River Tamar breach forms new marshland helping wildlife and climate

Image credit: National Trust Working with and for nature: creating new habitat at Cotehele quay | National Trust

In September 2021 water from the River Tamar on the Devon/Cornwall boundary flooded onto farmland through man-made breaches in the flood defences. The land at Cotehele Quay was drained in Victorian times by building a large embankment to keep the river out and provide safe grazing for livestock. Rising sea levels and more frequent storms have created problems maintaining this barrier and have increased flood risks.

The rising tide now floods onto rich new marshland along three new channels and a 15-metre-wide breach in the embankment. The new 1.7-hectare wetland will create reedbeds and attract wildlife including herons, curlews, otters, fish fry and elvers. It will reduce risks of local flooding by creating more flood plain storage during storms and the developing marsh vegetation will help lock in carbon from the atmosphere.

The £250,000 project, run by National Trust and supported by the Environment Agency, Natural England and Plymouth University is one of several nature-based solutions planned for the River Tamar. The Cotehele breach is the first of three on the Lower Tamar, the other projects, led by the Environment Agency being at Calstock and South Hele. Three further sites on the Tamar are being assessed. In the future, several thousand tonnes of carbon could be locked up (sequestered) in the marshland.

The Cotehele project is an example of the National Trust’s    “shifting shores” programme, which focuses on nature-based solutions, rather than building defences against floods and storms. More details and useful teaching resources about how places can adjust to rising sea levels and storms can found at “shifting shores” programme

A similar project at the trust’s Cwm Ivy on the Gower peninsular allowed coastal marshland to develop after a sea wall failed during winter storms in 2013-2014.  Before it was flooded by the sea, the land was sheep pasture. Following the decision not to fix the sea wall it has become a new habitat for wildlife attracting over 150 species to the area. This is an example of managed retreat creating a natural coastline more resilient to storms and rising sea levels. More details can be found from the National Trust and in this news article Cwm Ivy