Carrick-On-Suir Piltown Portlaw
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4 HYDRAULIC MODEL DETAILS 4.1 CARRICK-ON-SUIR 4.1.1 Introduction Model 7 comprises four of the AFAs under the Suir CFRAM Study; these are Carrick-on-Suir, Piltown, Portlaw and Clodiagh. Model 7 is subject to both fluvial and tidal flood risk. It encompasses a 33km stretch of the River Suir, as well as nine associated tributaries and one canal reach. The Carrick-On-Suir AFA is affected by the River Suir (at the upstream extent of the model) and its tributaries the Glen River, Lingaun River and the Suir Trib 1. The Piltown AFA is affected by a tributary of the Suir River, the Pil River. The Fiddown AFA is affected by the Suir River. The Portlaw AFA is affected by a tributary of the Suir River, the Clodiagh River, two small tributary of the Clodiagh and a short stretch of canal. The Suir catchment catchment is predominantly rural. The majority of the Suir catchment drainage enters Model 7 at the Suir River upstream of Carrick-on-Suir AFA. The tributaries of the Suir River that drain that largest areas are the Clodiagh River draining an area of 130km2, the Pil River draining an area of 85km2 and the Glen River draining an area of almost 44km2. There are two gauging stations located along the length of the Model: Fiddown (16061) has continuous tide data from 1968 to 2005 which is considered to be of good quality and therefore can be used for verification of the hydrometric model for this reach of the Suir. Carrick-on-Suir (16062) has continuous tide data from 1972 to 2005. For the purpose of the CFRAM study, the tide data for this gauge is to be used as part of the development for the hydraulic model. A number of watercourse have been identified as HPW in Model 7. Stretches of the Suir River, Glen River and Ligaun River are identified as HPW as they pass through the Carrick-on-Suir AFA. These reaches have been modelled as 1D-2D using the MIKE suite software. A short stretch of the Pil River has been identified as HPW as it passes through the Piltown AFA. A stretch of the Clodiagh River and canal are identified as HPW as they pass through the Portlaw AFA. All of these reaches and the associated designated MPW reaches have been modelled as 1D using MIKE. 4.1.2 Hydraulic Model Schematisation The maps below illustrate the extent of the modelled catchment, river centre line, HEP locations and AFA extents as applicable. Model 7 contains 9 Upstream Limit HEPs, 1 Downstream Limit HEP, 2 Gauging Station HEPs, 10 Intermediate HEPs and 16 Tributary HEPS. Due to the quantity of tributary HEPS, the intermediate HEPs are not shown. The maps below illustrate the modelled extents and general topography of the catchment. 4.1.3 Hydraulic Model Construction 4.1.3.1 Critical Structures Photographs of the structures are not available. As such the cross-section of the structure is shown below for reference. 2775 (Creamery Rd., Piltown AFA) - Restricts flow in the River Pil 2860 (Main St., Piltown AFA) – Restricts flow in the River Pil 697J (Sir Johns Rd., Carrick-on-Suir AFA) – Restricts flow in the Glen River (4612 chainage) 662J (Railway Bridge, Carrick-on-Suir AFA) – Restricts flow in the Glen River (4650 chainage) 418J (Orchard Crescent, Carrick-on-Suir AFA) – Restricts flow in the Glen River (4888 chainage). 218J (Clonmel Rd., Carrick-on-Suir AFA) – Restricts flow in the Glen River 4.1.3.2 Defences Type Watercourse Bank Model Start Model End Modelled Chainage Chainage Standard of (approx.) (approx.) Protection (AEP) 1 WALL GLEN/GLEN LEFT GLEN TRIB GLEN 4974 2% AEP TRIB 231 2 EMBANKMENT GLEN LEFT 4974 5080 2% AEP 3 EMBANKMENT GLEN RIGHT 4884 5020 2% AEP 4 WALL GLEN RIGHT 5020 5080 2% AEP 5 WALL GLEN LEFT 5094 5244 2% AEP 6 WALL GLEN RIGHT 5094 5244 2% AEP 7 EMBANKMENT SUIR LEFT 9215 9408 2% AEP 8 WALL SUIR LEFT 9408 9769 2% AEP 9 EMBANKMENT SUIR RIGHT 9446 9515 2% AEP 10 WALL SUIR RIGHT 9515 9769 2% AEP 11 WALL SUIR LEFT 9787 10058 2% AEP 12 WALL SUIR LEFT 10078 10280 2% AEP 13 EMBANKMENT SUIR LEFT 10280 10496 2% AEP 14 WALL GLEN TRIB 1 LEFT 158 210 2% AEP Informal 15 WALL SUIR LEFT 17443 17545 0.1% AEP The figure below shows the locations of the flood defences in Carrick-on-Suir: 14 3 1 4 6 2 5 7 8 13 11 9 12 10 There are 14 formal defences (6 walls and 8 embankments) in the Carrick-on-Suir AFA. The main defences are located along the right and left banks of the Suir River, with seven located along the left and right banks of the Glen River. All defences have been represented using the survey crest heights. All of the flood defences in Carrick-on-Suir are designed to defend up to a 1 in 50 year event (2% AEP). There are no formal flood defences in the Piltown or Portlaw AFAs. There is a short stretch of flood wall in the Fiddown AFA (shown above). 4.1.3.3 Information on Other Structures No survey data was available for a culvert at the downstream end of the Glen River at 1556 chainage, this was estimated from a site visit and using aerial mapping. On the River Suir in Fiddown AFA the bridge is too large to be hydraulically significant. As such it was not included in the model. However, to ensure the affect of the bridge piers was accounted for in the model the resistance was locally increased. In addition to this, the data on the southern limb (right) of the Suir River here was estimated as no data was available. In Fiddown AFA the watercourse splits into two. No data was available for the bridge on the southern limb (right) the Suir River (chainage 17453). The data on the southern limb (right) of the Suir River here was estimated using aerial imaging as no data was available (see below). 4.1.3.4 Data Review & Quality Survey data for this model was surveyed in 1960s in the MPWs and 2007 in the HPW reaches. The original survey data was not available and so verification of this data has not been possible. The downstream reach (1.5km) of the Piltown River survey data was not available, including the dimensions of the railway bridge crossing. Cross-sections were interpolated along this reach. In Carrick-on-Suir AFA there were no levels available for the flood wall at the downstream end of the Glen River. This level was taken from the parapet of the bridge which is considered an acceptable approach; see photo below. Floodwall Culvert Parapet The bathymetry has been adjusted to account for the deck levels of roads and bridges. 4.1.3.5 Model Boundaries Full details of the flow estimates are provided in the Suir CFRAM Hydrology Report. The boundary conditions implemented in the model are shown below. A number of inflow hydrographs are used as the upstream boundaries of the model. No adjustments have been made to the hydrological inputs. The below figure below provides an example of the associated upstream hydrograph generated for the 0.1% AEP return period in the Suir River. The downstream boundary condition is a tide hydrograph. Outputs from the Irish Coastal Protection Strategy Study (ICPSS) have resulted in extreme tidal and storm surge water levels being made available around the Irish Coast for a range of Annual Exceedance Probabilities (AEPs). The locations of the ICPSS nodes along with the relevant AFA locations are shown in the figure below. The associated AEP water levels for each of the nodes are contained in the table following the location diagram. The coastal boundary for this model is set across Waterford Harbour. The closest ICPSS point to the boundary is W_5. This was used to provide the extreme water level information. ICPSS AEP (%) Node 50 20 10 5 2 1 0.5 0.1 Highest Total Water Level to OD Malin (m) W_5 2.33 2.42 2.49 2.55 2.63 2.69 2.76 2.9 A representative tidal profile for Waterford Harbour was generated based on Admiralty Tide Table data for Dunmore East. A normalised 48 hour surge profile was scaled based on the difference between the peak water level of the generated tidal profile and the target extreme water level from the table above. The scaled surge profile was then appended to the tidal profile to achieve a representative combined tidal and storm surge profile for the required AEP events. The figure below illustrates the tidal profile, storm surge profile and resultant combined water level profile. The water level profile was applied as a dynamic water level boundary at the downstream extent of the Suir River in Model 7 (chainage 32750). The figure below provides an example of the associated downstream tide hydrograph in the Suir River. 4.1.3.6 Model Roughness Canal - CLOM_0720W Canal - CLOM_1093W Manning’s n = 0.060 Manning’s n = 0.040 Clean winding, some weeds and stones, medium to Clean winding, gravel bottom, light brush on banks dense brush in winter Pil Trib – 744 Clodiagh River – 19CLOD004608 Manning’s n = 0.035 Manning’s n = 0.040 Clean fairly straight with stones and weeds, Clean, winding, with some pools and shoals floodplain has short grass Clodiagh River – 19CLOD002333 Clodiagh Trib 1 – 16CLO10002363 Manning’s n = 0.040 Manning’s n = 0.0400 Clean, winding some pools and shoal, floodplain Straight, lower stages, ineffective slopes and has light brush and trees in summer sections, floodplain has short grass Clodiagh Trib 1 – 16CL3000110 Clodiagh Trib 2 – 19CL2000387 Manning’s n = 0.040 Manning’s n = 0.040 Clean straight, lower stages more ineffective slopes Clean winding, some pools and shoals, floodplain and sections has light brush and trees in summer Glen River – 719 Glen River – 3101 Manning’s n = 0.035 Manning’s = 0.035 Clean, straight, full stage, no rifts or deep pools, Clean, winding, some pools and shoals, with some some stones and weeds weeds and stones Glen Trib 1 – 119A Linguan River – 1796 Manning’s