Marazion Marsh

This part of the Long Rock Coastal Improvements Project addresses the condition of Marazion Marsh, in particular the siltation problem in Long Rock Pool.

The Marsh is Cornwall's largest reedbed. According to the RSPB, more than 250 bird, 500 plant, 500 insect and 18 mammal species have been recorded here and bitterns are now regular winter visitors.

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Restricted freshwater inputs and siltation put this rare habitat at continued risk of failing. Siltation is considered to have increased flood risk to properties within Long Rock, by reducing the water storage capacity provided by the Marsh. The removal of sediment and the installation of silt traps would generate improved water storage capacity and a favourable status for the Marsh. On site treatment of the sediment and the creation of an embryonic dune within the Marsh were originally proposed as an innovative solution to sediment disposal. However, when detailed planning was undertaken, including discussions with Natural England and RSPB, it became clear that this solution was not a viable approach.  We have therefore modified the project to attain the same outputs by raising and controlling the water level in the Marsh, rather than by lowering the bed and by installing a substantial silt trap to avoid further sedimentation.