Eastern Valleys Catchment Flood Management Plan Final Plan, March 2009 Environment Agency Wales i Eastern Valleys Catchment Flood Management Plan - Final Plan, March 2009 We are Environment Agency Wales. 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. Environment Agency Wales. Out there, making your environment a better place. Published by: Environment Agency Wales Ty Cambria, 29 Newport Road, Cardiff. CF24 0TP Tel: 08708 506506 © Environment Agency Wales, March 2009 All rights reserved. This document may be reproduced with prior permission of the Environment Agency. ii Environment Agency Wales Eastern Valleys Catchment Flood Management Plan - Final Plan, March 2009 Foreword I am pleased to introduce the Eastern Valleys Catchment Flood Management Plan (CFMP). Flooding and coastal erosion are the greatest natural threats our communities and environment face. Past flood events have very clearly demonstrated the devastation, hardship and risk to lives flooding can cause. Climate change predictions tell us we can expect more frequent and extreme weather conditions in the future, as well as rising sea levels. As a consequence it is predicted we will experience an increase in all types of flooding. To respond to the challenge of climate change we need to adapt our management of flood risk. We recognise it is not technically feasible, economically justifiable or environmentally acceptable to stop flooding happening altogether. Tackling flooding is more than just defending against floods. It means understanding the complex causes of flooding and taking co-ordinated action to reduce both the probability and impact of floods. We also need to recognise flooding may need to increase in some areas to reduce it in other, more sensitive locations. There are many factors within a catchment that affect flood risk. This plan assesses these factors and will allow us to better understand flood risk now and in the future. The plan describes how the river catchments behave and what the most sustainable flood risk management policies may be over the next 50 to 100 years. We can then use this direction to plan the most acceptable actions to manage flood risk for the long term, taking into account potential climate change and land use change pressures that may be placed on the natural water system. We will use the plan to steer our future investment, policies and overall flood risk management activities for the catchments. Our public and private partners will find it useful in adopting the principles of flood risk management in their decision making, especially where it can guide the planning of land use and avoid inappropriate development. Tim England South East Area Flood Risk Manager Environment Agency Wales Environment Agency Wales iii Eastern Valleys Catchment Flood Management Plan - Final Plan, March 2009 Contents List of Tables .......................................................................................................................... vii List of Figures ......................................................................................................................... xi Executive summary .............................................................................................................. xvi 1 Introduction........................................................................................................................ 1 1.1 Background 1 1.2 Aims and scope 2 1.3 Policies 5 1.4 Links with other plans 6 1.4.1 Shoreline Management Plans 6 1.4.2 Water Framework Directive: River Basin Management Plans 7 1.4.3 European Union Directive: Assessment and Management of Flood Risks 9 1.4.4 Welsh Assembly Government Environment Strategy 9 1.4.5 Planning documents and guidance 9 1.5 Environmental Assessment 14 1.5.1 Strategic Environmental Assessment 14 1.5.2 Habitats Directive 15 1.6 Involving others 15 2 Catchment overview........................................................................................................ 17 2.1 Definition and extent of the catchment 17 2.2 Topography 22 2.3 Geology and hydrogeology 25 2.3.1 Geology 25 2.3.2 Hydrogeology 25 2.4 Geomorphology 28 2.4.1 Geomorphology of the Eastern Valleys watercourses 28 2.5 Soils 29 2.6 Land use and land management 31 2.6.1 Land types 31 2.6.2 Land Management 32 2.6.3 Agri-Environment Schemes 33 2.6.4 Urban land use 37 2.7 Hydrology 38 2.7.1 Introduction 38 iv Environment Agency Wales Eastern Valleys Catchment Flood Management Plan - Final Plan, March 2009 2.7.2 Ebbw (excluding the Wentlooge Levels) 42 2.7.3 Rhymney 44 2.8 The Natural and Historic Environment 46 2.9 Communities and the local economy 63 3 Current flood risks and management............................................................................ 66 3.1 History of flooding 68 3.2 Sources and probability of flooding 77 3.2.1 Introduction 77 3.2.2 Identification of main areas 78 3.2.3 River flooding 84 3.2.4 Tidal flooding 103 3.2.5 Surface water and sewer flooding 111 3.2.6 Groundwater flooding 115 3.3 Consequences of flooding 116 3.3.1 Introduction 116 3.3.2 Methodology 116 3.3.3 Risks to people 117 3.3.4 Risks to property and infrastructure 138 3.3.5 Risks to the environment 156 3.4 Summary of flood risk 159 3.5 Existing flood risk management 167 3.5.1 Flood mapping and data management 167 3.5.2 Strategic planning and development control 176 3.5.3 Flood defence asset management and operations delivery 177 3.5.4 Flood forecasting and flood incident management 189 4 Future flood risk ............................................................................................................ 193 4.1 Introduction 193 4.1.1 Urban development 193 4.1.2 Climate change 195 4.1.3 Land use management 195 4.2 Future scenarios 196 4.2.1 Sensitivity Testing 196 4.2.2 Development of future scenario 199 4.3 Assessment of future flood risk 201 4.3.1 Introduction 201 River flooding 202 Environment Agency Wales v Eastern Valleys Catchment Flood Management Plan - Final Plan, March 2009 4.3.2 Flood risk to people 225 4.3.3 Risks to property and infrastructure 255 4.3.4 Flood risk to the environment 285 4.4 Flood risk at key locations 288 4.5 Comparison of current and future flood risk 297 5 Catchment Objectives................................................................................................... 308 5.1 Introduction 308 5.2 Catchment opportunities and constraints 309 5.3 CFMP Objectives 315 6 Policy appraisal ............................................................................................................. 340 6.1 Introduction 340 6.2 Policy Units 341 6.3 Policy Appraisal 352 6.4 Potential interaction between policy units 380 7 Delivering the CFMP...................................................................................................... 382 7.1 Introduction 382 7.2 Action plan 386 7.3 Consequences of our policies 423 7.4 Monitoring, review and evaluation 425 Glossary of Terms................................................................................................................ 426 List of abbreviations ............................................................................................................ 450 References............................................................................................................................ 455 Appendix A – Responsibilities for Flood Risk Management and associated activities Appendix B – Environment Report and Policy Appraisal Tables Appendix C – Links to Wales Environment Strategy and Water Framework Directive Appendix D – CFMP Consultation Response vi Environment Agency Wales Eastern Valleys Catchment Flood Management Plan - Final Plan, March 2009 List of Tables Table 1.1 Review of plans, policies and programmes and relevance to the Eastern Valleys CFMP ..................................................................................................................................11 Table 2.1 Eastern Valleys CFMP catchment overview ..............................................................18 Table 2.2 Agricultural Land Classification ..................................................................................32 Table 2.3 Flow and level hydrometric stations in the Eastern Valleys .......................................39 Table 2.4 Event and storage rain gauges in Eastern Valleys ....................................................40 Table 2.5 Flood peak travel time between gauging stations on the River Ebbw........................43 Table 2.6 Sites of international and European nature conservation importance in the Eastern Valleys .................................................................................................................................47 Table 2.7 Priority LBAP habitats and species ............................................................................51 Table 2.8 Salmonid waters in the Eastern Valleys.....................................................................53 Table 2.9 Summary of historic environment assets in Eastern Valleys CFMP area ..................54 Table 2.10 Population statistics for the Eastern Valleys administrative areas (Source: Census 2001) ...................................................................................................................................63 Table