Field Verification of Computer Models Predicting Plume Dispersion in Hong Kong

Sand is being dredged from the seabed in Hong Kong by large trailer suction hopper dredgers to provide fill material for land reclamation. The major environmental concern is the dispersion and deposition of fine sediment in the overflow plume and the resulting potential impacts on the nearby capture and culture fisheries resources, coral assemblages, bathing beaches, and water intakes. In addition to the comprehensive Environmental Monitoring and Audit program designed to safeguard sensitive receivers, a series of sediment profile imaging surveys were performed in early 2001 to verify sediment settlement predictions made at the time of the environmental impact assessment using computer hydraulic modeling techniques. The survey results revealed that the rate of deposition and thickness of deposits are broadly similar to predictions from the hydraulic modeling, but the extent of deposition is different than predicted. The sediment profile imaging also indicates that in most locations, recolonization of the settled material by benthic fauna has managed to keep pace with the deposition.