Allerdale Borough Council 2010 SFRA Update Volume 2 Final Report January 2011 Allerdale Borough Council Allerdale House Workington Cumbria CA14 3YJ JBA Office JBA Consulting The Brew House Wilderspool Park Greenall's Avenue Warrington WA4 6HL JBA Project Manager Chris Smith Revision History Revision Ref / Date Issued Amendments Issued to Version 1.0 Draft Report Allerdale BC and EA Final report. Version 2.0 Updated following EA and Allerdale BC and EA ABC reviews Contract This report describes work commissioned by Steve Robinson, on behalf of Allerdale Borough Council, by an email dated 26/08/10. Allerdale Borough Council’s representative for the contract was Steve Robinson. Sam Wingfield and Chris Smith of JBA Consulting carried out this work. Prepared by .................................................. Samuel Wingfield BSc MRes Analyst Prepared by .................................................. Chris Isherwood BSc MSc DipWEM Analyst Purpose This document has been prepared as a final report for Allerdale Borough. 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 Allerdale Borough Council. 2010s4396_ABC_SFRA_Vol2_final.docx i Copyright © Jeremy Benn Associates Limited 2011 Carbon Footprint 514g A printed copy of the main text in this document will result in a carbon footprint of 404g if 100% post-consumer recycled paper is used and 514g if primary-source paper is used. These figures assume the report is printed in black and white on A4 paper and in duplex. JBA is a carbon neutral company and the carbon emissions from our activities are offset. 2010s4396_ABC_SFRA_Vol2_final.docx ii Executive Summary 2010 Allerdale SFRA In 2006 JBA Consulting were commissioned by Allerdale BC to undertake a Strategic Flood Risk Assessment (SFRA) for the Allerdale area, this was completed in 2007. The purpose of this assessment was to identify the strategic flood risk constraints to the area. This report is an update to the 2007 SFRA. For this update, the SFRA has been broken down in to two volumes. Volume 1 covers the more general policy and guidance information that requires updating. It includes updates to the planning framework, flood risk policy, SFRA methodology and strategic guidance for developers. Volume 1 also includes specific flood risk policy ideas for areas at a high risk of flooding. This volume (Volume 2) contains flood risk information specific to Allerdale. It includes a review of the November 2009 flood event, updates to the Flood Zones, production of a Flood Zone 3b for the Derwent and the production of new surface water and Flood Zone mapping. The impact of the new Flood Zones on Allerdale’s proposed future development allocations along the Derwent has been assessed. All of the allocations have been initially assessed within the Sequential Test Spreadsheet. Surface water / local drainage flooding information has been collected and displayed in figures that show the main surface water flood risk locations. These maps have also been used in the Sequential Test spreadsheet to show the allocations that may have surface water flooding issues. Main Findings During the November 2009 flood event, an intense, prolonged rain storm lead to high river flows and flooding problems which were exacerbated by the very wet ground conditions. The rainfall totals and river flows were the highest on record in the Derwent catchment. The worst hit areas were affected by flooding from the Rivers Derwent & Cocker. Cockermouth was impacted the most, but flood damage also occurred in Keswick and Workington. Following this flood event, some updates to the Flood Zones have been made along with a hydrology study by the Environment Agency. This work will eventually lead to full flood mapping updates along the River Derwent. The hydrology study indicates that Flood Zones 3a (1 in 100 year fluvial flood event) and 3b (1 in 20 year fluvial flood event) will increase in extent. The latest information available has been used to assess flood risk to Allerdale’s proposed development allocations. Some sites may need to be removed or a more detailed study undertaken as a result of these updates, while others are shown to be at a reduced risk of flooding. Recommendations have been made on how to take these sites forward. Local drainage flooding information and the Environment Agency’s Areas Susceptible to Surface Water Flooding maps have been collected. This information has been used to identify the main surface water hot spot locations which will be taken forward in the Cumbria SWMP. These are: • Workington • Flimby • Maryport • Cockermouth • Keswick • Wigton The Sequential Test spreadsheet also shows that a number of proposed development allocations are vulnerable to surface water flooding. 2010s4396_ABC_SFRA_Vol2_final.docx iii Recommendations The policy ideas produced in Volume 1 should be used to produce specific policies for the areas at high risk of flooding in Allerdale. These policies should be produced in consultation with the Environment Agency, in order to get an agreement before being submitted in the Core Strategy. Volume 1 of this SFRA update also provides guidance for developers and planners with regards to development and flood risk. This should be referred to and provided to developers where appropriate. The Sequential Test spreadsheet should be used to complement the Sequential Test along with the updated guidance produced for this SFRA. The evidence for the completion of the Sequential Test should be recorded and submitted as part of the Sustainability Appraisal of the Core Strategy. The recommendations provided in Table 7 (including the development sites at risk near to Cockermouth) should be reviewed. If any of these sites are essential to the Core Strategy, then a more detailed assessment (Level 2 SFRA) may be required. The Sequential Test spreadsheet should also be used to highlight allocations where surface water flooding may be an issue. Once the full flood mapping for the Derwent has been undertaken, the existing and any additional future development allocations should be reviewed to ensure they are not at risk of flooding and can be allocated in the Core Strategy. The Cumbria Surface Water Management Plan (SWMP) is underway. The areas at greatest risk of surface water flooding will be taken forward to an ‘intermediate assessment’ and some of these will then be taken forward into the options appraisal stage. This will not pick up all of the surface water / local drainage issues. Allerdale BC should maintain their Making Space for Water (MSFW) group hotspots list and continue to tackle to local flood risk issues. Some of these smaller flood risk locations may be picked up by the Cumbria SWMP ‘quick wins’ option or registered on the SWMP Action Plan. 2010s4396_ABC_SFRA_Vol2_final.docx iv Contents Executive Summary .......................................................................................................... iii 1. Introduction .......................................................................................................... 1 1.1 SFRA Update ......................................................................................................... 1 1.2 Study Area ............................................................................................................. 1 1.3 Flood Risk in Allerdale ........................................................................................... 2 2. Review of November 2009 Flood Event ............................................................. 6 2.1 Summary 2009 flood event .................................................................................... 6 2.2 Keswick .................................................................................................................. 10 2.3 Cockermouth ......................................................................................................... 15 2.4 Workington ............................................................................................................. 17 3. Latest Flood Zones .............................................................................................. 20 3.1 Introduction ............................................................................................................ 20 3.2 Changes to the Flood Zones ................................................................................. 20 4. New Flood Zones and future development ....................................................... 27 4.1 Introduction ............................................................................................................ 27 4.2 Allocations at risk of flooding in Cockermouth ....................................................... 27 4.3 Allocations at risk of flooding in Workington .......................................................... 29 4.4 Sequential Test spreadsheet ................................................................................. 30 5. Surface Water Flooding and CDAs .................................................................... 35 5.1 Introduction ............................................................................................................ 35 5.2 Data provided ........................................................................................................ 36 5.3 Critical Drainage Areas .........................................................................................