Drainage Improvement Work For High Density Development...

Rivers’04 1st International Conference on Managing Rivers in the 21st Century: Issues & Challenges

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Drainage Improvement Work For High Density Development: Case Study of Taman Mangga, Taman Pinang, Taman Sentul and Taman Sentul Jaya LAU TZE LIANG, Research Associate, River Engineering and Urban Drainage Research Centre (REDAC), Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Penang, Malaysia AMINUDDIN AB. GHANI, Deputy Director, REDAC, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Penang, Malaysia NOR AZAZI ZAKARIA, Director, REDAC, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Penang, Malaysia ROZI ABDULLAH, Research Associate, REDAC, Universiti Sains Malaysia, Engineering Campus, Seri Ampangan, 14300 Nibong Tebal, Penang, Malaysia ABSTRACT Taman Pinang, Taman Mangga, Taman Sentul and Taman Sentul Jaya are situated in district of Seberang Perai Tengah, Penang. These high density residential areas are subjected to frequent flood whenever it rains heavily due to its low lying ground platform and the areas are affected by the tidal influence. The flood woes in the study area have been a long-standing issue since 1990’s. Frequent floods have caused extensive damage and inconvenience to the community. Internal drainage inventory has been carried out for the existing drainage system. It was found that the existing drains are in poor conditions and has insufficient capacity to cater for increased stormwater discharge. For alleviating flood woes in these areas, flood mitigation and drainage improvement measures have been formulated which include the enlargement of internal drain, provision of stormwater storage facilities, construction of pumping stations and installation of backflow prevention gates. Keywords: Flooding; flood mitigation; drainage improvement; storage facility; pumping. 1 Introduction The study area consists of four high-density residential areas, Taman Pinang, Taman Mangga, Taman Sentul and Taman Sentul Jaya, situated in district of Seberang Perai Tengah, Penang as shown in Figure 1. This area is built up with high density housing estates. This area is frequently flooded whenever it rains heavily for duration more than 1 hour.

The flooding problems in the study area are caused by the inadequacy of existing drainage system and tidal effect. Moreover, the level of construction platform is lower than the desirable platform levels. Frequent floods

have caused extensive damage and inconvenience to the community.

The Government and the municipal council, Majlis Perbandaran Seberang Perai (MPSP), have long been conscious of the above actual situation, and the subsequent immediate need for establishment of proper drainage system in the Municipality. River Engineering and Urban Drainage Research Centre (REDAC), University Science Malaysia, has been appointed by MPSP to carried out feasibility study and detailed design for this area.


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Figure 1 Map of Seberang Perai [2]. 2 Project Background The project area for the study, Taman Pinang, Taman Mangga, Taman Sentul and Taman Sentul Jaya, is located in Mukim 13, Seberang Perai Tengah,Penang as depicted in Figure 2. The study area is located adjacent to Parit No. 5. The catchment covers the total area of 3.5 ha (Taman Pinang), 10.5 ha (Taman Mangga), 3.25 ha (Taman Sentul) and 11.5 ha (Taman Sentul Jaya). Parit No. 5 serves this project area.

The project area is subjected to the effect by tidal influence and is liable to occurrence of the flooding or inundation when the high intensity storms occur and coincide with the high spring tide.

The existing drainage facilities in the project area are mostly of the open drain either lined or unlined, consisting of trunks, secondary and roadside drains. Due to rapid development at surrounding area where the

platform is relatively higher and lack of improvement to the existing drainage infrastructure, the project area is affected by flash flood. This situation becomes worse with their originally low platform level in the project area.

Figure 2 Location for Taman Mangga, Taman Pinang, Taman Sentul and Taman Sentul Jaya [4]. 3 Flood Condition The climate within the study area is tropical with generally uniform temperature and high relative humidity throughout the year. The mean annual temperature, the mean annual humidity and the annual rainfall are given in Table 1. The distributions of temperature, humidity, evaporation rate and rainfall for typical year are given in Figure 3(a) to Figure 3(d).

Project Area

Sungai Juru

North-South Highway

Juru Tol

Sungai Junjung

Taman Mangga

Taman Sentul Jaya

Taman Sentul

Taman Pinang

Parit No. 5

Parit No. 5

N


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There are two wet periods during the year which occur between April to May and September to November, when the Intertropical Convergence Zone passes over the area. Dry period occurs from December to March whilst a transitional period of moderate rains occurs from June to August.

Table 2 gives the characteristic of flood in Seberang Perai. During the period, 1986-2000, flooding was most common in the months of September to November, which coincided with the main rainy period of the year as shown in Figure 3(c).

Table 1 Summary of Climatologic Data [2]. Mean annual air temperature

27.3 0C

Mean annual humidity

80 %

Annual rainfall Generally convective in origin; from around 2000 mm/yr (coastal plain) to

over 3200 mm/yr (mountainous region);

Orographic effects produce higher rainfalls

Table 2 Common Flooding Months in Seberang Perai Tengah.

Year Months 1986# 1988# 1989# 1990# 1991# 1995# 1998# 1999#

2000#

2002* 2003*

September, October, November September, November October September, October June September November August, September, October February May October

Source: # MPSP (2001) * Newspaper

The most frequent duration of flooding occurred between 1-2 days. The range of flood depth varied from 0.1m to 1.2m. The most severe flood was recorded up to 4 feet depth.

Figure 3(a)-(d) Temperature, Mean Relative Humidity, Mean Monthly Rainfall Distribution and Mean Daily Evaporation Rate of Seberang Perai [2].

(b)

(a)

(c)

(d)


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4 Existing Drainage System The study area is served by Parit No. 5 which is a tributary of Sungai Juru and Sungai Junjung (Figure 2). There are few residential estates (Perkampungan Juru and Taman Duku) situated at upstream of the study area. The study area is subjected to flooding or inundation (Figure 4 and 5) due to its flat and low-lying condition and is affected by tidal influence. The flooding situation becomes worse when the high intensity storm occurs and coincides with the high spring tide.

Figure 4 Flooding in Taman Sentul Jaya [3].

Few site visits, interviews with local communities, internal drainage inventories and drain capacity computation have been carried out in order to evaluate the existing drainage system. Through these assessments, the current condition of the existing drainage system are summarised as follow: i) The existing channel capacities

especially at the main drains are generally inadequate to cater for both initial and major storms.

ii) The existing drains are highly silted and depth of sediment can be noticed to a significant extent. This may be caused by lack of maintenance and consequently reduce the effective depth of the drain.

iii) The flow of water remains stagnant due to tidal effect and existing flat low-lying ground platform. The existing drainage system has poor conveyance capacity.

iv) Structural defects in hydraulic structures that lead to flow constraint have been observed.

v) Indiscriminate littering and dumping are easily seen.

vi) Lack of maintenance for the existing main waterways.

vii) Ad hoc pumping system is not functioning effectively and efficiently.

Base on the informal interview with local residents, flood mark measurement and survey reports, the flood prone areas in the study area are outlined as delineated in Figures 6 to 8.

Considering this high density development of residential areas, the frequent minor floods have caused inconvenience to local residents

Figure 5 Flooding in Taman Sentul Jaya [3].


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especially whose are studying and working. For severe floods, they have affected daily life, disrupted the traffic flow and caused extensive damage to the property. Figure 6 Flood Prone Area in Taman Mangga and Taman Pinang [4].

Figure 7 Flood Prone Area in Taman Sentul [4]. Figure 8 Flood Prone Area in Taman Sentul Jaya [4]. 5 Flood Mitigation and Drainage

Improvement Work

Two stages flood mitigation measure have been carried out which consist of construction of pumping station and upgrading internal drainage system. The detailed design was proposed in accordance to D.I.D Planning and Design Procedure No. 1 “Urban Drainage Design Standards and Criteria for Peninsular Malaysia” [1] since the new stormwater management manual for Malaysia (MSMA) is yet not published at that moment.

The pumping station was designed to drain out approximately 35% of the total runoff generated from these fully built up housing estates. The excess runoff will be stored in the storage facilities which are mainly monsoon drains and trunk drains. The provision of on-site and community detention/retention storages are not feasible in these development areas because of the lack of available open space.

Two pumping station have been constructed within 32 weeks period, i.e. Taman Mangga Pumping Station (Figure 9) and Taman Sentul Jaya Pumping Station (Figure 10). Both pumping station are equipped with 2 nos. pump with capacity of 300 l/s each.

To prevent backflow during high water level of Parit No. 5, Tideflex® Check Valve (Figure 11) was installed at low flow diversion channel at each pumping station.

Drainage upgrading with widening and deepening of existing internal drains and main drains were carried out during 46-week construction period. The typical drainage upgrading works are shown in Figures 12 to 14.


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Figure 9 Taman Mangga Pumping Station. Figure 10 Taman Sentul Jaya Pumping Station.

Figure 11 Tideflex® Check Valve [5].

Figure 12 Concrete Drain (3000mm Width) in Taman Mangga. Figure 13 Concrete Drain (1200mm Width) at Jalan Sentul 1, Taman Sentul.

Figure 14 Covered Concrete Drain (1200mm Width) in Taman Sentul.


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6 Post Flood Mitigation and Drainage Improvement Work

The flood mitigation and drainage improvement work has been completed on December 2001. However, there was a minor flood occurred in Taman Mangga and Taman Pinang on May 2002 as shown in Figures 15 and 16. That flood has caused minor disruption and damages to the residents in this area compared to previous floods which were occurred before the flood mitigation and drainage improvement been carried out. One of the main causes of this flood incident is the contribution of subtantial water load from upstream of this area which is not been a part of the catchment originally. This incident also caused by the inadequacy of receiving water body at futher downstream as illustrated in Figures 17 and 18.

Figure 15 Flood Condition in Taman Mangga on 6 May 2002. Figure 16 Flood Condition in Taman Pinang on 6 May 2002.

Figure 17 Flood Condition in Taman Sentul Pumping Station on 6 May 2002.

Figure 18 Flood Condition in Taman Sentul Jaya on 6 May 2002. The most recent flood in Seberang Perai area was happened on October 2003. Incessant rain and strong winds which lashed Penang has caused widespread havoc. The flood level up to 3 feet height was recorded in Taman Mangga. Again, the addition water load from outside catchment area is one of the major causes.

From the data and information gathered from Department of Irrigation and Drainage, the receiving water body of this area, Sungai Juru, has exceeded its maximum capacity and overflow has occurred in few stretches. This has affected the study area where the stormwater are not able to be drained out from this residential area as soon as possible. The flood mitigation and drainage


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improvement measure was not able to function as what it was designed during this event. 7 Conclusion Taman Mangga, Taman Pinang, Taman Sentul and Taman Sentul Jaya are similar to other residential estates in Lembah Sungai Rambai, Seberang Perai Tengah, which are located in low-lying flat area and subjected to flooding. Flooding is a long-standing issue in these high density development areas and the pumping solution is the most acceptable and favourable solution here. Even though the conventional storm drainage approach which adopt the rapid disposal, localised, reactive and mono-functional drainage concepts solution has encounted some shortcomings, the drainage enlargement and pumping has relief the stress of flooding in the study area. To alleviate the flood problems throughoutly, the comprehensive and total catchment management strategies are essential. Acknowledgment The authors would like to express sincere gratitude to Majlis Perbandaran Seberang Perai for granting this contract research for

this project. The authors also would like to thank Mr. Shanker Kumar Sinnankaudan, Mr. Paker Mohamad and all REDAC’s staff for their involvement in this project.

References 1. JPS (1974), D.I.D Planning and

Design Procedure No. 1 “Urban Drainage Design Standards and Criteria for Peninsular Malaysia.

2. JPS (1994), Feasibility Study And Detailed Design On River System Of Sg Perai, Sg Juru And Sg Jejawi-Sg Tengah.

3. Kwong Wah Yit Poh, 6 September 1999.

4. MPSP (2001), Kajian Kebolehlaksanaan Dan Rekabentuk Terperinci Tebatan Banjir Dan Saliran Taman Sentul, Taman Sentul Jaya, Taman Pinang Dan Taman Mangga, Juru, Seberang Perai Tengah, Pulau Pinang.

5. RedValve (2004), http://www.redvalve.com

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