The original managed retreat was created in the early 90's in Tollesbury (also in Essex), and it has taken ages for the prairie the original sea wall protected to form any sort of creeks or channels, and is still for the large part a flat muddy expanse with dead trees dotted about. It is obviously being closely studied for the reemergence of flora and fauna, but it has had an ill-considered drawback. Because the twenty acre site is a heck of a reservoir, the falling tide has scoured the North Channel, and silted the South Channel accordingly. All the water commerce uses the South Channel, which feeds the marina, as well as the fisherman's hard. This map shows the channels, but the managed retreat isn't shown yet (it is at the western end of the map area).

At the seaward end of South Channel, by what is known locally as the Shram Hill, low water springs gave at least ten feet of depth, and now it is barely covered. There has been massive coastal engineering going on at the same time, with thousands of tonnes of ballast dredged from Harwich Harbour deposited on the seaward end of the north bank of the River Blackwater, designed to control wave action from north easterly gales before they hit the crumbling sea walls that in this case protect an internationally important bird reserve (although Bunnahabhain has a valid point about barley barons!).

Thanks, Lizzie, for drawing my attention to this, as I was characteristically clueless.