Stockton-On-Tees BC Tees BC
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Stockton-on-Tees BC Level 2 Strategic Flood Risk Assessment Final Report June 2010 Matthew Clifford Spatial Planning Stockton-on-Tees Borough Council Gloucester House Church Road Stockton-on-Tees TS18 1TW JBA Office JBA Consulting The Brew House Wilderspool Park Greenalls Avenue Warrington WA4 6HL JBA Project Manager Jonathan Cooper Revision History Revision Ref / Date Amendments Issued to Issued Draft Report (v.1.0) 1 Digital Copy (as a pdf) September to Matthew Clifford and Cameron Sked Final Report (v.2.2) Updated following 1 Digital Copy (as a pdf) June 2010 comments from SBC to and EA. Matthew Clifford Contract This report describes work commissioned by Stockton-on-Tees Borough Council under Order Number P1 1867691. Stockton-on-Tees Borough Council’s representative for the contract was Matthew Clifford. Sam Wingfield of JBA Consulting carried out the work. Prepared by ........................................... Samuel Wingfield BSc MRes Analyst Reviewed by .......................................... Jonathan Cooper BEng MSc CEng MICE MCIWEM MloD DipCD Purpose This document has been prepared as a Final Level 2 SFRA for Stockton-on-Tees Borough 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. 2009s0156 SBC Level 2 SFRA V2.2.docx i Copyright © Jeremy Benn Associates Limited 2010 Carbon Footprint First publication of this document resulted in a carbon footprint of 223g. 283g Further printed copies of this document will result in a carbon footprint of 223g if 100% post-consumer recycled paper is used and 283g if primary-source paper is used. These figures assume the report is printed in black and white and in duplex. JBA is a carbon neutral company and the carbon emissions from our activities are offset. 2009s0156 SBC Level 2 SFRA V2.2.docx ii Executive Summary Introduction This Level 2 SFRA follows on from Volumes I, II and III which formed the level 1 SFRA. The purpose of this report is to provide an assessment of flood risk at key development and regeneration locations within Stockton BC. These areas have been identified in the Level 1 SFRA as being at risk of flooding but also necessary for Stockton's regeneration and development plans. These proposed regeneration allocations are: • Bowesfield North Phase 1 and Phase 2 - on the fluvial River Tees. • Boathouse Lane and Chandlers Wharf - on the fluvial River Tees. • Tees Marshalling Yard (TMY) - by the Old River Tees and tidal Tees. • Seal Sands (also includes North Tees Pools and Port Clarence sites) - by the tidal Tees. • Haverton Hill (also includes Casebourne and Billingham Reach sites) - by the Tidal Tees. Existing Flood Risk Management The first section of this report reviews the flood defences in Stockton BC. It is important to understand where the flood defences are, and what level of protection they provide. The Environment Agency's Flood Zone maps do not take into account flood defences so flood risk to defended areas will vary depending on the standard of the defences and the type of flooding they are subject to. The fluvial River Tees has significant stretches of raised defences along its course. The majority of these are agricultural defences and upstream of Stockton BC. There are some defences protecting small settlements by the River Tees in Stockton BC, e.g. Yarm. However, on the lower reaches, where the Bowesfield North (Phase 1 and 2), Boathouse Lane and Chandlers Wharf development sites are, the floodplains are undefended. The Tees Marshalling Yard (TMY) site is separated from the tidal Tees by an area of raised land. Whilst not considered a formal flood defence it has a significant role to play in reducing flood risk. Adjacent to the TMY, on the Old River Tees, there are raised defences, protecting the retail centre from tidal flooding. The tidal Tees has a number of formal and informal flood defence structures near to the proposed development allocations. On the north Tees Estuary boundary, the original frontage has been raised, which protects the hinterland from more frequent floods. The Port Clarence railway embankment partially blocks a tidal flood pathway to the Haverton Hill allocations (although this is not a flood defence structure). A defunct embankment to the west of Seal Sands prevents inundation from high probability flooding to the lower areas, although this embankment is considered (by the Environment Agency) to provide no flood defence benefits and is therefore not a formal flood defence. The Greatham Creek flood defence embankments have the greatest influence on flood risk in the area. These defences have been known to breach in the past and although improvements have been made, they are the main flood risk pathway to the allocations. 2009s0156 SBC Level 2 SFRA V2.2.docx iii Flood risk to the Level 2 allocations The Bowesfield North (Phase 1 and 2), Boathouse Lane and Chandlers Wharf sites are at risk of flooding from the River Tees. Parts of Bowesfield North Phase 1 are at risk from more frequent flooding while the remainder of the Bowesfield sites are at risk from less frequent flooding. Climate change increases the flood risk to these sites, especially due to tidal flooding when the predicted increase in sea levels is factored in. The Tees Marshalling Yard site has been predicted to be at risk of tidal flooding through modelling from the Old River Tees and the River Tees. However, only a very small part of the site is at risk of high probability flooding but the majority of the site is flooded when the effects of climate change are added. The Haverton Hill and Seal Sands sites are at risk of tidal flooding from the Tees Estuary. A breach in the Greatham Creek tidal defences is the primary flood pathway for both sets of allocations. The Haverton Hill sites are at risk of high probability flooding. A large proportion of the Seal Sands sites are free from flooding (even when climate change is added) but they are cut off by flood waters to the west and the Tees Estuary to the east. Outcomes The detailed modelling for the sites has produced flood extents, depths and hazards for different probability flood events, including the impacts of climate change. From these outputs it has been possible to provide evidence as to whether an allocation can be brought forward for development safely, without increasing flood risk elsewhere. This evidence has been presented to fulfil part c) of the Exception Test. It is recommended that the element of the Bowesfield North Phase 2 site at risk of high probability flooding, should be kept free from development by integrating this area into masterplans as green infrastructure or public open space It would be technically possible to provide flood mitigation as part of a development proposal for the area of the Bowesfield North Phase 2 site at risk of medium probability flooding. However, sequentially it is more difficult to justify development of a greenfield site which is at risk of flooding under the Sequential Test in PPS25. This site will also be at greater risk of flooding in the future. The Boathouse Lane and Chandlers Wharf sites could be developed with mitigation measures in place. The areas at risk from medium probability flooding should be relatively easy to mitigate. However, the Boathouse Lane site also includes an area at risk of high probability flooding (Boathouse Lane 2). The development layout within this area will need to factor in first floor only development (allowing the ground floor to flood) if development in this area is to go ahead. The Tees Marshalling Yard can be brought forward for a wide range of uses including residential development as the small area at risk of high probability flooding could be left free from development. Mitigation options for reducing flood risk from the more extreme flood events include land raising and tying in access roads to the high land to the north of the site. Two other mitigation options (including raised defences) were modelled for this site. The Haverton Hill sites can be brought forward for development if some ground and floor raising and raised access roads (or pedestrian access roads) can be implemented. The Seal Sands sites can be brought forward, although there are two sections of this allocation that are at risk of deep flooding. Planning permission for 2009s0156 SBC Level 2 SFRA V2.2.docx iv significant land raising has already been submitted for one of these areas. The main issue with Seal Sands is emergency access and egress. Measures to mitigate this are proposed which includes further consultation and planning with Stockton BC's emergency planning department. 2009s0156 SBC Level 2 SFRA V2.2.docx v Contents Executive Summary .......................................................................................... iii 1. Introduction ........................................................................................... 1 1.1 Background ............................................................................................. 1 1.2 Scope and objectives .............................................................................. 1 1.3 Study area ............................................................................................... 2 1.4 Outline methodology ................................................................................ 5 2. Flood Defence Asset Review ................................................................ 7 2.1 Flood defences at the Level