ASL has been involved in sediment transport studies since the early 1980s in the Beaufort Sea. These projects were related to offshore oil and gas exploration and government studies. More recent projects have included offshore Nova Scoria, the Fraser River delta and the Columbia River. ASL uses various technologies for sediment transport studies including OBS sensors, acoustic backscatter from Doppler current meters, and an Imagenex 881A scanning sonar. Numerical modelling is often incorporated to simulate "what if" scenarios. Following are several examples of sediment transport studies conducted by ASL.
ASL has developed a platform for the study of sediment transport. This tripod-based system uses a combination of off-the-shelf and custom elements to measure waves, currents, optical backscatter and sea bottom imaging. The instruments are generally stand alone data loggers which allows for customization for specific projects. Typically we include Doppler current profilers, OBS sensors, and a scanning sonar. Other sensors can easily be added. ASL developed a data logging and control module [IRIS] for the Imagenex scanning sonar instrument.
This system has been used on several occasions in the Fraser River delta foreslope area of the Strait of Georgia in BC, Canada as part of the Georgia Basin Geohazards Initiative. The figure below shows the tripod being deployed on Roberts Bank using the Canadian Coast Guard Hovercraft SIYAY.
The underwater power cables between Vancouver Island and the mainland required upgrading. This involved the removal of three existing 138 kV cables and the installation of three 230 kV submarine transmission cables. Measurements were made of the currents, particularly around the Galiano Ridge where cable suspension and strumming had previously resulted in cable wear. There was a concern over possible high suspended sediment levels during the removal of the old cables and deployment of the new. A three dimensional integrated numerical model for computing ocean currents and sediment transport in shallow coastal areas was applied to simulate the dispersal and deposition of suspended sediments resulting from the construction activity.
Distribution of total suspended sediment concentration (figure left).
As part of a study of possible effects of construction of a second power plant at the Waneta Dam, measurements were made of the circulation and suspended sediment in the forebay. Excessive suspended sediment during construction could have a detrimental effect on downstream fisheries habitat. These data were then used to calibrate and validate a high resolution numerical model which was then used to simulate the detailed flow field and suspended sediment concentrations for various flow scenarios.