Coastal Defence
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Dorset Marine and Coastal Topic Paper Series 2010 Coastal Defence Dorset has a dynamic coastline: in the past, uninterrupted coastal processes created some of its most beautiful and important features . However, the issue of coastal retreat in this area was first recorded in 1366 at Highcliffe. Erosion and flooding by the sea are hazardous to property and infrastructure on the coast, and so there will always be demands for coastal defence works to protect property. This will mean that natural processes are inevitably interrupted. Data regarding climate change and sea level rise (SLR) suggest that these natural processes will accelerate during the 21st century and this will place greater pressure on both available finances and engineering solutions. Balancing the desire to protect property whilst maintaining the integrity of the natural coast requires creative engineering solutions, and difficult decisions have to be made about where and how to protect. • Coast protection works which protect the processes in neighbouring coastal against erosion. This is where the process units. land behind the works is higher than Sediment cell is a term frequently used any expected tidal flooding level. with regards to Shoreline Management These works are carried out under the Plans. It indicates a section of coastline Coast Protection Act 1949 and its associated nearshore area within which the movement of coarse sediment Coastal defence is a broad term used to (sand and shingle) is largely self- include both flood defence and coast contained. The movement and behaviour protection . of sand and shingle within one cell should Flood defence (river and sea) refers to not significantly affect beaches in a systems (including both hard engineering neighbouring sediment cell, but this Gabion filed wire baskets. Copyright: as well as management methods) that demarcation is rarely clear-cut because a Dorset Coast Forum reduce the risk of flooding of land. number of cells might be arranged as part Coast protection refers to systems and of a single coastal process unit. Terminology structures such as sea-walls, promenades Coastal Change Management Areas There are two different types of coast etc, that stabilise the coastline and reduce (CCMA). Under new (July 2009) planning defence works and the terminology is the risk of loss to land and property policy, all inappropriate residential often used interchangeably. There are: caused by erosional processes and / or development, such as housing, will encroachment by the sea. continue to be banned in areas vulnerable • Sea defence works which are works Sea and tidal defence refers to systems to coastal erosion. But there will no longer which protect against flooding of the that prevent (usually temporary) flooding be a blanket ban on temporary land and are carried out in accordance of sea water over land. development that has wider economic with the Land Drainage Act 1991 Coastal process units are defined as a benefits, an acceptable coastal use and length of shoreline in which the physical could be relocated when required. processes are relatively independent from Planning authorities have to define the 1 Dorset Marine and Coastal Topic Paper Series 2010 Coastal Defence 'Coastal Change Management Area' in powers. The Environment Agency (EA) there are still a number of areas, such as which the policy applies. has the responsibility of approving all social benefit and public access, where it Shoreline Management Plans (SMP’s), is less straightforward to reach a Natural processes and natural hazards allocate funding for new or ongoing satisfactory assessment of costs vs Natural forces (wind, wave, tide and coastal defence works and assisting local benefits. The Dorset coastline is regarded current) shape Dorset’s coastline and give authorities in completing defence works. as probably the most valuable tangible rise to two groups of hazards which can asset that the County has in generating affect coastal property: Costs and Benefits tourism income. Therefore, the socio- Defra / EA policy is that publicly funded economic benefits /disbenefits must be • Coastal erosion is the process that coastal defence schemes must typically considered when new engineering cuts, shapes and retreats our cliff achieve a cost / benefits ratio of schemes are proposed, especially if ‘hard’ coastlines. On much of the Dorset approximately 1:5. This means that a schemes are being considered. coast, erosion is accompanied by £10M scheme must be able to landslips, including some of the largest demonstrate that £50M of infrastructure The legislative and grants application and most active in Europe. will be fully protected. National guidelines process for obtaining funds for coastal The lead responsibility for assessing and are set for the cost calculations. However defence works is becoming more stringent (where appropriate) controlling erosion (commonly referred to as coast protection ) lies with the District and Unitary Councils. • Flooding - property can be affected by seawater inundation brought about by high tides or swamping with large waves - or often a combination of the two. The times of greatest risk are during spring high tides when accompanied by low-pressure storm surges and high winds from the south west, south or south east. The Environment Agency has ultimate responsibility for managing coastal flood and erosion risk, although District/Unitary Councils do have some permissive Beach replenishment at Overcombe Beach, Weymouth. Copyright: Dorset Coast Forum 2 Dorset Marine and Coastal Topic Paper Series 2010 Coastal Defence and a points system is employed based maintenance requirement. The design life vulnerable to flooding include upon: requirement for a new sea-wall is usually Christchurch, West Bay, Chiswell and o The type of scheme: flood defence 60-70 years and this figure assumes full Weymouth. is the highest priority, and urban and ongoing maintenance throughout the coast defence is a higher priority working life of that structure. However, it is Within the last 10 years, new or upgraded than rural unlikely that those protecting the large coast protection schemes have been o The SMP2 policies for the coastal town will be abandoned. implemented at Ringstead, the Nothe cells involved, especially in the first (Weymouth), Lyme Regis, Durlston, epoch (today until 2030) Seatown and Charmouth. Flood protection o Urgency of work schemes have been built at Chiswell and o Shortfall in standard of protection Preston. Future schemes are currently (as defined by the Environment being appraised for Lyme Regis (Church Agency) Cliff and East Cliff), Poole and West Bay. o The cost / benefits ratio At Chiswell, on Portland, the EA has put in Dorset’s coastal defences place a major flood defence scheme and The locations (where significant coastal maintains an advanced flood warning defences exist) reflect the geographical system for all local residents. They are extent of property along Dorset’s coast. seeking to further improve the The coastlines of urban Christchurch, effectiveness of the early warning system. Bournemouth, Poole, Swanage, Weymouth and Lyme Regis are almost Coast Protection: the historical legal entirely defended against erosion and Newtons Cove Sea Defence. Copyright: perspective Dorset Coast Forum flooding. There are sea-walls, artificial shingle banks and beaches retained by In England and Wales, there is an historic Developments along the majority of the groynes. Solid walls can provide important common law duty on the Crown to protect Dorset coast is light, and open coast extra amenities such as level promenades. the coast (from loss) and this duty may be sections remain without man-made Such defences are usually well passed down to an appointed statutory defences. It is therefore the smaller established, but their use is more body. The right for landowners to protect coastal towns and villages which are most questionable now than in the past. The their property is a longstanding legal at risk from loss. Example include: Lyme cost / benefit of hard defences have to be principle. However, such individuals do not Regis, Seatown, West Bay, Portland and carefully calculated and the long-term have to exercise these rights and Swanage. At these there is a considerable sustainability of such structures is suspect landowners constructing sea-walls for their amount of property and infrastructure because there is usually a continual own benefit are not obliged to maintain threatened by landsliding. Towns more 3 Dorset Marine and Coastal Topic Paper Series 2010 Coastal Defence these to protect others. Recent case law 2003. The aim is to ensure a better managing flood defences both inland as has further established that an occupier of quality of water within lakes, streams well as on the coast. This approach gives coastal land owes a measured duty of and rivers but also includes estuaries the EA a ‘gatekeeper’ role as compared to care at common law in this respect. Other and coastal waters (out to 1 mile from the previous arrangements whereby permissions such as planning permission low water). Plans for coastal defences grants were made by Defra directly to the and consent in relation to any are assessed against their likely Local Authority. environmental designations would impact upon water quality. normally be required before individuals • River Basin Management Plans (under • The Coast Protection Act, 1949 can commence with private defence the WFD) have to drawn up for every provides an integrated approach to works. river basin district in England and coast protection works. This embodies Wales. Coastal defences are deemed any construction, alteration, to be those that reach the tidal limit of demolition, modifications and repairs Sources of Coastal and Environmental a river or estuary and so are subject to for the purpose for protecting land from Law the controls set out in the WFD. erosion or encroachment by the sea. o International treaties (e.g. Law of Coincidentally, the same criteria are The power to undertake coastal the Sea) now used for defining the boundaries defence projects is vested in the o EU Legislation for Shoreline Management Plan (SMP) relevant Coast Protection Authority.