Design criteria for the creation of brackish lagoons

Abstract

This paper deseribes the criteria important for the successful construction of brackish lagoonal habitats in the UK, as appropriate to creative conservation. These criteria are also of value for the optimal management of existing lagoons. The priority for these criteria is the maintenance of conditions appropriate to the successful survival of the specialist communities and rare species of natural lagoons, with high diversity of these species considered as advantageous. The lagoon should be as large as space and proposed land use will allow, and if greater than 5 ha, should have a high shoreline-length to area ratio. The design and management of water inlets should aim at maintaining a salinity approaching full ambient levels, preferably above 20%.; a fresh-water input is not necessary, but on a small scale would increase diversity. Water depth should be mainly of 1m or less. Saline water input is ideally achieved via a sluice or weir, or a culvert or pipeline through shingle, set such that water enters the lagoon at a level a little below heap tide high water level. Management of the lagoon should be minimal, but would include clearance of encroaching terrestrial plants and protection from pollutant impacts and vandalism. Maintenance of the lagoon water is paramount.