Available at: https://digitalcommons.calpoly.edu/theses/2729
Date of Award
12-2023
Degree Name
MS in Civil and Environmental Engineering
Department/Program
Civil and Environmental Engineering
College
College of Engineering
Advisor
Stefan Talke
Advisor Department
Civil and Environmental Engineering
Advisor College
College of Engineering
Abstract
The primary motivation of this study is to analyze the 1D-2DH hydrodynamic model of the San Francisco Bay and Sacramento-San Joaquin Delta (SFBD) outlined in Nederhoff et al. (2021). I compared model water level data to 70 tidal records from the National Oceanic and Atmospheric Association (NOAA), the United States Geological Survey (USGS), the California Data Exchange Center (CDEC), and from local municipalities throughout the Bay Area to investigate how the model captures water levels and tidal constituent amplitudes. While the Nederhoff et al (2017) model analyzed an extended time period from 1950-2019, I analyzed M2 amplitude and tidal water levels for the water year of 2017 (WY2017) with a larger dataset that extended into the Sacramento-San Joaquin Delta. Because WY2017 was a high river flow year for the Sacramento Delta, the model was able to be evaluated throughout a large range of flow regimes.
I used harmonic analysis through the MATLAB package UTide (Codiga et al. 2011) to assess the model’s ability to replicate M2 amplitudes. I assessed the error for these M2 values as well as for tidal water levels. The average RMSE for M2 amplitude is 0.111 m across the entire model domain during WY2017, performing fairly consistent throughout the model. The one exception being the shallow and complex Grizzly Bay, which performed significantly worse, with RMSE values around 0.5 m. The model better replicated water levels in the 2DH grid representation of the San Francisco Bay (
Attempts to improve the model were mostly unsuccessful. I tried to increase the grid resolution at the Carquinez Strait to improve tidal propagation upstream, but altering the grid caused the coupling between the 2DH grid and 1D network to detach. This prevented the propagation of water flow in either direction at the coupling near Collinsville. The software required to fix this coupling was non-standard and unavailable for my usage, so I was unable to resolve the issue. I also attempted to create a new wind forcing file using in-situ data rather than the ERA5 reanalysis. This new wind forcing made negligible difference in water level and M2 model skill.
An experiment in removing river flow showed that riverine impacts on elevating extreme water levels only have effects (>0.05 m) east of the Carquinez Strait. Extreme water levels west of this point in the San Pablo, Central, and South Bays are dominated by tides, storm surge, and to a lesser extent local wind. A decrease in tidal amplitude by river flow potentially decreases flood risk in some parts of the Bay during times of high outflow from the Sacramento-San Joaquin Delta. I also investigated maximum equilibrium effects of constant wind in the two prevailing wind directions (southerly and westerly) of the San Francisco Bay. The wind setup effect become more prominent (>0.05 m) at and above a steady 10 m/s in both directions. This study also showed that wind likely exerts a small influence on tidal properties, especially for winds greater than 10 m/s.