Modelling of sediment plumes caused by dredging operations

While attempting to improve their efficiency in abstracting marine sediments, trailing suction hopper (‘trailer’) dredgers release large quantities of fine sediment into the waters in which they operate. This procedure causes a substantial local increase in suspended sediment concentration, particularly in the area close the water surface, where visible plumes are created. If operations are carried out without adequate control, these plumes can result in breaches of water quality standards and the associated detrimental impacts on marine life, on commercial and industrial uses (such as fisheries and cooling water intakes), and the aesthetic quality of the water. This paper documents the development and application of two mathematical models, an advectiondispersion model and a surface plume model, which were designed to predict the impact of trailer dredgers operating in a marine environment. The models were first used in an assessment of dredging to extract marine sand in Hong Kong’s coastal waters.