Cobmarsh and the harbour entrance
Cobmarsh is one of the low marsh islands sheltering the waters of Mersea Quarters from the open Blackwater Estuary. The channel between Cobmarsh, Packing Marsh and the West Mersea shore is used by working and pleasure craft.
The island's exposed seaward edge is made up of shifting saltmarsh and shingle. Erosion gradually reduced the amount of land interrupting waves before they reached the moorings, oyster beds and waterfront.
A smaller island than a century ago
A 1923 survey recorded Cobmarsh at 32 acres. In 2015 its measured area was about 16 acres. Those figures were assembled for the community-led Changing Minds Changing Coasts study and illustrate the long-term loss of marsh, rather than the effects of one storm. The exposed shingle and marsh edge are still changing.
The harbour protection scheme
The Mersea Harbour Protection Trust began developing its coastal recharge scheme in 2014. Instead of constructing a continuous wall, the project placed sand and gravel on eroding margins of Cobmarsh, Packing Marsh, Old Hall Point and Tollesbury Wick.
Cobmarsh was allocated about 48,000 cubic metres of dredged sand and gravel. Work started in late 2021, using material recovered during navigation dredging near Harwich. The dredgers Sospan Dau and Scald worked on the scheme, with material pumped through a floating pipeline. The final load for the wider project was placed on 16 January 2022.
Brushwood and shingle
Brushwood fencing was installed in September 2021 to help reduce movement of the new material in storms. The replenished shore is still exposed to tides and waves; the deposited shingle was designed to move and settle rather than form a rigid barrier.
Cobmarsh and Mersea Quarters
The island sits alongside Packing Marsh, with the Mersea Quarters waterway behind it. The harbour-protection construction updates record the dredgers, volumes and recharge sequence.