SRA Annual Report 2018-19: River Sowy-King’s Sedgemoor Drain enhancements (W1)

The River Sowy was originally known as the Parrett Flood Relief Channel. It is a man-made river conceived after floods deluged 50,000 acres of Somerset in October 1960. After long debates about cost and size, the Sowy was dug out between 1969 and 1972.

The Sowy is used by the Environment Agency to take excess water away from the River Parrett near Aller. Water flows down via Beer Wall to King’s Sedgemoor Drain (KSD) near Greylake, then re-joins the Parrett at Dunball.

Providing more capacity in the Sowy-KSD system, so that it can be used more effectively, is a key aim of Somerset’s 20 Year Flood Action Plan, which is overseen by Somerset Rivers Authority.

Sowy-KSD works in recent years have included the creation of new river channels under the A372 at Beer Wall, the refurbishment of a water level control structure near Chedzoy and the removal of obstructive masonry from under Dunball Old Bridge, which carries A38 traffic southbound. All these works are part of a programme to reduce flood risks across 150 square miles.

Activities during 2018-19

In autumn 2018, the SRA funded the dredging of two sites along King’s Sedgemoor Drain, at Parchey Bridge near Chedzoy and at Dunball railway bridge, to give these structures back the capacity to deal with flows they had nearly 50 years ago. Silt and overhanging vegetation were removed at Parchey Bridge. A floating excavator and barge were used to move silt and a digger spread it over land nearby. At Dunball more material than expected was removed, including a load of builders’ rubble and assorted debris from the KSD. The work will enable more water to pass through the two bridges as quickly and smoothly as possible, and it will reduce the risk of blockages caused by flood debris clogging up their arches.

Both jobs were done for Somerset Rivers Authority by the Environment Agency, using contractors GBV (Galliford Try and Black & Veatch) and dredging specialists Land & Water. Funding came from Heart of the South West Local Enterprise Partnership (HotSWLEP) Growth Deal money.

More generally, progress has been made on further improvements planned for Dunball and on designs for increasing the capacity of key parts of the Sowy and KSD through work in these rivers’ channels and on their banks. Several partners have been working together on a mitigation plan to ensure that proposed activities will be legally compliant. Options include replacing or refurbishing control structures at the Moorlinch and West Moor Raised Water Level Areas and Egypt’s Clyse.