Alviso Slough area, South San Francisco Bay, California, is the site of an ongoing effort to restore former salt production ponds to intertidal habitat. As restoration proceeds and the levees surrounding the former salt production ponds are breached, the increase in tidal prism and associated sediment scour in the sloughs will remobilize legacy mercury deposits. A numerical model that is able to assess patterns of sediment transport, erosion, and the fate of remobilized sediments can improve mercury remobilization estimates and inform management actions.
The goals of the current research are to (1) validate a 2D geomorphic model for Alviso Slough using bathymetric surveys and to (2) apply the validated model for Alviso Slough to investigate scenarios of sea level rise and levee breaching on the long-term scour in Alviso Slough. The 2D geomorphic numerical model applies the Delft3D Flexible Mesh (software by Deltares) that describes detailed interaction between hydrodynamics, sediment transport, and geomorphic change on a high resolution mesh.
The morphodynamic modeling exercise shows that observed erosion and sedimentation patterns can be reproduced with skill. The associated suspended sediment concentrations are more difficult to reproduce. The model reveals tide residual flow patterns that are difficult to measure. These residual flow and transport patterns are the result of subtle, tide residual transport trends so that their effect becomes visible in multi-year simulations. Scenario model simulations show possible, illustrative impacts of sea level rise and potential management interventions (additional levee breaches).
