Bristol Avon 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 Bristol Avon Catchment Flood Management Plan (CFMP). This CFMP gives an overview of the flood risk in the Bristol Avon catchment and sets out our preferred plan for sustainable flood risk management over the next 50 to 100 years. The Bristol Avon CFMP is one of 77 CFMPs for England The Bristol Avon catchment has a history of flood risk, and Wales. Through the CFMPs, we have assessed and over the last 60 years numerous engineering inland flood risk across all of England and Wales for the schemes have been implemented to reduce flood risk first time. The CFMP considers all types of inland in the catchment. At present 7,000 properties are at risk flooding, from rivers, ground water, surface water and in the catchment in a 1% event. This is likely to increase tidal flooding, but not flooding directly from the sea to over 20,000 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: Bristol City policies which will deliver sustainable flood risk Council, 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 Bristol Avon 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 Bristol sub-area 12 2 Bath sub-area 13 3 Upper Avon sub-area 14 4 Lower Avon sub-area 16 5 Upper Bristol Frome sub-area 17 6 Mendip slopes and Long Ashton sub-area 18 7 Wootton Bassett and Dauntsey sub-area 19 8 Wiltshire Towns sub-area 20 9 Bradford-on-Avon and Frome sub-area 21 10 Markham Brook and Avonmouth sub-area 22 Map of CFMP policies 23 2 Environment Agency Bristol Avon 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 Bristol Avon Catchment Flood Management Plan 3 Catchment overview The Bristol Avon catchment is The overall catchment area is about The main geological features of the located in the west of England. It 2,221 square kilometres, and has a catchment are the limestone Mendip drains parts of Gloucestershire, population of around 1,050,000. Ten Hills, the oolitic limestone Cotswolds Wiltshire and Somerset and flows per cent of the catchment is and the chalk downs in the east, all through the major cities of Bristol urbanised. As well as Bristol and of which are major aquifers affecting and Bath to the Severn Estuary at Bath, its main urban areas include the hydrology of the catchment. Avonmouth. Chippenham, Frome, Trowbridge, Impermeable clays lie between the Devizes, Melksham, Malmesbury, west-sloping strata of the limestone Map 1 shows the location and extent Calne, Keynsham, Westbury, and the chalk, while sandstone and of the River Avon CFMP area. It Midsomer Norton and Radstock, Yate mudstone are exposed in the west of includes the Somerset Frome and and Chipping Sodbury, Bradford-on- the catchment. the Bristol Frome, plus a number of Avon and Corsham. other tributaries including Within the River Avon catchment Semington Brook, the River Chew The Bristol Avon catchment is there are a number of sites and Midford Brook. The downstream delineated by the Mendip Hills to the designated for their environmental limit of the CFMP area overlaps with south, the Cotswold Hills to the importance including Special Areas the upstream boundary of the Severn north, the Marlborough Downs and of Conservation (SAC), Special Estuary Shoreline Management Plan Salisbury Plain to the east and the Protection Areas (SPA) and Ramsar (SMP). Severn Estuary to the west. The River sites. Important environmental sites Avon’s direction and path is dictated in the catchment include four Areas The Severn Estuary SMP deals with by the catchment’s topography and of Outstanding Natural Beauty coastal flood management, while the results in the river following a (AONB) including the Cotswolds and CFMP considers tidal flood risk along crescent shape, initially flowing the Mendip Hills, five SACs, 23 SPAs, the River Avon upstream of Netham south from the Cotswolds before 98 Sites of Special Scientific Interest Weir to the tidal limit at Keynsham. bending west through Bath and (SSSIs) and 299 Scheduled Bristol. Monuments. 4 Environment Agency Bristol Avon Catchment Flood Management Plan Map 1. Location and extent of the Bristol Avon CFMP area Legend Bristol Avon CFMP Thornbury Urban areas Tetbury Swindon Malmesbury Main rivers Railway Motorway Chipping Sodbury Chippenham Nailsea Bath Calne Bristol Yatton Devizes N Radstock Cheddar Westbury Frome Wells Warminster Glastonbury 0 4 8 12 16 Kilometres Bruton © Crown Copyright. Environment Agency 100026380. ➜ High water levels on the Avon at Old Bridge – since replaced by Churchill Bridge – in Bath in 1960 Environment Agency Bristol Avon 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 17,000 chance (probability) of a particular risk for people, property, people and 7,000 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 Avon have if it happened. The probability probability river flood. This means and its tributaries, particularly in of a flood relates to the likelihood of that 1.6% of the total population Bristol, Bath, Malmesbury, a flood of that size occurring within a living in the catchment are currently Chippenham, Chew Magna, one year period.