Eastern CFRAM Study HA09 Hydraulics Report - DRAFT FINAL Eastern CFRAM Study HA09 Hydraulics Report Leixlip Model DOCUMENT CONTROL SHEET Client OPW Project Title Eastern CFRAM Study Document Title IBE0600Rp0027_HA09 Hydraulics Report Model Name Leixlip Rev Status Author(s) Modeller Reviewed by Approved By Office of Origin Issue Date . D01 Draft Various S. Patterson M. Brian G. Glasgow Belfast/Limerick 10/07/14 F01 Draft Various S. Patterson M. Brian G. Glasgow Belfast/Limerick 23/01/15 Final F02 Draft Various S. Patterson M. Brian G. Glasgow Belfast/Limerick 13/08/15 Final IBE0600Rp0027 4.16-1 Rev F02 Eastern CFRAM Study HA09 Hydraulics Report - DRAFT FINAL Table of Reference Reports Report Issue Date Report Reference Relevant Section(s) Eastern CFRAM Study Flood December IBE0600Rp0001_Flood Risk Review_F02 3.5.12 Risk Review 2011 Eastern CFRAM Study August 2012 IBE0600Rp0008_HA09 Inception 4.3.2 Inception Report UoM09 Report_F02 Eastern CFRAM Study September IBE0600Rp0016_HA09_Hydrology 4.7 Hydrology Report UoM09 2013 Report_F01 CFRAM Survey Contract 2 - January 2013 2011s4884_SC2 Survey Report v3 1.2, 1.7, 1.8 Liffey Survey Report IBE0600Rp0027 4.16-2 Rev F02 Eastern CFRAM Study HA09 Hydraulics Report - DRAFT FINAL 4 HYDRAULIC MODEL DETAILS 4.16 LEIXLIP 4.16.1 General Hydraulic Model Information (1) Introduction: The Eastern CFRAM Flood Risk Review (IBE0600 Rp0001_Flood Risk Review_F02) highlighted Leixlip as an Area for Further Assessment for fluvial flooding based on a review of historic flooding and the extents of flood risk determined during the PFRA. The Leixlip model encompasses the middle and lower reaches of the Liffey. The Maynooth model and Celbridge Hazelhatch model are located immediately upstream (on the Rye Water and River Liffey respectively) with this model connected to the Lucan to Chapelizod model at its downstream extent. The total contributing catchment area of the model to the downstream extents is 730 km2 (excluding the upper catchment, upstream of Golden Falls dam). Included within this area is the Rye Water (or River Rye) catchment which joins the River Liffey at Leixlip and accounts for 209 km2. The Leixlip AFA is affected by a number of small tributaries - the Sion and Moor of Meath (River) are tributaries of the Rye Water and the Moor of Meath watercourse is a tributary of the River Liffey, which has two tributaries of its own - Walterstown and Leavalley (Figure 4.16.2). The remaining modelled watercourse is the Ryvale which is a short millrace adjacent to the Rye Water. There are four gauging stations within the model extents, two of which are hydrometric gauging stations with both water level and flow information. One is located on the Rye Water approximately 1 km upstream of its confluence with the River Liffey (09001) and also one on the River Liffey at the Leixlip power generation plant (09022 - Figure 4.16.2). The Rye Water station is named Leixlip (09001 – OPW) and was given an A1 classification under FSU and a long record period with data received covering the complete hydrological years of 1956 – 2009 (A1 applies to 1980 onwards). Therefore the Qmed flow of 33.7 m3/s derived from the AMAX series at the Leixlip gauging station representing the Rye Water catchment can be considered to have a high degree of confidence. The gauging station located at the Leixlip hydro-electric power generation station on the Liffey main 3 channel is owned and operated by ESB (09022). The Qmed derived from the AMAX series of 61.64 m /s (catchment area of 510km2) can be considered to have a low degree of statistical confidence. There is a further historic gauging station located on the main channel of the Liffey just upstream of the model extents called Celbridge (09006 – ESB) representing a catchment area of 479 km2 which has continuous flow data available for the periods of 1967 – 1986 and from 1995 - 1997. This gauging station was not given a classification under FSU but data provided by ESB indicates that there is confidence in the rating 3 at the Qmed value from the extracted AMAX series of 56.5m /s. Although there is some uncertainty in the Qmed value this figure is in good agreement with observed value at the dam at Leixlip from the later, shorter period. IBE0600Rp0027 4.16-3 Rev F02 Eastern CFRAM Study HA09 Hydraulics Report - DRAFT FINAL The other two gauging stations (09012 and 09050) have insufficient data to be of any benefit during model calibration. As the Leixlip Power Station Gauging Station (09022) is located close to the upstream extent of this model on the River Liffey, there is gauged information (see Section 4.16.5 (4)) available to base design flow estimates for the inflows to the model (see Section 4.16.3 (5)). Similarly, the Leixlip Gauging Station (09022) provides gauged information on which to base design flow estimates for the inflows to the model on the Rye Water. The downstream boundary condition is a water level - time relationship, extracted from the draft final (F01) Lucan to Chapelizod model (Chapter 4.17) located immediately downstream of this model (see Section 4.16.3 (6)). All of the modelled watercourses are high priority in this area and so have been modelled as 1D-2D. Channel markers have been located at the right and left banks of all cross sections. Flow within these markers is calculated by the 1D model component; however when the water level rises sufficiently to meet the bank markers flow can enter the 2D domain which represents the floodplain. (2) Model Reference: HA09_LEIX3A (3) AFAs included in the model: LEIXLIP (4) Primary Watercourses / Water Bodies (including local names): LIFFEY MOOR OF MEATH LEAVALLEY RYE WATER SION RYVALE WALTERSTOWN MOOR OF MEATH (RIVER) (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) 4.16.2 Hydraulic Model Schematisation (1) Map of Model Extents: IBE0600Rp0027 4.16-4 Rev F02 Eastern CFRAM Study HA09 Hydraulics Report - DRAFT FINAL Figure 4.16.1: Map of Model Extents within HA09 Figure 4.16.2: Map of Model Extents in AFA vicinity IBE0600Rp0027 4.16-5 Rev F02 Eastern CFRAM Study HA09 Hydraulics Report - DRAFT FINAL Figure 4.16.1 and Figure 4.16.2 illustrate the extent of the modelled catchment, river centre line, HEP locations and AFA extents as applicable. The Leixlip model contains 6 Upstream Limit HEPs, 1 Downstream Limit HEP and 5 Trib HEPs. It also contains 2 Gauging Station HEPs but no Intermediate HEPs. (2) x-y Coordinates of River (Upstream extent): River Name x y 09LIFF LIFFEY 300544 235560 09RYEW RYE WATER 296824 237795 09RYVA RYVALE 300503 236446 09SION SION 298702 238640 09MEAT MOOR OF MEATH 300398 238287 09WALT WALTERSTOWN 301358 238186 09LEAV LEAV 301375 237280 09MOOR MOOR OF MEATH (RIVER) 300037 238251 (3) Total Modelled Watercourse Length: 16.6 km (4) 1D Domain only Watercourse Length: 0 km (5) 1D-2D Domain 16.6 km Watercourse Length: (6) 2D Domain Mesh Type / Resolution / Area: Rectangular / 5 metres / 21.9 km2 (7) 2D Domain Model Extent: Figure 4.16.3 represents the general topography of the catchment within the 2D model domain. The river centre-line is shown in black with white areas representing blocked cells i.e. river centre lines, buildings or the area beyond the 2D model domain. There was no further post processing of the data contained within the mesh required. Changes in the vertical scale of this map are outlined by the index, all levels have been set to OD Malin (metres). IBE0600Rp0027 4.16-6 Rev F02 Eastern CFRAM Study HA09 Hydraulics Report - DRAFT FINAL Figure 4.16.3: 2D Domain Model Extent Figure 4.16.4 provides an overview drawing of the model schematisation. This 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. Figure 4.16.5 includes the surveyed cross-section locations, AFA boundary and river centre. They also show the location of the critical structures as discussed in Section 4.16.3, 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 diagrams show the full extent of the surveyed cross-sections. Note that the 1D model considers only the cross-section between the 1D-2D links. The upstream extent of the model on the River Rye Water commences approximately 500 metres upstream of the structure at Ch. 14503 m (to allow accurate representation of flows through the bridge). The flood mapping commences at this location (as flood mapping upstream of this location is covered by the Maynooth model). On the River Liffey, flood mapping covers the modelled reach from the upstream extent to Ch. 52207 m, as the remainder of the modelled extent is covered by the Lucan to Chapelizod flood maps. IBE0600Rp0027 4.16-7 Rev F02 Eastern CFRAM Study HA09 Hydraulics Report - DRAFT FINAL Figure 4.166.4: Overview of Model Schematisation Figure 4.166.5: Model Schematisation of the lower Rye Water, Liffey and Moor of Meath. IBE0600Rp0027 4.16-8 Rev F02 Eastern CFRAM Study HA09 Hydraulics Report - DRAFT FINAL (8) Survey Information (a) Survey Folder Structure: First Level Folder Second Level Folder Third Level Folder Murphy_E09_M03A_WP5_120801_09LEA V0_09LEAV_GIS and Structure_Register V Floodplain Photos Surveyed_Cross_Section_Lines Leixlip V1_09LEAV_Ascii Murphy: Surveyor Name V0_09LEAV_Videos E09: Eastern CFRAM Study Area, Hydrometric Area 09 V2_09LEAV_XS Drawings & PDFs M03A: Model Number 3A 09LEAV: River Reference