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South Eastern CFRAM Study HA15 Hydraulics Report - DRAFTFINAL

IBE0601Rp0015 F02

DOCUMENT CONTROL SHEET

Client OPW

Project Title South Eastern CFRAM Study

Document Title IBE0601Rp0015_HA15Hydraulics Report

Model Name Ballyroan

Rev.

Status Author(s) Modeller Reviewed by Approved By Office of Origin Issue Date

D01 Draft T. Carberry L. Howe I Bentley G, Glasgow Belfast 21/02/2014

D02 Draft T. Carberry L.Howe M. Brian G.Glasgow Belfast 12/06/2014

F01 Draft Final

T. Carberry R.Clements

L.Howe K.Smart G.Glasgow Belfast 25.11.2014

F01 Draft Final

T. Carberry R.Clements

L.Howe K.Smart G.Glasgow Belfast 13/08/2015

South Eastern CFRAM

Study

HA15 Hydraulics Report

Ballyroan Model

South Eastern CFRAM Study HA15 Hydraulics Report –DRAFT FINAL

IBE0601Rp0015 F02

Table of Reference Reports

Report Issue Date Report Reference Relevant Section

South Eastern CFRAM Study Flood Risk Review

November 2011

IBE0601 Rp0001_Flood Risk Review_F01 3.4.1

South Eastern CFRAM Study Inception Report UoM15

July 2012 IBE0601Rp0008_HA 15 Inception Report_F02

4.3.2

South Eastern CFRAM Study Hydrology Report UoM15

October 2013

IBE0601Rp0010_HA15_Hydrology Report_F01

4.2

South Eastern CFRAM Study HA11-17 SC4 Survey Contract Report

January 2014

IBE0601Rp0016_South Eastern CFRAMS Survey Contract Report_F01

1.8

4 Hydraulic Model Details ................................................................................................................... 1

4.2 Ballyroan model ....................................................................................................................... 1

4.2.1 General Hydraulic Model Information .............................................................................. 1

4.2.2 Hydraulic Model Schematisation ..................................................................................... 2

4.2.3 Hydraulic Model Construction .......................................................................................... 9

4.2.4 Sensitivity Analysis ........................................................................................................ 16

4.2.5 Hydraulic Model Calibration and Verification ................................................................. 16

4.2.6 Hydraulic Model Assumptions, Limitations and Handover Notes .................................. 18

South Eastern CFRAM Study HA15 Hydraulics Report – DRAFT FINAL

IBE0601Rp0015 4.2-1 F02

4 HYDRAULIC MODEL DETAILS

4.2 BALLYROAN MODEL

4.2.1 General Hydraulic Model Information

(1) Introduction:

The South Eastern CFRAM Study Flood Risk Review report (IBE0601 Rp0001_Flood Risk Review_F01)

highlighted Ballyroan as an AFA forfluvialflooding based on a review of historic flooding and the extents of

flood risk determined during the PFRA.

The Ballyroan AFA is located on the Gloreen Stream, a tributary of the River Nore.The Ballyroan AFA is

affected by both the Gloreen Stream and its tributary the Crubeen Stream.The Gloreen Stream is split into

the ‘Gloreen’ Stream and ‘Gloreen A’Stream in the model extent. The Gloreen Stream passes through the

AFA and flows southwest, where it joins part way along the Gloreen A Stream at 2,300m chainage (as

shown in Error! Reference source not found.). The Gloreen A Stream then continues southwest for

approximately 5km and discharges into the River Nore. A survey of the Gloreen reach shows that the

Gloreen A reach, at its upstream extent (0m chainage), was originally linked to the Gloreen reach.

However, no connection exists at this location now, and there is no hydraulic interaction between the two.

Three gauging stations are located on the modelled reaches; however, there are no flow or level

dataavailable for these stations.The total contributing catchment area at the downstream end of the model

is 39.4km2, with approximately 15km

2 of this area entering the model above Ballyroan. This includes the

Crubeen Stream, an HPW tributary of the Gloreen Stream, which flows through Ballyroan from Cullenagh

Mountain. Downstream of the AFA, a number of small tributaries join the Gloreen Stream before it enters

the River Nore.

All watercourses are modelled using the MIKE suite of software. The Gloreen Stream, and its tributary the

Crubeen Stream, are modelled as 1D-2D to the confluence with the Gloreen A Stream. These

watercourses are designated as entirely high priority due to them being located in the AFA.Gloreen A

Stream is modelled as 1D-2Dfrom its upstream extent down tothe Mounteagle Road Bridge, this is due to

its close proximity to the AFA. The downstream extent of the Gloreen A Stream from the Mounteagle Road

Bridge is modelled as 1D only; this part of the channel is designated as entirely medium priority.

Input from Model 1 (Ballyragget) at the downstream extent of Model 2 (Ballyroan) is not considered, as the

Ballyroan AFA is more than 6 km upstream of the downstream boundary. Refer to Section 4.2.3 of this

report for upstream and downstream model interaction

(2) Model Reference: HA15_BALL2

(3) AFAs included in the model: Ballyroan


IBE0601Rp0015 4.2-2 F02

(4) Primary Watercourses / Water Bodies (including local names):

Reach IDName

15GLOR Gloreen Stream

15CRUB Crubeen Stream

15GLORAGloreen A Stream

(5) Software Type (and version):

(a) 1D Domain:

MIKE 11 (2011)

(b) 2D Domain:

MIKE 21 – Rectangular Mesh

(2011)

(c) Other model elements:

MIKE FLOOD (2011)

4.2.2 Hydraulic Model Schematisation

(1) Map of Model Extents:

Figure 4.2.1 and 4.2.2 illustrate the extent of the modelled catchment, river centre line, HEP locations and

AFA extents as applicable. The Gloreen catchment contains three Upstream Limit HEPs, one Downstream

Limit HEP, two Intermediate HEPs and one Tributary HEP which is modelled. The Gloreen catchment

contains three Gauging Stations but no Gauging Station HEPs as flow data is unavailable.


IBE0601Rp0015 4.2-3 F02

Figure 4.2. 1 Map of Model Extents


IBE0601Rp0015 4.2-4 F02

Figure 4.2. 2 Map of Model Extents at the AFA

(2) x-y Coordinates of River (Upstream extent):

Table 4.2.1Watercourses included in the model

Reach ID River Name x y

15GLOR Gloreen Stream 247052.0 187673.5

15CRUB Crubeen Stream 247792.4 188838.6

15GLORA Gloreen A Stream 244638.2 189404.5

(3) Total Modelled Watercourse Length: 14.6 km (approx.)

(4) 1D Domain only Watercourse Length: 5.0 km

(approx.)

(5) 1D-2D Domain

Watercourse Length:

10.0 km

(approx.)

(6) 2D Domain Mesh Type / Resolution / Area: Rectangular / 5 metres / 13.5 km2

The DTM has been adjusted to account for key features. Details of this have been included in Section

3.3.2 of this report. Bridge and road deck levels are occasionally not picked up in raw LiDAR data and so

they have been represented in the 2D domain by adjusting the z levels of grid cells at their locations. The

deck levels are based on topographic survey data.


IBE0601Rp0015 4.2-5 F02

(7) 2D Domain Model Extent:

Figure 4.2.3 illustrates the modelled extents and the general topography of the catchment.

Figure 4.2. 3 2D Model Extent

Figure 4.2.4 shows an overview drawing of the model schematisation. Figure4.2.5 and Figure 4.2.6 show

detailed views. The overview diagram covers the model extents, showing the surveyed cross-section

locations, AFA boundary and river centreline. It also shows the area covered by the 2D model domain.

The detailed areas are provided where there is the most significant risk of flooding. These diagrams

include the surveyed cross-section locations, AFA boundary and river centreline. They also show the

location of the critical structures, as discussed in Section 4.2.3(1), along with the location and extent of the

links between the 1D and 2D models.


IBE0601Rp0015 4.2-6 F02

Figure 4.2. 4 Model Schematic Overview

Figure 4.2. 5 Model Schematic (A)


IBE0601Rp0015 4.2-7 F02

Figure 4.2. 6 Model Schematic (B)

(8) Survey Information

(a) Survey Folder Structure:

First Level Folder Second Level Folder Third Level Folder

CCS_S15_M02_15CRUB_WP2_Finals_13

0118

Where: Ballyroan

CCS - Surveyor Name

S15 – South Eastern CFRAM Study Area,

Hydrometric Area 15

M02 - Model Number 02

15CRUB - River Reference

WP2 - Work Package 2

130118 - Date issued (18 Jan 2013)

Data Files

Drawings

GIS Files

Photos (Naming

convention is in the

format of Cross-Section

ID and orientation -

upstream, downstream,

left bank or right bank)

(b) Survey Folder References:

Reach IDName File Ref.

15GLORGloreen A Stream CCS_S15_M02_15GLOR_A_WP2_Finals_130118

South Eastern CFRAM Study

IBE0601Rp0015

15 GLOR Gloreen B Stream

15CRUB Crubeen Stream

(9) Survey Issues:

(a) 15CRUB00038 (Access track culvert at 247100E 188400N) in Figure 4.2.7 was not surveyed as

surveyors advised that they would flood out easily and did not warrant surveying due to

As such no further actions were required.

(b) 15GLOR00741 (A=access track culvert at 24

advised that they would flood out easily and did not warrant surveying due to

further actions were required. The structure is located approximately 400m upstream of the u

boundary of Gloreen A. A map is included in Figure 4.2.8 to show the

Figure 4.2. 715CRUB00038 (Access track)

Figure 4.2. 815GLOR00741 (Access track)

(c) A query was raised as to whether there is a connecting channel between Gloreen and Gloreen A


4.2-8

Gloreen B Stream CCS_S15_M02_15GLOR_B_WP2

CCS_S15_M02_15CRUB_WP2_

(a) 15CRUB00038 (Access track culvert at 247100E 188400N) in Figure 4.2.7 was not surveyed as

advised that they would flood out easily and did not warrant surveying due to

As such no further actions were required.

ccess track culvert at 244900E 189502N) was not surveyed as

ld flood out easily and did not warrant surveying due to the rural location. As such no

The structure is located approximately 400m upstream of the u

map is included in Figure 4.2.8 to show the location of the structure (red circle).

15CRUB00038 (Access track)

15GLOR00741 (Access track)

) A query was raised as to whether there is a connecting channel between Gloreen and Gloreen A

Hydraulics Report – DRAFT FINAL

F02

15GLOR_B_WP2_Finals_130118

_Finals_130118

(a) 15CRUB00038 (Access track culvert at 247100E 188400N) in Figure 4.2.7 was not surveyed as the

advised that they would flood out easily and did not warrant surveying due to the rural location.

N) was not surveyed as the surveyors

rural location. As such no

The structure is located approximately 400m upstream of the upstream

location of the structure (red circle).

) A query was raised as to whether there is a connecting channel between Gloreen and Gloreen A


IBE0601Rp0015 4.2-9 F02

Streams. CCS Surveyors confirmed that there is no longer a connecting channel between the two

reaches, see Figure 4.2.9. There is a dry ditch present but no water flows between these reaches any

more. As there is no critical flow path remaining, no survey was required.

Figure 4.2. 9Gloreen & Gloreen A Stream former connecting channel

No processing of the bathymetry was carried out.

4.2.3 Hydraulic Model Construction

(1) 1D Structures (in-channel along

modelled watercourses):

See Appendix A.1

Number of Bridges and Culverts: 15

Number of Weirs: 0

The survey information recorded includes a photograph of each structure, which has been used to

determine the Manning's n value. Further details are included in Chapter 3.5.1. A discussion on the way

structures have been modelled is included in Chapter 3.3.4.

Critical structures:

15GLOR01047D – Main Street Bridge

Culvert capacity is insufficient during the higher return periods (1% and 0.1% AEP). This leads to localised

flooding within the AFA. Flooding during the 1% AEP return period is limited to immediately upstream of

the bridge and does not affect any properties in the AFA. During the 0.1% AEP event, flood extents widen

affecting several properties.

Gloreen A

Gloreen

Former connecting channel


IBE0601Rp0015 4.2-10 F02

Figure 4.2. 10Main Street Bridge Culvert (15GLOR01047D)

15GLOR0670E – Mounteagle Road Bridge

Culvert capacity is insufficient to convey flood flows during the simulated return periods 10%, 1% and

0.1% AEP. Flood waters are held back and exceed the channel capacity innundating local agricultural

areas. The flood extents widen with the more extreme return periods (1% and 0.1% AEP). No properties

are affected by the flooding.

Figure 4.2. 11Mounteagle Road Bridge Culvert (15GLOR0670E)

15GLOR00404D – Portlaoise Road Bridge (N77)

Bridge capacity is insufficient to convey flood flows during all return periods (10%, 1% and 0.1% AEP).

Floodwaters back up and exceed channel capacity on both banks.


IBE0601Rp0015 4.2-11 F02

Figure 4.2. 12 Portlaoise Road Bridge N77 (15GLOR00404D)

15GLOR00108D – Blackhill/Tullyroe Road Bridge

Bridge structure is insufficient to convey flood flows during all return periods (10%, 1% and 0.1% AEP).

This results in elevated water level upstream of the bridge, flood waters inundate both banks, but extent is

wider on left bank. Flood extent widens with more extreme events (1% and 0.1% AEP), water depths

increase significantly from the 1% to the 0.1% AEP return period.

Figure 4.2. 13 Blackhill/Tullyroe Road Bridge (15GLOR00108D)

(2) 1D Structures in the 2D domain

(beyond the modelled watercourses):

None

(3) 2D Model structures: None

(4) Defences:

Type Watercourse Bank Model Start

Chainage(approx.)

Model End

Chainage (approx.)

None

(5) Model Boundaries - Inflows:

Full details of the flow estimates are provided in the Hydrology Report (IBE0601Rp0010_HA15 Hydrology

Report_F01 - Section 4.2 and Appendix D). The boundary conditions implemented in the model are


IBE0601Rp0015

shown below:

Figure 4.2. 14MIKE 11 Boundary Information

The time-to-peak of inflow hydrographs generated during the hydrological analysis have been reviewed

during the calibration process.In addition to this, Laois County Council drainage engineers advised that

land upstream of Main Street in the AFA (see Section 4.2.6.3) should flood more frequently. Modelled

flows were less than those estimated

timings werereviewed so thepeaks

validate the model. The updated flows now match the estimated flows

discussed in Appendix A.3.

Figure 4.2. 15Upstream Inflow (HEP 15_12_1)

The upstream boundary of the Gloreen catchment is located at HEP 15_12_1

location is 15GLOR01162D. A point inflow was therefore applied at this node to account for flow entering

the Gloreen River upstream of this location.


4.2-12

MIKE 11 Boundary Information

peak of inflow hydrographs generated during the hydrological analysis have been reviewed

In addition to this, Laois County Council drainage engineers advised that


flows were less than those estimated at the HEP check locations. As such, the inflow hydrograph peak

peaks coincide. This was done to ensure a worst

. The updated flows now match the estimated flows at the downstream boundary

Upstream Inflow (HEP 15_12_1)

Gloreen catchment is located at HEP 15_12_1, the model node ID at this

point inflow was therefore applied at this node to account for flow entering

River upstream of this location.The figure above shows the upstream HEP 15_12_1 input, for


F02

peak of inflow hydrographs generated during the hydrological analysis have been reviewed

In addition to this, Laois County Council drainage engineers advised that the


he inflow hydrograph peak

as done to ensure a worst–case scenario and to

at the downstream boundary as

, the model node ID at this

point inflow was therefore applied at this node to account for flow entering

figure above shows the upstream HEP 15_12_1 input, for


IBE0601Rp0015 4.2-13 F02

the 0.1% AEP return period.

(6) Model Boundaries –

Downstream Conditions:

The downstream boundary condition is a Q-h relationship, generated

based on the cross-section at the downstream extent of the model.

This is located just upstream of the confluence of the Gloreen A Stream

(Ch 7816.52) and the River Nore.Joint probability with Model 1

(Ballyragget) has not been considered and a Q-h boundary has been

applied at the downstream extent. The Ballyroan AFA is greater than 6km

upstream of the downstream boundary of the model. Therefore backwater

from Model 1 (Ballyragget) is considered to have no affect on flood flows

within the AFA. The Q-h boundary is to be assessed during sensitivity

analysis. Please refer to Section 6.3.1 of the Hydrology Report and

Section 3.6.1 of this report for the approach.

(7) Model Roughness:

(a) In-Bank (1D Domain) Minimum 'n' value: 0.030 Maximum 'n' value: 0.050

(b) MPW Out-of-Bank (1D) Minimum 'n' value: 0.030 Maximum 'n' value: 0.070

(c) MPW/HPW Out-of-Bank

(2D)

Minimum 'n' value: 0.034

(Inverse of Manning's 'M')

Maximum 'n' value: 0.059

(Inverse of Manning's 'M')


IBE0601Rp0015 4.2-14 F02

Figure 4.2. 16 Map of 2D Roughness (Manning's n)

This map illustrates the roughness values applied within the 2D domain of the model. Roughness in the

2D domain was applied based on land type areas defined in the Corine Land Cover Map with

representative roughness values associated with each of the land cover classes in the dataset.

(d) Examples of In-Bank Roughness Coefficients

Crubeen Stream - 15CRUB00002 Gloreen Stream - 15GLOR0896


IBE0601Rp0015 4.2-15 F02

Figure 4.2. 17 15CRUB00002 Roughness

Manning’s n = 0.050

Clean, winding stream, trees and heavy brush

along banks (submerged at high water levels)

Figure 4.2. 18 15GLOR0896 Roughness


Clean, winding stream, brush along banks

(submerged at high water level)

Gloreen A Stream - 15GLOR00281

Figure4.2. 19 15GLOR00281 Roughness


Clean, winding stream, brush along banks


Gloreen A Stream – 15GLOR0034



Clean, winding stream, some brush along banks


Gloreen Stream - 15GLOR1078 Crubeen Stream - 15CRUB00062I


IBE0601Rp0015 4.2-16 F02



Standard natural stream or river in stable condition

Figure 4.2. 22 15CRUB00062I Roughness


Concrete lined channel

4.2.4 Sensitivity Analysis

Sensitivity analysis to be reported in Final Version of report (F02), as agreed with OPW.

4.2.5 Hydraulic Model Calibration and Verification

(1) Key Historical Floods (fromIBE0600Rp0008_HA15 Inception Report_F02 unless otherwise

specified):

(a) Nov 2013 Laois County Council Drainage Engineers advisedat a workshop of draft flood

mapping on 13th November 2013 that flooding previously affected Chapel Road within

the AFA, and that the floodwaters originated from the Crubeen Stream. The model

results do not show any flooding of Chapel Road. The 1% AEP water level is well

below top of bank along this stretch (as shown in Appendix A.2). Since the Crubeen

Stream is small and heavily channelized it may be susceptible to blockage. It is

therefore considered that this flooding may have been caused by a blockage in the

Crubeen Stream channel. Blockage analysis will be carried out during sensitivity

analysis and discussed in Final Version of report (F02).


IBE0601Rp0015 4.2-17 F02

Figure 4.2. 23 0.1% AEP flood extent near Chapel Street

(b) Jan 1995 Taken from the County Laois Strategic Flood Risk Assessment – Table 5-1 Historical

flood eventreports: ‘Major flooding is reported in the Portaloise area. Flooding also

reported in Ballyroan, Stradbally, Mountmellick, Mountrath, Portarlington, Durrow,

Timahoe and Rosenallis’.

No further information is available for this event. Flooding is shown to occur in

Ballyroan during all modelled events (10%, 1% and 0.1% AEP).

Summary of Calibration

Very little historical data relating to flooding in the Ballyroan AFA is available. Therefore, quantifying

historical flood events is difficult as there is no data available for the hydrometric gauges within the model

extents.

There are no significant model instabilities. There are minor fluctuations in the discharge (<0.5m3/s) during

the 1% and 0.1% AEP events where large quantities of flow exchange over the lateral links between

approximately 3,000m and 4,800m chainage (see Section 4.2.6.2). This does not affect the model results

and the model is considered to be performing satisfactorily. The mass balance of the model is -1.54%, as

such the model is considered fit for purpose.

Model flows were checked against the estimated flows at HEP check points where possible to ensure they

were within an acceptable range. During the lower severity event 10% AEP, the modelled flows matched

well (within 5%, or within 0.5m3/s) with the estimated flows. During the more extreme events, large

quantities of flow leaves the channel due to lack of capacity in the channel causing lower than estimated

modelled flows in the middle reach of the model. However, at the downstream extent of the model the

modelled flows are within 5% of the estimated flows suggesting the model is well anchored to the

hydrological estimates.

Overall, as there is very little data available and as the return period of historical events is very uncertain,

the model should be described as poorly calibrate. However, despite lack of calibration and verification

data, it is considered to be performing satisfactorily for design event simulation and matches well to

Chapel St

Crubeen Stream

Gloreen Stream


IBE0601Rp0015 4.2-18 F02

estimated flows.

(2) Public Consultation Comments and Response:

To be completed for final version of the report (F02)

(3) Standard of Protection of Existing Formal Defences:

Defence

Reference

Type Watercourse Bank Modelled Standard

of Protection (AEP)

None

(4) Gauging Stations:

There are three gauging stations within the model extents:

(a)Ballydine Bridge (15028)No flow or water level data is available for this gauging station and it has

therefore not been used to calibrate the model.

(b)Ballyroan (15032)No flow or water level data is available for this gauging station and it has therefore

not been used to calibrate the model.

(c)Tonduff (15054)No flow or water level data is available for this gauging station and it has therefore not

been used to calibrate the model.

(5) Other Information:

Although there are no recorded historical flood events in Ballyroan, discussions with Laois County Council

Drainage Engineers highlightedthat areas downstream of the AFA (in the proximity of the Gloreen and

Gloreen A confluence, and upstream of the confluence) were not shown to flood as often as they

should.However, this flooding is over 5km upstream of the River Nore and so is not caused by high flows

in the Nore River.

4.2.6 Hydraulic Model Assumptions, Limitations and Handover Notes

(1) Hydraulic Model Assumptions:

(a) The in-channel and structureroughness coefficients initially selected based on normal bounds were

reviewed during the calibration process. It is considered that the selected values are representativeof the

channel and surrounding floodplain.

(b) The time-to-peak of inflow hydrographs generated during the hydrological analysis have been

reviewed during the calibration process. The inflow hydrograph peak timings for all watercourses have

been adjusted to coincide as the modelled peak flows were less than those estimated. This was validated

by the comments received during consultation with Local Authority staff who advised that modelled results

did not show flooding occurring as often as it should.Flood hydrographs are statistical estimates based on

catchment descriptors; occasionally the modelled peak flows do not coincide in the main channel.

Adjusting the hydrograph timings so peaks coincide is justifiable as it ensures a worst case scenario


IBE0601Rp0015 4.2-19 F02

forflooding in the AFA.

(c) For design run simulations it has been assumed that all culverts and screens are free of debris and

sediment.

(2) Hydraulic Model Limitations and Parameters:

(a) No gauging stations are available to provide flow/stage calibration.

(b) Where only the upstream/downstream face of a structure has been surveyed, the surveyed face has

been duplicated and used as the opposite face of the structure. This is considered acceptable as all these

structures were of short length and so there should be minimal difference between the upstream and

downstream orifice of each structure.

(c) Grid cell size is 5m. Features smaller than 5m wide, such as walls or flow paths, may not be accounted

for within the 2D domain. This may be less accurate in urban areas. The Gloreen and Gloreen A

watercourses are represented in the LiDAR (prior to watercourse blockout in MIKE FLOOD). As such, it is

assumed that any depression in the terrain where the former flow path between the Gloreen A and

Gloreen Stream was located, would also be represented if present.

(d) A large portion of the model is medium priority watercourse, 1D-only,providing less detail than the high

priortity 1D-2D portion of the model.Where glass walling was an issue in the MPW,

cross-sections have been extended using NDHM data allowing for wider flood extents and more accurate

water levels than the surveyed sections.

(e) All culverts with only the upstream or downstream face surveyed had the upstream invert level raised

by 0.02m to improve model stability.

Hydraulic Model Parameters:

MIKE 11

Timestep (seconds) 2

Wave Approximation High Order Fully Dynamic

Delta 0.85

MIKE 21

Timestep (seconds) 2

Drying / Flooding depths (metres) 0.02 / 0.03

Eddy Viscosity (and type) 0.25 (Flux Based)

MIKE FLOOD

Link Exponential Smoothing Factor

(where non-default value used)

River Gloreen, Ch 3080.17 - Ch 4159.72: 0.8;

River Gloreen A, Ch 364.264 – Ch 1091.73: 0.8;

River Gloreen A, Ch 2318.9 – Ch 2516.68: 0.8;


IBE0601Rp0015 4.2-20 F02

River Gloreen A, Ch 2530.03 – Ch 2790.0: 0.8.

Lateral Length Depth Tolerance (m)

(where non-default value used)

All default

(3) Design Event Runs & Hydraulic Model Handover Notes:

This model is influenced by fluvial sources only. The 10%, 1% and 0.1% AEP events were simulated.

There is little flooding within the AFA extent itself, but some localised flooding does occur. The only

significant flooding in the AFA during all return periods (10%, 1% and 0.1% AEP) is caused by the Main

Street culvert.A lack of capacity in the Main Street culvert, diverting flow in Gloreen A Stream, causes

localised flooding of grassland in the Ballyroan AFA during higher return periods (0.1% AEP) (Figure

4.2.24Error! Reference source not found.). The lack of capacity of the structure causes flood waters to

back up, inundating the area upstream of the bridge.

Figure 4.2. 24 0.1% AEP flood extent in the Ballyroan AFA

The section of Gloreen A Stream passing through Ballyroan town is heavily channelised. This section is

found to have sufficient capacity for high return periods (10% and 1% AEP). However, during the more

extreme return periods (0.1% AEP), flooding occurs in the AFA. This results from a combination of

insufficient channel capacity and water backing up, upstream of the Main Street Bridge.

The capacity of the Crubeen Stream was found to be adequate during all events simulated

(10%, 1% and 0.1% AEP).

Downstream of the Ballyroan AFA there is large amount of out-of-bank flooding, this is due to a lack of

capacity in the Gloreen A Stream and the Gloreen Stream during high return periods

(1% and 0.1% AEP). No properties are affected.

The Mounteagle Road bridge is a critical structure. During all return periods simulated

(10%, 1% and 0.1% AEP), the bridge restricts flow and increases water levels upstream, resulting in

flooding of limited extent upstream of the bridge.

Main Street Bridge

(15GLOR01047D)

AFA Extent

(Red Line)


IBE0601Rp0015 4.2-21 F02

Figure 4.2. 25 0.1% AEP return period downstream of the Ballyroan AFA

Downstream of the AFA, the Gloreen Stream is directed under an N77 Road Bridge on Portlaiose Road

(15GLOR00404D). This bridge is insufficient to convey flood flows. This results in backing up of water and

localised flooding during all return periods (10%, 1% and 0.1% AEP). The backwater effect from this

bridge has a direct impact on flooding at the bridge location approximately 100m upstream

(15GLOR00417D), which causes increased water levels upstream as a result of water backing up from

15GLOR00404D. Local agricultural land is affected but no properties are affected by this flooding.

Figure 4.2. 26 Flood extent in the Gloreen Stream at the Portlaoise Rd (N77) Bridge

Downstream of the Portlaoise Road (N77) Bridge to the Ballydine Bridge (R430), the Gloreen Stream has

sufficient capacity to convey the 10% AEP return period. During the more extreme return periods

(1% and 0.1% AEP), the Gloreen Stream has insufficient capacity to convey flood flows. This results in

some flooding on the left bank, downstream of the Portloaise Road Bridge, and significant flooding on the

right bank along this reach. Local agricultural land is affected, but no properties are affected by this

0.1% AEP

Flood Extent

Mounteagle Road Bridge

(15GLOR00670E)

0.1% AEP Flood Extent

Unknown Rd Bridge

(15GLOR00417D)

Portlaoise (N77) Rd Bridge

(15GLOR00404D)


IBE0601Rp0015 4.2-22 F02

flooding.

Figure 4.2. 27 Flood extent in the Gloreen Stream between the Portloaise Rd (N77) Bridge and the Ballydine (R430) Bridge during the 0.1% AEP return period

From the Ballydine Road Bridge (N77) to the Gloreen Bridge (15GLOR00108D), the Gloreen Stream has

insufficient capacity to convey flood flows during all return periods (10%, 1% and 0.1% AEP). Floodwaters

inundate both banks along this reach. The area is largely agricultural and no properties are affected by this

flooding.

The Gloreen Bridge (15GLOR00108D) is a critical structure which causes flooding during all return periods

(10%, 1% and 0.1% AEP). The bridge structure is insufficient to convey flood flows, resulting in elevated

water levels upstream of the bridge, which exceed channel capacity and overtop both banks, flooding

affects local agricultural land and no properties.

Downstream of the Gloreen Bridge, the Gloreen Stream has insufficient capacity to convey flood flows

during all return periods. Floodwaters exceed channel capacity and inundate both banks. Left bank

flooding extends from the Gloreen Bridge, approximately 200 m downstream. Flooding on the right bank

extends from the Gloreen Bridge to the downstream extent of the Gloreen Stream at its confluence with

the River Nore.

Ballydine Bridge

(15GLOR000245D)

0.1% AEP

Flood Extent


IBE0601Rp0015 4.2-23 F02

Figure 4.2. 28 0.1% AEP flood extent in the Gloreen Stream, from the Gloreen Bridge to its confluence with the River Nore

As noted in the survey queries in Section 4.2.2(9),the Gloreen A Stream and the Gloreen Stream used to

be connected. The lack of capacity of the Gloreen Stream at this location causes localised flooding during

all modelled return periods.

(4) Hydraulic Model Deliverables:

Please see Appendix A.4 for a list of all model files provided with this report.

(5) Quality Assurance:

Model Constructed by:

Model Reviewed by:

Model Approved by:

Laura Howe

Malcolm Brian

Grace Glasgow

Gloreen Bridge

(15GLOR00108D)

0.1% AEP

Flood Extent

River Nore


IBE0601Rp0015 4.2-24 F02

APPENDIX A.1

MODELLED STRUCTURES


IBE0601Rp0015 4.2-25 F02

Structure Details – Bridges & Culverts

RIVER BRANCH

CHAINAGE ID LENGTH (m)

OPENING SHAPE

HEIGHT (m)

WIDTH (m)

SPRING HEIGHT FROM INVERT (m)

MANNING’S N

Bridges

CRUBEEN 300 15CRUB00105I 212.28 CIRCULAR 1.20 1.20 - 0.015

CRUBEEN 547 15CRUB00078D 11.4 CROSS-SECTION DB 2.58 1.94 1.63 0.045

CRUBEEN 730 15CRUB00062I 40.07 CROSS-SECTION DB 0.80 1.79 - 0.03

GLOREEN A 2123 15GLOR00568D 8.3 CIRCULAR 1.00 1.00 - 0.015

GLOREEN A 2523.5 15GLOR00525D 5.35 CROSS-SECTION DB 2.49 3.06 1.50 0.04

GLOREEN A 3647 15GLOR00417D 3.74 CROSS-SECTION DB 1.74 3.23 - 0.045

GLOREEN A 3794 15GLOR00404D 22.2 CROSS-SECTION DB 2.14 3.87 - 0.045

GLOREEN A 5365 15GLOR00245D 9.19 LW-TABLE 2.51 4.87 1.30 0.035

GLOREEN A 6747 15GLOR00108D 1 6.55 LW-TABLE 2.57 2.69 0.99 0.035

GLOREEN 1204 15GLOR01047D 9.43 CROSS-SECTION DB 2.04 3.14 0.78 0.04

GLOREEN 1843.5 15GLOR00980E 4.53 CROSS-SECTION DB 1.37 3.15 - 0.035


IBE0601Rp0015 4.2-26 F02

Structure Details – Bridges & Culverts

RIVER BRANCH

CHAINAGE ID LENGTH (m)

OPENING SHAPE

HEIGHT (m)

WIDTH (m)

SPRING HEIGHT FROM INVERT (m)

MANNING’S N

Bridges

GLOREEN 4833.5 15GLOR00670E 4.83 CROSS-SECTION DB 1.80 2.10 0.92 0.04

GLOREEN 1633.5 15GLOR01000E 4.58 CROSS-SECTION DB 1.67 3.11 - 0.04

GLOREEN A 1098 15GLOR00667E 8.1 CIRCULAR 1 1 - 0.015

GLOREEN A 6747 15GLOR00108D 2 6.55 LW-TABLE 2.53 2.77 0.74 0.035

All weirs in the Network file are overtopping weirs which form part of a composite structure with the culvert / bridge at the corresponding

chainage.


IBE0601Rp0015 4.2-27 F02

APPENDIX A.2

RIVER LONG SECTION PROFILES


IBE0601Rp0015

Crubeen River 1% AEP Peak Water Levels


4.2-28

Crubeen River 1% AEP Peak Water Levels


F02


IBE0601Rp0015 4.2-29 F02

APPENDIX A.3

ESTIMATED PEAK FLOW AND MODEL FLOW

COMPARISON


IBE0601Rp0015 4.2-30 F02

IBE0601 SE CFRAM STUDY RPS

PEAK WATER FLOWS

AFA Name BALLYROAN

Model Code HA15_BALL2

Status DRAFT

Date extracted from model 01/04/2014

Peak Water Flows River Name & Chainage AEP Check Flow (m3/s) Model Flow (m3/s) Diff (%) GLOREEN A 2321.96

15_378_6_Inter_RPS

10% 7.21 6.98 3.19

1% 12.78 9.36 26.76

0.1% 21.88 12.94 40.87

GLOREEN A 7794.07

15_1938_5_RPS

10% 8.64 8.99 4.02

1% 15.00 15.22 1.44

0.1% 25.21 26.02 3.20

GLOREEN 3683.75 10% 5.39 5.81 7.68

15_281_4_Inter_RPS 1% 9.88 6.05 38.77

0.1% 17.44 6.14 64.82

CRUBEEN 1327.1 10% 1.10 1.11 0.97

15_467_5 1% 2.02 2.03 0.22

0.1% 3.59 3.58 0.24

The table above provides details of flow in the model at every HEP inflow, check point, modelled

tributary and gauging station.

The difference between modelled peak flows and estimated flows in the Crubeen River at chainage

1327.1is less than 1%during all return periods simulated (10%, 1% and 0.1% AEP). As such the

modelled peak flows in this river are well anchored to the estimates.

The modelled peak flows in the Gloreen A River at chainage 7794.07 are within 5% of the estimated

peak flows during all return periods simulated (10%, 1% and 0.1% AEP). As such the modelled peak

flows in this river are well anchored to the estimates.

The modelled peak flow in the Gloreen A River at chainage 2321.96 is within 5 % of the estimated

peak flow during the 10% AEP return period. During the more extreme return periods

(1% and 0.1% AEP), modelled peak flow is between 36-40% lower than the estimates. During the 1%

and 0.1% AEP return periods, the Gloreen A River has insufficient capacity to convey flood flows as

such large quantities of flow exceed channel capacity and flow overland away from the the HEP

location.


IBE0601Rp0015 4.2-31 F02

The modelled peak flow in the Gloreen River chainage 3683.75 is 7% higher when compared with the

estimated peak flow during the 10% AEP return period. This difference is less than 0.5m3/s and

caused by a lesser degree of hydraulic attenuation than is captured in the design flow estimations.

During the more extreme return periods (1% and 0.1% AEP), the flows in the Gloreen River chainage

3683.75 are between 38-64% lower when compared with the estimated peak flows. During the 1% and

0.1% AEP return periods, channel capacity upstream of the HEP is insufficient to convey flows. Water

flows north, away from the HEP location. This attenuation is higher than captured in design

estimations and accounts for the lower than estimated peak flows.


IBE0601Rp0015 4.2-32 F02

APPENDIX A.4

DELIVERABLE MODEL AND GIS FILES


IBE0601Rp0015 4.2-33 F02

Model Files

Fluvial Model Files

MIKE FLOOD MIKE 21 MIKE 21 – DFS2 FILE MIKE 21 RESULTS

HA15_BALL2 _MF_DES_Q10_7 HA15_BALL2_M21_DES_Q10_7 HA15_BALL2_DFS2_Rec_DES_Mesh_2 HA15_BALL2_M21_DES_Q10_7

HA15_ BALL2 _MF_DES_Q100_7 HA15_BALL2_M21_DES_Q100_7 HA15_BALL2_M21_DES_Q100_7 HA15_ BALL2 _MF_DES_Q1000_7 HA15_BALL2_M21_DES_Q1000_7 HA15_BALL2_M21_DES_Q1000_7

MIKE 11 - SIM FILE & RESULTS FILE MIKE 11 - NETWORK FILE MIKE 11 - CROSS-SECTION FILE MIKE 11 - BOUNDARY FILE

HA15_BALL2_M11_DES_Q10_7 HA15_BALL2_NWK_DES_7 HA15_BALL2_XNS_DES_7 HA15_BALL2_BND_DES_Q10_7

HA15_BALL2_M11_DES_Q100_7 HA15_BALL2_BND_DES_Q100_7 HA15_BALL2_M11_DES_Q1000_7

HA15_BALL2_BND_DES_Q1000_7

MIKE 11 - DFS0 FILE MIKE 11 - HD FILE & RESULTS FILE

HA15_BALL2_TS_Q10_edit

HA15_BALL2_HD_DES_Q10_7

HA15_BALL2_TS_Q100_edit HA15_BALL2_HD_DES_Q100_7 HA15_BALL2_TS_Q1000_edit HA15_BALL2_HD_DES_Q1000_7


IBE0601Rp0015 4.2-34 F02

GIS Deliverables - Hazard

Flood Extent Files (Shapefiles) Flood Depth Files (Raster) Water Level and Flows (Shapefiles)

Fluvial Fluvial Fluvial

O05EXFCD001C0 o15dpfcd001c0 O05NDFCDC0

O05EXFCD010C0 o15dpfcd010c0

O05EXFCD100C0 o15dpfcd100c0

Flood Zone Files (Shapefiles) Flood Velocity Files (Raster) Flood Defence Files (Shapefiles)

To be issued with Final version of this report Defended Areas O05ZNA_FCDC0 NA O05ZNB_FCDC0 Defence Failure Extent NA

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