Investigation of the impacts of Gulf sediments on Calcasieu Ship Channel and surrounding water systems

摘要

Calcasieu Ship Channel is located in southwest Louisiana, connecting the port of Lake Charles to the Gulf of Mexico. The 40 ft deep ship channel is surrounded by water systems including Calcasieu Lake, Gulf Intracoastal Water Way (GIWW), and several wetlands. Excessive sediment depositions were found on the bottom of the ship channel in many locations, which requires expensive dredging process to remove those unwanted sediments. There are several suspected sediment sources, such as the Gulf of Mexico, upstream Calcasieu River and GIWW, bank erosions, and discharge from surrounding wetlands. However, how significant of each source to the total sedimentation in the ship channel is unknown, which hinders the design of sediment prevention mechanism. In this study, numerical and experimental investigations were conducted to study the sediment transport and deposition in this target area. Sediment transport from one of the major sediment sources, the Gulf of Mexico, was studied to see the effects of this source on the total sedimentation in the ship channel. The effects of storm-surge flood on the sediment transport and deposition were also studied. The 2-d depth-averaged shallow water flow equation set was solved for water phase, along with a scalar transport equation for the sediment phase. Both sediment deposition and re-suspension effects are included in the model. The accumulated depositions on the seabed and wetland surface were calculated. The deposition results were compared to the sampling data in the area and yielded good agreement which verify the accuracy of the numerical model.