Hydro-Morphological Impacts of Longshore Current and Riverine Sediment in the San Luis Rey River

Longshore sediment transport is heavily impacted by the dynamic connection between riverine and coastal processes. The management and flood protection strategies of the San Luis Rey River, located in Oceanside, California, USA has been heavily impacted by this process. Hydro-Morphological numerical modeling, completed under the USACEs Regional Sediment Management Program indicated significant flood risk to the area due to the interaction between these processes and resulting sedimentation in the lower river channel. In this work, Adaptive Hydraulics 2D Shallow Water (AdH-SW2D), a high fidelity, finite-element model, is used to simulate riverine hydrodynamic and sedimentary conditions in the river channel for multiple river management strategies for current and future hydrographic conditions. Similarly, STWAVE (STeady-state spectral WAVE), was used to model the coastal portion of this combined system. To study the interaction between the riverine and coastal processes and their impact on the hydro-morphological characteristics of the system, the Coastal Storm Modeling System (CSTORM-MS), was used to couple the two previously described models. Results show that sedimentation in the San Luis Rey River is heavily impacted by the longshore current, river conditions, and backwater impacts present in both current and future predictions and that the shoaling due to these processes has a direct, negative impact on flood conditions throughout the channel.