Arun and Western Streams Catchment Flood Management Plan Summary Report December 2009 Managing Flood Risk We Are the Environment Agency

Arun and Western Streams Catchment Flood Management Plan Summary Report December 2009 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 Guildbourne House Chatsworth Road Worthing, West Sussex BN11 1LD Tel: 08708 506 506 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. Introduction I am pleased to introduce our summary of the Arun and Western Streams Catchment Flood Management Plan (CFMP). This CFMP gives an overview of the flood risk in the Arun and Western Streams catchment and sets out our preferred plan for sustainable flood risk management over the next 50 to 100 years. The Arun and Western Streams CFMP is one of 77 The Arun and Western Streams CFMP has a history of CFMPs for England and Wales. Through the CFMPs, we fluvial, surface water, groundwater flooding and tidally have assessed inland flood risk across all of England influenced flooding. Flood risk is located in Arundel, and Wales for the first time. The CFMP considers all Littlehampton and Horsham. types of inland flooding, from rivers, groundwater, We cannot reduce flood risk on our own, we will surface water and tidal flooding, but not flooding therefore work closely with all our partners to improve directly from the sea (coastal flooding), which is the co-ordination of flood risk activities and agree the covered by Shoreline Management Plans (SMPs). Our most effective way to management flood risk in the coverage of surface and groundwater is however future. The key partners we have worked with to carry limited due to a lack of available information. out the actions to reduce flood risk include Arun The role of CFMPs is to establish flood risk District Council, Chichester District Council, East management policies which will deliver sustainable Hampshire District Council, Natural England, flood risk management for the long term. This is Hampshire County Council, Havant Borough Council, essential if we are to make the right investment Horsham District Council, Mole Valley District Council, decisions for the future and to help prepare ourselves Southern Water, Waverley Borough Council, West effectively for the impact of climate change. We will Sussex County Council. use CFMPs to help us target our limited resources This is a summary of the main CFMP document, if you where the risks are greatest. need to see the full document an electronic version This CFMP identifies flood risk management policies to can be obtained by emailing assist all key decision makers in the catchment. It was [email protected] or alternatively produced through a wide consultation and appraisal paper copies can be viewed at any of our offices in process, however it is only the first step towards an Southern Region. 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 what has been achieved and consider where we may Toby Willison need to review parts of the CFMP. Regional Director, Southern Region Environment Agency Arun and Western Streams Catchment Flood Management Plan 3 Contents The purpose of a CFMP in managing flood risk 5 Catchment overview 6 Current and future flood risk 8 Future direction for flood risk management 11 Sub-areas 1 Rother Valley/Middle Arun/The Weald 13 2 Horsham 14 3 Petersfield and Midhurst 15 4 Pulborough 16 5 The South Downs (East and West) 17 6 Coastal Plains and East Wittering 18 7 Lower River Arun 19 8 Manhood Peninsula and Rural Chichester Harbour/ 20 Upper Chalk Streams 9 Chichester and Lower Chalk Streams 22 Map of CFMP policies 24 4 Environment Agency Arun and Western Streams Catchment Flood Management Plan The purpose of a CFMP in managing flood risk CFMPs help us to understand the • IDBs, water companies and CFMPs aim to promote more scale and extent of flooding now other utilities to help plan their sustainable approaches to managing and in the future, and set policies activities in the wider context flood risk. The policies identified in for managing flood risk within the of the catchment; the CFMP will be delivered through a catchment. CFMPs should be used combination of different approaches. • Transportation planners; to inform planning and decision Together with our partners, we making by key stakeholders such as: • Land owners, farmers and will implement these approaches land managers that manage through a range of delivery plans, • The Environment Agency, who will and operate land for projects and actions. use the plan to guide decisions agriculture, conservation on investment in further plans, The relationship between the CFMP, and amenity purposes; projects or actions; delivery plans, strategies, projects • The public and businesses to and actions is shown in figure 1. • Regional planning bodies and enhance their understanding local authorities who can use the of flood risk and how it will plan to inform spatial planning be managed. activities and emergency 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 • Make sure our spending delivers the best and restore floodplains. possible outcomes. • Prepare for and manage floods • Focus on risk based targets, for example (including local flood warning plans). numbers 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 • Surface water management plans. identify the need and encourage their development. Environment Agency Arun and Western Streams Catchment Flood Management Plan 5 Catchment overview The river catchments of this CFMP Although largely rural, the area is The CFMP covers an area lie mainly in the West Sussex home to approximately 300,000 approximately 1400km2 drained by Districts of Chichester, Arun and people, with urban centres including the River Arun and its tributary the Horsham, together with small parts Littlehampton, Chichester, Bognor Rother, together with the of East Hampshire and of the Regis and Arundel on the coastal catchments of several smaller Waverley and Mole Valley in Surrey. plain, and Petersfield, Midhurst, streams to the west of the River Pulborough and Horsham to the Arun that discharge directly into The landscape varies from the hills north of the South Downs. Chichester Harbour. These include and steep scarp slopes of the South the Aldingbourne Rife; the Rifes Downs, to the gently rolling hills of Much of the area is recognised for surrounding Selsey and East the Low Weald and the wide Arun its environmental and cultural Wittering; the River Lavant, the valley flood plain south of value, with the South Downs being Bosham Stream and the River Ems. Pulborough. Flow characteristics of an Area of Outstanding Natural the rivers vary correspondingly, with Beauty (AONB) and a proposed Most watercourses have been fast flowing streams emerging from National Park. heavily modified over the years, for the High Weald area to the north, example the land beside the middle There are many valuable natural flowing into the low-lying coastal reaches of the Arun and Rother was habitats in the area, such as the plain where the gradient is less and drained to provide fertile Arun Valley south of Pulborough, the river flows are much slower. agricultural land from the original which contain spring fed floodplain marshes and the lower reaches of Tidal influence affects the character marshes and wetlands designated the Arun were trained and dredged of the lower parts of the River Arun by national, international and for navigation. In Roman times the and extends to above Pulborough. European conservation law. River Lavant was diverted through Chichester to provide water. ➜ Amberley Wildbrooks – part of the Arun Valley SPA and Ramsar site. 6 Environment Agency Arun and Western Streams Catchment Flood Management Plan Map 1. Overview of Arun and Western Streams CFMP. ‘The CFMP covers a large catchment drained by the River Arun and its tributary the Rother, together with the catchments of several smaller streams to the west of the River Arun that discharge directly into Chichester Harbour.’ Environment Agency Arun and Western Streams Catchment Flood Management Plan 7 Current and future flood risk Overview of the current flood risk Where is the risk? Flood risk is the combination of the Notable flood events have occurred The map on page 10 illustrates the probability of flooding and its impact, seven times in the last 40 years, consequences of a 1% annual that is, the chance of it happening with the most serious being in probability event (1 in a 100 year) and the consequences if it does December 1993 when over 200 occurring within the CFMP area. happen. We have assessed flood properties were flooded across the The areas with the highest risk across the CFMP area using catchment, and in Autumn 2000 concentration of properties at risk broad-scale computer modelling, when over 150 houses flooded. from river flooding are tabulated though making best use of existing Flood risk is likely to increase in the opposite: knowledge and models where future, as climate change increases appropriate. Flood risk figures take the magnitude and frequency of into account current flood defences.

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