SRA Annual Report 2019-20: Feasibility study of the Knapp Hill catchment in Wells

A study of problems around Knapp Hill on the eastern side of Wells, out along Bath Road which floods regularly during periods of heavy rain. Several options for improvements have been identified. Further investigations have also been suggested because Wells – as its ancient name suggests – has a complex pattern of springs and underground flows.

This project was organised for the SRA by Mendip District Council’s Flood Risk Consultants CALM Engineering and carried out by contractors Ghyston Engineering under the supervision of Hydromorph.

Jane Moon of Hydromorph (left) and Alex Hughes of Ghyston Engineering.

The team focused on three watercourses.

St Andrews Stream (1) rises north-east of Knapp Hill at Haydon Drove and flows down through Biddle Combe and Beryl Wood before crossing Bath Road. The stream then runs south through Wells Golf Club where it meets another tributary (2). Next it goes west through the semi-urban Tor Hill area. After being joined by the Woodbury Brook (3) it carries on down towards the Bishop’s Palace in Wells city centre.

Possible improvements

Possible improvements identified include:

Additional attenuation ponds in Beryl Wood and Tor Hill park
Footpath moving and raising in Beryl Wood
Additional road gullies on Bath Road to capture road run-off water better
Cattle grid and pipe to attenuation feature at South Horrington
Grips and swale cut on south side of Old Frome Road

Possible further investigations

Further investigations could cover:

1) Existing ineffective attenuation pond and drainage system at South Horrington. Work would include flow monitoring.

2) Whether potential sources of groundwater emergence are contributing to flooding in the Tor Hill area of Wells. This could form part of the Water Resources project being led by the Environment Agency within the wider Brue Catchment.

3) CCTV surveys and analysis of existing culverts:

under Bath Road
in South Horrington
along Woodbury Brook from Paray Drive to the south of Bath Road
along St Andrews Stream through the back gardens of Bekynton Avenue

Next steps

Next steps will be to review all options with SRA partners such as Somerset County Council’s Flood Risk Management Team and Highways Department and the Farming & Wildlife Advisory Group SouthWest.

Discussions will help to determine which activities would produce the best results and how works could be funded, possibly by the SRA.