Rye SWMP Stage 1 Technical Report
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Rye Stage 1 Surface Water Management Plan Final Report June 2015 East Sussex County Council County Hall St Anne's Crescent LEWES East Sussex BN7 1UE JBA Project Manager Jennifer Hill 35 Perrymount Road Haywards Heath West Sussex RH16 3BW Revision History Revision Ref / Date Issued Amendments Issued to Tom Schindl (East Sussex Draft Report v1 / May 2015 N/A County Council) Address comments from the Tom Schindl (East Sussex Final Report v2 / June 2015 steering group County Council) Address comments from Nick Claxton (East Sussex Final Report v3 / July 2015 Rother District Council County Council) Contract This report describes work commissioned by Tom Schindl, on behalf of East Sussex County Council, by an email dated 06/08/2014. East Sussex’s representative for the contract was Tom Schindl. Jenny Hill and Robert Waygood of JBA Consulting carried out this work. Prepared by .................................................. Jennifer Hill BSc MSc Analyst Reviewed by ................................................. Rachel Huitson MSc CEnv MCIWEM C.WEM Director Purpose This document has been prepared as a Final Report for East Sussex County Council. JBA Consulting accepts no responsibility or liability for any use that is made of this document other than by the Client for the purposes for which it was originally commissioned and prepared. JBA Consulting has no liability regarding the use of this report except to East Sussex County Council. Acknowledgements JBA would like to acknowledge and thank Rother District Council, Romney Marshes Internal Drainage Board, Southern Water, the Environment Agency, East Sussex County Council and REACT for all their assistance during this project. 1 Executive Summary A Surface Water Management Plan (SWMP) is a study to understand the flood risk that arises from local flooding, which is defined by the Flood and Water Management Act 2010 as flooding from surface runoff, groundwater, and ordinary watercourses. SWMPs are led by a partnership of flood risk management authorities who have responsibilities for aspects of local flooding, including the County Council, Local Authority, the Environment Agency, Sewerage Undertaker, Internal Drainage Boards and other relevant authorities. East Sussex County Council as Lead Local Flood Authority (LLFA) has led the production of the Rye Stage 1 SWMP in partnership with Rother District Council, the Environment Agency, Southern Water, Romney Marshes Area IDB and REACT. This steering group was established as part of the SWMP process. It is proposed that the monitoring and reporting of the implementation of the action will be undertaken locally and it is expected that partners will take forward actions independently, and convene as and when appropriate. Rye is a town in the Rother district in East Sussex. Expansion of the town is constrained by the Walland Marshes to the east and the High Weald Area of Outstanding Natural Beauty to the west. As a result, growth of the town has been restricted and the population has remained around 4,500 for the last 60 years. Relatively impermeable geological formations coupled with a high soil saturation creates conditions for high surface water flood risk in Rye. To better understand flood risk in Rye the SWMP has strived to collate all the available incident records of flooding along with any modelling of flood risk. This data has been supplied by the project partners. In attempting to understand the flood risk, a Source-Pathway-Receptor model was applied. The application of such a model facilitates flood risk mitigation by potentially addressing the source (often very difficult), blocking or altering the pathway and even removing the receptor e.g. navigate development away. Priority areas have been identified where there are repeated flood incidents and/or multiple flood mechanisms along with areas of predicted flood risk. The priority areas identified are: The Strand; The Tilling Green Estate, which includes the sub area of Tilling Green School; North Salts; and The Grove. The flood history and risk data has been used to draw up three action plans to manage the local flood risk. Each of these action plans operate at a different scale, with the generic action plan relevant to all of Rye the priority area action plan relevant to the identified priority areas and the incident specific action plan relating to individual flood incidents reported. Prioritised actions in Rye include commissioning a study to understand the flood mechanisms operating at the Strand; targeting highway gully maintenance on North Salts; and undertaking investigation works to understand the culvert condition under The Old Brickyard. There is the potential for future developments to be at risk of flooding and/or exacerbate the existing problem. Consequently, it is recommended that Rother District Council incorporate the SWMP findings into its development plans. 2 List of Figures Figure 1-1: A map to identify the location of all the watercourses in Rye ................................ 8 Figure 1-2: Conceptualisation of the integration of flooding mechanisms. ............................... 9 Figure 1-3: A map of Rye, the underlying geology ................................................................... 10 Figure 3-1: Flood history in Rye................................................................................................ 16 Figure 3-2: Main River flood risk ............................................................................................... 17 Figure 3-3: uFMfSW in Rye ...................................................................................................... 18 Figure 3-4: Frism output for the number of residential receptors affected by surface water flooding at a 1 in 1000 year return period ................................................................ 19 Figure 3-5: Groundwater flood risk in Rye ................................................................................ 20 Figure 3-6: Priority areas identified in Rye ............................................................................... 21 Figure 3-7: The Grove priority area .......................................................................................... 22 Figure 3-8: Tilling Green Estate priority area ............................................................................ 23 Figure 3-9: RY18 potential development site ........................................................................... 24 Figure 3-10: The Strand priority area ....................................................................................... 25 Figure 3-11: North Salts priority area ....................................................................................... 26 Figure 4-1: Strategic development areas identified in Rye. ...................................................... 27 Figure 5-1: Action plan for The Strand ..................................................................................... 31 Figure 5-2: Action plan for Tilling Green estate ........................................................................ 32 Figure 5-3: Action plan for Tilling Green School development site .......................................... 33 Figure 5-4: Action plan for North Salts ..................................................................................... 33 Figure 5-5: Action Plan for The Grove ...................................................................................... 34 List of Tables Table 2-1: Partners involved in the SWMP process ................................................................. 12 Table 2-2: Catchment data and data supplier .......................................................................... 13 Table 2-3: Flood risk modelling data and supplier .................................................................... 13 Table 2-4: Data quality scoring system .................................................................................... 14 Table 2-5: Received data and allocated quality score .............................................................. 14 Table 3-1: Number of receptors in Rye at risk from surface water flooding ............................. 19 Table 3-2: The Grove Source-Pathway-Receptor model ......................................................... 22 Table 3-3: Source-Pathway-Receptor for Tilling Green Estate ................................................. 23 Table 3-4: Source-Pathway-Receptor for Tilling Green School ............................................... 24 Table 3-5: Source-Pathway-Receptor for the Strand ............................................................... 25 Table 3-6: Source-Pathway-Receptor for North Salts .............................................................. 26 Table 4-1: Strategic development areas allocated in Rye ......................................................... 28 Table 5-1: Action plans ............................................................................................................. 29 3 Abbreviations AONB .............................. Area of Outstanding Natural Beauty AStGWF .......................... Areas Susceptible to Ground Water Flooding AStSWF .......................... Areas Susceptible to Surface Water Flooding BGS ................................ British Geological Survey CAM ................................ Condition Assessment Manual CFMP .............................. Catchment Flood Management Plan CIL .................................. Community Infrastructure Levy DAP ................................