Sedimentation Analysis of the Proposed San Rafael Canal Tidal Barrier, San Rafael, California.

摘要

A tidal barrier is proposed as a control measure to prevent tidal flooding in the San Rafael Canal. This study investigated at a feasibility level the interaction between sedimentation and the tidal barrier. A brief site trip with limited sampling of suspended sediments and bottom cores was conducted, historical dredging records for San Rafael Canal were analyzed, historical suspended sediment data from nearby San Francisco Bay were obtained, sediment characteristics for erodibility from prior flume tests conducted on San Francisco Bay bottom sediments were obtained, and freshwater inflow exceedance interval hydrographs were obtained for the 2-, 10-, 50-, 100-, and 500-year events. A zero-dimensional numerical model was developed to evaluate erosion and deposition for the 1989 astronomical tides at two alternative tidal barrier locations. In the vicinity of San Rafael Canal where the tidal barrier would be located, tidal sediment movement appears to predominate rather than riverine sediment transport. The numerical model results, substantiated by the dredging records, indicated that the existing San Rafael Canal has a net depositional pattern. Increased velocities from the reduced cross section of the tidal barrier changed the numerical results to predict net erosion tendencies at both tidal barrier sites evaluated. These results indicate that the tidal barrier concrete apron will be kept relatively free of deposits that might otherwise interfere with operation of the barrier. (edc)