South Eastern CFRAM Study HA14 Hydraulics Report - DRAFT FINAL South Eastern CFRAM Study HA14 Hydraulics Report New Ross Model DOCUMENT CONTROL SHEET Client OPW Project Title South Eastern CFRAM Study Document Title IBE0601Rp0017_HA14 Hydraulics Report Model Name New Ross Rev Status Author(s) Modeller Reviewed by Approved By Office of Origin Issue Date . D01 Draft T. Carberry D. Irwin M. Brian G. Glasgow Limerick/Belfast 20/06/2014 F01 Draft E. Holland D. Irwin M. Brian G. Glasgow Belfast 10/03/2015 Final F02 Draft E. Holland D. Irwin M. Brian G. Glasgow Belfast 13/08/2015 Final IBE0601Rp0017 F02 South Eastern CFRAM Study HA14 Hydraulics Report - DRAFT FINAL Table of Reference Reports Report Issue Date Report Reference Relevant Section South Eastern CFRAM Study November IBE0601 Rp0001_Flood Risk Review_F01 3.10.14 Flood Risk Review 2011 South Eastern CFRAM Study July 2012 IBE0601Rp0005_HA 14 Inception Report_F02 4.3.2 Inception Report UoM14 South Eastern CFRAM Study December IBE0601Rp0011_HA14_Hydrology Report_F01 4.14, 6.2 Hydrology Report UoM14 2013 South Eastern CFRAM Study January IBE0601Rp0016_South Eastern CFRAMS 4 HA11-17 SC4 Survey 2014 Survey Contract Report_F01 South Eastern CFRAM Study May 2014 IBE0601Rp0017_HA14_Hydraulics 3 HA14 Hydraulics Report Report_D01 IBE0601Rp0017 F02 South Eastern CFRAM Study HA14 Hydraulics Report - DRAFT FINAL 4 HYDRAULIC MODEL DETAILS 4.10 NEW ROSS MODEL 4.10.1 General Hydraulic Model Information (1) Introduction: The South Eastern CFRAM Flood Risk Review (IBE0601 Rp0001_Flood Risk Review_F01) highlighted New Ross as an AFA for ‘mechanism 1 tidal flooding’ and fluvial flooding based on a review of historic flooding and the extents of flood risk determined during the PFRA. The New Ross Model constitutes the River Barrow as it makes the transition from river to estuary and directly affects New Ross AFA which is located on the Upper Barrow Nore Estuary. The River Barrow is tidally influenced approximately 17km upstream from New Ross and therefore so is the majority of the New Ross Model. See Chapter 3 of the Hydrology Report and Section 4.10.5(4) of this report for further details (IBE0601Rp0011_HA14 Hydrology Report_F02). The total contributing area at the downstream limit of the model is 3093.5km2 i.e. the entire Barrow catchment. 91% of this comes from upstream of the Graiguenamanagh model. The remaining fluvial flows come from small unmodelled tributaries entering the tidal Barrow from the east and west along the length of the Graiguenamanagh model. The largest of these are the Aughnavaud and Pollmounty Rivers, with catchment areas of 31 and 48km2 respectively. There are no useable hydrometric stations within the model. Therefore hydrological estimates of design flows were based on FSU ungauged catchment methods as detailed in the Hydrology Report ((IBE0601Rp0011_HA14 Hydrology Report_F02). The central section of the River Barrow within the New Ross Model is HPW, as this is where it passes through the New Ross AFA. It was therefore modelled as 1D-2D using the MIKE suite of software. The upper and lower segments of the River Barrow within the model are MPW and therefore modelled in 1D only. New Ross AFA was identified as at risk from both fluvial and coastal flood sources during the PFRA. An initial screening process was undertaken to ascertain whether the flooding mechanisms in New Ross warrant further considerations of the joint probability of occurrence. This analysis identified that there is overlap of flood extents within the AFA and that large flows on the River Barrow combined with high tides could exacerbate flooding, (refer to Chapter 6.3.2 of IBE0601Rp0011_HA14 Hydrology Report_F02). Therefore joint probability scenarios were further considered for this area. These scenarios included (as detailed in Chapter 3.7.3): Coastal events of 10%, 0.5% and 0.1% AEP were combined with a fluvial event of 50% AEP in order to produce joint AEPs of 10%, 0.5% and 0.1% AEP for a coastal dominated scenario. Conversely, fluvial events of 10%, 1% and 0.1% AEP were combined with a coastal event of 50% AEP for IBE0601Rp0017 4.10-1 F02 South Eastern CFRAM Study HA14 Hydraulics Report - DRAFT FINAL joint AEPs of 10%, 1% and 0.1% AEP for a fluvial dominated scenario. (2) Model Reference: HA14_NEWR14 (3) AFAs included in the model: New Ross (4) Primary Watercourses / Water Bodies (including local names): Reach ID Name 14BARO River Barrow (5) Software Type (and version): (a) 1D Domain: (b) 2D Domain: (c) Other model elements: MIKE 11 (2012) MIKE 21 - Flexible Mesh (2012) MIKE FLOOD (2012) 4.10.2 Hydraulic Model Schematisation (1) Map of Model Extents: IBE0601Rp0017 4.10-2 F02 South Eastern CFRAM Study HA14 Hydraulics Report - DRAFT FINAL Figure 4.10.1: Map of Model Extent IBE0601Rp0017 4.10-3 F02 South Eastern CFRAM Study HA14 Hydraulics Report - DRAFT FINAL Figure 4.10.2: Map of Model Extent - New Ross AFA Figure 4.10.1 and Figure 4.10.2 illustrate the extent of the modelled catchment, river centre line, HEP locations and AFA extents. The catchment contains 1no. Upstream Limit point (14023_RPS), 1no. Downstream Limit HEP, 1no. Intermediate HEP and 10no. Tributary HEPs. The Intermediate, Downstream Limit and Tributary HEPs (where modelled) are used in anchoring the model to observed / estimated flows as detailed in Appendix A.3. Hydrometric Station 14023 located at the upstream limit is an inactive station with no data available, and is therefore not used in anchoring the model to observed flow. (2) x-y Coordinates of River (Upstream extent): River Name Easting Northing 14BARO River Barrow 271425 142396 (3) Total Modelled Watercourse Length: 44.7 km (approx.) (4) 1D Domain only Watercourse Length: 34.1 km (5) 1D-2D Domain 10.6 km (approx.) Watercourse Length: (approx.) (6) 2D Domain Mesh Type / Resolution / Area: Flexible / 5-120 metres / 33 km2 (approx.) (7) 2D Domain Model Extent: IBE0601Rp0017 4.10-4 F02 South Eastern CFRAM Study HA14 Hydraulics Report - DRAFT FINAL Modelled River Centreline AFA Boundary Flood Defence Figure 4.10.3: 2D Model Extent Figure 4.10.3 illustrates the modelled extents, general topography and 2D extent. Buildings are excluded from the mesh and therefore represented as white spaces. Refer to Chapter 3 for details on representation of buildings in the model. Figure 4.10.4 shows an overview drawing of the model schematisation. Figure 4.10.5 shows detailed views. The overview diagram covers the model extents, showing the surveyed cross-section locations, AFA boundary and river centre line. 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 IBE0601Rp0017 4.10-5 F02 South Eastern CFRAM Study HA14 Hydraulics Report - DRAFT FINAL surveyed cross-section locations, AFA boundary and river centre line. They also show the location of the critical structures as discussed in Section 4.10.3(1), along with the location and extent of the links between the 1D and 2D models. For clarity in viewing cross-section locations, the model schematisation diagram shows the full extent of the surveyed cross-sections. Note that the 1D model considers only the cross- section between the 1D-2D links. Figure 4.10.4: Overview Drawing of Model Schematisation IBE0601Rp0017 4.10-6 F02 South Eastern CFRAM Study HA14 Hydraulics Report - DRAFT FINAL Figure 4.10.5: Detailed Area of Model Schematisation showing Critical Structures (8) Survey Information (a) Survey Folder Structure: First Level Folder Second Level Folder Third Level Folder CCS_S14_M14_14BARO_A&B_WP4_Final 14BARO_A&B Data _130430 Files New Ross 14BARO_A&B Drawings CCS: Surveyor Name 14BARO_A&B GIS S14: South Eastern CFRAM Study Area, Photos (Naming Hydrometric Area 14 convention is in the M14: Model Number 14 format of Cross-Section 14BARO: River Reference ID and orientation - WP4: Work Package 4 upstream, downstream, Final: Version left bank or right bank) th 130430: Date Issued (30 APR 2013) IBE0601Rp0017 4.10-7 F02 South Eastern CFRAM Study HA14 Hydraulics Report - DRAFT FINAL (b) Survey Folder References: Reach ID Name File Ref. 14BARO RIVER BARROW CCS_S14_M14_14BARO_A&B_WP4_Final_130430 CCS_S14_M14_14BARO_C_WP4_Final_130430 CCS_S14_M13_14BARO_D_WP4_Final_130430 CCS_S14_M12_13_14_14BARO_Weirs_ Final_130730 (9) Survey Issues: (a) Survey Query 1 Name: Conor Delaney Watercourse Name: Grid Reference: Location: Date: 28/11/2013 River Barrow 268090E 114814N Between cross-sections 14BARO00661 14BARO00542 Description: From aerial photography and photograph 14BARO00542_US (Figure 4.10.6), there appears to be a bridge located along this reach of the River Barrow. There does not appear to be any survey information available for this bridge within the AutoCAD drawing. Figure 4.10.6: Survey Query 1 Outcome: This query was not taken forward for follow up survey. An initial assessment estimated that this bridge has very little hydrodynamic impact on the River Barrow due to the narrow piers and high soffit level. It is also located on MPW, approximately 11 km from the AFA. It was therefore decided to omit this bridge from the model. (b) Survey Query 2 Name: David Irwin Watercourse Name: Grid Reference: Location: Date: 17/04/2014 River Barrow N/A Between cross-sections 14BARO02900 14BARO01831 IBE0601Rp0017 4.10-8 F02 South Eastern CFRAM Study HA14 Hydraulics Report - DRAFT FINAL Description: 13.293km of linear flood defence required. The flood defences in the New Ross area are critical for the completion of the New Ross modelling. If they were not in place flooding would occur; modelling of this area cannot be completed without this fundamental information. Outcome: Flood defences were surveyed from chainage 16524m to chainage 27734m. There was one area that was not covered by the survey as surveyors were unable to gain access to the site, see Figure 4.10.7. Therefore this section of the defence is only represented by the LIDAR information.