7. Protecting the Exe Estuary

Transcription

1 7. Protecting the Exe Estuary The Exe Estuary is an important resource which supports a variety of human uses, and an impressive array of wildlife. In order to protect the Estuary it is necessary to balance the various competing demands, and to be prepared to deal with events which may pose a threat to the resource. Good preparation may take the form of preventative measures, consistent monitoring and / or rapid response to harmful events. Image 7a: Groynes at Exmouth Source: EEMP 7.1 Contingency Planning There are various risks to the Exe Estuary and its environment. Local authorities and organisations have of different contingency plans in an attempt to mitigate these risks. Some of these plans are required by law whilst others have been prepared in response to a Image 7b: Boom deployment at the mouth of the Exe Source: EEMP Risks of Pollution on the Exe it each year. Despite the fact that most of this shipping passes incident free, there is always the risk of vessels having an incident and pollution affecting the Exe Estuary. Heritage coast, between Sidmouth and Branscombe. During the rescue and grounding the vessel lost over 100 containers, heavy fuel oil and diesel into the sea. The operation to remove fuel oils and containers took several weeks. The area was monitored by aerial surveillance and counter pollution measures were rapidly taken to protect environmentally sensitive sites by deploying booms. The Environmental Agency monitored the quality of water samples taken from beaches around the site of the incident, including Exmouth. The concentrations of chemical substances detected were well below harmful levels. State of the Exe Estuary

2 Contingency Flood Plan Emergency/Flood Plans with support from the Environment Agency s Flood Resilience team and Local Authorities. There is also a range of advice at on: Individual property level protection Contingency Pollution Plans Plan for Marine Pollution from Shipping and Offshore Installations which should be available from the end of The plan provides a practical framework to inform those dealing with marine pollution incidents. It sets out information requirements, advice on dealing with the media, information on waste management, enforcement and prosecution, monitoring and international co-operation arrangements. for 14 individual sites in Devon, including 12 estuaries in the county. This plan integrates with the National organisations involved must be compatible and linked. Other types of emergency which may occur in and around the Exe Estuary are covered by the different responding agencies Emergency Response Plans and the Joint Emergency Response Protocol. 140 State of the Exe Estuary 2014

3 Oil Spill Response Intervention, who oversees and approves any salvage operation and can intervene if appropriate. operations. centre co-ordinates the shoreline clean-up operations. Not all of these control centres will need to be set up in every incident and this will be dictated by the scale and type of incident. An Environment Group may also be set up at the early stages of an incident. This group provides environmental and public health advice to the incident control centres. The Environment Group is made up of representatives of the relevant statutory nature conservation body, environmental regulator, Government Tier One: A small operational spill employing local resources during any clean-up. This would be managed by the harbour authority, district or city council depending on the location. Tier Two: A medium sized spill, requiring regional assistance and resources. Tier Three: A large spill, requiring national assistance and resources. Environment Agency takes the lead in responding to pollution from land based sources and would be likely to deploy the booms to protect the Exe Estuary Local Authorities have accepted the non-statutory responsibility for shoreline clean-up State of the Exe Estuary

4 7.2 Flood and Coastal Risk Management Image 7c: Groynes in Dawlish Warren Image 7d: Sea defence work at Exmouth in 2006 Source: EEMP Source: EEMP other climate change impacts, including increasing frequency and severity of storms, coastal management partnership approach between organisations and needs to be prioritised to protect the maximum number of people and property around the Estuary. With the forecast effects of climate change, the aim now is to manage these risks before they cause problems and in those places with the greatest need. 142 State of the Exe Estuary 2014

5 wants a more strategic approach, with authorities working closely together to access partnership funding. Shoreline Management Plans policies over a large area and into the long term, for example over the next 100 years. The Exe Estuary is included in the South Devon and Dorset SMP, which was completed in June This covers an area assessment of risks, opportunities, limits and areas of uncertainty, and it is considered as part of land use planning. State of the Exe Estuary

6 Blackhorse Woodbury Sowton Kenniford Cross Clyst St Mary Clyst St George Ebford Exton Lympstone Barracks Exeter Topsham r Exminster Key Shillingford Abbot Exe Estuary Management Boundary Railways, roads, tracks and paths Buildings Location of settlement Inland water Inter Tidal Zone Tidal Water Land Figure 7a: Areas at risk of flooding near the Exe Estuary Source: DCC 2014 and OS 2014 background mapping. EA 2014 data 144 State of the Exe Estuary 2014

7 Marley Hayes Littleham Exmouth Lympstone Sowden Powderham Starcross Kenton Cockwood Eastdon Dawlish Warren Dawlish Kilometers Areas at risk of flooding Zone 2 (1000 years flood) Zone 3 (100 years flood) This map is reproduced from the Ordnance Survey material with the permission of Ordnance Survey on behalf of the Controller of Her Majesty's Stationery Office Crown copyright. Unauthorised reproduction infringes Crown copyright and may lead to prosecution or civil proceedings State of the Exe Estuary

8 A public consultation on the draft strategy was undertaken in early 2013 to gather views on the proposals for account social, economic and environmental considerations. In most areas the Strategy proposals are the same as those within the SMP, for example, providing improved of approach is needed. An example of this is at Dawlish Warren sand spit, where the latest proposal is to bring in sand to recharge the beach, remove gabion baskets and improve groynes as part of work to manage the spit increasingly in line with natural processes in the future. This will allow the spit to act as a natural wave barrier to coastal communities in the Estuary for longer, should improve the quality of the beach and help to improve the quality of the sand dunes, which are an internationally important wildlife habitat. Image 7e: Boat survey at Dawlish Warren Source: Maersk Maritime Technology Image 7f:

9 takes into account impacts on and the requirements of the natural environment. maintenance. breaching banks to allow the creation of saltmarshes which act as a buffer, or planting marram grass to stabilise sand dunes. The choice of coastal management options for different sections of the coastline is One coastal management approach is called Managed Realignment, although this can also be referred to as habitat creation. It involves setting back the line of actively maintained defence and creating new area of the situation and the requirements of the scheme the original front defence may be retained until it degrades naturally, or may be either wholly or partially removed. Managed realignment is not a do-nothing option but requires active management. This may be suggested as a response to coastal squeeze, where existing habitats are being drowned out by rising sea levels and are unable to move inland because of the presence of structures such as seawalls. State of the Exe Estuary

10 Protecting the Exe Estuary Blackhorse Woodbury Sowton Kenniford Cross Clyst St Mary Clyst St George Ebford Exton Lympstone Barracks Exeter Topsham r Exminster Shillingford Abbot Key Railways, roads, tracks and paths Buildings Location of settlement Inland water Inter Tidal Zone Tidal Water Natural coastal defences Natural channel Sea defence (sand dune) Land Exe Estuary Management Boundary Figure 7b: Flood and coastal defences situated on the Exe Estuary Source: DCC 2014 and OS 2014 background mapping. EA 2014 and N 2014 data 148 State of the Exe Estuary 2014

11 Protecting the Exe Estuary Marley Hayes Littleham Exmouth Lympstone Sowden Powderham Starcross Kenton Cockwood Eastdon Dawlish Warren Dawlish BAP Priority habitats contributing to flood defence Reedbeds Coastal sand dunes Coastal and floodplain grazing marsh Kilometers Man made coastal defences Location of flood defence structure Coastal protection Culverted channel Flood defence structure Maintained channel Raised coastal defence Raised defence Sea defence This map is reproduced from the Ordnance Survey material with the permission of Ordnance Survey on behalf of the Controller of Her Majesty's Stationery Office Crown copyright. Unauthorised reproduction infringes Crown copyright and may lead to prosecution or civil proceedings State of the Exe Estuary

12 Sediment Dynamics There are complex coastal processes present within the Exe Estuary. The sediment dynamics are determined Warren is closely associated with a series of sandbanks, of which Pole Sand, seaward of the spit, and Bull Hill processes. It is believed that there is a circular movement of sediment in the mouth of the Exe, with limited input of railway to the west which prevents the sea from eroding the cliffs and providing fresh supplies of sediment via the process of longshore drift. The usual circulation pattern is interrupted during storm events when large quantities of sediment can be removed from Pole Sands, Dawlish Warren and the Exmouth frontage and deposited in the channels. This shows the dynamic nature of the coastline and results in ever changing each level. Historically the spit at Dawlish Warren has undergone periods of accretion and depletion, with movement of east of the Estuary, the beach at Exmouth also contributes to the complex sediment transport system. The of sediment at Exmouth and Dawlish which means that whatever happens at one site will affect the situation at the other. For example, there is a long-term trend of retreat along the Dawlish Warren seafront dunes, with Lympstone coastal defences in the village, including a new seawall and reinforcements to the stone groyne on the highest tide ever seen at Lympstone in early Image 7g: Image 7h: Flood gate at Lympstone Source: EA Erosion at Lympstone Source: EEMP 150 State of the Exe Estuary 2014

13 Exmouth Since the early 1980s sediment in the Exmouth approach channel has been steadily accreting. By the mid-1980s accretion was such an issue that it Following the grounding, 40,000m 3 of material was dredged from the channel, with further dredging work taking place was in 1998 and the need for an open accessible commercial channel has now been reduced. However, a serviceable navigation channel is still very important area to assess the channel depth every six months. Image 7i: Source: David Weatherly There are extensive rock revetments, sea walls and groynes protecting Exmouth, and the beach and offshore sandbanks act as a soft defence structure. However, there has been a general reduction in beach levels on the Esplanade and Beach Gardens frontage over the past 15 years and this winter saw the devastation of the town s sand dunes. It has been observed that beach movements are quite volatile, sea wall by high tides and storm waves. State of the Exe Estuary

14 Dawlish Warren Agency and Network Rail are all partners in the development of the Exe Estuary Strategy, which considers future options for tidal defences around the Estuary. Following on from this, Teignbridge, East Devon and the Environment Agency are working together on the Dawlish Warren & Exmouth Beach this scheme, which will help to protect many Estuary communities into the future. The intention is to recharge the beach at Dawlish Warren with sand in order to lengthen the life of the sand spit as a of the internationally important sand dunes. Other works, as part of the scheme, involve the construction and the main railway line. Dawlish Warren sand spit has historically shown periods of accretion and depletion. In the 1930s there to stabilise the position of the spit, with a system of groynes on the beach to stop sand movement. Many of the gabions are now exposed by storms and the groynes are in various states of disrepair. The presence of the railway line to the west means that there is no new supply of sediment to replace that lost from the beach by the natural process of longshore drift, which explains why the beach is steepening and becoming less sandy. Figure 7c illustrates the dramatic changes in morphology that Dawlish Warren has seen over the last century. The increasing frequency and intensity of storms predicted as a result of climate change means that maintaining the current position of the sand spit time, by which time there will need to be improved defences in place in the inner Estuary to protect communities such as Starcross and Topsham. 152 State of the Exe Estuary 2014

15 Image 7k: Image 7l: Dawlish Warren in the 1930s - with a thriving community living in summer houses Source: EA Dawlish Warren circa 1949 the hook end is no longer attached due to storms Source: EA Dawlish Warren 1990s aerial view Image 7m: Dawlish Warren May 2013 aerial view Source: EA State of the Exe Estuary

16 Cockwood Bull Hill Bank Eastdon Pole Sand Dawlish Warren Key Railways, roads, tracks and paths Buildings Location of settlement Land Inland water Inter Tidal Zone Tidal Water Exe Estuary Management Boundary Figure 7c: The changing coastline of Dawlish Warren Source: DCC 2014 and OS 2014 background mapping. OS 2014 and LM 2014 data Kilometers Land above Mean High Water 2014 extent extent* 1930 extent* 1905 extent* * Approximate boundary digitised from OS historical mapping Crown copyright. All rights reserved State of the Exe Estuary 2014

17 1809 The old 1 inch Map of 1809 shows Warren Island, later incorporated into the Dawlish Warren Spit 1817 Five acres of the Warren were washed away in a single storm 1844 Dawlish Warren covered 300 acres A storm ripped through the Warren and closed an oyster farm The Warren Halt railway platforms were built by the Great Western Railway 1911 The Gale washes away several homes metre rock armoured revetment was constructed to protect the railway line 1937 A series of storms and high tides removed bungalows on the Warren 1939/1940 Winter storms destroy more homes 1949 to 1959 Protection of the Warren by British Rail: brushwood fences were erected, trees planted and barriers made of railway sleepers s The last home is removed from the Warren in a south-easterly gale Severe storms breached the Warren and dune heights were lowered 300m long concrete sea wall was built to the east of the railway rock revetment, a promenade was provided on the top of the wall; at the end of the sea wall 300m of gabions, 1989 and 1990 Storms damaged the revetments and emergency work was carried out by Teignbridge 1992 The National Rivers Authority began work to reconstruct the rock armoured revetment; landward of the timber piles, a 300m line of steel sheet piles were sunk to offer further stability; 35,000 tonnes of Norwegian granite boulder were imported 2014 A series of severe storms combined with high tides and winds damaged the groynes and and man-made impacts on the coast at The following photos highlight the destructive power of a single storm event in early 2014 as they illustrate how the gabions were exposed and a considerable amount of sediment was lost from Dawlish Warren beach. During this time the railway line at Dawlish was also breached. State of the Exe Estuary

18 Image 7n: Rock gabions exposure (2014) Image 7o: Source: EA Severe beach erosion (2014) Source: EA of this novel approach. The RTE area at Goosemoor has been used by a much greater variety and number of 7.3 Spatial Planning Spatial planning encompasses a very wide range of issues and is guided and informed by a range of documents. Government legislation has increasingly placed an emphasis on sustainable development The Exe Estuary covers four Local Planning Authority areas, each with their own local planning policy. Both Exeter and Teignbridge have relatively new plans setting out planning policy for their areas. Teignbridge the process of writing new versions of these documents, anticipating adoption of a new Devon Waste Plan later in Habitats Regulations Assessments are undertaken on emerging policies to ensure that there will not be adverse effects on the internationally and European designated sites on the Exe Estuary. Where planning policy is contributions will be sought from new development towards management and other schemes to protect the Plan supporting the local plan.