South Eastern CFRAM Study HA15 Hydraulics Report – DRAFT FINAL

South Eastern CFRAM Study

HA15 Hydraulics Report Kilkenny Model

DOCUMENT CONTROL SHEET

Client OPW

Project Title South Eastern CFRAM Study

Document Title IBE0601Rp0015_HA15 Hydraulics Report

Model Name Kilkenny

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

D01 Draft T. Carberry L. Howe I. Bentley G. Glasgow Limerick/Belfast 01/07/2014

Draft L. Howe / L. Howe / F01 K. Smart G. Glasgow Belfast 14.04.2015 Final R. Clements R. Clements

Draft L. Howe / L. Howe / F02 K. Smart G. Glasgow Belfast 13/08/2015 Final R. Clements R. Clements

IBE0601Rp0015 F02 South Eastern CFRAM Study HA15 Hydraulics Report – DRAFT FINAL

Table of Reference Reports Relevant Report Issue Date Report Reference Section

South Eastern CFRAM November 3.3.9 IBE0601 Rp0001_Flood Risk Review_F01 Study Flood Risk Review 2011 3.3.10

South Eastern CFRAM IBE0601Rp0008_HA 15 Inception Study Inception Report July 2012 4.3.2 Report_F02 UoM15 South Eastern CFRAM October IBE0601Rp0010_HA15_Hydrology Study Hydrology Report 4.5 2013 Report_F01 UoM15 South Eastern CFRAM January IBE0601Rp0016_South Eastern CFRAMS Study HA11-17 SC4 1.1 2014 Survey Contract Report_F01 Survey Contract Report

4 Hydraulic Model Details...... 1

4.1 Kilkenny model ...... 1

4.1.1 General Hydraulic Model Information ...... 1

4.1.2 Hydraulic Model Schematisation ...... 3

4.1.3 Hydraulic Model Construction ...... 10

4.1.4 Sensitivity Analysis ...... 20

4.1.5 Hydraulic Model Calibration and Verification ...... 21

4.1.6 Hydraulic Model Assumptions, Limitations and Handover Notes ...... 37

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4 HYDRAULIC MODEL DETAILS

4.1 KILKENNY MODEL

4.1.1 General Hydraulic Model Information

(1) Introduction:

The South Eastern CFRAM Flood Risk Review (IBE0601 Rp0001_Flood Risk Review_F01) highlighted Kilkenny, in the Nore catchment, as an AFA for fluvial flooding based on a review of historic flooding and the extents of flood risk determined during the PFRA.

Model 5 represents the Kilkenny AFA and encompasses the mid to lower reaches of the River Nore, River Baun, River Breagagh, River Pococke, River Kingsland, and associated tributaries the River Cellar, and Ardboy Stream. The Kilkenny AFA is affected by these watercourses. The River Breagagh joins the River Nore from the west in Kilkenny city; the River Pococke meets the Nore at the downstream end of the AFA. The River Baun joins the Nore just north of the AFA, and the River Kingsland just south of the AFA. The Ballyragget model is located upstream and the Thomastown model is located downstream of the Kilkenny model. All three models are sited on the River Nore.

The total contributing area at the downstream limit of the model is 1744.5km2. 71% of this area comprises the upstream Ballyragget model. A significant tributary, the River Dinin, enters the River Nore at the upstream limit of the Kilkenny model (where the Ballyragget model ends). The contributing area of the River Dinin catchment is almost 300km2 and makes up 17% of the total catchment area for the model. A further 4% of the total contributing area comes from the River Breagagh catchment, and 2% from the River Pococke catchment.

There are three gauging stations on the River Nore within the Kilkenny model:

• Station 15104 Sycamores – OPW – no flow or level data available

• Station 15002 Johns Bridge – OPW – was classified “A2” under FSU in 2004 - there is confidence 3 in flow values up to around 1.3 times Qmed. Qmed gauged is 216 m /s (based on AMAX series from 1953 to 2009, but missing 2002 – 2005 during flood relief works).

• Station 15105 Archers Grove – OPW – no flow or level data available

There is one gauging station on the River Breagagh within the Kilkenny model:

• Station 15050 Blackfriar’s Bridge – OPW – classified “C” under FSU, therefore confidence in flow

values only extends to 0.8 x Qmed. The OPW hydrometrics team have also advised that the rating is not reliable post May 2004. A new rating is required following the installation of a data logger following the flood relief works at the end of 2005. The FSU ungauged catchment descriptor 3 based equation predicts Qmed at 8.02 m /s. The OPW have not requested a rating review for this

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gauging station to be undertaken as part of the Study. However rainfall runoff modelling was 3 undertaken for this station during hydrological analysis which yielded a Qmed value of 11.1m /s that carries greater statistical certainty (Refer to UoM 15 Hydrology Report (IBE0601Rp0010) for details).

Initial Qmed estimates at the various HEPs were adjusted based on the gauges at John’s Bridge (Station 15002 - Nore) or Blackfriar’s Bridge (Station 15050 - Breagagh). However the initially estimated index flow from the Dinin River was adjusted using the upstream pivotal site at Dinin Bridge (Station 15003). Refer to UoM 15 Hydrology Report (IBE0601Rp0010) for full details on hydrology estimation.

The Kilkenny Flood Relief Scheme was completed in 2005. It consisted of a combination of river widening and deepening, flood walls, embankments and associated drainage works.

A number of rivers have been identified as HPW within the Kilkenny Model, including Ardboy River, Baun River, Breagagh River, Cellar River, Crokershill Link River, Kingsland River, Pococke River, Robertshill Link River and a portion of the River Nore which passes through the AFA. These reaches have been modelled as 1D-2D using the MIKE suite of software. Upstream and downstream of the AFA, the River Nore is designated as MPW and has been modelled as 1D.

(2) Model Reference: HA15_KILK5

(3) AFAs included in the model: KILKENNY

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

Reach ID Name 15NORE NORE_E

15POCO POCOCKE

15ROBE ROBERTSHILL LINK

15ARDB ARDBOY (STREAM)

15BAUN BAUN_A

15BAUN BAUN_B

15BREA BREAGAGH

15CELL CELLAR

15CROK CROKERSHILL LINK

15KLND KINGSLAND

15NORE NORE_F

(5) Software Type (and version):

(a) 1D Domain: (b) 2D Domain: (c) Other model elements: MIKE 11 (2011) MIKE 21 – Rectangular Mesh MIKE FLOOD (2011) (2011)

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4.1.2 Hydraulic Model Schematisation

(1) Map of Model Extents:

Figure 4.1.1: Overview Map of Model Extents – Kilkenny Model

Figure 4.6.1 illustrates the extent of the modelled catchment, the river centre line, HEP locations and AFA extents. The Nore catchment contains 7 Upstream Limit HEPs, 1 Downstream Limit HEP, 3 Intermediate HEPs, 8 Tributary HEPs (five of which are modelled) and 2 Gauging Station HEPs.

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Figure 4.1.2: Enlarged View of the Kilkenny Model at the AFA

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

River Name x y 15NORE NORE_E 254225 153205 15POCO POCOCKE 252700 158000 15ROBE ROBERTSHILL LINK 249280 455835 15ARDB ARDBOY (STREAM) 247990 157340 15BAUN BAUN_A 250281 158960 15BAUN BAUN_B 250735 159090 15BREA BREAGAGH 248745 153180 15CELL CELLAR 253825 157020 15CROK CROKERSHILL LINK 249425 156050 15KLND KINGSLAND 254300 155720 15NORE NORE_F

249555 159415 (3) Total Modelled Watercourse Length: 37.17 (km)

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(4) 1D Domain only Watercourse Length: 7.43 (km) (5) 1D-2D Domain 29.74 Watercourse Length: (km)

(6) 2D Domain Mesh Type / Resolution / Area: Rectangular / 5 metre / 56.33 (km2)

(7) 2D Domain Model Extent:

Figure 4.1.3: 2D Model Domain - Kilkenny Model

Figure 4.6.3 shows the extent of the LiDAR data used in the 2D model. Buildings are excluded from the mesh and are therefore represented as black spaces - please refer back to Chapter 3.3.2 for further details on the representation of buildings in the model.

Figure 4.6.4 shows the extent of the NDHM data used. The black line shows the river network and the red boundary represents the LiDAR extent (also seen in Figure 4.6.3). A buffer zone was created between the two datasets which were smoothed together by interpolation.

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Figure 4.1.4: NDHM Extent – Kilkenny Model

Figure 4.6.5 shows an overview of the model schematisation. Figure 4.4.6 provides a more detailed view. The overview diagram covers the model extents, showing the surveyed cross-section locations, AFA boundary and river centrelines. It also shows the area covered by the 2D model domain. The detailed view has been provided for the area 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 4.6.3(1), along with the location and extent of the links between the 1D and 2D models.

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Figure 4.1.5: Kilkenny Model Schematic - Overview

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Figure 4.1.6: Kilkenny Model Schematic - Critical Structures

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(8) Survey Information

(a) Survey Folder Structure:

First Level Folder Second Level Folder Third Level Folder

CCS_S15_M05_07_15NORE_E 15NORE_E Data Files _WP2_Finals_131118 15NORE_E Drawings Kilkenny 15NORE_E PDF P635-15NORE-LP CCS: Surveyor Name P635-15NORE-LS S15: South Eastern CFRAM Study Area, Hydrometric Area 15 P635-15NORE-XS

M05: Model Number 05 Photos (Naming 15NORE: River Reference convention is in the

WP2: Work Package 2 format of Cross-Section ID and orientation - Final: Version upstream, downstream, 131118: Date Issued (18th NOV 2013) left bank or right bank)

(b) Survey Folder References:

Reach ID Name File Ref.

15NORE NORE_E CCS_S15_M05_07_15NORE_E _WP2_Finals_131118

15POCO POCOCKE CCS_S15_M05_15POCO_WP2_Finals_130118

15ROBE ROBERTSHILL LINK CCS_S15_M05_15ROBE_WP2_Finals_130118

15ARDB ARDBOY (STREAM) CCS_S15_M05_15ARDB _WP2_Finals_130118

15BAUN BAUN_A CCS_S15_M05_15BAUN_A_WP2_Finals_130118

15BAUN BAUN_B CCS_S15_M05_15BAUN_B_WP2_Finals_130118

15BREA BREAGAGH CCS_S15_M05_15BREA_WP2_Finals_130118

15CELL CELLAR CCS_S15_M05_15CELL_WP2_Finals_130118

15CROK CROKERSHILL LINK CCS_S15_M05_15CROK_WP2_Finals_130118

15KLND KINGSLAND CCS_S15_M05_15KLND_WP2_Finals_130118

15NORE NORE_F CCS_S15_M05_15NORE_F_WP2_Finals_130121

(9) Survey Issues:

John’s Bridge (15002) gauging station (250795E 155835N (approx.) was not captured by the surveyors. Its location in the Kilkenny AFA is shown in Figure 4.6.7. The gauging board and channel, and survey cross-section upstream and downstream of gauging station have been surveyed and added to the model.

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Figure 4.1.7 Location of John’s Bridge Gauge (15002)

4.1.3 Hydraulic Model Construction

(1) 1D Structures (in-channel along See Appendix A.1 modelled watercourses): Number of Bridges and Culverts: 40

Number of Weirs: 11

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 3.4.1. A discussion on how the structures have been modelled is included in Chapter 3.3.3.

Two critical structures have been identified in the model. These are the 15BREA00601D (N76 Bridge) located on the Breagagh River (Figure 4.6.8) and 15POCO00219D (N10 Bridge) located on the Pococke River (Figure 4.6.9).

The capacity of these two structures is insufficient to convey flood flows during the modelled events (10%, 1% and 0.1% AEP). The N76 Bridge structure restricts flows during all modelled events, causing flow to build up upstream and inundating properties and agricultural land/grassland adjacent to the Breagagh River. 1 property is affected during the 10% and 1% AEP events and 7 properties are affected during the 0.1% AEP event. The N10 Bridge structure signifcantly restricts flows during the more extreme modelled events (1% and 0.1% AEP), causing flows to build up upstream where they overtop the west bank. Floodwaters inundate the road at the junction of the N77 and N10 in the Kilkenny AFA. No properties are affected, but some residential gardens are shown to flood. A longitudinal plan of the 0.1% AEP event at the N10 bridge is included in Appendix A.2. Photographs and survey details are included below in Figures 4.6.8 and 4.6.9.

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Figure 4.1.8: N76 Bridge (15BREA00601D)

Figure 4.1.9: N10 Bridge (15POCO00219D))

Two structures haven’t been included in the model, as their orifices have been considered to be too large to be hydraulically significant. The 15NORE04410D and 15NORE03718E structures are located on the Nore River. Photographs of the structures are shown in Figures 4.6.10 and 4.6.11. The maximum water level during 0.1% AEP event at 15NORE04410D and 15NORE03718E is over 5m below the soffit level of

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In addition to these, a third structure was also omitted from the model. The 02KILK00024D footbridge (shown in Figure 4.9.12) is located at the confluence of River Nore and Kilkenny Mill Race. Due to the structure’s location and thin deck (<0.2m), major instabilities are created in the model. The 10% AEP water level here is 42.60m AOD. The structure deck is 42.38m AOD and so the structure will be drowned out during the 10% AEP event and greater. The structure is therefore not considered to be hydraulically significant.

Figure 4.1.10: 15NORE03718E

Figure 4.1.11: 15NORE04410D

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Figure 4.1.12: 02KILK00024D

(2) 1D Structures in the 2D domain None (beyond the modelled watercourses):

(3) 2D Model structures: None

(4) Defences:

Type Watercourse Bank Model Start Chainage Model End (approx.) Chainage (approx.)

1 EMBANKMENT 15NORE_F RIGHT 2802 3490 (Nore) 2 EMBANKMENT 15NORE_F LEFT 3417 3839 (Nore) 3 WALL 15NORE_F RIGHT 3490 3764 (Nore) 4 WALL 15NORE_F LEFT 4354 4491 (Nore) 5 EMBANKMENT 15NORE_F LEFT 4491 4849 (Nore) 6 WALL 15NORE_F LEFT 4849 4871 (Nore) 7 EMBANKMENT 15NORE_F LEFT 4871 4957 (Nore) 8 WALL 15NORE_F RIGHT 4871 5080 (Nore) 9 WALL 15BREA RIGHT 5909 6200 (Breagagh) 10 WALL 15BREA RIGHT 6246 6294

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(Breagagh) 11 WALL 15BREA RIGHT 6333 6409 (Breagagh) (5) Model Boundaries - Inflows:

Full details of the flow estimates are provided in the Hydrology Report (IBE0601Rp0010_HA15_Hydrology Report_F01 Section 4.5 and Appendix D). The boundary conditions implemented in the model are shown below.

Figure 4.1.13: MIKE 11 Boundary Information – Kilkenny Model

A review of flows was carried out during the calibration process, and no change was made. The modelled flows match well with the estimated flows, so no change was required. As the modelled flows match the estimated flows, the time-to-peak of inflow hydrographs generated during the hydrological analysis was considered acceptable. Figure 4.6.14 below provides an example of the associated upstream hydrograph generated.

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Figure 4.1.14 Inflow Upstream, HEP 15_1850_6_RPS

The upstream boundary of the Nore catchment is located at HEP 15_1850_6_RPS (the downstream HEP for the Ballyragget model). The model node ID at this location is 15NORE05431; a point inflow was applied at this node to account for flow entering the River Nore upstream of this location. A number of distributed sources have then been applied evenly to all nodes downstream of the Upper Limit HEPs to account for flow entering the watercourses downstream. Point inflows have been eventually added at specific nodes in order to account for flow entering from main tributaries not directly included in the model.

(6) Model Boundaries – The downstream boundary condition is a Q-h relationship, based on the Downstream Conditions: cross-section at the downstream extent of the model.

There is approximately 0.8 km of overlap between the Kilkenny model and the Thomastown model, to ensure that all flow paths are accurately represented. A comparison of the generated downstream boundary Q-h relationship in the Kilkenny model was made with the modelled Q-h relationship at the same location in the Thomastown model; shown below in Figure 4.6.15. These are in close agreement with one another, up to top of bank level (31 m AOD).

In addition to this, joint probability with the Thomastown model has not been considered and a Q-h boundary was applied at the downstream extent. The Kilkenny AFA is greater than 5 km upstream of the downstream boundary of the model. Therefore backwater from the Thomastown model was not considered to have an effect on flood flows within the AFA. The Q-h boundary is to be assessed during sensitivity

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analysis. For more details see Section 6.3.1 of the Hydrology Report and Section 3.6.1 of this report.

Figure 4.1.15 Comparison of Kilkenny model downstream boundary & the simulated Q-h relationship from the Thomastown model

(7) Model Roughness:

(a) In-Bank (1D Domain) Minimum 'n' value: 0.035 Maximum 'n' value: 0.045

(b) MPW Out-of-Bank (1D) Minimum 'n' value: 0.03 Maximum 'n' value: 0.08

(c) MPW/HPW Out-of-Bank Minimum 'n' value: 0.011 Maximum 'n' value: 0.071

(2D) (Inverse of Manning's 'M') (Inverse of Manning's 'M')

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Figure 4.1.16: Map of Kilkenny Model 2D Roughness (Manning's n) values

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. Null Manning's M values on inland water bodies were corrected to Manning's n of 0.033.

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(d) Examples of In-Bank Roughness Coefficients

Ardboy River – 15ARDB00034 Ardboy River – 15ARDB00201

Figure 4.1.17: 15ARDB00034 Roughness

Manning’s n = 0.035 Figure 4.1.18: 15ARDB00201 Roughness Standard natural stream or river in stable condition Manning’s n = 0.045

River or stream with rocks and stones, shallow and weedy

Baun River – 15BAUN00045J Breagagh River – 15BREA00060

Figure 4.1.19: 15BAUN00045J Roughness Figure 4.1.20: 15BREA00060 Roughness

Manning’s n = 0.045 Manning’s n = 0.035

River or stream with rocks and stones, shallow and Standard natural stream or river in stable condition weedy

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Breagagh River – 15BREA00339 Breagagh River – 15BREA00111

Figure 4.1.21 15BREA00339 Roughness Figure 4.1.22 15BREA00111 Roughness

Manning’s n = 0.040 Manning’s n = 0.045

River with shallows and meanders and noticeable River with shallows and meanders noticeable aquatic growth aquatic growth

Cellar River – 15CELL00048 Crokershill link River – 15CROK00001

Figure 4.1.23 15CELL00048 Roughness Figure 4.1.24 15CROK00001 Roughness

Manning’s n = 0.045 Manning’s n = 0.040

River or stream with rocks and stones, shallow and River or stream with rocks and stones, shallow and weedy weedy

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Kingsland River – 15KLND00068 River Nore – 15NORE04830

Figure 4.1.25 15KLND00068 Roughness Figure 4.1.26 15NORE04830 Roughness

Manning’s n = 0.040 Manning’s n = 0.035

River with shallows and meanders and noticeable Standard natural stream or river in stable condition aquatic growth

Pococke River – 15POCO00162 Robersthill link River – 15ROBE00002

Figure 4.1.28 15ROBE00002 Roughness Figure 4.1.27 15POCO00162 Roughness Manning’s n = 0.045 Manning’s n = 0.043 River or stream with rocks and stones, shallow and River with shallows and meanders and noticeable weedy aquatic growth

4.1.4 Sensitivity Analysis

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

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4.1.5 Hydraulic Model Calibration and Verification

(1) Key Historical Floods (From IBE0601Rp0008_HA 15 Inception Report_F02 unless otherwise specified):

(a) AUG Aerial photographs were found on www.floodmaps.ie during the review process, which 2008. indicated that flooding occurred in Mountrath, Kilkenny, and Thomastown on 16th August 2008. The photographs of Kilkenny are not included as they were taken 7 hours after the event and the flood waters had receded so all flow was in-channel, leaving no visible areas of flooding. At the Kilbricken hydrometric station downstream of Mountrath, a peak level of 87.62mOD (Malin Head) was recorded with an estimated peak flow of 365m3/s (http://www.opw.ie/hydro). This was the 5th highest flood level since the station’s establishment in 1953.

A peak flood level of 43.252mOD (Malin Head) was recorded at John’s Bridge hydrometric station, where the estimated peak flow was 350m3/s as per http://www.opw.ie/hydro. A peak flood level of 44.853mOD (Malin Head) was recorded as Blackfriar’s Bridge hydrometric station.

The modelled peak water level at John’s Bridge gauge during the 10% AEP event is 43.26m AOD and the corresponding peak flow is 289.6m3/s. The model has been calibrated against the OPW John’s Bridge rating curve and it matches well with the rating curve up to its highest reliable rating of 134m3/s. The recorded peak flow for this event is above the reliable rating and as such flows cannot be calibrated. However, the recorded and modelled peak water levels match well. The modelled peak water level at Blackfriar’s Bridge during the 10% AEP event is 45.3m AOD. This is higher than the recorded peak water level of 44.853m OD. This suggests that the event on the River Nore was close to a 10% AEP event and the event on the Breagagh River was less than a 10% AEP event.

(b) NOV The historical data on www.floodmaps.ie indicated that flooding occurred in Kilkenny on th 2006. 15 November when the Breagagh River overflowed, following a rainfall of 40mm in a 24 hour period. Approximately a dozen houses near the Circular Road, with floor levels of 53.846mOD or greater, were flooded for a period of approximately 4 hours. Water was 750mm above road level at the White Bridge. A mean daily flood level of 44.6mOD (Malin) was recorded at Blackfriar’s Bridge Hydrometric Station on 16th November (as per http://www.opw.ie/hydro) – the peak flood level was not available on the website for this event.

The mean flood level at Blackfriar’s Bridge gauging station during the 10% AEP modelled event is 44.6m AOD. The peak modelled water level during the 10% AEP event is 45.3m AOD. A comparison of the modelled and recorded peak water levels suggests this event was less than a 10% AEP event. This compares well with rainfall frequency estimates taken from the OPW Hydronet website which estimates that the rainfall event was a

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20.4% AEP event. A review of the 10% AEP event flood extents show that 12 houses near Circular Road are flooded for between 4-6 hours, see Figure 4.6.30. The model validates well with these records.

During the 10% and 1% AEP modelled events, the water level along the road is approximately 500mm in depth (above road level). It is possible that this higher water level was caused by a blockage of White Bridge. Photographs taken during the survey works (presented below in Figure 4.6.29) show debris to be built up against the upstream face of the bridge.

Figure 4.1.29 10% AEP Flood Extent near Circular Road

Circular Road

Figure 4.1.30 10% AEP Flood Extent near Circular Road

th (c) OCT The historical review indicated that a flood event occurred in Kilkenny on 26 October 2006. following 25mm of rainfall over a twenty-four hour period. Prior to this rainfall event the ground was already saturated due to previous rainfall. The Breagagh River burst its banks and lands were flooded at Water Barrack Road Sports Pitch (see photograph below in Figure 4.6.32) and at Circular Road in the Robertshill area. The water level

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came to within 290mm of houses at Circular Road which have floor levels of 53.846mOD or greater. A daily average flood level of 44.53mOD (Malin) was recorded at Blackfriar’s Bridge Hydrometric Station on 26th October as per http://www.opw.ie/hydro – the peak flood level was not available on the website for this event.

The mean flood level at Blackfriar’s Bridge gauging station during the 10% AEP modelled event is 44.7m AOD. The peak modelled water level during the 10% AEP event is 45.3m AOD. A comparison of the modelled and recorded peak water levels suggests this event was less than a 10% AEP event. The rainfall frequency estimates taken from the OPW Hydronet website suggests that the rainfall event was a 76.9% AEP event. This is a low severity event; therefore as the ground was already saturated it’s likely the watercourses were near capacity and so the additional water caused this flooding.

A review of the 10% AEP event model results shows that when the modelled water level reaches 44.7m AOD at Blackfriar’s Bridge, the flood extents, shown below in Figure 4.6.31, come close to the house at Circular Road. A review of the 10% AEP event model results shows that the Water Barrack Road Sports Pitch is inundated with floodwaters from the Breagagh River, see Figure 4.6.32. The model appears to validate well with this event.

Circular Road

Figure 4.1.31 Modelled flood extents at Circular Road when the Blackfriar’s Bridge level is 44.7m AOD

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Water Barrack Road Sports Pitch

Direction photograph taken

Water Barrack Road Sports Pitch

Figure 4.1.32 10% AEP Photograph (top) and modelled flood extent (bottom) for Water Barrack Road Sports Pitch

Pre-2005 The Kilkenny Flood Defence Scheme was completed in 2005 protecting the town from the River Nore and Breagagh River. Flood defences (walls and embankments) were constructed along the River Nore and Breagagh River, as well as channel dredging and widening of the Nore River. All events below occurred before completion of the Kilkenny Flood Defence Scheme and so calibration is problematic. The modelled water level at Johns Bridge cannot be compared with any events pre-2005 as the River Nore channel was widened and dredged throughout Kilkenny and so levels and flows will now be different. The modelled water level at Blackfriar’s Bridge cannot be compared with any events pre-2005 as the watercourse has had a number of retaining walls constructed which will increase recorded water levels. Where possible comparisons have been made

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with the events and model results.

nd (d) NOV The historical review indicated that a flood event occurred in Kilkenny on 2 November 2005. 2005. Although details on the rainfall are not available, increased flows in the Breagagh River led it to overflow in the Water Barrack Road Sports Pitch area and flood these lands.

The modelled 10%, 1% and 0.1% AEP events all show floodwaters overtop the banks of the Breagagh River banks at the Water Barracks and inundate the sports pitch, to which the 10% AEP event can be seen on Figure 4.6.32. The 10% and 1% AEP events are shown at the end of the section.

(e) NOV Evidence gathered on www.floodmaps.ie indicates localised flooding outside Kilkenny th 2002. town on 27 November 2002. There are photos which show flooding of roads at Newpark Lower and Circular Road (Figure 4.6.33) as well as evidence showing other roads, fields and at least one property in areas such as Brownstown/Castleinch, Cuffesgrange, Kells Road, Bennetsbridge Road, Newpark Lower and Ballynalina were inundated by flood waters. A peak flood level of 45.07mOD (Malin) was recorded at Blackfriar’s Bridge Hydrometric Station on 27th November as per http://www.opw.ie/hydro.

Figure 4.1.33 Photographs of 2002 flooding extent at Circular Road (left) and Newpark Lower (right)

Floodwaters inundate properties on Circular Road during all events simulated (10%, 1% and 0.1% AEP), of which the 10% AEP extent of Circular Road can be seen in Figure 4.6.30. All other locations mentioned, including Newpark Lower which is photographed in Figure 4.6.33, are now considered defended and protected up to a 1% AEP event. No further verification of this event can be carried out, see note above.

(f) NOV 2000. A press article in the Kilkenny People and a letter from the County Engineer of Kilkenny County Council to the County Secretary, dated 9th November 2000, were found on www.floodmaps.ie during the historical review which indicated that a flood event occurred in Ballyragget, Kilkenny, Thomastown, Inistioge, and Ballyhale on November 2000. The

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flooding was caused by heavy rainfall causing the River Nore to overflow.

In Kilkenny, Irishtown, Green Street, Johns Quay, Bateman Quay, St. Canice's Place and Water Barracks were flooded. Approximately 100 premises were flooded and 24 properties were evacuated by their owners or occupiers during the flood. A peak flood level of 44.9mOD (Malin) was recorded at Blackfriar’s Bridge Hydrometric Station on 6th November as per http://www.opw.ie/hydro.

Floodwaters overtop the banks of the Breagagh River banks at the Water Barracks during all events simulated (10%, 1% and 0.1% AEP), Figure 4.6.32 shows the 10% AEP flood extent. All other locations mentioned are now considered defended and protected up to a 1% AEP event. No further verification of this event can be carried out, see note above.

rd (g) NOV A memo dated 3 December 1997 was found on www.floodmaps.ie during the historical 1997. review process, from a Senior Executive Engineer of Kilkenny Corporation to the County Engineer of Kilkenny County Council, which indicated that flooding occurred in Kilkenny following heavy rainfall on 17th November 1997. Houses were flooded at Green Street, Irishtown and Vicar Street. A peak flood level of 45.38mOD (Malin) was recorded at Blackfriar’s Bridge Hydrometric Station on 18th November, while a peak flood level of 44.21mOD (Malin) and a corresponding peak flow of 281m3/s were recorded at John’s Bridge Hydrometric Station on 18th November, as per http://www.opw.ie/hydro.

No verification of this event can be carried out, see note above.

th (h) JAN 1996. Kilkenny, Callan, Thomastown and Inistioge endured floods on 6 January 1996 following heavy rainfall. Press articles from the Kilkenny People and the Munster Express were found on www.floodmaps.ie containing information on this event.

In Kilkenny flooding occurred when the Breagagh and Nore Rivers burst their banks. A peak flood level of 45.04mOD (Malin) was recorded at Blackfriar’s Bridge Hydrometric Station on 7th January, while a peak flood level of 44.09mOD (Malin) and a corresponding peak flow of 263m3/s were recorded at John’s Bridge Hydrometric Station, as per http://www.opw.ie/hydro.

Floodwaters overtop the banks of the Breagagh River banks at the Water Barracks during all events simulated (10%, 1% and 0.1% AEP), of which Figure 4.6.32 shows the 10% AEP event. No further verification of this event can be carried out, see note above.

(i) JAN 1995. A Kilkenny People press article, a Kilkenny Corporation memo to the County Manager (dated 31st January 1995) and OPW notes found in www.floodmaps.ie indicated that a flood event occurred in Ballyragget, Kilkenny, Callan and Thomastown at the end of January 1995. The flooding was caused by heavy rainfall.

In Kilkenny, the River Nore burst its banks flooding 10 properties on John Street, 20

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properties on John's Quay, one property on Bateman’s Quay, 12 properties on Green Street, 20 properties in Irishtown and six properties on Vicar Street. Most of these were private dwellings. The minimum cost of the damage was estimated at IR£28,000 in a memo from a Senior Executive Engineer of Kilkenny Corporation to the County Manager, dated 31st January 1995. This was based on an allowance of IR£400 per property; however it was estimated that in some cases the costs involved could be up to IR£2,500 per property. A peak flood level of 44.3mOD (Malin) and a corresponding peak flow of 297m3/s were recorded at John’s Bridge Hydrometric Station, as per http://www.opw.ie/hydro.

No verification of this event can be carried out, see note above.

(j) FEB 1990. The historical data indicated that flooding occurred in Ballyragget, Freshford, Kilkenny, and Callan on 6th February 1990. Press articles from the Irish Independent, Kilkenny People, Munster Express and the Cork Examiner were found on www.floodmaps.ie containing information on the event.

In Kilkenny, there was over 600mm of water on Green Street houses. John’s Quay was under approximately 1m of water (reported as several feet). Houses and shops in Irishtown and Vicar Street were inundated to a depth of several centimetres. A peak flood level of 44.31mOD (Malin) and a corresponding peak flow of 299m3/s were recorded at John’s Bridge Hydrometric Station, as per http://www.opw.ie/hydro.

No calibration of this event can be carried out, see note above.

(k) AUG The review of information indicated that a flood event occurred in Ballyragget, Freshford, th 1986. Kilkenny and Callan on 25 August 1986 due to heavy rainfall. Press articles from the Kilkenny People and the Cork Examiner were found on www.floodmaps.ie containing information on the event.

In Kilkenny the Nore and Breagagh rivers burst their banks causing flooding on John's Quay, John Street and Irishtown. Vicars Street was flooded to a depth of 0.3m while Green Street was flooded to a depth of 0.1-0.15m. Flood levels for Kilkenny at different locations as recorded in a letter from M.C. O’Sullivan Consulting Engineers to Kilkenny Corporation (dated 4th September 1986) can be seen below and give an indication of flooded areas.

Table 4.6.1: Kilkenny Flood Levels – August 1986

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Lowest floor Flood Level Street Level Location level of house (mOD Malin) (mOD Malin) (mOD Malin) River Nore Upstream of Green's 45.30 44.80 (land level) - Bridge. Green's Street 44.95 44.73 44.83 Upstream of Green's 44.70 45.00 44.93 Bridge weir Adjacent to OPW Guaging 44.20 43.80 - station At Library 44.15 43.50 43.77 Upstream of weir no. 2 43.45 43.25 - Downstream of weir no. 2 43.00 43.10 - Lacken walk 42.15 41.60 - River Breagagh Waterbarracks 46.00 46.00 45.8-45.3 Watergate 44.76 44.60 44.62

A peak flood level of 44.2mOD (Malin) and a corresponding peak flow of 281m3/s were recorded at John’s Bridge Hydrometric Station, as per http://www.opw.ie/hydro.

The modelled peak water level at the Water Barracks is 46.6-47.2m AOD and at Watergate is 45.0m AOD along the Breagagh River during the 10% AEP modelled event. This suggests this event was less than a 10% AEP event. However, as noted above, flood mitigation works have been carried out, so modelled water levels are likely to be lower than the recorded levels pre-mitigation.

In addition, no calibration can be made with the recorded water levels along the Nore, as the river has since been dredged and so modelled flood levels will be lower. Flooding no longer occurs on Vicars Street or Green Street therefore depths cannot be compared.

th (l) JAN 1984. The historical review indicated that a flood event occurred in Kilkenny on 16 January. According to T.J. O’Connor & Associates Consulting Engineers (July 1998) “Report on flooding of the Lower Robercon Area, New Road, Co Wexford”, the flood had an AEP of approximately 10%. A peak level of 44.26mOD (Malin) and a corresponding flow of 285.9m3/s were recorded at John’s Bridge Hydrometric Station, as per the same report. No information on damage caused by the flood was found.

No calibration of this event can be carried out, see note above.

th (m) DEC A flood event was found to have occurred in Kilkenny on the 27 December 1979. The 1979. Nore and Breagagh Rivers broke their banks and an Irish Independent article described how floodwater rose to approximately 900mm deep in parts of John Street, Irishtown and John's Quay. A consultant’s report estimated that the flood had an AEP of approximately

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10%. A peak level of 44.31mOD (Malin) and a corresponding flow of 289m3/s were recorded at John’s Bridge Hydrometric Station.

No calibration of this event can be carried out, see note above.

th (n) DEC A flood event was found to have occurred on 27 December in Kilkenny due to heavy 1978. rainfall. An Irish Times article described how John's Quay and Blackmill Street were flooded. According to a consultant’s report, the flood had an AEP of approximately 20%. A peak level of 44.12mOD (Malin) and a corresponding flow of 259m3/s were recorded at John’s Bridge Hydrometric Station as outlined in the same consultant’s report.

No calibration of this event can be carried out, see note above.

th (o) JAN 1974. A flood event was found to have occurred on 8 January in Kilkenny due to heavy rainfall. A consultant’s report estimated that, the flood had an AEP of approximately 20%. A peak level of 44.09mOD (Malin) and a corresponding flow of 255m3/s were recorded at John’s Bridge Hydrometric Station. No information on damage caused by the flood was found.

No calibration of this event can be carried out, see note above.

(p) DEC The review of the data indicated that a flood event occurred in Mountrath, Kilkenny and th 1968. Rathdowney on 25 December 1968. Details were contained in an Irish Independent press article downloaded from www.floodmaps.ie.

In Kilkenny 48 hours of continuous rainfall caused the Nore and Breagagh rivers to break their banks. This was the largest flood since 1947 with an approximate AEP of 4% (T.J. O’Connor & Associates Consulting Engineers (July 1998) “Report on flooding of the Lower Robercon Area, New Road, Co Wexford”,). Flooding occurred at Blackmill St, Green St., Greens Bridge and John St. A peak level of 44.83mOD (Malin) and a corresponding flow of 378m3/s were recorded at John’s Bridge Hydrometric Station as outlined in a consultant’s report.

No calibration of this event can be carried out, see note above.

(q) DEC Review of the historical data indicated that flooding occurred in Kilkenny, Callan, st 1960. Thomastown and Inistioge on 1 December caused by heavy rainfall and snowmelt. Information on the event was found on www.floodmaps.ie in the form of photos and as press articles from the Kilkenny Journal, Kilkenny People, Munster Express, Irish Independent, Irish Times, Cork Examiner and Evening Press (Dublin).

In Kilkenny, the Nore and Breagagh Rivers broke their banks flooding Blackmill Bridge, John's Quay and the Dominican Black Abbey. Houses were flooded in the low lying areas of the town. The event had an AEP of approximately 10% (T.J. O’Connor & Associates Consulting Engineers (July 1998) “Report on flooding of the Lower Robercon Area, New

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Road, Co Wexford”,) and, at the time, it was the largest flood since 1947. A peak level of 44.29mOD (Malin) and a corresponding flow of 309.8m3/s were recorded at John’s Bridge Hydrometric Station.

No calibration of this event can be carried out, see note above.

(r) OCT 1954. The historical review indicated that a flood event occurred in Kilkenny, Callan and Thomastown on 29th October caused by heavy rainfall. An Irish Independent press article and Kilkenny Corporation correspondence (dated 9th November 1954) were found on www.floodmaps.ie containing details of the event.

In Kilkenny, John Street was flooded to a depth of 400mm, the Dominican Black Abbey was flooded and Waterbarrack road was also flooded. The flood had an estimated AEP of 10%, while a peak level of 44.153mOD (Malin) and a corresponding flow of 287.9m3/s were recorded at John’s Bridge Hydrometric Station.

Waterbarrack road is shown to flood in the modelled 10% AEP results. No further verification of this event can be carried out, see note above.

th (s) MAR A major flood event was found to have occurred on 14 March in Freshford, Kilkenny, 1947. Callan, Thomastown and Inistioge. Information on the event was contained in press articles from the Kilkenny Journal, Kilkenny People and the Irish Independent, downloaded from www.floodmaps.ie.

Kilkenny suffered the second worst known flood in the history of the area, second only to the flood of October 1763. The flood had an AEP of less than 0.5% (T.J. O’Connor & Associates Consulting Engineers (July 1998) “Report on flooding of the Lower Robercon Area, New Road, Co Wexford”,). There was severe flooding in the town, particularly in John Street, Irishtown, Vicar Street and Green Street. A peak level of 45.81mOD (Malin) and a corresponding flow of 520m3/s were recorded at Smithwick’s Brewery. A report by Kilkenny County Council stated that a local committee investigation found that 235 houses were rendered temporarily unfit for habitation and some houses were rendered permanently unfit, while damage to furniture and goods was estimated at IR£14,000.

No calibration of this event can be carried out, see note above.

th (t) AUG 1946. A flood event was found to have occurred in Kilkenny on 12 August when heavy rainfall caused the Nore and Breagagh River to burst their banks. A peak level of 44.67mOD (Malin) and a corresponding flow of 302m3/s were recorded at Smithwick’s Brewery.

No calibration of this event can be carried out, see note above.

st (u) MAR A flood event was found to have occurred in Kilkenny on 1 March 1933 when heavy 1933. rainfall caused the Nore and Breagagh River to burst their banks. The flood had an

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approximate AEP of 4%. A peak level of 44.75 mOD (Malin) and a corresponding flow of 314m3/s were recorded at Smithwick’s Brewery (T.J. O’Connor & Associates Consulting Engineers (July 1998) “Report on flooding of the Lower Robercon Area, New Road, Co Wexford”,).

No calibration of this event can be carried out, see note above.

rd (v) NOV A flood event was found to have occurred in Kilkenny on 23 November 1931 following 1931. heavy rainfall. The flood had an approximate AEP of 2%. A peak level of 45.17mOD (Malin) and a corresponding flow of 390m3/s were recorded at Smithwick’s Brewery.

No calibration of this event can be carried out, see note above.

(w) JAN Review of the historical data on www.floodmaps.ie indicated that flooding occurred in th 1926. Kilkenny and Thomastown on 29 January following a period of heavy rainfall.

In Kilkenny, a peak level of 44.99mOD (Malin) and a corresponding flow of 359m3/s were recorded at Smithwick’s Brewery. The flood had an approximate AEP of 2%. No information on damage caused by the flood was found.

No calibration of this event can be carried out, see note above.

(x) OCT Review of the historical data indicated that flooding occurred in Kilkenny, Thomastown nd 1763. and Inistioge on 2 October caused by 24 hours of incessant rain. It was reported that every bridge on the Nore was washed away except for one in Ballyragget and one in Inistioge, which was badly damaged. This is the worst known flood in the history of the area.

In Kilkenny, Johns Bridge was washed away. Fourteen men and women on the bridge died when it collapsed. Greens Bridge was also washed away.

No calibration of this event can be carried out, see note above.

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Figure 4.1.34 Defended 10% AEP flood event of Kilkenny Town Centre within AFA extent

Figure 4.1.35 Defended 1% AEP flood event of Kilkenny Town Centre within AFA extent

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Summary of Calibration There are a large number of historic events to calibrate the model to in the AFA. However, the majority of these occurred before the Kilkenny Flood Relief Scheme (walls, embankments, dredging, channel widening) was completed and so the modelled flood extents, flows and levels are now different. Of the three events which have occurred since the works were completed, the known flood extents validate well with the modelled flood extents.

John’s Bridge gauge is the only gauge to have a reliable rating, unfortunately the recorded peak levels/flows are above the reliable rating. Therefore, calibration with gauged data was not possible.

The modelled flood extents match the recorded flood extents well for all recorded events, showing the model is validated well again to the higher frequency events (10% AEP). There are limited estimates for frequencies of the recorded events. A number of estimates have been made using the modelled results; however, these are limited to the 10% AEP event.

The model calibrates well with the John’s Bridge rating curve up to its reliable rating. No calibration with the Blackfriar’s gauge rating curve was possible as the OPW rating curve requires updating.

A mass balance check has been carried out on the model to ensure that the total volume of water entering and leaving the model at the upstream and downstream boundaries balances with the quantity of water remaining in the model domain at the end of a simulation. The mass error in the 1% AEP design run was 1.24%, which is within acceptable limits (Section 3.11 of this report details acceptable limits).

Model flows were validated against the estimated flows at HEP check points to ensure the model is well anchored to hydrological estimates. For example, at HEP 15_521_3_RPS, the estimated flow during the 1% AEP event was 449.21 m3/s and the modelled flow was 455.02 m3/s. Refer to appendix A.3 for flow tables.

There are no significant instabilities shown in the model results. Overall, the model is performing well and is supported by historic information. No calibration with recorded gauge data was possible due to the limited flood events following the flood mitigation works.

(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 Type Watercourse Bank Modelled Standard Reference of Protection (AEP)

1 EMBANKMENT 15NORE_F (Nore) RIGHT 10% AEP - 1% AEP

2 EMBANKMENT 15NORE_F (Nore) LEFT 1% AEP - 0.1% AEP

3 WALL 15NORE_F (Nore) RIGHT 10% AEP - 1% AEP

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4 WALL 15NORE_F (Nore) LEFT 1% AEP - 0.1% AEP

5 EMBANKMENT 15NORE_F (Nore) LEFT 1% AEP - 0.1% AEP

6 WALL 15NORE_F (Nore) LEFT 0.1% AEP

7 EMBANKMENT 15NORE_F (Nore) LEFT 0.1% AEP

8 WALL 15NORE_F (Nore) RIGHT 10% AEP

9 WALL 15BREA (Breagagh) RIGHT 1% AEP

10 WALL 15BREA (Breagagh) RIGHT 1% AEP

11 WALL 15BREA (Breagagh) RIGHT 1% AEP

1

2

3

11 6 7 10 5

9 8 4

Figure 4.1.36: Map of 11 Formal Flood Defences in the Kilkenny AFA. There are 11 formal defences (7 walls and 4 embankments) in the Kilkenny AFA. A map of these defences is included below. The majority of the defences are located along the right and left banks of the River Nore, and the remaining three are located along the right bank of the Breagagh River. All of the defences have been represented using the survey crest heights. However, Defence 3 is a wall with approximately 20 open pipes (Est. 0.15m diameter) located approximately 0.4m above ground level. These pipes would allow flood flows to pass through them during a flood event as such the crest height of this defence has been set using the surveyed invert levels of the 20 pipes. The pipes do not have non-return flaps/valves fitted on them to prevent water passing through them.

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The OPW have provided undefended flood extents (see below), showing the area that would flood during the 1% AEP event if the flood defences were removed.

Figure 4.1.37 OPW 1% AEP Flood Event without Defences

(4) Gauging Stations:

There are four gauging stations in total, 3 on the River Nore and 1 on the River Breagagh. The three gauging stations located on the River Nore are detailed below: a) Sycamores (15104)

This gauging station has no flow data and only a short water level record available (2006 - 2010) available for calibration; as such no rating comparison has been made. b) Johns Bridge (15002)

This gauging station has a FSU rating of A2, suggesting that there is confidence in the rating up to around 3 1.3 times the Qmed. The OPW Qmed value for the station is 216 m /s (based on AMAX series from 1953 to 2009, but missing 2002 – 2005 during flood relief works). Flood mitigation works carried out in Kilkenny have altered the reliability of the OPW rating curve. This rating is now reliable up to the highest gauged flow of 134m3/s (water level of 42.57m OD); flow values above this have been extrapolated and should be treated with caution. A comparison of the OPW rating curve and the modelled RPS rating curve are shown

IBE0601Rp0015 4.6 - 35 F02 South Eastern CFRAM Study HA15 Hydraulics Report – DRAFT FINAL in Figure 4.6.38. This shows the curves to be in close agreement (within 0.1m) up to the reliable rating.

Figure 4.1.38: Comparison of Existing OPW Rating Curve, RPS Rating Curve, and Spot Gaugings c) Archers Grove (15105)

This OPW gauging station has no flow data and only a short water level record available (2006 - 2010) available for calibration, as such no rating comparison has been made.

The gauging station located on the River Breagagh, a tributary of the River Nore is: d) Blackfriar’s Bridge (15050)

This gauging station has a FSU rating of C, therefore confidence in flow values only extends to 0.8 x Qmed. The OPW have advised that the rating is not reliable post May 2004, and that a new rating is required following the installation of a data logger following the flood relief works at the end of 2005. As such, no rating comparison has been made. The OPW have not requested a rating review for this gauging station is undertaken as part of the Study.

There is also a gauging station located on the River Dinin upstream of its confluence with the River Nore. This is detailed in the hydrology report and was used in estimation of flow from the River Dinin entering the model. However the River Dinin itself is not part of the Kilkenny model and so this gauging station has not been used for calibration.

(5) Other Information:

None

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4.1.6 Hydraulic Model Assumptions, Limitations and Handover Notes

(1) Hydraulic Model Assumptions:

(a) The in-channel structure and floodplain roughness coefficients, initially selected based on normal bounds, were reviewed using aerial photography and survey data during the calibration process. It is considered that the selected values are representative.

(b) A review of flows was carried out during the calibration process and no changes were made. The time- to-peak of inflow hydrographs generated during the hydrological analysis has also been reviewed and no changes were made.

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

(d) 15NORE03718E and 15NORE04410D were not included in the model as in each case their orifice is too large to be hydraulically significant.

(e) 02KILK00024D was not included in the model as it causes major model instabilities due to the thin deck size. It will be drowned quickly during the 10% AEP event and so is not considered to be hydraulically significant.

(f) It should be noted that observed flooding of rural roads and outlying properties may be represented less accurately than flooding within the AFA. The MPW is modelled using cross section data only; it was found during the preparation of the draft flood maps that the cross sections did not contain enough data on the left and right banks. As water levels increased, the floodplain could not be accurately represented as water was not able to spill as required. During the preparation of the draft final flood maps, the most upstream and downstream of cross sections on the Nore River, from chainage -3982m to 86m and chainage 10888m to 14417m, were extended with the use of the NDHM to provide enough information on the floodplain and to allow water to spill as necessary. Background mapping from the NDHM was applied to the MPW which allowed for more accurate floodplain representation between the 1D cross sections. Finally, specific areas where floodwaters were still subject to glass-walling beyond the 1D cross sections were highlighted and connected to the nearest cross section to produce a more accurate mapping output. It should be noted that this method simply projects the water level from the associated cross section onto the topography. This methodology is further discussed in Section 3, essentially it provides no attenuation for the MPW but provides improved mapping. This is reflected in the model check flows which are discussed in Appendix A.3.

(2) Hydraulic Model Limitations and Parameters:

(a) Grid cell size is 5 m. Features smaller than 5 m wide, such as walls or flow paths, may not be accounted for within the 2D domain. This may be less accurate in urban areas.

(b) Out-of-bank flooding in the 1D-only MPW reaches of the model may be over-conservative due to the mapping techniques used.

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(c) 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 assumed to be 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.

(d) All culverts with only the upstream or downstream face surveyed have had the upstream invert level raised by 0.02m to improve model stability. This was only used where structures were of a short length (less than 10 m) and so this will have a negligible effect on the model results.

(e) Defences 1 & 3 on the River Nore were designed to protect the adjacent land during the 1% AEP event. The defences were reviewed and are accurately replicated in the model. It was found that Defence 1 is overtopped in two locations (see below, arrows show overtopping location) during the 1% AEP event. The water level at the defence is 45.3m AOD; the majority of the embankment is above this level, except two short stretches ranging between 45.18-45.23m AOD. The wall is overtopped at these low points flooding a small area of New Road Bridge. Defence 3 is overtopped as the water level exceeds the height of the invert levels of the small pipes (see Figure 4.6.39 below), red circle shows rough location of pipes through flood defence). The pipes do not have non-return flaps/valves fitted on them to prevent water passing through them.

Figure 4.1.39 1% AEP flood extent as Defence 1 is overtopped

Hydraulic Model Parameters:

MIKE 11

Timestep (seconds) 1

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Wave Approximation High Order Fully Dynamic

Delta 0.85

MIKE 21

Timestep (seconds) 1

Drying / Flooding depths (metres) 0.02 / 0.03

Eddy Viscosity (and type) 0.5 (Flux Based)

MIKE FLOOD

Link Exponential Smoothing Factor River Kingsland Ch 975 -1241: 0.8

(where non-default value used) River Nore Ch 4518 – 5196: 0.8

Kilkenny Mill Race Ch 0 – 255: 0.8

Lateral Length Depth Tolerance (m) Default

(where non-default value used)

(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.

Model results show the AFA to experience limited flooding from the River Nore during the 10% and 1% AEP events. This is due to a number of flood defences (retaining walls and embankments) along the River Nore. During lower frequency events (0.1% AEP) the AFA is shown to experience large amounts of flooding as the flood defences along the River Nore are overtopped. This flooding inundates an area along the right bank of the River Nore upstream of the confluence with the Breagagh River, and along the left bank around the John’s Bridge area. During the 0.1% AEP event, 152 properties are shown to flood.

Model results show the town centre (at the centre of the AFA) to experience limited flooding from the Breagagh River during the 10% and 1% AEP events. This is due to a number of flood defences (retaining walls and embankments) along the Breagagh River. Further upstream on the outskirts of the AFA, both the Breagagh River and its tributary Ardboy River exceed channel capacity during these events, flooding the local area. This flooding affects grassland and 16 properties off Circular Road during the 10% AEP event. The flood extent widens, affecting 35 properties off Circular Road during the 1% AEP event. During lower frequency events (0.1% AEP), all of the AFA is shown to experience large amounts of flooding as the flood defences along the Breagagh River are overtopped and flows exceed channel capacity upstream of the defences. In the 0.1% AEP event, 70 properties are shown to flood on Circular Road. During this event, floodwaters overtop the defences along the Breagagh River in the area around Blackfriar’s Bridge affecting 113 properties. A culvert structure, 15BREA00024E, diverting flow beneath Watergate, restricts flows in the Breagagh River during all events simulated.

Model results show the AFA to experience some flooding from the Pococke River and Kingsland River during all simulated design events (10%, 1% and 0.1% AEP). This flooding is due to the incapacity of the

IBE0601Rp0015 4.6 - 39 F02 South Eastern CFRAM Study HA15 Hydraulics Report – DRAFT FINAL channels. This flooding inundates grassland and roads, but does not affect any properties.

(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: Laura Howe

Model Reviewed by: Stephen Patterson

Model Approved by: Malcolm Brian

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APPENDIX A.1

MODELLED STRUCTURES

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STRUCTURE DETAILS – BRIDGES SPRING HEIGHT RIVER LENGTH OPENING SHAPE HEIGHT WIDTH MANNING’S CHAINAGE ID FROM BRANCH (m) (m) (m) N INVERT (m) Bridges BAUN 320 15BAUN00045J 250 CIRCULAR 0.20 0.20 - 0.015 Cellar 650 15CELL00110I 65.9 CIRCULAR 1.50 1.50 - 0.018 Cellar 351 15CELL00137I 7.25 CIRCULAR 0.85 0.85 - 0.012 Pococke 1000 15POCO00288D 7.23 1 of 2 ARCHES (LW TABLE) 1.43 4.04 0.49 0.021 Pococke 1000 15POCO00288D 7.23 2 of 2 ARCHES (LW TABLE) 1.5 4.06 0.21 0.021 Pococke 1700 15POCO00219D 7.34 1 of 3 ARCHES (LW TABLE) 1.89 2.86 1.15 0.021 Pococke 1700 15POCO00219D 7.34 2 of 3 ARCHES (LW TABLE) 1.89 2.38 0.8 0.021 Pococke 3123 15POCO00078D 10.1 1 of 2 ARCHES (LW TABLE) 2.01 4.59 0.45 0.022 Pococke 3123 15POCO00078D 10.1 1 of 2 ARCHES (LW TABLE) 1.87 3.95 1.01 0.022 Pococke 3182 15POCO00073D 10.4 1 of 2 RECTANGULAR (LW TABLE) 2.12 2.48 0 0.013 Pococke 3182 15POCO00073D 10.4 2 of 2 RECTANGULAR (LW TABLE) 2.12 2.45 0 0.013 NORE 3609 01KILK00217D 6.5 3 of 5 ARCHES (LW TABLE) 7.24 9.45 3.85 0.020 NORE 3609 01KILK00217D 6.5 2 of 5 ARCHES (LW TABLE) 6.36 7.76 4.06 0.020 NORE 14154 15NORE03629D 7.66 2 of 6 ARCHES (LW TABLE) 7.44 11.84 2.24 0.022

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SPRING HEIGHT RIVER LENGTH OPENING SHAPE HEIGHT WIDTH MANNING’S CHAINAGE ID FROM BRANCH (m) (m) (m) N INVERT (m) NORE 14154 15NORE03629D 7.66 2 of 6 ARCHES (LW TABLE) 7.04 10.07 1.84 0.022 NORE 14154 15NORE03629D 7.66 1 of 6 ARCHES (LW TABLE) 4.93 7.50 1.89 0.022 NORE 14154 15NORE03629D 7.66 1 of 6 ARCHES (LW TABLE) 4.97 7.46 1.97 0.022 Kingsland 898 15KLND00088D 24.6 1 of 3 ARCHES (LW TABLE) 1.39 1.94 0.75 0.022 Kingsland 898 15KLND00088D 24.6 1 of 3 ARCHES (LW TABLE) 1.46 1.50 0.97 0.022 Kingsland 898 15KLND00088D 24.6 1 of 3 ARCHES (LW TABLE) 1.36 1.74 0.83 0.022 Breagagh 479 15BREA00601D 15.8 1 of 2 RECTANGULAR (LW TABLE) 1.87 3.66 0 0.020 Breagagh 479 15BREA00601D 15.8 1 of 2 RECTANGULAR (LW TABLE) 1.93 3.66 0 0.020 Breagagh 1821 15BREA00469D 8.6 1 of 3 ARCHES (LW TABLE) 2.69 2.62 1.49 0.025 Breagagh 1821 15BREA00469D 8.6 1 of 3 ARCHES (LW TABLE) 2.84 3.12 1.47 0.025 Breagagh 1821 15BREA00469D 8.6 1 of 3 ARCHES (LW TABLE) 2.77 2.78 1.42 0.025 Breagagh 1989 15BREA00451D 4 1 of 2 ARCHES (LW TABLE) 1.54 2.39 1.02 0.022 Breagagh 1989 15BREA00451D 4 1 of 2 ARCHES (LW TABLE) 1.59 2.50 1.12 0.022 Breagagh 2830 15BREA00371D 16.5 1 of 3 ARCHES (LW TABLE) 1.75 1.98 1.11 0.025 Breagagh 2830 15BREA00371D 16.5 1 of 3 ARCHES (LW TABLE) 1.67 3.10 0.99 0.025 Breagagh 2830 15BREA00371D 16.5 1 of 3 ARCHES (LW TABLE) 1.72 1.81 1.29 0.025

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SPRING HEIGHT RIVER LENGTH OPENING SHAPE HEIGHT WIDTH MANNING’S CHAINAGE ID FROM BRANCH (m) (m) (m) N INVERT (m) Breagagh 3442.5 15BREA00309D 0.5 1 of 3 ARCHES 1.83 2.9 1.35 0.025 Breagagh 3442.5 15BREA00309D 0.5 2 of 3 ARCHES 1.71 2.96 1.29 0.025 Breagagh 3984 15BREA00257D 7.5 1 of 3 ARCHES (LW TABLE) 1.46 2.48 0.79 0.025 Breagagh 3984 15BREA00257D 7.5 1 of 3 ARCHES (LW TABLE) 1.99 3.57 0.76 0.025 Breagagh 3984 15BREA00257D 7.5 1 of 3 ARCHES (LW TABLE) 1.28 2.43 1.31 0.025 Breagagh 4886.25 15BREA00172D 5.6 1 of 2 ARCHES (LW TABLE) 3.39 4.21 2.16 0.022 Breagagh 4886.25 15BREA00172D 5.6 1 of 2 ARCHES (LW TABLE) 3.42 4.7 2.14 0.022 Breagagh 6205 15BREA00043D 8.3 1 of 3 ARCHES (LW TABLE) 2.21 2.84 1.39 0.025 Breagagh 6205 15BREA00043D 8.3 1 of 3 ARCHES (LW TABLE) 2.59 3.72 1.21 0.025 Breagagh 6205 15BREA00043D 8.3 1 of 3 ARCHES (LW TABLE) 2.22 3.00 1.18 0.025 Breagagh 6378 15BREA00024E 29.5 1 of 2 ARCHES (LW TABLE) 1.99 2.44 0.86 0.025 Breagagh 6378 15BREA00024E 29.5 1 of 2 ARCHES (LW TABLE) 1.91 2.69 0.96 0.025 Ardboy 652 15ARDB00230D 7.4 1 of 2 ARCHES (LW TABLE) 1.85 2.87 0.42 0.025 Ardboy 652 15ARDB00230D 7.4 1 of 2 ARCHES (LW TABLE) 2.89 2.69 1.18 0.025 Ardboy 2877 15ARDB00012E 6.4 CROSS-SECTION DB 1.24 2.22 0 0.022 Ardboy 1266 15ARDB00170D 3.4 CROSS-SECTION DB 1.59 3.45 0 0.022

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SPRING HEIGHT RIVER LENGTH OPENING SHAPE HEIGHT WIDTH MANNING’S CHAINAGE ID FROM BRANCH (m) (m) (m) N INVERT (m) Ardboy 1692.5 15ARDB00130D 5.1 CROSS-SECTION DB 0.85 2.59 0 0.022 Ardboy 2044.51 15ARDB00095D 4.3 CROSS-SECTION DB 1.40 3.27 0 0.025 Ardboy 2126 15ARDB00085E 19.7 CROSS-SECTION DB 1.71 1.70 0 0.025 Breagagh 2914 15BREA00362D 29.1 CROSS-SECTION DB 2.05 7.49 0 0.020 Breagagh 3608 15BREA00294D 14.4 CROSS-SECTION DB 2.44 6.31 0 0.022 Breagagh 4286 15BREA00227E 10.5 CROSS-SECTION DB 2.05 7.55 0 0.025 Breagagh 6009 15BREA00062D 16.8 CROSS-SECTION DB 2.38 8.99 0 0.020 Crokershill Link 34 15CROK00001D 4.25 CROSS-SECTION DB 1.29 2.31 0 0.022 Robertshill Link 215 15ROBE00003D 4.5 CROSS-SECTION DB 1.31 2.68 0 0.022 Pococke 3801.4 15POCO00010E 6.9 CROSS-SECTION DB 1.99 6.06 0 0.022 Kingsland 970 15KLND00082D 8 CROSS-SECTION DB 2.63 5.42 0 0.022 Kingsland 1511.65 15KLND00032D 6.4 CROSS-SECTION DB 1.83 2.66 0 0.022 Pococke 1846.42 15POCO00204D 3.2 CROSS-SECTION DB 1.94 4.44 0 0.02 Pococke 3098.42 15POCO00081D 9.35 CROSS-SECTION DB 9.65 12.11 0 0.022 Pococke 1679.4 15POCO00221D 20.7 CROSS-SECTION DB 2.88 12.38 0 0.013

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SPRING HEIGHT RIVER LENGTH OPENING SHAPE HEIGHT WIDTH MANNING’S CHAINAGE ID FROM BRANCH (m) (m) (m) N INVERT (m) BAUN 1189 15BAUN00002E 6.9 CROSS-SECTION DB 1.27 2.07 0 0.018 NORE 4349.5 15NORE04606D 10 CROSS-SECTION DB 7.17 39.57 0 0.018

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Structure Details - Weirs RIVER BRANCH CHAINAGE ID Type Pococke 1829.4 15POCO00204W Broad Crested Weir

NORE 1510 15NORE04889W Broad Crested Weir

NORE 3260 01KILK00249W Broad Crested Weir

NORE 5006 01KILK00074W Broad Crested Weir

NORE 7267.94 15NORE04317W Broad Crested Weir

Kingsland 664.78 15KLND00110W Broad Crested Weir

NORE 4769 15KILK00108X Broad Crested Weir

Ardboy 2802 15ARDB00020W Broad Crested Weir

Breagagh 3434.5 15BREA00310W Broad Crested Weir

Breagagh 3591 15BREA00295X Broad Crested Weir

Nore Link2 78 01KILK00074W(Link2) Broad Crested Weir

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APPENDIX A.2

RIVER LONG SECTION PROFILES

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Peak water levels during the 10%AEP event in the Breagagh River at the Water Barracks

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N10 Bridge

Peak water levels during the 0.1%AEP event in the Breagagh River at the N10 Bridge

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APPENDIX A.3

ESTIMATED PEAK FLOW AND MODEL FLOW COMPARISON

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IBE0601 SE CFRAM STUDY

PEAK WATER FLOWS

KILKENNY (NORE) & KILKENNY AFA Name (BREAGAGH) Model Code HA15_KILK5 Status DRAFT FINAL Date extracted from model 08/04/2015

Peak Water Flows River Name & Check Flow Model Flow Chainage AEP (m3/s) (m3/s) Diff (%) 10% 289.17 207.70 -28.17 NORE 2673.39 1% 407.75 241.87 -40.68 15104_RPS 0.1% 561.49 285.65 -49.13 10% 300.24 289.59 -3.55 NORE 4320.76 1% 423.36 409.14 -3.36 15002_RPS 0.1% 582.98 574.20 -1.51 10% 1.74 1.02 -41.00 BAUN 200.5 1% 3.19 1.88 -41.00 15_671_2_RPS 0.1% 5.67 3.35 -40.94 10% 0.87 0.82 -6.68 CELLAR 1603.39 1% 1.61 2.49 +55.24 15_1323_5_RPS 0.1% 2.85 5.78 +102.40 10% 15.66 17.69 +12.92 POCOCKE 3758.24 1% 27.43 29.47 +7.44 15_1332_4_RPS 0.1% 46.49 49.29 +6.02 10% 5.33 5.25 -1.57 KINGSLAND 1499.02 1% 9.67 7.87 -18.62 15_1257_7 0.1% 16.91 13.36 -20.97 10% 3.81 3.54 -7.15 ARDBOY 2694.97 1% 7.13 6.55 -8.21 15_1922_7_RPS 0.1% 12.93 11.51 -10.96 10% 18.18 21.01 +15.55 BREAGAGH 6219.23 1% 30.26 36.08 +19.25 15050_RPS 0.1% 48.61 50.51 +3.91 10% 18.24 21.03 +15.27 BREAGAGH 6378 1% 30.35 36.11 +18.95 15_1269_4_RPS 0.1% 48.76 48.41 -0.72 10% 318.58 313.16 -1.70 NORE 14393.5 1% 449.21 455.02 +1.29 15_521_3_RPS 0.1% 618.59 646.27 +4.48

The table above provides details of flow in the model at ever HEP inflow, check point, modelled tributary and gauging station. These flows have been compared with the hydrology flow estimation and a percentage difference provided. The table shows that during all three design events (10%, 1% and 0.1% AEP) modelled flow within the River Nore (Ch 4320.76) and at the downstream boundary in the River Nore (Ch 14393.5) is within 5% of the estimated peak flow.

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The modelled peak flows in the River Nore (Ch 2673.39) are between 28-49% lower when compared with the estimated peak flows during all three design events (10%, 1% and 0.1% AEP). The River Nore here (Ch 2673.39) has high water levels which exceed channel capacity. Upstream (1km) of the HEP, large areas of land are flooded; this attenuates flow dramatically in the hydraulic model which explains the lower than estimated peak flows.

The modelled peak flows in the Baun River are between 40-41% lower when compared with estimated peak flows during all three design events (10%, 1% and 0.1% AEP). However there is significant floodplain flow within the models including a joining of the Baun and Nore floodplains. A culvert structure on the Baun River (Ch 240) further complicates floodplain flow paths and as such it is difficult to make like for like comparisons of hydrological estimates and modelled flows.

The modelled 10% AEP peak flow in the Cellar River is 6% less than the estimated peak flow, the difference is less than 0.5m3/s. The modelled 1% and 0.1% AEP peak flows in the Cellar River are between 55 and 102% more than estimated peak flow. This is due to the Pococke and Cellar floodplains joining at the confluence of the rivers, giving higher than estimated flows at the Cellar HEP.

The modelled peak flows in the Pococke River at the confluence with the River Nore are between 6-12% higher than the estimated peak flows during all simulated events (10%, 1 % and 0.1% AEP). The River Nore has high water levels which merge with the Pococke River flooplain, leading to additional flood flow and higher than estimated flows at the Pococke HEP.

The modelled 10% AEP peak flow in the Kingsland River is 1% less than the estimated peak flow, the difference is less than 0.5m3/s. The modelled 1% and 0.1% AEP peak flows in the Kingsland River are between 18 and 20% lower than the estimated peak flow. This is due to the large amounts of out of channel flow which attenuates flows in the Kingsland River, giver lower than estimated flows at the Kingsland HEP.

The modelled peak flow at the downstream limit of the Ardboy River is between 7 and 11% lower when compared with the estimated peak flow during all simulated events (10%, 1% and 0.1% AEP). Simulated flood flows exceed channel capacity upstream of the HEP and flow away from the channel.

The modelled 0.1% AEP peak flows in the Breagagh River (Chainages 6219.23 and 6378), at the confluence with the River Nore and 150m upstream of the confluence, are less than 5% higher when compared with the estimated peak flows. However, the 10% and 1% AEP modelled peak flows are between 15-19% higher when compared with the estimated peak flows. During all three simulated events the River Nore has high water levels which back up into the Breagagh River and therefore is the source of higher than estimated peak flows during the more extreme event.

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APPENDIX A.4

DELIVERABLE MODEL AND GIS FILES

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MIKE FLOOD MIKE 21 MIKE 21 RESULTS HA15_KILK5_MF_DES_Q10_1 HA15_KILK5_M21_DES_Q10_1 HA15_KILK5_M21_DES_Q10_1 HA15_KILK5_MF_DES_Q100_1 HA15_KILK5_M21_DES_Q100_1 HA15_KILK5_M21_DES_Q100_1 HA15_KILK5_MF_DES_Q1000_1 HA15_KILK5_M21_DES_Q1000_1 HA15_KILK5_M21_DES_Q1000_1 HA15_KILK5_MESH_DFS2_DES_1 HA15_KILK5_MESH_DEF2_RES_DES_1

MIKE 11 - SIM FILE & RESULTS FILE MIKE 11 - NETWORK FILE MIKE 11 - CROSS-SECTION FILE MIKE 11 - BOUNDARY FILE HA15_KILK5_NWK_DES_1 HA15_KILK5_XNS_DES_1

HA15_KILK5_M11_DES_Q10_1 HA15_KILK5_BND_DES_Q10_1 HA15_KILK5_M11_DES_Q100_1 HA15_KILK5_BND_DES_Q100_1 HA15_KILK5_M11_DES_Q1000_1 HA15_KILK_BND_DES_Q1000_1 MIKE 11 - DFS0 FILE MIKE 11 - HD FILE & RESULTS FILE HA15_KILK5_M11_DES_Q10_1 HA15_KILK5_HD_DES_Q10_1 HA15_KILK5_M11_DES_Q100_1 HA15_KILK5_HD_DES_Q100_1 HA15_KILK5_M11_DES_Q1000_1 HA15_KILK5_HD_DES_Q1000_1

GIS Deliverables – Hazard

Flood Extent Files (Shapefiles) Flood Depth Files (Raster) Water Level and Flows (Shapefiles) Fluvial Fluvial Fluvial O21EXFCD001C0 O21dpfcd001c0 O21NFCDC0 O21EXFCD010C0 O21dpfcd010c0 O21EXFCD100C0 O21dpfcd100c0 Flood Zone Files (Shapefiles) Flood Velocity Files (Raster) Flood Defence Files (Shapefiles) To be issued with Final version of this report Defended Areas O21ZNA_FCDC0 NA O21ZNB_FCDC0 Defence Failure Extent NA

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