Modeling River Restoration Impact on Flow and Sediment in a California Watershed

A channel restoration utilized the pond and plug technique along several river reaches in the Last Chance Creek sub-watershed in Feather River Basin, California, during 2002–2004, in order to rehabilitate the floodplain functions such as mitigating floods, retaining groundwater and removing excessive levels of sediment, and to significantly alter the hydrologic regime. This paper describes an integrated approach to modeling flow and sediment transport in the connected stream-aquifer system to quantify the influence of the river restoration activities. Flow in the stream network is modeled as an unsteady, spatially varying flow with consideration of the flood spreading on floodplain, while sediment transport modeling is based on a one-dimensional advection-dispersion equation with consideration of the erosion and deposition processes. The interaction between surface water and groundwater is accommodated by the leakage and recharge terms and is implemented in the model using an iterative procedure to ensure mass conservation across the interface between the two systems. A comparison of the pre-restoration and post-restoration scenarios for the river network in the Last Chance Creek watershed will show the influence of the restoration efforts. The quantification of the restoration impact on flow and sediment will contribute to greater efficiency and a better prediction of the opportunities for restoration and development of riverine wetlands.