Flood Risk Management Plan

LIT 10224 Flood risk management plan South West river basin district summary March 2016 What are flood risk management plans? Flood risk management plans (FRMPs) explain the risk of flooding from rivers, the sea, surface water, groundwater and reservoirs. FRMPs set out how risk management authorities will work with communities to manage flood and coastal risk over the next 6 years. Risk management authorities include the Environment Agency, local councils, internal drainage boards, Highways Authorities, Highways England and lead local flood authorities (LLFAs). Each EU member country must produce FRMPs as set out in the EU Floods Directive 2007. Each FRMP covers a specific river basin district. There are 11 river basin districts in England and Wales, as defined in the legislation. A river basin district is an area of land covering one or more river catchments. A river catchment is the area of land from which rainfall drains to a specific river. Each river basin district also has a river basin management plan, which looks at how to protect and improve water quality, and use water in a sustainable way. FRMPs and river basin management plans work to a 6- year planning cycle. The current cycle is from 2015 to 2021. We have developed the South West FRMP alongside the South West river basin management plan so that flood defence schemes can provide wider environmental benefits. Both flood risk management and river basin planning form an important part of a collaborative and integrated approach to catchment planning for water. Building on this essential work, and in the context of the Governments 25-year environment plan, we aim to move towards more integrated planning for the environment over the next cycle. This will be done on a catchment basis and will draw together and integrate objectives for flood risk management, water management, and biodiversity, with the aim of maximising the multiple benefits that can be achieved. Flood risk in the South West river basin district The South West river basin district covers 21,000km2 and includes Cornwall, the Isles of Scilly, Devon, Dorset, Somerset, and parts of North Somerset, Hampshire and Wiltshire. It is divided into 9 management catchments and includes 1 strategic area, the Somerset Levels and Moors, as shown in Figure 1. Strategic areas consider flood risk management across more than one river catchment, so that organisations can work together in a co-ordinated way. River catchments in the South West river basin district vary considerably, leading to lots of different types of flood risk. Somerset has predominantly flat catchments with wide rivers that take a long time to respond to rainfall. Devon, Cornwall and West Dorset have smaller, steep catchments with fast-flowing rivers that respond rapidly to rainfall. Rivers in the Avon Hampshire management catchment receive large flows from chalk aquifers (where water is stored underground). These rivers react relatively slowly to rainfall but long periods of wet weather can result in prolonged flooding. The long thin maritime nature of the river basin, with two exposed Atlantic coastlines of almost 1,000km in length mean that it’s very vulnerable to storms, coastal flooding and river tide locking (when the level of the incoming high tide stops the river water flowing out to sea). These flood risks have been clearly demonstrated over the last few years. High energy waves and storms from the Atlantic can cause extensive physical damage to defences and property, including the Isles of Scilly. www.gov.uk/environment-agency 1 of 9 In the South West river basin district there are over 36,000 people living at high risk of flooding from rivers and the sea. Over 25,000 people are at high risk of surface water flooding (flooding which happens when drainage systems become overloaded with high volumes of rainfall). Towns such as Plymouth, Exeter, Taunton, Bridgwater and Poole have large numbers of properties at risk from multiple sources of flooding. In these areas, risk management authorities will work together to manage the risks of flooding from rivers, the sea, surface water and sewers. Being largely rural, many people live outside major towns and cities. Delivering protection to these remote communities provides challenges but improving community resilience and flood warning is a very important part of the solution. In parts of Devon, Cornwall and Dorset where there are steep valleys, river levels can rise very quickly during intense rainfall. These are known as ‘rapid response areas’. This poses a big risk, particularly to these small or dispersed communities. The agricultural nature has a major influence on the water environment. Learning from those who manage the land provides opportunities to work in partnership to deliver benefits to key communities. In some lowland areas, such as the Somerset Levels and Moors, land is at or near sea level and lies on manmade drainage systems, including channels, pumping stations and land drainage. Flooding in these areas can be significant and can last for months at a time. The South West river basin district has a limited network of major roads and there is a single railway line in and out of Devon and Cornwall. Flooding can significantly affect main transport networks affecting residents, visitors and the economy, both locally and nationally. Figure 1: Management catchments and the strategic area in the South West river basin district www.gov.uk/environment -agency 2 of 9 During December 2015, Storms Desmond, Eva and Frank brought record breaking levels of rainfall and significant flooding to some parts of the country. On 5 and 6 December the highest ever river flows were registered in several large catchments including the Eden, Lune and Tyne. On 25 and 26 December further record river levels were registered for many large rivers draining the Pennines. The Met Office confirmed that December 2015 was the wettest on record in parts of the UK. Across the country over 19,000 properties were flooded, with thousands more affected by loss of power supply and travel disruption. Existing flood defences played an essential part in protecting thousands of homes during December with 12,500 benefitting during Storm Desmond and 10,900 during Storm Eva. Support to affected communities, business and the agricultural sector is in place, along with a programme of inspections and repairs to damaged defences. It is essential to ensure that we have the very best possible plans in place for flood management across the whole country. In response to the December floods the Government has put in place a National Flood Resilience Review pinpoint where our defences and modelling need strengthening. The Local Flood Partnerships in Cumbria and Yorkshire, also set up in response to the December floods, will bring together a wide range of organisations and communities to develop Flood Action Plans. These actions will complement the measures in the FRMP and the learning from this approach will be shared across the country. Characteristics of the South West river basin district Dorset and Avon Hampshire management catchments The rivers in west Dorset are small, fast-reacting streams, where rainfall run-off travels quickly from hills either directly into the sea or into the Fleet (the lagoon behind Chesil beach). There are the wetlands of Radipole and Lodmoor and the unique coastal features of Portland Harbour, the Fleet Lagoon, Chesil beach and Lyme Bay. The River Frome (Figure 2) and the River Piddle drain from the North Dorset Downs, flowing through Dorset into Poole Harbour. The steep slopes inland lead to fast run-off after rain. The large, low-lying wetland areas around Poole Harbour help to disperse run-off from rain in this area. The Dorset Stour river starts in Stourhead gardens (Wiltshire) and flows Figure 2: River Frome in flood in the south-east to the English Channel at Christchurch Harbour. Wareham area of Dorset The water in rivers in the Hampshire Avon management catchment comes mainly from chalk aquifers. The rivers react slowly to rainfall because rain soaks into the ground and travels underground through the aquifer before it reaches the river. After long periods of very wet weather, the towns and villages between Salisbury and Christchurch can experience flooding lasting several weeks. North Devon, South Devon and East Devon management catchments The North Devon management catchment includes areas drained by the rivers Taw and Torridge and the north Devon coastal rivers. Steeply sloping tributaries (smaller rivers flowing into a bigger river) drain from the high ground of Exmoor and Dartmoor to the low-lying Taw and Torridge estuaries, or directly to the sea. Most of the properties at risk of flooding are in Barnstaple, Bideford and Braunton. The South Devon management catchment covers the catchments of the rivers Teign, Dart, Erme and Avon. Steeply sloping tributaries drain from the high ground of Dartmoor, to the wider valleys downstream and Figure 3: River Axe floodplain at Bow eventually into estuaries. Several small rivers drain the Torbay area. Bridge, Axminster Most of the properties at risk of flooding are in Torbay, Newton Abbot www.gov.uk/environment -agency 3 of 9 and Totnes. The East Devon management catchment includes the catchments of the rivers Exe, Sid, Otter, Axe, Lim and their tributaries. The land in the catchment varies, with steep, narrow valleys where the rivers start, that respond rapidly to rainfall. Further downstream there are wide flood plains that store large volumes of flood water (Figure 3). Most of the properties at risk of flooding are in Tiverton, Exeter and Exmouth. Tamar; North Cornwall, Seaton, Looe and Fowey; West Cornwall and the Fal (including the Isles of Scilly) management catchments The north and east of the Tamar catchment drains from Dartmoor, including the rivers Plym, Yealm and Lyd.

Load more