Eastern CFRAM Study HA10 Hydraulics Report Avoca Model
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Eastern CFRAM Study HA10 Hydraulics Report ‐ DRAFT FINAL Eastern CFRAM Study HA10 Hydraulics Report Avoca Model DOCUMENT CONTROL SHEET Client OPW Project Title Eastern CFRAM Study Document Title IBE0600Rp0028_HA10 Hydraulics Report Model Name Avoca Rev Status Author(s) Modeller Reviewed by Approved By Office of Origin Issue Date . D01 Draft Various J. Canavan S Patterson G Glasgow Belfast Feb 2014 D02 Draft Various J. Canavan S Patterson G Glasgow Belfast 20/06/2014 D03 Draft Various J. Canavan S Patterson G Glasgow Belfast 13/10/2014 F01 Draft Various J Canavan S Patterson G Glasgow Belfast 23/12/2014 Final F02 Draft Various J Canavan S Patterson G Glasgow Belfast 13/08/2015 Final F03 Draft Various J Canavan S Patterson G Glasgow Belfast 02/08/2016 Final IBE0600Rp0028 Rev F03 Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL Table of Reference Reports Report Issue Date Report Reference Relevant Section Eastern CFRAM Study Flood December IBE0600Rp0001_Flood Risk Review_F02 3.11.5 Risk Review 2011 Eastern CFRAM Study July 2012 IBE0600Rp0005_HA10 Inception Report_F02 4.3.2 Inception Report UoM10 Eastern CFRAM Study November IBE0600Rp0003_HA10_Hydrology 4.8 Hydrology Report UoM10 2013 Report_D01 Eastern CFRAM Study HA10 May 2013 IBE0600Rp0019_HA10 Wicklow Survey 1.6 Wicklow Survey Contract Contract Report_F01 IBE0600Rp0028 Rev F03 Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL 4 HYDRAULIC MODEL DETAILS 4.3 AVOCA MODEL 4.3.1 General Hydraulic Model Information (1) Introduction: The Eastern CFRAM Flood Risk Review (IBE0600 Rp0001_Flood Risk Review_F02) highlighted Avoca 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 Avoca model represents the lower reaches of the Avoca River catchment, beginning just upstream of the Avoca AFA, approximately 5km upstream of its confluence with the Aughrim River and ending at Arklow, where the river flows into the sea. The model also includes a number of small tributaries, which directly affect the Avoca AFA. The Avoca catchment is relatively flat in comparison to other catchments within HA10, with an S1085 value of 6 m/km. Land use within the catchment is a mix of pasture (32%), peatlands (37%) and forested areas (31%) with the only significant urbanisation at the villages of Rathdrum and Avoca. The catchments of the three smaller tributaries that affect the AFA range in size from 3 to 12 km2. These catchments are predominantly steep (S1085 of 32 to 54 m/km) and made up of pasture (82 – 100%). Note Arklow AFA is not being addressed under this Eastern CFRAM Study as it is being progressed via a separate OPW study. The Avoca model itself is ungauged along its reaches however there is an FSU pivotal site gauging station approximately 9km upstream of the modelled reaches at Rathdrum (10002 – EPA) and also a gauging station on Arklow town bridge (10042 – OPW) and on the Aughrim River upstream of the confluence point with the Aughrim River on Model 12 at Knocknamohill (10028 – EPA). The Rathdrum gauging station was given a B classification under FSU and has been subject to rating review. There is some uncertainty with the current EPA rating although the FSU, EPA and CFRAM Study rating review rating all show that the observed Qmed value is significantly higher than that which is predicted using the FSU physical catchment descriptors. In light of this catchment descriptor based estimates for all of the HEPs in the Avoca catchment have been adjusted upwards based on the relationship between the physical catchment descriptor based estimate of Qmed and the observed value (FSU plus additional years based on EPA rating) giving an adjustment factor of 1.31. This is consistent with the average adjustment factor for HA10 pivotal sites. Refer to UoM 10 Hydrology Report (IBE0600Rp0003_HA10_Hydrology Report) for full details on hydrology estimation for this model. The river network through Avoca AFA is HPW including the Avoca River (upstream reach of the Aughrim River) and tributaries (refer to Error! Reference source not found.). They were therefore modelled as 1D-2D using the MIKE suite of software to adequately represent floodplain flow conditions. The remainder of the Avoca River is designated as a MPW and 1D modelling was carried out for this reach (9km of the IBE0600Rp0028 4.3-1 Rev F03 Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL watercourse towards the downstream limit). The mapping limit of the model is at the M11 (XS ID:1028M00315D chainage 10290m) as the Arklow model is downstream and is a separate OPW study.. 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. Refer to Section Error! Reference source not found. for further details on model schematisation. (2) Model Reference: HA10_AVOC11 (3) AFAs included in the model: Avoca (4) Primary Watercourses / Water Bodies (including local names): Reach ID Name 1028M AVOCA RIVER 1040M AVOCA TRIB 1 1040A AVOCA TRIB 2 1039M AVOCA TRIB 3 1039A AVOCA TRIB 4 1039B AVOCA TRIB 5 1039C AVOCA TRIB 6 1038M AVOCA TRIB 7 (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 4.3.2 Hydraulic Model Schematisation (1) Map of Model Extents: Figure 4.3.1 and Figure 4.3.2 illustrate the extent of the modelled catchment, river centre line, HEP locations and AFA extents as applicable. The catchment contains 7 Upstream Limit HEPs, 8 Tributary HEPs, 1 gauging station Arklow town bridge (10042 – OPW) and 1 downstream limit point. IBE0600Rp0028 4.3-2 Rev F03 Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL Figure 4.3.1: Map of Model Extents Figure 4.3.2: Detail of AFA Extents IBE0600Rp0028 4.3-3 Rev F03 Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL (2) x-y Coordinates of River (Upstream extent): River Name x y 1028M AVOCA RIVER 319955 181268 1040M AVOCA TRIB 1 320693 180966 1040A AVOCA TRIB 2 321190 180265 1039M AVOCA TRIB 3 321999 178537 1039A AVOCA TRIB 4 321936 179419 1039B AVOCA TRIB 5 321462 178215 1039C AVOCA TRIB 6 321652 178523 1038M AVOCA TRIB 7 319452 179283 (3) Total Modelled Watercourse Length: 20.1 kilometres (approx.) (4) 1D Domain only Watercourse Length: 9.3 km (5) 1D-2D Domain 10.8 km (approx.) Watercourse Length: (approx.) (6) 2D Domain Mesh Type / Resolution / Area: Rectangular / 5 metres / 14.4 km2 (7) 2D Domain Model Extent: Figure 4.3.3 illustrates the modelled extents and the general topography of the catchment. The grid illustrates the 2D extent, the 1D model is illustrated as a light-blue line. 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. IBE0600Rp0028 4.3-4 Rev F03 Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL Figure 4.3.3: 2D Domain Model Extent Figure 4.3.4 shows an overview drawing of the model schematisation. Figure 4.3.5 to Figure 4.3.8 show 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 views 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 4.3.3 (1), along with the location and extent of the links between the 1D and 2D models. For clarity in viewing cross-section locations, the 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. IBE0600Rp0028 4.3-5 Rev F03 Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL Figure 4.3.4: Overview Drawing of Model Schematisation Figure 4.3.5: Detailed Area of Model Schematisation showing Critical Structure (1 of 4) IBE0600Rp0028 4.3-6 Rev F03 Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL Figure 4.3.6: Detailed Area of Model Schematisation showing Critical Structure (2 of 4) Figure 4.3.7: Detailed Area of Model Schematisation showing Critical Structure (3 of 4) IBE0600Rp0028 4.3-7 Rev F03 Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL Figure 4.3.8: Detailed Area of Model Schematisation showing Critical Structure (4 of 4) (8) Survey Information (a) Survey Folder Structure: First Level Folder Second Level Folder Third Level Folder Murphys_E10_M11_WP2_121127_ GIS and Floodplain Photos Flood Defence Register 1028M Floodplain Photos and Avoca Shapefiles Murphy - Surveyor Name Structure Register E10 - Eastern CFRAM Study Area, Surveyed Cross Section Lines Hydrometric Area 10 M011 - Model Number 11 V0_20121012_Photos_Videos WP2 - Work Package 2 _Ascii 121127 - Date issued (27 November 2012) Drawings and PDFs 1028M - River Reference Photos (Naming convention is in the format of Cross-Section ID and orientation - upstream, downstream, left bank or right bank) IBE0600Rp0028 4.3-8 Rev F03 Eastern CFRAM Study HA10 Hydraulics Report - DRAFT FINAL (b) Survey Folder References: Reach ID Name File Ref. 1028M AVOCA Murphys_E10_M11_WP2_121127_1028M 1040M AVOCA TRIB 1 Murphy_E10_M11_WP2_1040M_20120910 1040A AVOCA TRIB 2 Murphy_E10_M11_WP2_1040A_20120911 1039M AVOCA TRIB 3 Murphy_E10_M11_WP2_1039M_20120910 1039A AVOCA TRIB 4 Murphy_E10_M11_WP2_1039A_20120910 1039B AVOCA TRIB 5 Murphy_E10_M11_WP2_1039B_20120910 1039C AVOCA TRIB 6 Murphy_E10_M11_WP2_1039C_20120910 1038M AVOCA TRIB 7 Murphy_E10_WP2_M11_V0_20120910_1038m (9) Survey Issues: In some locations the surveyors were unable to gain access to record all information (these areas are discussed in section 4.3.6 (1)).The surveyors made efforts to acquire survey information and no further action was required having established areas were inaccessible due to overgrown vegetation.