Dorset Stour Catchment Flood Management Plan Summary Report June 2012 managing flood risk We are the Environment Agency. It’s our job to look after your environment and make it a better place – for you, and for future generations. Your environment is the air you breathe, the water you drink and the ground you walk on. Working with business, Government and society as a whole, we are making your environment cleaner and healthier. The Environment Agency. Out there, making your environment a better place. Published by: Environment Agency Manley House Kestrel Way Exeter EX2 7LQ Tel: 0870 8506506 Email: [email protected] www.environment-agency.gov.uk © Environment Agency All rights reserved. This document may be reproduced with prior permission of the Environment Agency. June 2012 Introduction I am pleased to introduce our summary of the Dorset Stour Catchment Flood Management Plan (CFMP). This CFMP gives an overview of the flood risk in the Dorset Stour catchment and sets out our preferred plan for sustainable flood risk management over the next 50 to 100 years. The Dorset Stour CFMP is one of 77 CFMPs for England The Dorset Stour catchment has a history of flood risk. and Wales. Through the CFMPs, we have assessed Over the last 50 years engineering schemes have been inland flood risk across all of England and Wales for the implemented to reduce flood risk in the catchment. At first time. The CFMP considers all types of inland present 780 properties are at risk in the catchment in a flooding, from rivers, ground water, surface water and 1% event (taking into account flood defences). This is tidal flooding, but not flooding directly from the sea likely to increase to over 2,900 properties in the future. (coastal flooding), which is covered by Shoreline We cannot reduce flood risk on our own, we will Management Plans (SMPs). Our coverage of surface therefore work closely with all our partners to improve and ground water is however limited due to a lack of the co-ordination of flood risk activities and agree the available information. most effective way to manage flood risk in the future. The role of CFMPs is to establish flood risk management We have worked with others including: Dorset District policies which will deliver sustainable flood risk Councils, Natural England, Wessex Water and the management for the long term. This is essential if we National Farmers Union to develop this plan. are to make the right investment decisions for the This is a summary of the main CFMP document, if you future and to help prepare ourselves effectively for the need to see the full document an electronic version can impact of climate change. We will use CFMPs to help us be obtained by emailing target our limited resources where the risks are [email protected] greatest. or alternatively paper copies can be viewed at any of This CFMP identifies flood risk management policies to our offices in South West Region. assist all key decision makers in the catchment. It was produced through a wide consultation and appraisal process, however it is only the first step towards an integrated approach to Flood Risk Management. As we all work together to achieve our objectives, we must monitor and listen to each others progress, discuss Richard Cresswell what has been achieved and consider where we may South West Regional Director need to review parts of the CFMP. Environment Agency Dorset Stour Catchment Flood Management Plan 1 Contents The purpose of a CFMP in managing flood risk 3 Catchment overview 4 Current and future flood risk 6 Future direction for flood risk management 10 Sub-areas 1 Bournemouth and Christchurch sub-area 12 2 St Leonards, Verwood and West Moors sub-area 14 3 Wimborne Minster, Corfe Mullen and Sturminster Marshall sub-area 16 4 Middle Stour, Tarrant, Winterborne and Allen sub-area 18 5 Blandford Forum sub-area 20 6 Hambledon Hills sub-area 21 7 Upper Stour and Blackmore Vale sub-area 22 8 Gillingham sub-area 24 9 Stourhead sub-area 25 Map of CFMP policies 26 2 Environment Agency Dorset Stour Catchment Flood Management Plan The purpose of a CFMP in managing flood risk CFMPs help us to understand the • Internal Drainage Boards (IDB), CFMPs aim to promote more scale and extent of flooding now and water companies and other sustainable approaches to in the future, and set policies for utilities to help plan their managing flood risk. The policies managing flood risk within the activities in the wider context of identified in the CFMP will be catchment. CFMPs should be used to the catchment; delivered through a combination of inform planning and decision different approaches. Together with • transportation planners; making by key stakeholders such as: our partners, we will implement • land owners, farmers and land these approaches through a range • the Environment Agency, who will managers that manage and of delivery plans, projects and use the plan to guide decisions operate land for agriculture, actions. on investment in further plans, conservation and amenity projects or actions; The relationship between the CFMP, purposes; delivery plans, strategies, projects • Regional Assemblies and local • the public and businesses to and actions is shown in Figure 1. authorities who can use the plan enhance their understanding of to inform spatial planning flood risk and how it will be activities and emergency managed. planning; Figure 1. The relationship between CFMPs, delivery plans, projects and actions Policy planning • CFMPs and Shoreline Management Plans. • Action plans define requirement for delivery plans, projects and actions. Policy delivery plans (see note) Projects and actions • Influence spatial planning to reduce risk and • Make sure our spending delivers the best restore floodplains. possible outcomes. • Prepare for and manage floods (including local • Focus on risk based targets, for example numbers Flood Warning plans). of households at risk. • Managing assets. • Water level management plans. • Land management and habitat creation. Note: Some plans may not be led by us – we may identify the • Surface water management plans. need and encourage their development. Environment Agency Dorset Stour Catchment Flood Management Plan 3 Catchment overview The Dorset Stour catchment is Towns within the catchment include sites. Important environmental sites located in the south west of England. Gillingham, Wincanton, Shaftesbury, in the catchment include Dorset It extends from the headwaters of the Sturminster Newton, Blandford Heaths (Ramsar, Site of Special River Stour at Stourhead flowing Forum, Verwood, Wimborne Minster Scientific Interest (SSSI), SPA, south east through Gillingham and and Corfe Mullen. Environmentally Sensitive Area) and Blandford Forum to Christchurch The Cranborne Chase and Wiltshire The landscape of the Dorset Stour Harbour where it enters the English Downs Area of Outstanding Natural catchment varies considerably with Channel. Beauty (AONB). Important the varying geology along the Stour’s environmental sites in the catchment Map 1 shows the location and extent course. This influences both the include two AONB, three SAC, one of the Dorset Stour CFMP area. It river’s characteristics and the causes Ramsar and SPA, 13 SSSI (including includes the Rivers Stour and its of flood risk across the catchment. the River Frome SSSI), two National tributaries including the rivers Crane, The upper catchment consists of Nature Reserves and 1,800 Allen, Tarrant, Winterbourne and impermeable clays of the Blackmore Scheduled Monuments. Lodden. The downstream limits of Vale resulting in shallow valleys with the CFMP area meets with the wide floodplains. The central band of upstream boundary of the Poole and permeable chalk on Cranborne Christchurch Bay Shoreline Chase results in steeper valleys and Management Plan (SMP) at narrow floodplains. The lower Christchurch. catchment has the semi-permeable The Poole and Christchurch Bay SMP sands, clays and gravels of the deals with coastal flood Dorset Heaths. management, while the CFMP Run-off and changes in water levels considers the risk from tidal flooding. are rapid in the many streams on the The overall catchment area is about clays. Water levels rise more slowly 1,240 square kilometres, and has a in the rivers across the chalk, the population of around 400,000. rivers being fed by groundwater. Almost three quarters of these Within the River Stour catchment people live in the Bournemouth, there are a number of sites Poole and Christchurch designated for their environmental conglomeration in the south of the importance including Special Areas catchment. Away from this urban of Conservation (SAC), Special conglomeration the catchment is Protection Areas (SPA) and Ramsar largely rural. 4 Environment Agency Dorset Stour Catchment Flood Management Plan Map 1. Location and extent of the Dorset Stour CFMP area Legend Stour CFMP Mere Urban areas Wincanton Salisbury Main rivers Railway Shaftesbury Motorway Marnhull Fordingbridge Sherborne Sturminster Newton Verwood Ringwood N Blandford Forum Wimborne Minster Dorchester Wareham Bournemouth 0 3 6 9 12 Kilometres © Crown Copyright. Environment Agency 100026380. ➜ The Stour in flood at Wimborne Minster Environment Agency Dorset Stour Catchment Flood Management Plan 5 Current and future flood risk Overview of the current flood risk What is at risk? Flood risk has two components: the Currently, the main sources of flood At present there are around 1,500 chance (probability) of a particular risk for people, property, people and 800 commercial and flood and the impact (or infrastructure and the land are: residential properties at risk in the consequence) that the flood would whole catchment from a 1% annual • river flooding from the River Cale have if it happened. The probability probability river flood taking into at Wincanton and River Stour in of a flood relates to the likelihood of account current flood defences. This Sturminster Newton and a flood of that size occurring within a means that 1% of the total Blandford Forum; one year period.