South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

South Eastern CFRAM

Study HA15 Hydraulics Report

Thomastown Model

Client OPW

Project Title South Eastern CFRAM Study

Document Title IBE0601Rp0015_HA15 Hydraulics Report

Model Name Thomastown

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

D01 Draft T. Carberry L. Howe I Bentley G. Glasgow Limerick/Belfast 14/04/2014

L. Howe / L. Howe / Draft F01 K. Smart G. Glasgow Belfast 19.12.2014 Final R. R. Clements Clements L. Howe / L. Howe / Draft F02 K. Smart G. Glasgow Belfast 13/08/2015 Final R. R. Clements Clements

IBE0601Rp0015 Rev 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 Study Flood Risk IBE0601 Rp0001_Flood Risk Review_F01 3.3.13 2011 Review

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 4.7 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

4.8 thomastown model ...... 1

4.8.1 General Hydraulic Model Information ...... 1

4.8.2 Hydraulic Model Schematisation ...... 2

4.8.3 Hydraulic Model Construction ...... 10

4.8.4 Sensitivity Analysis ...... 17

4.8.5 Hydraulic Model Calibration and Verification ...... 17

4.8.6 Hydraulic Model Assumptions, Limitations and Handover Notes ...... 32

IBE0601Rp0015 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

4 HYDRAULIC MODEL DETAILS

4.8 THOMASTOWN MODEL

4.8.1 General Hydraulic Model Information

(1) Introduction:

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

Model 7 represents the Thomastown AFA and encompasses the River Nore upstream and downstream of its extent, plus associated tributaries.

The total contributing area at the downstream limit of the model is 2,417km 2. A total of 72% of this comes from Model 5 upstream (Kilkenny).Both Model 6 (Callan) and Model 8 (Ballyhale) enter the River Nore at Model 7 (Thomastown). Model 6 (Callan) joins the Nore at the uppermost reach of the River Nore in Model 7 (Thomastown); whereas Model 8 (Ballyhale) joins the River Nore just upstream of the AFA in Model 7 (Thomastown).

There are two gauging stations located along the length of the Thomastown model:

• Mount Juliet (15011) – This gauge was not included in the FSU;

• Brownsbarn (15006) – This gauge has an FSU rating of A2.

Further information on these gauges is provided in Section 4.9.5. CFRAM rating reviews were carried out for both gauges in order to derive new Q med values at the stations. See Section 4.9.5(a) and (b) for full review details.

Rainfall run-off (NAM) models have been developed for the contributing catchments of each gauging station in order to simulate longer AMAX series and increase confidence in the Q med . Following this process it was noted that there was significant discrepancy between simulated and gauged Q med values moving downstream. Details on how this was resolved and final Q med values is included in Section 4.4.5(e) of this report and Section 3.1 of the HA15 Hydrology Report. The simulated Q med values at each of these stations have been used to adjust FSU predicted values at each HEP within the Ballyragget model as appropriate.

Qmed estimates at the various HEPs were derived using an FSU catchment descriptor-based equation, and adjusted based on the gauge at Brownsbarn or Mount Juliet as appropriate.

A number of rivers have been identified as high priority watercourses within the Thomastown model, including Cloghabrody River, Jacks Stream River and a portion of the Nore River 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 Nore River is designated MPW and has been modelled as 1D only. The

IBE0601Rp0015 4.8-1 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Brownsbarn (15006) gauging station is located at the downstream extent of the model reach, as such the model has been extended downstream by 900m to enable calibration of this gauge.

(2) Model Reference: HA15_THOM7

(3) AFAs included in the model: THOMASTOWN

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

Reach IDName

NORE RIVER NORE_E

NORE RIVER NORE_C&D

CLOG CLOGHABRODY

JACK JACKS STREAM

BROW BROWNSBARN

(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)

4.8.2 Hydraulic Model Schematisation

(1) Map of Model Extents:

Figure 4.8.1 and 4.8.2 below illustrate the extent of the modelled catchment, river centre line, HEP locations and AFA extents. The Nore catchment contains 3 Upstream Limit HEPs, 1 Downstream Limit HEP, 2 Gauging Station HEPs, 2 Intermediate HEPs and 5 Tributary HEPs.

IBE0601Rp0015 4.8-2 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.1Map of Model Extents

IBE0601Rp0015 4.8-3 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.2Map of Model extents at the AFA

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

Table 4.8.1Watercourses included in the model

River Name x y NORE NORE C AND D 257265 140735 NORE NORE E 254185 154285 NORE NORE AT BROWNSBARN 260775 138865 CLOG CLOGHABRODY 259165 138885 JACK JACKS STREAM 259745 140735

(3) Total Modelled Watercourse Length: 22.8 (km)

(4) 1D Domain only Watercourse Length: 16.5(km) (5) 1D-2D Domain 6.3(km) Watercourse Length:

(6) 2D Domain Mesh Type / Resolution / Area: Rectangular / 5 metres / 7.5 (km 2)

IBE0601Rp0015 4.8-4 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

(7) 2D Domain Model Extent:

Figure 4.8.32D Model Extent

Figure 4.8.3shows the extent of the LiDAR data used in the 2D model. Buildings are illustrated in red. For details of the approach to the modelling of buildings in the 2D area, please refer to section 3.3.2 of this report.

Figure 4.8.4 shows the extent of the NDHM data used. The black line shows the river network and the red boundary represents the LiDAR extent (as shown in Figure 4.8.3). A buffer zone was created between the two datasets which were smoothed together by interpolation.

IBE0601Rp0015 4.8-5 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.4NDMH Extent

Figure 4.8.5 below shown an overview drawing of the model schematisation. Figures 4.8.6and Figure 4.8.7 show detailed views of critical structures in the model. The overview design 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 4.8.3(1) along with the location and extent of the links between the 1D and 2D models.

IBE0601Rp0015 4.8-6 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.5Model Schematic Overview (A – Full Extent)

IBE0601Rp0015 4.8-7 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.6Model Schematic Overview - Critical Structures (B – Upper MPW Section)

Figure 4.8.7Model Schematic Overview - Critical Structures (C – AFA Section)

IBE0601Rp0015 4.8-8 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

(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 Thomastown 15NORE_E GIS CCS: Surveyor Name Photos (Naming S15: South Eastern CFRAM Study Area, convention is in the Hydrometric Area 15 format of Cross-Section M05: Model Number 5 ID and orientation - 15NORE_E: River Reference upstream, downstream, WP2 : Work Package 2 left bank or right bank)

Finals: Version

131118 – Date Issued (18 th NOV 2013)

(b) Survey Folder References:

Reach IDName File Ref.

NORE RIVER NORE_E CCS_S15_M05_07_15NORE_E _WP2_Finals_131118

NORE RIVER NORE_C&D CCS_S15_M07_15NORE _C_D_WP2_Finals_130118

CLOG CLOGHABRODY CCS_S15_M07_15CLOG_WP2_Finals_130118

JACK JACKS STREAM CCS_S15_M07_15JACK_WP2_Finals_130115

BROW BROWNSBARN CCS_S15_M07_10_Brownbarn_GS_15006_WP1_Finals_130123

(9) Survey Issues: (a) Mount Juliet 15011 gauging station (255083E 142502N) was not captured by the surveyors; its location is shown in Figure 4.8.8. Several attempts were made to survey the gauge but persistently bad weather made this impossible. The OPW have since abandoned the survey. A Rating Review was carried out using the information available; details of this are included in Section 4.8.5(4).

IBE0601Rp0015 4.8-9 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.8Location of Mount Juliet (15011)

4.8.3 Hydraulic Model Construction

(1) 1D Structures (in-channel along See Appendix A.1 modelled watercourses): Number of Bridges and Culverts: 7

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.

Two critical structures have been identified in the model. These are the 15NORE02903D (Mount Juliet Bridge) and 15NORE02425D (Mill Street Bridge); both are located on the Nore River.

The capacity of these two structures is insufficient to convey flood flows during the modelled events (10%, 1% and 0.1% AEP).The 15NORE02903D structure restricts flows during all modelled events, causing flow to build up upstream of the structure and inundating agricultural land or grassland adjacent to the Nore River; no properties are affected. The 15NORE02425D structure restricts flows during the more extreme modelled events (1% and 0.1% AEP), causing flow to build up upstream of the structures and inundating the north (left) bank upstream of the bridge on Marsh’s Street in the Thomastown AFA; properties in the AFA are affected but this is due to insufficient channel capacity as well as structure capacity.A longitudinal plan of the 1% AEP event at the bridge is included in Appendix A.2. Photographs and survey details are included below in Figures 4.8.9 and 4.8.10.

IBE0601Rp0015 4.8-10 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.9Mount Juliet Bridge (15NORE02903D)

Figure 4.8.10Mill Street Bridge (15NORE02425D)

One structure hasn’t been included in the model due to its orifice being too large to be hydraulically significant. The 15NORE02554E (railway bridge) structure is located on the Nore River. The walls of the structure were input into the model as these will affect hydraulics. A photographand the model cross- section are shown in Figures 4.4.11 and 4.4.12; maximum water level during 0.1% AEP event at this location is shown for clarification. Soffit of structure is not shown in survey drawing as survey states it will not affect flow of channel.

IBE0601Rp0015 4.8-11 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.11 Photograph of railway bridge (15NORE02554E)

Max 0.1% AEP water level (mOD)

Figure 4.8.12 Modelled cross-section of railway bridge (15NORE02554E) at Nore River 10997 Ch.

(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.)

None

(5) Model Boundaries - Inflows:

Full details of the flow estimates are provided in the Hydrology Report(IBE0601Rp0010_HA15_Hydrology Report_F01 ,Section4.8 and Appendix D). The boundary conditions implemented in the model are shown below in Figure 4.8.13.

IBE0601Rp0015 4.8-12 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.13MIKE 11 Boundary Information

A review of flows and time-to-peak of inflow hydrographs was carried out during the calibration process. The Cloghabrody River and Jacks Stream peak earlier than the Nore River, and therefore flood extents around each of the watercourses peak at different times. To ensure worst case scenario of flood extents and depths in the AFA, design hydrograph timings in the Cloghabrody River and Jacks were moved so that theall three watercourses peak in the AFA at the same time.

Figure 4.8.14Upstream Inflow (HEP 15_521_3_RPS) and two tributaries

A review of flows was carried out during the calibration process. The modelled flows were significantly higher than the hydrological estimates. This was due to the cross-sections in the MPW 1D domain not

IBE0601Rp0015 4.8-13 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL containing enough data, and so flow was unable to spill as required, causing flow to build up at the edge of the cross-sections (known as ‘glass walling’). This reduces attenuation that would naturally occur, causing modelled flows downstream to be higher than they should be. Cross-sections were extended to enable a more accurate representation of the catchment attenuation. Modelled flows now match well with the hydrological estimates as discussed in Appendix A.3. Further detail on the MPW cross-section extension is included in Section 4.8.6(1)(e).

The upstream boundary of the Nore catchment is located at HEP 15_521_3_RPS (downstream HEP for Model 5 - Kilkenny). The model node ID at this location is 15NORE03650. A point inflow was therefore applied at this node to account for flow entering the Nore River upstream of this location.

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

There is an approximate 1.8km overlap between Model 7 (Thomastown) and Model 9 (Inistioge) to ensure that all flow paths are accurately represented. A comparison of the generated downstream boundary Q-h relationship in Model 7 (Thomastown) has been made with the modelled Q-h relationship at the same location in Model 9 (Inistioge); shown below in Figure 4.8.15. These are in close agreement with one another up to top of bank level (6.8 m AOD).

In addition to this, joint probability with Model 9 (Inistioge) has not been considered and a Q-h boundary has been applied at the downstream extent. The ThomastownAFA is greater than 5km upstream of the downstream boundary of the model. Therefore backwater from Model 9 (Inistioge) is considered to have no effect on flood flows within the AFA. The Q-h boundary is to be assessed during sensitivity analysis. For more details see Section 6.3.1 of the Hydrology Report and Section 3.6.1 of this report.

IBE0601Rp0015 4.8-14 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.15Comparison of Model 7downstream boundary & the modelled Model 9 Q-h relationships

(7) Model Roughness:

(a) In-Bank (1D Domain) Minimum 'n' value: 0.035 Maximum 'n' value: 0.085

(b) MPW Out-of-Bank (1D) Minimum 'n' value: 0.035 Maximum 'n' value: 0.07

(c) MPW/HPW Out-of-Bank Minimum 'n' value: 0.059 Maximum 'n' value: 0.035

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

IBE0601Rp0015 4.8-15 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.16 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

Cloghabrody River – 15CLOG00005E_DS Nore River – 15NORE02188_US

IBE0601Rp0015 4.8-16 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8 .17 15CLOG00005E Roughness Figure 4.8 .18 15NORE02188 Roughness

Manning’s n = 0.045 Manning’s n = 0.04

River with shallows and meanders and noticeable Standard natural stream or river in stable condition, aquatic growth clean and winding, with some pools and shoals

Jacks Stream River – 15JACK00145_DS Nore River at Brownsbarn – 15NORE01768_DS

Figure 4.8.1915JACK00145 Roughness Figure 4.8.2015NORE01768 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

4.8.4 Sensitivity Analysis

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

4.8.5 Hydraulic Model Calibration and Verification

(1) Key Historical Floods (FromIBE0601Rp0008_HA 15 Inception Report_F02 unless otherwise specified):

(a)NOV 2009 Flooding occurred in Thomastown and Inistioge on 19 th November 2009. It was reported in a Seanad Éireann Debate (Vol. 198 No. 7) on 25 th November 2009 (http://debates.oireachtas.ie) to be the worst flooding in Thomastown for 41 years. Photographs found on www.flickr.com illustrate flooding of low lying lands and roads in Thomastown. Photographs show shallow flooding on Mill Street, at the edge of Market Street Bridge.

The peak flow recorded at the Mount Juliet gauging station upstream of the AFA was 403.12m 3/s. The reliable rating for this gauging station is up to 368m 3/s and so this

IBE0601Rp0015 4.8-17 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

event cannot be used for model validation.The peak flow recorded at the Brownsbarn gauging station downstream of Thomastown was 412m 3/s. The reliable rating for this gauging station is up to 389m3/s and so this event cannot be used for model validation.

As this was the worst flooding seen in the AFA for 41years,the event is likelyto have been between a 10% and 1% AEP event. A review of the 10% AEP and 1% AEP model results show shallow depth flooding downstream of Market Street Bridge on the right bank in Figures 4.8.22 and 4.8.23. Deep flooding (1m depth) is shown just downstream, this also matches the photograph in Figure 4.8.21. The red arrow on the flood map shows the direction the photograph was taken from.

Figure 4.8.21 Photograph taken at unknown time during 2009 flood event

Market St

Castle

Figure 4.8.22 10% AEP event flood depths at Thomastown Castle

IBE0601Rp0015 4.8-18 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Market St

Castle

Figure 4.8.23 1% AEP event flood depths at Thomastown Castle

(b)AUG 2008 Aerial photographs were found on www.floodmaps.ie which indicated that flooding occurred in Mountrath, Kilkenny, and Thomastown on 16 th August 2008. Aerial photographs of Thomastown were also found depicting flooding of low lying land adjacent to the river. It is not clear if roads or houses were flooded as the flood level had dropped by approximately 1.27m from its peak prior to the photo being taken. The peak flood level recorded at the Brownsbarn hydrometric station downstream of Thomastown was 7.94mOD (Malin Head), as per http://www.opw.ie/hydro .

A review of the 10% AEP model results peak water level is8.32m AOD (Malin) at the Brownsbarn hydrometric station. When the water level is 6.67m AOD (7.94-1.27), the flood extents shown in the model results are shown below in Figure 4.8.25. The extents match those in the photograph in Figure 4.8.24; see the red circled area below.

IBE0601Rp0015 4.8-19 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Figure 4.8.24 Photograph of flooding downstream at Thomastown AFA (Brownsbarn gauge water level 6.67m OD Malin) N

Figure 4.8.25 Modelled flood depths after the 10% AEP event when water levels at Brownsbarn gauge lowered to 6.67mOD Malin

th (c)JAN 2008 A flood event occurred on 10 January 2008 in Thomastown and Inistioge. A letter written by Kilkenny County Council dated 3 rd March 2008, found on the www.floodmaps.ie website, reported that at the Met Eireann weather station in Kilkenny, 33.6mm of rain fell mainly during a 12 hour period on 9 th -10 th January and caused the River Nore to burst its banks. The FSU webportal was used to calculate

IBE0601Rp0015 4.8-20 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

that this was a 50% AEP event.

In Thomastown, photos found on www.floodmaps.ie indicate flooding near the Quay, the Castle, the library and surrounding areas. The Kilkenny County Council letter reported that three private houses, two commercial premises and the library were flooded. Marshes Street and a section of the R700 had to be closed. Marshes Street car park was flooded and a number of cars were affected. A sewage pumping station was flooded for 24 hours resulting in sewage overflowing to the river. A weir on the Nore River upstream of Thomastown was also damaged where it appears that a section of it was washed away, causing the water level to drop upstream of the weir. No information on flows or levels was available.

A review of the 10% AEP model results show all the places detailed above to experience flooding; see Figures 4.8.27 to 4.8.29 at the end of this section.It is also noted that the Marshes Street Car Park isshown to experience flooding of 500mm in depth,most cars would be flooded at this depth. All areas detailed above to have been flooded during this event are shown to be flooded in the 10% AEP modelled event, suggesting that the event wasaround a 10% AEP.

(d) 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 9 th November 2000, were found on www.floodmaps.ie which indicated that a flood event occurred in Ballyragget, Kilkenny, Thomastown, Inistioge, and Ballyhale in November 2000. The flooding was caused by heavy rainfall causing the River Nore to overflow. No further information was found on the damage caused to Thomastown.

A review of the 10% AEP model results shows Thomastown as flooding; see figures at the end of this section.

th (e) 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.

References to flooding in Inistioge, where the Green and GAA pitch were flooded, and Thomastown on this date were also found. A pub and a number of houses on the Quay in Thomastown were under approximately 1 metre of water, while the library and Concert Hall on Marshes Street were also flooded. Parts of Market Street were also flooded. At the Brownsbarn Hydrometric Station (between Thomastown and Inistioge) on 7 th January, the peak flood level reached 8.06mOD (Malin) with a corresponding peak flow of 389m3/s, as per http://www.opw.ie/hydro . There is 3 confidence in this gauge up to 389m /s (1.3 x Q med ).

The peak flow during the 10% AEP modelled event is 427.5m3/s as such the 10%

IBE0601Rp0015 4.8-21 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

AEP modelled flood extent should be approximatelyrepresentative of the above mentioned flooded areas; see figures at the end of this section. The 10% AEP modelled results do show Marshes Street to be flooded, however Market Street is not flooded in the model. Informal feedback via the LA representatives at a mapping workshop confirmed that water ingress occurs via walk ways between buildings. As buildings in the model are removed from the floodplain and it is likely that small flow paths (such as a walk way between buildings on Market Street) are not represented in the model and so floodwaters are not shown to pass through the buildings onto Market Street.The Quay is shown to flood to a depth of 1m in places (see Figure 4.8.26).

The Quay

Figure 4.8.2610% AEP modelled flood extents at The Quay

(f) JAN 1995 A Kilkenny People press article, a Kilkenny Corporation memo to the County Manager (dated 31 st 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 Thomastown, shops and private houses in Marsh Street, Market Street and the Quay were flooded with 75-100 mm of water. The GAA pitch at Grennan was also flooded. A peak flood level of 7.98mOD (Malin) and a corresponding peak flow of 368m 3/s were recorded at Brownsbarn Hydrometric Station on 28 th January, as per http://www.opw.ie/hydro .The gauged data for this event is within the reliable limit so a comparison of the 10% AEP modelled results has been made. Model results show that when the peak water level at this gauge reaches 7.98mOD (Malin), the corresponding modelled peak flow is 359m 3/s; this is within 5% of the gauged flow and so the model is calibrated well to the gauged data for this event.

The peak flow at the Brownsbarn gauging stationduring the 10% AEP modelled event is 427.5m3/s, and as such the 10% AEP modelled flood extent should be fairly representative of the above mentioned flooded areas (see figures 4.8.27 to 4.8.29).

IBE0601Rp0015 4.8-22 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

The 10% AEP modelled results do show Marshes Street to be flooded. However, Market Street is not flooded in the model. Informal feedback via the LA representatives at a mapping workshop confirmed that water ingress occurs via walkways between buildings. As buildings in the model are removed from the floodplain and it is likely that small flowpaths (such as a walkway between buildings on Market Street) are not represented in the model and so floodwaters are not shown to pass through the buildings onto Market Street.As shown above in Figure 4.8.26, The Quay is shown to flood. It is likely this event was much less than a 10% AEP event, as the flooding at The Quay was much shallower than shown in the modelled 10% AEP event.

(g) JAN 1969 Press articles in the Kilkenny People and Munster Express downloaded from www.floodmaps.ie during the historical review indicated that a flood event occurred in Thomastown on 24 th January 1969 due to heavy rainfall causing the River Nore to overflow. Private houses were flooded to a depth of up to three metres.

It is unknown where the private houses mentioned above are. In the 10% AEP modelled results there are areas of 3m flood depths adjacent to the river, it is likely these houses were/are located here; see figures 4.8.27 to 4.8.29.

th (h) NOV 1965 Flooding occurred in Thomastown on 27 November 1965 due to heavy rainfall. An article in the Kilkenny People described water entering houses in Marshes Street and the Quay. There is no information on levels or flows available for this date.

A review of the 10% AEP model results show houses on Marshes St and The Quayexperience flooding; see figures 4.8.27 to 4.8.29.

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

In Thomastown, streets and surrounding countryside were inundated with up to 1.6m of water. Areas worst affected were Marshes Street, Low Street and the Quay. Homeowners in the town were forced to retreat to upper storeys. Portions of the old town wall collapsed. The concert hall was flooded to a depth of 1m.

A review of the 1% AEP model results show flooding of 1.6m depth in the grassland surrounding the town and on Station Road. Marshes Street, The Quay and Low Street are shown to experience flooding of depths up to 1m.

(j) OCT 1954 The historical review indicated that a flood event occurred in Kilkenny, Callan and

IBE0601Rp0015 4.8-23 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Thomastown on 29 th October 1954 caused by heavy rainfall. An Irish Independent press article and Kilkenny Corporation correspondence (dated 9 th November 1954) were found on www.floodmaps.ie containing details of the event.

In Thomastown, the Nore burst its banks flooding shops and private premises to a depth of 150mm. No information on flows or levels was found.

A review of the 10% AEP model results show shops and private premises adjacent to the River Nore to experience flooding of over 150mm in depth.

th (k) MAR 1947 A major flood event occurred on 14 March 1947 in Freshford, Kilkenny, 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.

In Thomastown, shops and private premises were flooded to a depth of 1.2m. In Marshes Street, where water rose to a depth of almost 2m, a boat was used to convey food to people marooned in their homes; 115 houses were affected. No information on flows or levels was found.

A review of both the 1% and 0.1% AEP model results show that approximately 80- 120+ properties are at risk of flooding in the Thomastown area itself. The 1% AEP modelled results show Marshes Street flood depths to reach 2m, this increases to over 3m during the 0.1% AEP modelled event. The shops and private premises in the town are shown to be flooded to 0.75m depth in the 1% AEP modelled event and to 1.5m depth in the 0.1% AEP modelled event.

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

Flooding was also found to have occurred in Thomastown. No information on flood levels, flows or damage caused by the flood was found.

A review of the 10% AEP model results show Thomastown to flood; see figures 4.8.27 to 4.8.29.

nd (m) OCT 1763 Flooding occurred in Kilkenny, Thomastown and Inistioge on 2 October 1763 as a result of 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 (Kilkenny County Council Report, Jul 1985). This is the worst known flood in the history of the area. A bridge was also washed away in Thomastown.

During all modelled events (10%, 1% and 0.1% AEP) the Market St bridge across the Nore River is inundated with high discharges. As this event is the worst known flood

IBE0601Rp0015 4.8-24 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

in history for the area, the model results show it is reasonable that the bridge would have washed away.

IBE0601Rp0015 4.8-25 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Market Street R700/The Quay Marshes Street

Library

Castle

Station Road

Figure 4.8.27 Modelled 10% AEP results in the AFA

Low Street

Figure 4.8.28 Modelled 1% AEP results in the AFA

IBE0601Rp0015 4.8-26 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Marshes Street

Figure 4.8.29 Modelled 0.1% AEP results - Focussed on the town centre

Summary of Calibration

There are a large number of historic flood events to calibrate the model to in the AFA. There have been no known major works (i.e. flood mitigation works) carried out on the model reach.Unfortunately, only one of the gauged events had a recorded peak flow of below the reliable limit for the Brownsbarn and Mount Juliet gauging stations. This event (January 1995) indicates that the model is well calibrated to the Brownsbarn gauging station.Therefore, the gauged flow data calibrates well with the model results at a low return period (10% AEP), however there is limited gauge data with relevant flood information (extents, depths) for the higher return periods. The modelled flood extents match the recorded flood extents well for all recorded events, showing the model is validated well again to the low return periods (10% AEP). There are limited estimates of return periods for the recorded events. A number of estimates have been made using the modelled results; however, these are limited to between 10% and 1% AEP events.

A rating review was carried out for both gauging stations on the model reach (Brownsbarn and Mount Juliet). Brownsbarn calibrates well with the recorded rating review and Mount Juliet calibrates fairly well with the recorded rating review.

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 found to be -0.15%, 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 15006_RPS, the estimated flow during the 1% AEP event was 586.63m 3/s and the modelled flow was 604.93m 3/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. The model calibrates well with the one event where calibration of recorded gauge data was possible.

(2) Public Consultation Comments and Response:

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

IBE0601Rp0015 4.8-27 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

(3) Standard of Protection of Existing Formal Defences:

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

None

(4) Gauging Stations:

There are 2 gauging stations on the model reach:

(a) Mt Juliet (15011)

Gauging station 15011 is located in County Kilkenny on the River Nore. Figure 4.8.30 shows the location of the gauge.

Figure 4.8.30Mt Juliet (15011) Gauging Station Location

This gauging station has an FSU classification C, suggesting that there is confidence in the rating up to

0.8 times the Q med and as such was not included in the FSU.

A rating review has been carried out for this gauge. During initial calibration of the model, a lack of agreement between the modelled rating and the OPW rating was found. A Manning’s n value of 0.025 on the cross section at the gauge was required for the model to replicate the existing OPW spot gaugings. This is towards the lower limit for a clean, straight channel with minimal vegetation on banks. A review of the survey photography and aerial photography of the river confirmed that this is an appropriate value for

IBE0601Rp0015 4.8-28 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL this reach. A Manning’s n value of 0.018 was applied to each of the arches comprising the controlling bridge structure. The arches on the controlling structure, 7m downstream of the gauge, required an Inflow loss coefficient of 0.2 and an Outflow loss coefficient of 0.2. After applying these values, the model Q-h represented the existing OPW rating fairly well.

The gauging station is located on an MPW reach, and as such the model has been constructed from extended cross sections in a 1D model. The model produced a stable rating curve up to 734 m 3/s at top- of-bank (stage 5.6 m; 24 m OD Malin). At higher stages, flow is constrained between the top of bank marker points and so is not accurately representing the water level/ flow relationship. The rating curve for the 1D cross-section model is considered reliable up to 734 m 3/s (stage 5.6m; 24 m OD Malin) which is just below an estimated 0.1% AEP flow.

The results of the rating review are shown in Figure 4.8.31. The graph depicts the RPS modelled rating curve against the OPW rating curve. The graph shows that the model accurately represents the OPW rating curve based on the highest flow spot gaugings up to the highest spot gauging 118.395 m 3/s (approx. 1.7m stage; 20.1 m OD Malin). The model passes through some of the spot gaugings at the upper edge of the scatter but is up to 150mm higher than the spot gaugings on the lower edge of the scattered range. Improved calibration such that the model Q-h passes through the middle of the spot gaugings range would have required adjusting model parameters outside of the ranges which are considered appropriate.

6

5

4

Spot Gaugings (All) 3 OPW Existing Equation

2 RPS Calculated Equation Stage h (m above SG0) above (m h Stage

RPS 0.1% AEP Model Q-h (15011) 1

0 0 100 200 300 400 500 600 700 800 Discharge Q m3 /s

Figure 4.8.31Comparison of Existing OPW Rating Curve,RPS Rating Curve, and Spot Gaugings

IBE0601Rp0015 4.8-29 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

(b) Brownsbarn (15006)

Gauging station 15006 is located in County Kilkenny on the River Nore. Figure 4.8.32 shows the location of the gauge.

Figure 4.8.32Brownsbarn (15006) Gauging Station Location

This gauging station has an FSU rating of A2, suggesting that there is confidence in the rating up to 3 approximately 1.3 times the Q med . For FSU, a Q med value of 299.3m /s was extracted from records between 1972 and 2011. The OPW have assigned the rating standard at the Brownsbarn station, a data quality code of 36 up to 1.37m and a data quality code 56 from 1.37m up to 3.23m above staff gauge zero.

A rating review was carried out for this gauge. During calibration the model was adjusted to focus best fit of the modelled rating to the highest flow spot gauging (316.52 m 3/s; stage 3.395 m, 7.79 m OD Malin).During initial calibration of the model, a lack of agreement between the modelled rating and the OPW rating in the low flow Q-h range was found, regardless of the roughness values used. Only the upstream face cross-section of the bridge structure was surveyed and a review of the cross-sections downstream of the bridge suggests that there may be a high point in the channel at a location downstream of the bridge, which was not captured in the survey, and which controls the low stage Q-h relationship. To account for this, a cross-section was interpolated downstream of the bridge structure with the bed levels raised until agreement could be achieved with the low flow spot gaugings. This low flow control point is currently being investigated. A Manning’s n value of 0.028 on the cross section at the gauge was required for the model to replicate the existing spot OPW spot gaugings. This is slightly lower than the usual value

IBE0601Rp0015 4.8-30 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL of 0.03 for a clean straight channel with minimal vegetation on the banks. A review of survey photography and aerial photography of the river confirmed that this is an appropriate value for this reach. A Manning’s n value of 0.02 was applied to each of the arches comprising the bridge structure and an Inflow loss coefficient of 0.3 was applied to each arch. After applying these values, the model Q-h represented the existing OPW rating fairly well.

The gauging station is located on a HPW reach, and as such the model has been constructed from surveyed cross-sections in the 1D channel of the model and LiDAR Digital Terrain Model (DTM) representing the 2D floodplain. Flow is accurately represented both in channel and within the floodplain. The model produced a stable rating curve up to 799.19 m 3/s (stage 3.43 m; 9.58 m OD Malin). The rating curve for the 1D-2D linked model is considered reliable up to 799.19 m 3/s (stage 3.43 m; 9.58 m OD Malin), which is an estimated 0.1% AEP flow.

The results of the rating curve are shown in Figure 4.8.33. The graph depicts the RPS modelled rating curve against the OPW rating curve. The graph shows that the model accurately represents the OPW rating curve based on the highest flow spot gaugings up to the highest spot gauging 317.15 m 3/s (stage 3.43; 7.2 m OD Malin). The model passes through the highest flow spot gauging and can be considered well calibrated to the spot gaugings.

Figure 4.8.33Comparison of Existing OPW Rating Curve, RPS Rating Curve and Spot Gaugings

(5) Other Information:

None

IBE0601Rp0015 4.8-31 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

4.8.6 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) The time-to-peak of inflow hydrographs generated during the hydrological analysis have been reviewed during the calibration process. The Cloghabrody River and Jacks Stream peak earlier than the Nore River, as such flood extents around each of the watercourses peak at different times. Adjusting the hydrograph timings so peaks coincide within the AFA is justified, as it ensures that maximum flood extents and depths are achieved, simulating a worst-case scenario.

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

(d) Structure 15NORE02554E was not included in the model as the structure soffit is too high to constrict flows. This is assumed to be acceptable. e) 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 majority of cross sections on the Nore River, from chainage 0m to 10567 m and chainage 14351 mto 17838 m, 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.

(c) In instances where only the upstream or downstream face of a structures in the model was surveyed, the surveyed face has been duplicated and used as the unsurveyed face of the structure. This is assumed

IBE0601Rp0015 4.8-32 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL to be acceptable as all structures with only one face surveyed were of short length and so there should be minimal difference between the upstream and downstream orifices.

(d) All culverts with only the upstream or downstream face surveyed 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 10m) and so this will have a negligible effect on the model results.

(e) The 1D network is only linked (laterally) to the 2D domain downstream of the 15NORE02554E bridge. If flow were to enter the 2D domain from the 1D network upstream of here, it would build up against the edge of the 2D domain. This method is considered the best method to accurately represent flow routes.

(f) Due to buildings being located directly adjacent to the watercourse, the 1D network cannot be laterally linked to these locations. The buildings are located between Nore River chainage 12307 to 12340 and between chainahe 12447 to 12469.

(g) At Nore River chainage 13572 to14449, the left bank isn’t linked (laterally) to the 2D domain as flow leaves the right hand bank and doesn’t reach the top of the left bank during all modelled events.

(h) The Inflow Head Loss Factor (LPI) has been altered to 0.2 for 15NORE02903D and 0.4 for 15CLOG00005E. This is within the DHI recommended range of 0.2 to 0.7.

Hydraulic Model Parameters:

MIKE 11

Timestep (seconds) 1

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 Nore, Ch 11010 - 11689

(where non-default value used) River Nore, Ch 13622 - 13897

River Nore, Ch 14162 – 14449

River Cloghabrody, Ch 1724 - 1798

Lateral Length Depth Tolerance (m) All 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.

During all modelled events upstream of Thomastown, the capacity of Cloghabrody River and Jacks

IBE0601Rp0015 4.8-33 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Stream is inadequate, and limited localised out-of-channel flooding occurs affecting mostly the riparian strip and some localised grassland. At the confluence of the Cloghabrody River and the Nore River, approximately two properties are affected during the 10% AEP event, and six during the 1% and 0.1% AEP events.

Extensive out-of-channel flooding occurs from the Nore River during all modelled return periods (10%, 1%, and 0.1% AEP), both in the HPW and the MPW. This is due to incapacity of the channel during flood flows. Incapacity of the Mill Street Bridge (15NORE02425D) in the Nore River, combined with channel incapacity, also causes higher water levels upstream of the bridge, resulting in flooding of the AFA.

Floodwaters exceed channel capacity along the entire reach of the Nore River passing through the AFA, inundating the rear of properties adjacent to the watercourse and flowing over grassland to inundate areas of the town itself. Approximately 50 properties in the AFA are shown to be affected during the 10% AEP event, 80 properties during the 1%, and 120 properties during the 0.1% AEP event.

The MPW stretch of the Nore River shows that flood flows exceed channel capacity along the entire modelled reach during all simulated events.During all modelled return periods large areas of low lying agricultural land surrounding the Nore River are inundated with depths of up to 2.0-3.5 metres. This area is mostly rural and so only two properties are shown to flood during the modelled events.

A small town, Bennettsbridge, is located at the uppermost reach of the MPW stretch of the model. All but one property in Bennettsbridge remain flood free from the Nore River during the modelled 10% and 0.1% AEP events. During the 0.1% AEP event the Nore River flood extent widens to cause flooding of approximately 10 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

IBE0601Rp0015 4.8-34 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

APPENDIX A.1

MODELLED STRUCTURES

IBE0601Rp0015 4.8-35 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

STRUCTURE DETAILS - BRIDGES

SPRING LENGTH OPENING SHAPE HEIGHT WIDTH HEIGHT MANNING’S RIVER BRANCH CHAINAGE ID FROM N (M) (M) (M) INVERT (M)

15NORE01718D 3 of 8 ARCHES 7.6 12.8 3.9 NORE 19388 8 0.014 (LW TABLE) 15NORE01718D 5 of 8 ARCHES 4.3 7.3 4.3 NORE 19388 8 0.014 (LW TABLE) 2 of 6 ARCHES 7.4 11.8 5.0 NORE 284 15NORE03629D 1 7.66 0.018 (LW TABLE) 2 of 6 ARCHES 6.4 10 4.3 NORE 284 15NORE03629D 1 7.66 0.018 (LW TABLE) 2 of 6 ARCHES 4.9 7.5 3.0 NORE 284 15NORE03629D 1 7.66 0.018 (LW TABLE) 5 of 10 ARCHES 3.2 6.2 3.2 NORE 6158 15NORE03041D 1 8.5 0.021 (LW TABLE) 2 of 10 ARCHES 6.0 8.5 3 NORE 6158 15NORE03041D 1 8.5 0.021 (LW TABLE) 3 of 10 ARCHES 7.9 13 4.8 NORE 6158 15NORE03041D 1 8.5 0.021 (LW TABLE) 7 of 9ARCHES 4.6 4.9 1.4 NORE 7521 15NORE02903D 1 4 0.018 (LW TABLE) 2 of 9ARCHES 2.6 2.3 1.1 NORE 7521 15NORE02903D 1 4 0.018 (LW TABLE) 3 of 6 ARCHES 6.6 12.0 3.9 NORE 12291.5 15NORE02425D 1 9.05 0.013 (LW TABLE)

IBE0601Rp0015 4.8-36 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

STRUCTURE DETAILS - BRIDGES

SPRING LENGTH OPENING SHAPE HEIGHT WIDTH HEIGHT MANNING’S RIVER BRANCH CHAINAGE ID FROM N (M) (M) (M) INVERT (M)

2 of 6 ARCHES 4.9 9.1 2.8 NORE 12291.5 15NORE02425D 1 9.05 0.013 (LW TABLE) 1 of 6 ARCHES 2.8 6.0 1.8 NORE 12291.5 15NORE02425D 1 9.05 0.013 (LW TABLE) 2.25 16.61 0 CLOGHABRODY 1709 15CLOG00007E 4 CROSS-SECTION DB 0.021

2.29 12.63 0 CLOGHABRODY 1719 15CLOG00005E 9.9 CROSS-SECTION DB 0.022

IBE0601Rp0015 4.8-37 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

APPENDIX A.2

RIVER LONG SECTION PROFILES

IBE0601Rp0015 4.8-38 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

Maximum water levels in the Nore River during the 1% AEP event in the AFA

IBE0601Rp0015 4.8-39 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

APPENDIX A.3

ESTIMATED PEAK FLOW AND MODEL FLOW COMPARISON

IBE0601Rp0015 4.8-40 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

IBE0600 SE CFRAM STUDY RPS PEAK WATER FLOWS

AFA Name THOMASTOWN Model Code HA15_THOM7 Status DRAFT FINAL Date extracted from model 15/12/2014

Peak Water Flows River Name & Chainage AEP Check Flow (m 3/s) Model Flow (m 3/s) Diff (%) 10% 386.84 387.91 0.28 542.61 NORE 7499.91 1% 545.47 0.52 15_011_RPS 0.1% 751.13 740.45 1.42 10% 416.03 427.40 2.73 604.93 NORE 19359.89 1% 586.63 3.12 15006_RPS 0.1% 807.81 836.67 3.57 10% 15.99 19.49 21.88 CLOGHABRODY 1699.00 1% 25.14 33.45 33.06 15_1848_RPS 0.1% 38.04 55.04 44.68 10% 4.75 6.17 29.72 9.45 JACKS STREAM 625.03 1% 8.74 8.03 15_1106_5 0.1% 15.53 14.36 7.55

The table above provides details of flow in the model at every 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 flows in the River Nore are within approximately 4% of the estimated flows.

The modelled peaks flows in Cloghabrody Stream are between 21 to 45% higher when compared to the estimated peak flows. The location of the Cloghabrody HEP is at the confluence with the River Nore. During all events simulated (10%, 1% and 0.1% AEP) the River Nore has high water levels and a wide floodplain which covers the Cloghabrody Stream HEP causing higher than estimated flows.

Modelled peak flows in Jacks Stream (at its confluence with Cloghabrody Stream) are 30% higher than estimated during the 10% AEP event. This is due to the shape of the Cloghabrody Stream at the confluence (meandering), as flow from the Cloghabrody flows overland joining Jacks Stream, increasing modelled flows at the HEP point. However, during the 1% AEP event, modelled flows are only 7% higher than estimated in Jacks Stream. This is due to flows from Cloghabrody flowing overland into Jacks Stream increasing flows, but also flows exceeding channel capacity in Jacks Stream upstream of the HEP and flowing overland to rejoin Cloghabrody downstream. The flow leaving Jacks Stream causes the lower increase in flows. Finally, during the 0.1% AEP event,modelled

IBE0601Rp0015 4.8-41 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL flows are 7% lower than the estimated flows. This is due to large amounts of flow exceeding channel capacity upstream of the HEP point in Jacks Stream, and flowing south away from the watercourse to join the Cloghabrody Stream downstream.

IBE0601Rp0015 4.8-42 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

APPENDIX A.4

DELIVERABLE MODEL AND GIS FILES

IBE0601Rp0015 4.8-43 Rev F02 South Eastern CFRAM Study HA15 Hydraulics Report - DRAFT FINAL

MIKE FLOOD MIKE 21 MIKE 21 RESULTS HA15_THOM7 _MF_CAL_1_Q10 HA15_THOM7_M21_CAL_1_Q10 HA15_THOM7_M21_CAL_1_Q10 HA15_THOM7 _MF_CAL_1_Q100 HA15_THOM7_M21_CAL_1_Q100 HA15_THOM7_M21_CAL_1_Q100 HA15_THOM7 _MF_CAL_1_Q1000 HA15_THOM7_M21_CAL_1_Q1000 HA15_THOM7_M21_CAL_1_Q1000 HA15_THOM7_MESH_DFS2_CAL_1 HA15_THOM7_MESH_DFS2_RES_CAL_1

MIKE 11 - SIM FILE & RESULTS FILE MIKE 11 - NETWORK FILE MIKE 11 - CROSS-SECTION FILE MIKE 11 - BOUNDARY FILE HA15_THOM7_M11_CAL_1_Q10 HA15_THOM7_NWK_CAL_1 HA15_THOM7_XNS_CAL_1 HA15_THOM7_BND_CAL_1_Q10 HA15_THOM7_M11_ CAL_1_Q100 HA15_THOM7_BND_ CAL_1_Q100 HA15_THOM7_M11_CAL_1_Q1000 HA15_THOM7_BND_ CAL_1_Q1000 MIKE 11 - DFS0 FILE MIKE 11 - HD FILE & RESULTS FILE Q10 HA15_THOM7_HD_CAL_1_Q10 Q100 HA15_THOM7_HD_CAL_1_Q100 Q1000 HA15_THOM7_HD_CAL_1_Q1000 GIS Deliverables – Hazard

Flood Extent Files (Shapefiles) Flood Depth Files (Raster) Water Level and Flows (Shapefiles) Fluvial Fluvial Fluvial o35exfcd001c0 o35dpfcd001c0 O35NFCDC0 o35exfcd010c0 o35dpfcd010c0 o35exfcd100c0 o35dpfcd100c0 Flood Zone Files (Shapefiles) Flood Velocity Files (Raster) Flood Defence Files (Shapefiles) To be issued with Final version of this report Defended Areas o35zna_fcdc0 NA o35znb_fcdc0 Defence Failure Extent NA

IBE0601Rp0015 4.8-44 Rev F02