Applying HEC-RAS To Simulate The Complex Tidal Conditions For Estuaries And Bays: A Case Study Of The San Francisco Bay in California

Flood mitigation and planning is one of the primary objectives for the US Army Corps of Engineers (USACE) Civil Works Mission. Towards meeting the needs of the flood control mission, USACE relies on HEC-RAS for inland flood inundation mapping for standard or routine events. Recently there has been an interest in the investigation of HEC-RAS to perform more complex hydrodynamic simulations such as those that occur in Estuaries and Bays.

Hydraulic modeling of geophysical flows in Estuaries and Bays is complex. This complexity is caused not only by the complex bathymetry but also the interwoven flow pathways that are common in tidal wet- and marshlands. These complexities are not easy to translate to inland hydraulic simulation codes such as HEC-RAS, therefore there is a need to investigate and document the ability of HEC-RAS to accurately, efficiently and robustly simulate these complex flows.

The behavior of Estuaries and Bays is often governed by the type of tides they experience. For example, the tides on the Gulf Coast are micro-tidal, the East Coast are meso tidal and the West Coast experiences meso to macro tides. To have confidence that a numerical model can successfully simulate these tidal conditions and associated wetland hydrodynamic processes requires the application of the model to all tidal ranges.

This study will apply the release version of HEC-RAS Version 5.0.7 to the simulation of tidal movements in San Francisco Bay, California and will seek to show what HEC-RAS is capable of in a large bay and what deficiencies it has by comparing simulated data with observed data from the NOAA Ports database.