SRA Annual Report 2021-22: River Sowy-King’s Sedgemoor Drain enhancements
A major project to increase the capacity of key parts of the River Sowy and King’s Sedgemoor Drain (KSD) through work in these rivers’ channels and on their banks. Sowy-KSD works have been delivered for Somerset Rivers Authority (SRA) by the Environment Agency, as a partner in the SRA, since 2015.
The SRA has used Growth Deal funding from the Heart of the South West Local Enterprise Partnership to pay for these works, supplemented with money raised directly for the SRA through council tax.
The River Sowy was created in 1969-72 as a River Parrett Flood Relief Channel. It branches off the Parrett through Monk’s Leaze Clyse sluice near Aller, down to the KSD near Greylake, which then rejoins the Parrett through Dunball Sluice north of Bridgwater. Monk’s Leaze Clyse and Dunball Sluice are owned and operated by the Environment Agency.
The ultimate aim of all the Sowy-KSD enhancements of the last few years has been to increase the amount of water that can flow down through the system, under conditions managed by the Environment Agency, working with local partners, and thereby help to reduce flood risks across 150 square miles.
Activities in 2021-22
Following a successful public consultation in summer 2021 on additions to the Sowy-KSD’s scheme’s Environmental Statement, works were carried out in September and October. Sowy- KSD earth-moving works can generally only be done in late summer or autumn. One big reason is to avoid disturbing legally-protected birds which breed in the spring or early summer, and feed over the winter on local wetlands. Another reason is that wet winter weather can make it almost impossible to work in soft peaty ground with heavy machinery.
Works in September and October included filling low spots in the banks of the upper Sowy, upstream of Beer Wall on the A372 near Othery, and raising 1.32km of the right bank of the lower Sowy, downstream of Beer Wall. The eventual aim of these activities is to increase the river’s capacity to carry water. (Text continues below images).
Five out of seven planned ecological enhancements were also excavated. These enhancements consist of features such as different shelves along parts of the riverbank and smaller parallel channels, to create an enlivening variety of flows and more diverse habitats for wildlife.
The SRA Board was told in December 2021 that progress had been delayed by a range of problems, such as Covid-19, wet weather and especially a shortage of skilled plant drivers.
In March 2022, the last two ecological enhancements were excavated and planting was done around the five previously excavated.
Other works across different times of year consisted of vegetation clearance and the installation of temporary fencing, to keep livestock away from areas being improved.
Bank-raising resumed in July 2022 and is due to finish by the end of October.
Important side-stream structures at Parchey, Cossington and Chilton will also be upgraded in the autumn to match the increased capacity of the KSD and provide the same relative level of flood defence as before.
Additional works
In March 2022, the SRA Board agreed to allocate up to £200,000 for ‘design and preparation’ work on three outfalls into King’s Sedgemoor Drain downstream of Parchey Bridge, namely Chedzoy Tilting Weir, KSD Back Ditch, and Level Rhyne. The Board’s move followed discussions between the Environment Agency and the Parrett Internal Drainage Board (IDB) about the need to make modifications to these outfalls an extra part of the current phase of Sowy-KSD works. The concern is that if more water comes down through the Sowy-KSD system, then water will flow back out through these outfalls, as they are currently constituted, instead of being kept in the main river channel. SRA Board members were asked to take more decisions about the outfalls at their meeting in July 2022.