A358 near Combe Florey 2022-23 - Somerset Rivers Authority

SRA Annual Report 2022-23: A358 near Combe Florey

Somerset Rivers Authority funded drainage improvements to the section of the A358 near Combe Florey that was hit by three mudslides in 2022.

The A358 covered across both lanes with bright liquid mud, and a lorry stopped beyond a bridge. — Mud, mud, infamous mud on the A358 after a mudslide in August 2022.

A digger in thick mud under a bridge on the A358 near Combe Florey, with its front bucket full of scooped-up mud. — Clearing up mud from the A358.

In March 2023, Somerset County Council’s Highways Department, as a partner in the SRA, upgraded drainage grips along the eastern side of the road near Yarde Farm, to allow water to better drain off the road surface.

Roadside drainage grip, set into the verge with trees and a sloping green field beyond. — A new drainage grip funded by the SRA at the side of the A358 near Combe Florey.

New roadside drainage grip, set into the verge, with a hedge on one side, and on the other the road with a car approaching. — One of a series of new drainage grips funded by the SRA installed to help reduce flooding problems along this stretch of the A358 near Combe Florey.

The SRA has also been helping to address the underlying causes of problems along this important stretch of road. The A358 is one of only two main routes into – and out of – West Somerset, and it is classed as a county freight route.

In August and September 2022, the road was shut twice after mudslides dumped tonnes of soil, potatoes and surface water run-off onto the road. A smaller slip in December shut the road again.

The SRA funds a system known as ‘highways referrals’, whereby answers to problems affecting roads are sought in better management of land nearby. Through this partnership arrangement, Farming & Wildlife Advisory Group SouthWest (FWAG SW) advisers have made several visits in recent years to land adjoining sections of the A358 near Combe Florey. These visits resulted in measures being taken which have helped to reduce flooding and soil erosion problems.

The day after the August 2022 mudslide, a FWAG SW adviser visited the field where potatoes were being grown, analysed the situation, and made recommendations. For short-term protection of the road and nearby West Somerset Railway line, three filter fences were dug into the ground across flow pathways to slow any further run-off and silt loss. Unfortunately, intense rain in early September overwhelmed these temporary defences.

A tide of mud that has overtopped temporary filter fences, erected in front of a line of straw bales. — Temporary defences overwhelmed.

It was agreed with the landowner that after the tenant farmer’s remaining potatoes had been harvested in late September, the field should revert to being lower-risk grassland. Other recommendations made in a detailed report produced by FWAG SW included carrying out a deep primary cultivation of the soil to allow for more infiltration of water into the ground, planting a cover crop to reduce erosion, installing more filter fencing and planting trees in a particularly troublesome area. The field has reverted to grassland and at his own expense the farmer has installed a series of swales and check dams to divert runoff away from the road.