the sections above, runoff-duration curves can be derived

using Nedeco (1973) rainfall, Boerema areal reduction factors and SCS rainfall-runoff routing.

Figure A 4 shows the T10, T25, T50 and T100 runoff-mass peaks which are used in the

“spread sheet method”, explained in section 0. Note, the runoff mass is only valid for the

chosen catchment area (in this case 40km2). Larger catchments, lead to lower average runoff

estimates.

From rainfall to runoff

0

50

100

150

200

250

300

350

0 6 12 18 24 30 36 42 48

Time (hours)

Rain

fall

, ru

no

ff (

mm

)

Rain

ARF*Rain

Total runoff

Routed runoff



139

Figure A 4 – Typical runoff mass curves for different return periods (catchment area is 40km2).

A.3 Water Levels

A.3.1 Reference levels

Within this document reference levels are expressed by default in m + PP*; which is the Peil

Priok level measured from bench mark Pasar Rebo (BMNWP60). At PU-DKI sea water levels

are measured at the Pasar Ikan (PI) staff gauge. With “Pluit” the staff gauge at pump house of

Pluit, waduk side, is indicated. LWS2012 refers to Low Water Spring tide in 2012, as used in

NCICD (2014A). In Table A 3 the estimated relation between all values is given.

Note: as subsidence and sea level rise continue, relation between all references will change.

Name Unit (m + XX) to MSL to PP*

Peil priok BMNWP60 PP* -1.2 0

Pasar Ikan PI -1.6 -0.4

Pluit Pluit -2.6 -1.4

LWS2012 (NCICD) LWS2012 -0.45 0.75

Table A 4 Correction to be applied for transfer of reference levels

PP*

Peil Priok (PP) relates to the NWP reference system of Jakarta established in 1926 (from:

NEDECO 1973). Levels measured from NWP benchmarks in 1926 related to low water spring

tide (LWS). Mean Sea Level (MSL) in 1926 was estimated to be at 0.6m to the NWP

benchmarks.

Although, BMNWP60 is considered to be stable in present conditions, it is assumed that field

surveys taken from the benchmark relate to MSL by +1.2m. This number is estimated in


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]

T100 T50

T25 T10



140

2005. The 0.6m difference between the original value in 1926 and the current value is due to

0.2m consolidation and 0.4m sea level rise (see Figure A 5).

Figure A 5 – Estimation of BMNWP60/BMPP.60 to MSL (2005)

Pasar Ikan (PI) At Pasar Ikan long series of sea water level measurements are available (Figure A 6). From this series it has been estimated that the zero level of the Pasar Ikan staff gauge is at -1.6 m + PI.

Figure A 6 – Staff gauge reading at Pasar Ikan (PI), taken from Jakarta FEWS



141

Pluit

Levels in m + Pluit refer to the level of the staff gauge at the waduk side of the Pluit pump

house. We estimate that the zero level of the staff gauge is 1.4m lower than 0 m+PP*

combining two observations.

From field observations at 20/01/2013 15:00, when Pluit was flooded, we know that the water

level at the waduk-side of Pluit was close to the sea water level at that moment. If we

compare the PU-DKI posko piket readings at that same moment, we see that water level

recordings at Pluit are +/- 1m higher than the sea water level at 20/01/2013 15:00 (see Figure

A 7).

From the LIDAR (referenced to PP*), we know levels at Pluit are around -3 to – 3.5 m +PP*

for the waduk (see Figure A 8). We assume, the Lidar has been flown on a clear day (dry

season) in 2010, when the waduk was at target level (-2 m+ Pluit). This means we have to

apply a correction of -1 to -1.5 to convert Pluit levels into PP* levels.

LWS2012

NCICD (2014A) assumes LWS2012 is at -0.45m + MSL, this is 0.75m higher than our

assumption for the relation between MSL and PP*.

Figure A 7 – Staff gauge reading at Pasar Ikan (blue) and Pluit (red) 20/01/2013, taken from Jakarta FEWS



142

Figure A 8 – Lidar image of Pluit

A.4 Boundary conditions

For the hydraulic model, we apply sea water level boundary conditions shown in Figure A 9

and Table A 5. The model has PP* as datum, but sea water levels are usually interpreted

from the Pasar Ikan staff gauge. The values chosen are similar to NCICD (2014A) shown in

Table A 6. An offset of +0.6m as anomaly is applied, which is considered to be the T100

storm surge according to IPC (2013).



143

Figure A 9 – Time series boundary conditions available for Jakarta Flood Overview in m+ Pi (left) and m + PP*

(right)

Table A 5 Boundary conditions available for Jakarta Flood Overview

Stage Level [m + Pasar Ikan] [m + BMPP60]

High water spring tide + anomaly (2030) 3.8 3.4

High water spring tide + anomaly 2.7 2.3

High water spring tide 2.1 1.7

High water neap tide 1.8 1.4

Mean Sea Level 1.6 1.2

Low water neap tide 1.4 1

Low water spring tide 1.1 0.7

Low water spring tide + anomaly 1.7 1.3

Low water spring tide + anomaly (2030) 2.8 2.4



144

Table A 6 Boundary conditions available for Jakarta Flood Overview – 1000 year return period sea water level

conditions (NCICD, 2014)

A.5 Water Balance

A.5.1 Method

The water balance starts with the runoff mass curves as described above. A pump scheme is

designed by selecting a combination of storage and pumping capacity to handle the amount

of runoff available over a certain period. By expressing the storage and pump capacity in mm

related to the whole catchment area, the selected storage and pump capacity can be directly

compared with the runoff mass in mm (see Figure A 10). In the figure the available storage is

visible on the Y-axis at the point where the ‘polder capacity’ line starts. The pumping capacity

is indicated by the slope of the ‘polder capacity’ line. Depending on the selected design return

period, different combinations of storage and pump capacity can meet the design criteria

(return period). In the graph shown below, it is assumed that pumping immediately starts at

T=0. However, it is easy to delay the start of pumping so that it starts for instance half an hour

after the start of the rainfall.

Figure A 10 – ‘present situation’: limited storage, insufficient pumping capacity

2012 2022 2030 2040 2050 2080

[m+LWS2012] 1 1 1 1 1 1

[m] 0.69 0.69 0.69 0.69 0.69 0.69

[m] 0 0.08 0.14 0.22 0.3 0.54

design water level (DWL) [m+LWS2012] 1.69 1.77 1.83 1.91 1.99 2.23

stage year

mean high water spring (MHWS)

water level anomaly

sea level rise


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]

T100T50

T25T10Polder capacity

Storage [mm]

Pump capacity: Δy/Δx [mm/h]

Δx

Δy



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The existing storage can be directly determined from topography; all available surface water

serviced by the pump, multiplied by an allowed water level variation. The water level variation

is the difference between the operational level of the pump and a level at which no flooding

occurs in the polder (in principle including the secondary drainage system). In Jakarta (a

tropical region), a variation of 2 to 3 meters is allowed since storage space is limited and

rainfall intensities are high. For pump capacities, for now it is assumed that only pumps of 60-

80 m3/s can still be considered realistic (though large!!) to construct.

Assuming the existing given storage and realist pumps, it is very likely the preliminary design

graph is for any polder in Jakarta is similar to Figure A 10. In this (theoretical) case, the

system is only able to “absorb” runoff below T10 recurrence (the pink ‘polder capacity’ line is

always above the ‘T10’ light blue line). This means, flooding will occur with an average of

once every 10 years.

Using the water balance, a quick assessment can be made of the required combination and

pump capacity for different strategies like ‘maximise storage’ (see e.g. Figure A 11), ‘big

pumps’ (see e.g. Figure A 12) or other alternatives. Also the sensitivity of the system for the

selected design return period can be assessed. Important aspects for the selection of storage

and pump capacity are:

Hydraulic feasibility (what is possible from a hydrological and system hydraulics point

of view);

Social feasibility (creating large storage in urban area, requiring resettlement of a

large number of people can be very difficult); and

Financial feasibility (costs of creation of storage vs costs of large pumps).

The first (ambitious) goal is to design the polder systems such that events with return period

100 years can be handled. The designs are now typically using a return period T=25 years.

Figure A 11 – Polder optimization using “maximise storage approach”


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]

T100T50




146

Figure A 12 – Polder optimization using a “big pumps” strategy

A.5.2 Limitations

The water balance is a simple approach for quick assessment of different pumping schemes,

considering the total pump capacity and storage capacity of a polder. However, it is limited in

its use regarding hydrology and hydraulics:

It is limited in the consideration of rainfall runoff routing. In reality it is well possible that

travel times are larger or shorter than assumed, leading to changes in polder design.

It does not consider hydraulics (1). All assessed storage volume is assumed to be

available at any point in time. Hydraulic obstructions, preventing optimal use of storage

are not included. The detailed lay-out of the storage area related to the drainage

channels in catchment is not considered in this method, it just assumes all storage is

available. In the hydraulic model, the location of retention storages is taken into

account. For instance, in the hydraulic model (and in reality!) the Kali Sekretaris is

flowing next to Tomang reservoir and water can not enter the reservoir, while in the

method it is assumed it can.

The method does not consider hydraulics (2). All drains (primary and secondary) are

assumed to be able to convey the amount of runoff to the pump. Especially, when big

pumps are chosen, it is well possible drains are not able to convey the amount of water

supplied, resulting in empty canals downstream and flooding more upstream.

The water balance assumes pumping starts at full capacity immediately (or with a short

delay), while in the hydraulic model operational constraints are included like not

switching on all pumps at the same time, but one after each other, with different switch-

on and switch-off levels.

For this reason, promising alternatives should be checked with a full hydrological/hydraulic

model (the FHM Framework). In general, it can be expected that the hydraulic model will a

higher water level rise in retention areas than allowed the water balance. Or, to limit the water

level rise to a prescribed maximum, the pump capacities in the hydraulic model need to be a


0

50

100

150

200

250

300

350

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

TIME [hours]

Vo

lum

e [

mm

]

T100T50




147

little larger. In the verification calculations we checked whether the water levels computed in

the hydraulic model are still acceptable.

A.6 Verification using the FHM framework

A.6.1 Integrating hydrology and hydraulics using the FHM framework

As mentioned, the first estimate of the discharge capacity assumes uniform flow and no

backwater effect. However, the assumption of uniform flow is usually not met in polder

systems, and backwater effect cannot always be neglected. Therefore the available Sobek

hydraulic model is used to perform hydraulic calculations for the entire primary water system

of the polders. Sobek solves the full de Saint Venant equations and takes into account

backwater effects. Using the Sobek model we can verify whether the estimated storage

capacity and pumping capacity are sufficient, which operational levels are needed, and

whether the drainage system laid out according to JEDI has any hydraulic bottlenecks which

need to be resolved.

The default rainfall runoff boundary conditions differ in the FHM framework from the SCS

method, used in the water balance. Only for Kamal-Tanjungan area SCS is applied directly in

the framework, since it was not available in the framework yet. For all other areas,

Sacramento parameters and initial conditions have been set to meet the Rainfall-Runoff

response of the SCS method.

To summarise, important differences between the water balance and Sobek are:

The balance storage and pumping capacities are taken as first estimates for the more

detailed analysis in Sobek. The river and canal cross-sections are initially taken as

the cross-sections as they would be according to the JEDI design.

Sobek includes a hydraulic model of the main drainage canals and pump operation,

whereas the water balance does not. This is explained in the next 2 points.

The Sobek pumps do not immediately pump at full capacity (like the water balance),

but work with operational levels. A pump in Sobek is modelled using several stages

(or multiple pumps) with different switch-on and switch-off levels.

The Sobek hydraulic model takes into account the location of the retention areas in

the catchment. Some retention area might be available for a part of the catchment

only. For instance, the Tomang reservoir retention area is only for local drainage, not

for the upstream drainage already in Kali Sekretaris.

Sobek takes into account hydraulic bottlenecks in the drainage system modelled

using 1D-Flow. These hydraulic bottlenecks include locations where the discharge

conveyance capacity of the canals is not large enough (causing water levels to rise

above embankment levels), due to insufficient canal depth or width. The water

balance assumes the computed runoff is always available at the pumping station.

When Sobek-1D Flow shows that 1D-water levels rise above the embankments, a

combined Sobek1D2Dflow calculation can be made to analyse the inundation pattern.

The water balance does not check with embankment levels.

A.6.2 Integration of polder systems with JEDI packages

If canals are in one of the JEDI packages, the design drawings will be used as a primary

design for the canal geometry in the proposed polder system. If not, most recent surveys will



148

be used as a starting point. With the hydraulic model, we can determine how canal

geometries should be adjusted to be integrated in the proposed polder schemes.



149

B Appendix B: Sobek and the Jakarta FHM framework

B.1 Overview of FHM related activities 2007 – 2013

After the severe floods of February 2007, as part of the non-structural Dutch Assistance

Jakarta Flood Management initiative (DA JFM), a new successful approach to assist Jakarta

in understanding and counteracting the floods was introduced. An important part of the

approach was developed through the "Flood Hazard Mapping (FHM)" projects (2007-2009)

During the three consecutive FHM projects a unique FHM modelling framework was

developed and further updated including the 13 crossing rivers and the complete major

drainage system of Jakarta.

The developed GIS based FHM modelling framework starts in the upper Panggrango - Gede

area and runs to the northern coastal area of Jakarta. It includes complete hydrology, land-

use, major river and drainage system and is capable to simulate floods in the complete DKI

area. During the Situ Situ Safety Inspection (S3I) study (2009), the FHM modelling framework

was further expanded to include all major Situ Situ upstream and in Jakarta. The FHM

modelling framework was further used and updated during the Jakarta Flood Readiness Scan

(JFRS) in 2011, the Flood Management Information System (FMIS) in 2012 and during the

evaluation of the January 2013 floods. As the FHM modelling framework was setup for use as

part of an online monitoring / flood early warning system (FEWS), the FHM modelling

framework was connected to the Jakarta Flood Early Warning System (JFEWS) during the

Joint Cooperation Program (JCP 2011-2012). In the FMIS project JFEWS was further

enhanced and implemented at the flood operation and disaster centres in Jakarta.

Many different parts of the Jakarta have been analysed and evaluated with the FHM

modelling framework since 2007. An overview of the projects and related reports is presented

in Table B-11-1. Based on these projects a quick overview of main components and use of

the FHM modelling frame work is presented in chapters B.2 - B.6.

Table B-11-1, Overview of FHM and Hydraulic activities in Jakarta 2007 - 2013


Project Report nr


FHM1



2 Main Report 151207.pdf

3 Flood extent and Bottlenecks 151207.pdf

4 Hydraulics 151207.pdf

5 Hydrology and Sea Water Levels 15122007.pdf

6 Annex A, Sea Water Levels 15122007.pdf

7 Annex B, Discharge Measuring Stations 15122007.pdf

FHM2



2 FHM modelling framework 230309.pdf



150


Project Report nr


3 HU database and FEMapping 230309.pdf

4 Jakarta Flood Early Warning System, Main 230309.pdf

5 Jakarta Flood Early Warning System, Appendix A 230309.pdf

6 Jakarta Flood Early Warning System, Appendix B 230309.pdf

7 Jakarta Flood Early Warning System, Appendix C 230309.pdf

FHM3


1 01 Final Report.pdf

2 03 Evaluation Dredging in Jakarta.pdf

3 06 Evaluation Training Planning Unit with FHM Model.pdf

4 07 Long Term Rehabilitation & Maintenance Program.pdf

5 08 Inventory of Urban Drainage Systems in Pademangan Barat and Thamrin Monas.pdf

6 09 Performance Analysis Drainage System Sub catchment Jalan Thamrin Jakarta.pdf

7 10 Analysis Capacity Drainage System Pademangan Barat.pdf

8 14 GPS Based Flood Extent Mapping.pdf

S3I

Situ Situ Safety Inspection (2009)

1 Field inspection and investigation 270709.pdf

2 Safety inspection manual 270709.pdf

3 Short-term Action Plan 240709.pdf

4 Soil Investigation 270709.pdf

JFRS

Jakarta Flood Readiness Scan (2011 - 2012)

1 Jakarta Disaster Preparation December 2011.pdf

FMIS

Flood Management Information System (2012)

1 FMIS Main report 10022013.pdf

2 FMIS Annex A, FHM framework and measures 10022013.pdf

3 FMIS Annex B, Hydro-meteorological monitoring network Jakarta 10022013.pdf

4 FMIS Annex C, FMIS institutional framework 10022013.pdf

EA2013 FHM - Emergency Assistance Floods January 2013 (2013)

1 Jakarta Floods January 2013 - Emergency assistance - April 2013.pdf

B.2 The SOBEK modelling system

SOBEK is the main hydrologic and hydraulic modelling software used for analyzing the

propagation of water through the Ciliwung catchment. It consists of modules that can be used

separately or combined. The available Sobek-modules cover a wide range of processes, from

rainfall-runoff, to 1D/2D hydrodynamics, to water quality processes and emissions. SOBEK is



151

developed in close co-operation with several organizations in the water sector, based on a

long history of developments of flow modelling in systems.

The first release, SOBEK-RE, was launched in the early nineties. Next, SOBEK-Urban was

developed as a tool for integral studies of the effects of precipitation and waste water

management in urban areas. Subsequently, SOBEK-Rural was developed for drainage and

irrigation studies in low lying areas and the associated water management. Finally, SOBEK-

RIVER was launched a few years ago, focusing entirely on the modelling of river systems.

Both the 1D- and 2D flow modules solve the full set of the de Saint-Venant equations. This

makes SOBEK ideally suited for difficult-to-model systems, as it can handle flow conditions

that other packages cannot: super-critical flow, transition from super- to sub-critical flow

(hydraulic jumps), and both wetting and drying of grid-cells. It comes equipped with a variety

of boundary conditions, wind effects, hydraulic structure descriptions, lateral flows and cross-

section descriptions.

B.3 Sobek and the FHM-framework

B.3.1 Overview

In the Jakarta FHM modelling framework the following three SOBEK modules are used

(Figure B.11-8):

• The hydrological rainfall runoff module (RR) that simulates the transformation of rainfall

to runoff for each river catchment, and thus computes the inflows into the one

dimensional hydraulic river module.

• The one-dimensional hydraulic module (1D) that simulates the one-dimensional flow

(water levels and discharges) though the main rivers and the main drainage system.

• The 2-dimensional hydraulic module (2D) that simulates the inundation pattern over the

project area from the locations where the one dimensional water courses are

overtopped. The results from this module are used to construct the flood hazard maps.

Figure B.11-8 Overview of used Sobek Modules

Sections B.3.2 and B.3.3 illustrate the existing Rainfall-Runoff (RR) schematization and 1D-

2D schematization of the Jakarta basin.



152

B.3.2 The rainfall-runoff model

The rainfall-runoff model provides the 1D-flow model with runoff from the sub-catchments

using the following steps:

Step one simulates runoff from +/- 450 sub-catchments (see Figure B.11-9), based on rainfall

data and sub-catchment characteristics. The well-known Sacramento model concept has

been used for this purpose. The Sacramento model can be used for both event-based and

year-round continuous simulations. For each sub-catchment, main characteristics as surface

area, land use, slope, flow path length have been

determined.

The second step in the modelling process is to

connect the computed runoff from the various sub-

catchments to the 1D river schematisation. For the

upstream small rivers which are not modelled in

the 1D river model, the computed runoff is routed

in SOBEK-RR using the Muskingum method to the

outlet points of the catchments. At the outlet points

of the catchments, the computed runoff enters the

1D-river model as a lateral discharge. From there

onwards, the water is routed through the river

system using the hydraulic SOBEK-1D flow

module.

The rainfall-runoff model has been calibrated

during the JFM1 and JFM2 projects (Deltares,

2007-2009). During the FMIS project (Deltares,

2012), the parameters of the Sacramento model

have been adjusted for land-use changes in the

Jabotabek area.

Figure B.11-9 Sub-catchments in the Jakarta basin

B.3.3 The 1D-2D Flow schematization

Figure B.11-10 shows the hydraulic model of the drainage system as it was developed for the

Flood Management Information System (FMIS) December 2012. It contains all major rivers

and channels in the Jakarta area. Some aspects worth mentioning are:

• The 1D model consists of nodes and branches. The branches follow the alignment of

the drainage system. The nodes are objects that are placed on top of the branches.

They can represent for example surveyed cross-sections or structures (weirs, gates,

etc.).

• The hydraulic model simulates water levels/depths and discharges/velocities at grid

points. These grid points are defined by the computational grid. In the 1D model, the

user can manually specify the average distance between successive grid points. In the

2D model, this distance is set by the size of the grid elements.

1) simulation of runoff

using Sacramento

model (SOBEK-RR)

2) Hydrologic routing of

runoff towards main river

system using Muskingum

method (SOBEK-RR)

3) Hydraulic routing

through river

system towards sea

(SOBEK-1D)



153

• The 2D model consists of a rectangular DEM grid cells. The elevation in every grid cell

represents the average surface-level. The Jakarta model consists of two overlapping

grids: one with 100x100m grid cells, representing the entire flood-prone area, and one

nested grid with 50x50m cells, representing part of the Ciliwung River upstream of

Manggarai gate.

• SOBEK automatically connects the 1D and 2D grid points. This way, water will start to

flow from the 1D to the 2D domain as soon as the water level overtops the

embankments. Reverse flow is also possible: when 2D overland flow reaches a drain

modelled in 1D, it will enter that drain if the water level exceeds the embankment.

• The 1D model includes cross-sections, defining the river geometry. The data from these

cross-sections comes from a large number of different sources, using different survey

methods. Cross-sections are the most important data for 1D models, as they determine

the conveyance capacity of the system.

• Along the main river several large structures are used to regulate water during low and

peak flow conditions (e.g. Manggarai and Karet gate at the Banjir Kanal Barat). Most of

these structures are incorporated in the modelling framework.

• Most of the low-lying areas in Jakarta cannot drain into the sea by gravity as a result of

the continuous subsidence caused by compacting of the soils because of deep

groundwater abstractions. These low-lying areas usually drain into reservoirs (waduks),

from where the water is pumped to the main river system. Waduks and pumps are

included in the model.

• The combined schematization was

calibrated for the January/February

2007 flood event, and validated for the

January/February 2008 flood event in

the FHM1 and FHM2 studies (Deltares,

2007-2009).

• After the FHM1 and FHM2 studies the

Banjir Kanal Timur (BKT) was included

in the schematization for the Java Flood

Insurance studies (Deltares, 2011),

being the flood mitigating measure with

the largest impact on the flood patterns

in the east of Jakarta.

• During the FMIS project (Deltares,

2012), the major part of the FHM

framework has been updated (as far as

possible) to the system state of 2012.

Figure B.11-10 - Overview the FMIS hydraulic 1D &

2D flow model



154

B.4 Rainfall-Runoff

B.4.1 The Sacramento concept

Since the FHM2 studies (Deltares, 2009A) the rainfall-runoff processes in the FHM-

framework are described with the Sacramento concept as implemented into Sobek. This

concept is explained in detail in Appendix B.1. A first estimate or typical range of the

parameters is given in Appendix B.2. The FHM design storm rainfall events are extensively

described in Annex A.

The Sacramento concept is a significant improvement in describing hydrological processes of

the Ciliwung catchment compared to practices in previous studies (DKI 3-9 and DKI 3-10,

2005 and Deltares, 2007). In standard practice rainfall is “converted” to runoff by the rational

or curve-number method. Sacramento converts rainfall into runoff by taking into account all

significant hydrological processes in a conceptual manner.

An example of an important process to take into account is base flow. In the Ciliwung, flood

events are usually preceded by days of intensive rainfall. In such days, the hydrological

system of the Ciliwung is “filled up” by infiltrating water, resulting in a significant base-flow.

During the flood event this base-flow is accumulated with direct runoff to a peak discharge.

Therefore, peak discharges under these conditions can be better described using the

Sacramento concept than the rational method.

Figure B.11-11 - Runoff distribution hydrological unit 3909

B.4.2 Muskingum routing

Not always the outlet of a catchment is adjacent to a river discretized in 1D canal flow. At

locations in rivers or streams where geometrical data (cross sections) are available or water

levels are irrelevant, runoff is routed using Muskingum routing (McCarthy, 1938). In Appendix

B.3 the concept of Muskingum routing and default parameter choices are explained.

B.4.3 FHM RR discretization

The Ciliwung catchment is discretized in sub-catchments for which area-average rainfall (mm)

is converted to area-average runoff (mm). Over the years (2007 – 2012) the amount of

catchments have slightly changed due to changes in the water system and 1D2D river

Runoff hydrological unit 3909

Baseflow (mm) Direct runoff impervious area [mm]

5-2-20075-2-20074-2-20074-2-20073-2-20073-2-20072-2-20072-2-20071-2-20071-2-200731-1-200731-1-2007

1.1

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0



155

network. The FHM version after the FMIS project (Deltares, 2012) uses 449 sub-catchments

as primary hydrological units (see Figure B.11-12). An example of an area where runoff is

routed by Muskingum routing is the Ciliwung catchment upstream Katu Lampa (see the right

side of Figure B.11-12).

Figure B.11-12 - Hydrological Units (left) and the Sacramento model upstream Katulampa (right)

B.5 1D canal flow module

B.5.1 Historical overview of 1D geometry

FHM 1

- Import main river network from DKI3-9 and DKI3-10 studies. HEC-RAS models imported

to Sobek as YZ cross-sections. 10% of the cross sections was corrected for errors or

datum.

- Importing weirs and gates Most came from DKI3-9 HEC-RAS models

- Importing Pluit, Melati, Cideng and Ancol pumps from DKI3-9 study.

- Checking Standard Operation Procedure (SOP) under flood conditions from a JICA 1997

measuring campaign

- Application of Manning = 0.04 s/m1/3

as default friction value according to Chaw (1959).

FHM 2

- Incorporation of local pumps in the framework (see Figure B.11-13)

- Solving local issues (see Deltares, 2009B for details)



156

Figure B.11-13 – incorporation of waduk (yellow node) and local pump (orange triangle)

2009 – 2012

- Incorporation of Banjir Kanal Timur (BKT)

Jakarta Flood Readiness Scan

- Re-evaluation of pump SOP

- Re-evaluation of BKT profiles

Flood Management Information System (FMIS)

- Update of profile set for main rivers (See annex C.1). These sets where available from the

Jakarta Emergency Dredging Initiative in CAD-files. A set of “current” en “design” profiles

are available.

- Update functioning of main pumps and structures after field surveys (See annex C.2)

- “Lumping” the service areas Jelembar and Tomang Polders over different pumps

- Small improvements in hydraulics (incorporation of small pumps and gates, see annex

C.2)

Figure B.11-14 – Lumping Jelembar (left)) and Tomang polders (right). One hydrological unit (green square) is

serviced by multiple pumps (orange triangles)



157

B.6 2D Overland Flow module A digital elevation model represents the ground surface topography in a raster form. Buildings, trees etc. should not be represented in the DEM. Dikes, on the other hand, should be represented, as they influence the propagation of the water and limit the extent of the floodings. During FHM1, two types of Digital Elevation Models were prepared: a TIN (Triangulated Irregular Network) and a grid. First, a TIN was constructed from spot heights (78000) and contour lines with an interval of 1 meter. A TIN gives a continuous representation of the elevation. From the TIN a grid of 5x5 meter was constructed, from which larger versions are made for hydraulic computations. The overland model uses a grid of 100x100 meter for the province of Jakarta (DKI) and a 50X50 meter grid for the Ciliwung upstream Manggarai.

For the overland module, a Manning friction of 0.04 s/m1/3

is applied on the entire grid.

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