SRA Annual Report 2022-23: ‘Resetting’ the River Aller in West Somerset
Backed by Somerset Rivers Authority, the National Trust has been carrying out pioneering works to reconnect part of the River Aller on Exmoor to its original floodplain.
Major works on the Trust’s Holnicote estate in West Somerset have been inspired by the success of ‘Stage 0’ river restoration schemes in the United States. The aim is that the river should no longer run along a single incised channel but instead form part of a complex waterscape with channels, pools, wetland and marshes.
It’s the first time that ‘Stage 0’ techniques have been used on such a large scale in the UK. Part of the National Trust’s multi-million-pound Riverlands initiative, the 15-hectare River Aller project has been part-funded by the EU’s Interreg 2Seas Co-Adapt programme, the Environment Agency, the SRA, the Green Recovery Challenge Fund and Frugi.
Works in 2022-23 followed a successful 2019 pilot on a tributary of the Aller, in the area between Selworthy church and the A39, which was also part-funded by the SRA. The project will benefit wildlife by creating new habitats and rejuvenating the local area. It will help to tackle the impacts of climate change by holding water in the landscape. Slowing the flow of water will also help to reduce flooding downstream in places such as Allerford and Bossington.
Earthworks in autumn 2022 created shallowly-skimmed areas carefully designed to ‘reset’ the valley bottom and allow for a natural river flow. Around 4,000 tonnes of soil were moved, and 600 tonnes of large timbers were pinned or partially buried into the floodplain to slow flows, and help develop more hydrological and ecological diversity. These timbers all came from non-native tree species clear-felled on the Holnicote estate. Floodplain wildflower seeds were sown. In spring 2023, further habitat-enrichment work included the planting of about 25,000 native trees such as willow, bird cherry and black poplar.
Somerset Rivers Authority is part-funding a 125-hectare extension of the River Aller project upstream at Tivington Farm. This will help to further reduce flood risks for nearly 100 properties downstream in places such as Allerford and Bossington and roads such as the A39 between Porlock and Minehead. A planning application for this work was approved by Exmoor National Park Authority in August 2022. More information about Tivington Farm is here on the SRA website.