Modelling the Bay Area
We utilised 2D modelling to improve upon the methods that were available in the previous study. Using MIKE 21, we developed a system of regional scale coastal models in order to predict the following for the entire San Francisco Bay:
- Extreme tide (astronomical tide plus storm surge)
- Swell entering from the Pacific Ocean
- Sea waves generated from local winds in the Bay
Normally, we would apply a highly detailed study to a focused study area. However, this project required the same level of detail for the entire 250 mile-long Bay Area shoreline. Several factors contribute to the variability and complexity of the Bay shoreline geography, including:
- Orientation of the shoreline
- Exposure to wind and waves (sheltering for example)
- Water depths
- Regional/climactic variation in wind and wave conditions (micro-climates)
Because of these factors, it was very difficult to identify singular storm events that would apply equally across the entire Bay Area. To allow us to identify the storms in advance, we operated the models in hindcast mode to produce continuous results of water levels and waves covering:
- 31 years in the North and Central Bay
- 54 years in the South Bay
Following this, we used the regional model results to establish maximum 1% (100-year) and 0.2% (500-year) Still Water Levels (SWLs) – the maximum water level that will occur – and wave height conditions. We then utilised this information to drive local response-based models of:
- Water level
- Wave setup
- Wave run-up
- Overland waves
We calibrated and validated the models using National Oceanic and Atmospheric Administration (NOAA) tide gage measurements from around the bay as well as various wave measurements from inside and outside the bay.