Coastal management case study - N

(i) the management strategy being implemented and the reason for its implementation;
(ii) their intentional impacts on processes and flows of material, processes and/ or energy through the coastal system;
(iii) the effect of these impacts in changing coastal landforms;
(iv) the consequence of these changes on the landscape.

Wallasea Island → south of Crouch Estuary in Essex, East of England

In the past, this land was protected by a sea wall. Due to a lack of funding the sea wall began falling own in several places in 2004. This created a high risk of flooding which could affect: 2700 properties, 9500 hectares of high grade farmland, 168km of flood defences and a variety of natural habitats. Large areas of land are several metres below normal high water in the estuary. As sea levels rise the intertidal wetlands and salt marshes in front of sea defences become eroded = “coastal squeeze”

The Wallasea Island Project
→ managed realignment

Reduces the cost of hard defences by shortening the defence area

Recreates rivers, estuaries or coastal habits and uses them to absorb wave energy and stores water when its flooded

Creates natural habitats or replaces the ones lost

Its aim was to create the UK’s largest man-made marine wetland

The realignment involves the construction of a new sea wall along the length of the north bank and the islands then allowing the land to be inundated (flooded) by the sea. This widens the area of intertidal habitat = good for wildlife and recreation, helps to manage flood risks.
the reclaimed farmland used to absorb the high tide floods and surges. Since WW2 there has been a surplus in food meaning that the farmland isn’t vital. The project gives more space to water by working with natural processes

Why realignment was chosen at Wallasea:

• A sufficiently large site to attract vast number of birds.

• little chance of the surrounding estuary from. being damaged.

• No adverse effect on those using the area

• Remote estuary location

• Site was not a conservation interest and it was only a limited public interest

• Full support from the previous farmland owner “Wallasea Farms”

The Environment Agency (EA) investigated tidal and environmental impact to make sure they wouldn’t cause any sever damage. The EA took data to compare how the tides in the Crouch and Roach estuaries behave and how they would behave after the realignment. Other concerns were making sure there were no negative impacts on the people, business, fisheries and boats that use the river Crouch. Surveys were taken to make ensure maximum protection was possible for creatures such as reptiles, water voles, insects and ground nesting birds.

Development of the 110 hectares of new wetland began in May 2005 costing £8 million. Although this project is an example of managed realignment it still needed some hard management.

Stage 1:

• A new stronger sea wall was built at the back of the site on the landward side

• A new freshwater ‘borrow dyke’ was built. This formed a freshwater marsh for nesting avocet, redshank and water voles. In front of the wall there is a salt marsh, formed by pumping mud into the area.

• A robust retaining bund wall was built to hold the imported mud for the salt marsh and to ensure that no silt was swept back into the Crouch. The saline lagoons and a number of artificial islands were created.

• A new beach was developed inside the North East corner of the site.

Stage 2:    

• Over 700,00 tonnes of mud was pumped ashore to build the new salt marsh. The dredger “Medway Two” worked 24 hours a day 7 days a week, placing 40,000 tonnes a week. This mud was pollutant free and it was pumped through a pipeline that ran along the top of the sea wall.

Stage 3:

• In May 2006 the final landscaping took place, the old sea walls were breached in multiple places allowing the tide to flood in and start forming the wetland.

• The project was completed in 4th July 2006 and cost £8 million, when a 300metre sea wall was bulldozed to get the full affect of the tide on the wetlands.

• The hectares cover about 115 hectares, the amount of water entering on each tide ranges from 790,000 cubic metres on a neap tide and 1,700,000 cubic metres on a spring tide.

• It is expected that by 2011 the area will naturally turn into wetlands, lagoons and mudflats

RSPB Wild Coast Project

The Wallasea Island Wild Coast Project aims to extend the Defra funded Wallasea project by creating a series of mudflats, set marshes and lagoons to the south of the original project. RSPB’s vision for the Wallasea island is to change the farmland back to its original condition of mudflats and salt marsh habitats with approx. 133 hectares of mudflats, 276 hectares of salt marsh and 56 hectares of shallow saline lagoons. This will take a 6-phased plan in order to gather the research needed and the potential impacts on the tidal currents. Crossrail will provide clean recovered materials sent by ship.

Once completed it will be a landscape used by people and wildlife, being used for bird watching, walking, cycling, painting or photography. Public access will try to make people and the wildlife coexist on the island, with access along the Defra sea wall being unaffected by construction. after construction the RSPB will provide improved access routes and a range of visitor facilities.

Conclusion:

• The original restoration project has been very successful as its developed salt. marshes, saline lagoons and mudflats. The cost was mainly the new seal wall defences.

• Huge environmental benefits and an abundance of waterbirds - 7024 in 2006/7 to 16574 in 2010/11.

• 115hectares of natural flood defence

• The addition of the RSPB’s realignment project will add on another 500hectares of restoration. This of course will be with the aid of a private investor but the future completion is looking promising. there will be a new bank on the western end of the project to protect the flooding risk of properties and businesses on the island.

• Projects like the Wallasea Island Project offer the Uk a vital contribution towards the adaptation required for future coastal management. The Wallasea project spent wisely through providing flood defence and increasing the biodiversity. As well as this, the building of the vision centre has created a future income stream.