Case Study

Walthamstow Island Scrapes

Thames Water
Aquatic Engineering
East Warwick Reservoir

Created in the 1990s, the island on East Warwick Reservoir is described as a scrape which means that it is a shallow depression with gently sloping edges, holding water seasonally. The island has not been maintained for over 10 years, meaning it has not yet achieved its full potential for overwintering birds, such as shoveler and gadwall. The much-needed work on the East Warwick Island is now taken place outside of the 2019/2020 nesting bird season and before the peak over- wintering period, it was completed within approximately two weeks.

Habitat improvement works on the island have included cutting back the brambles to open up the ground for more plants and reprofiling the island to provide a permanent water body, along with seasonal wetland scrapes. Once the island’s water levels were firmed, a simple valve system to allow water to access as required, both automatically and manually. The island was be sympathetically profiled to an agreed shape and the woody chippings were used to create organic rich piles of variable habitat. The island was sown with a native grass mix and a planting regime is being decided with the London Wildlife Trust. Recycled zebra mussel shells (dead!) were used as an additional aggregate to benefit the wetlands and overwintering birds.

Our specialist amphibious excavator made short work of the 200m reservoir crossing to the island.

This is a very versatile machine which is at home working on both land and water, our specialist amphibious excavator made rapid progress. A silt retention curtain was deployed, which wrapped around the entire island thus protecting water quality and wildlife alike.

A balance between creating open water and wetland scrapes without any of the islands soils being deposited in the reservoir required careful design and operational planning.

As a designated Site of Special Scientific Interest – one of only 37 in Greater London – Walthamstow Wetlands is recognised as an animal and bird haven in London. It is with the support of the public and partners including Thames Water, the London Borough of Waltham Forest and the London Wildlife Trust, that dedicated conservation work can continue and improve the site for both wildlife and visitors alike.

As work progressed many representatives from The Environment Agency, London Wildlife Trust, Thames Water and other stake holders were ferried over to inspect the works… now complete it will be rarely accessed and left to the birds and wildlife it was designed for!

November 2022: