Farming in Protected Landscapes Case Study:

RSPB Cattawade Marshes Main Sluice Replacement

£16,340 was granted to the RSPB towards installation of a replacement sluice at RSPB Cattawade Marshes.

Cattawade Marshes and the Dedham Vale sits in an area with the lowest recorded rainfall in the UK, and holding water efficiently on the reserve will mitigate against climate change.

The sluice will control the water levels across the site, for the benefit of breeding waders and wintering waterbirds.

Cattawade Marshes is a Site of Special Scientific Interest near to the village of Flatford. The existing sluice at Cattawade was starting to fail. It was constructed using plastic piles which have not proved strong enough to cope with holding back the freshwater, required to flood the reserve.

Why is this work needed?

Water level control is absolutely critical to effective site management benefiting breeding waders and wintering waterbirds, which need high water levels in spring, so that freshwater invertebrate populations which grow well under those conditions can provide food for the breeding population.

Installation of an effective, fit-for-purpose sluice will ensure that water is backed up onto the rest of the marsh, leading to accurately controlled water levels across the site.

What work has been done?

A new steel-piled sluice wall has been installed to hold water back which is taken from the adjacent freshwater River Stour. A licence for Water Transfer was needed from the Environment Agency for this purpose. Contractors came to the site to carry out the work. The work included:

Installed a temporary earth dam upstream of the existing sluice to ensure a safe working site.
Removed the old existing plastic pile sluice.
Carried out necessary enabling groundworks (ensuring ground levels are correct, setting up machinery, removal of existing cattle fence to allow access).
Installed a new steel-piled sluice to agreed/approved levels, using c.13T excavator equipped with a pile driving machine.
Installed 450mm diameter twinwall pipe into the steel-pile structure. Compact clay found on site was packed around the pipe to make a watertight repair. The existing low-level bunds were tied into new steel piled sluice, to ensure high water levels cannot circumvent the new structure in future.
Re-installed exclusion fencing, and an access gate.

Visitors can not access the actual site, but can walk along the footpath along the river side and see over the marshes to the hundreds of wetland birds flocking to these marshes to graze. Oystercatchers, Lapwings and Redshank can be seen – dawn is the best time. In the winter, Teals and Wigeons visit. Here is a link to the RSPB site to help you plan your visit and learn more about this fascinating reserve.