EXO’s Mersea project update

As avid readers of our blogs may remember, in September 2021 Exo were involved in an exciting project on Mersea Island, Essex.  Exo worked to install over 140m of brushwood sea defences along Cobmarsh and Packing shed island in the Mersea harbour approaches.

The work formed part of a wider scheme of nature-based solutions and utilising natural processes for low-cost sea defence. The Mersea Harbour Protection Trust employed Exo based on our explicit experience of brushwood work and working with nature projects, such as USAR and SARCC https://www.sarcc.eu .

The purpose of these brushwood installations is to trap and control the movement of dredged sand and gravel. This function is crucial, as without the brushwood the prevailing wind and tide would entrain the sand and cover vulnerable and special saltmarsh habitats.

This dredged material has now been placed within retaining brushwood structures, as part of beneficial use of dredged material, to recharge areas lost to erosion.

The placement of the material, which has come from capital dredging at Harwich, occurred over a few days in November 2021 when the spring tides allowed the large Hopper dredger Sospan Dau to fill the compartments with the material, using a rainbow discharge/placement method.  A video showing this process can be seen down below.

It is now over to the brushwood to keep this sediment in place and stabilise it enough to prevent it covering valuable saltmarsh habitat and provide suitable substrate for beach nesting birds, which has been lost over the years due to coastal erosion.  

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