Sediment circulating near shore and in estuarine areas is often in transit towards a sand beach or bank, intertidal mud or salt marsh.
These geomorphological features are often of great environmental significance, providing a diversity of habitats for a wide variety of organisms, and are of great engineering importance in coastal protection from flooding.
Port or harbour develop ment and navigational operations in estuaries or on coasts often demand local changes to the morphology of the area which result in changes to patterns of water currents and therefore local sediment circulation. Development generally involves deepening of channels or excavation of shallow areas.
These modified areas form local traps for the sediment in transit by locally reducing the rate of transport. The usual and inevitable response to this is dredging to remove sediment.
The general approach and philosophy of dredging has far reaching consequences for the environment, says Beaumont. For example, the natural supply and circulation of sediment within an area is disrupted and this can lead to the starvation of many of the important morphological features in the system.
Equally the removal of large quantities of sediment in a short time can have a serious adverse impact.
The Wing excavator does not transport the unwanted sediment out of the system, it simply smoothes the topography out. In so doing 'it recognises the need to balance navigational and engineering requirements with the requirements of the natural evolving system and the need to minimise environmental impacts.'
From trials, the most effective method of operation is to track along the sandwave crests, displacing material into the deeper water on either side. The smoothing of the topography reduces drag created by the sandwaves, allowing greater tidal flow through the channel and reducing the rate of rebuilding of sandwave crests.