Lymington Intertidal Habitat Restoration
Lymington Harbour is located in the tidal estuary of the Lymington River which discharges into the Solent.
Extensive natural saltmarshes developed at the end of the 19th century and provided protection for the harbour. More recently these have been receding and as the level of protection reduces it has been necessary to construct breakwaters to maintain the viability of the harbour.
A condition of a licence permitting the construction of new breakwater structures for Lymington harbour required the level of an existing area of saltmarsh to be raised. This is intended to act as mitigation for the areas that will be affected by the construction of the breakwater. The aim is to use pumped sediment from maintenance dredging of the navigable channel to raise the level of the degraded salt marsh.
The consultant engineers (Black and Veatch) in conjunction with the Harbour Master agreed the area into which the silt was to be pumped. Willowbank designed and constructed retaining structures constructed from stakes, brushwood, coir and bales. These structures were designed to pen the pumped silt in the designated area and to slow the flow of the silt in order to encourage the sediment to drop out of suspension and deposit on to the marsh. A box structure with faggot and coir base was used at the outlet of the pipe to prevent the pumped silt form eroding the marsh, additional baffles were installed to further reduce the speed of the pumped silt
Lymington Yacht Haven used their cutter suction dredger to pump the silt onto the marsh. The structures worked well with a little tweaking and a gradual increase in levels occurred over the site.
Here is a report on the Crown Estate website