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1D-2D Still Water Level (SWL) Model


A one and two-dimensional hydrodynamic model of the San Francisco Bay and Delta using the Delft3D Flexible Mesh modeling suite to simulate still water levels (SWL; tide and surge) in the Bay, local tributaries, and Delta channels for hindcast and forecasting purposes by Nederhoff et al. (2021).


Model Description

The San Francisco Bay and Delta (SFBD) is the largest estuary on the U.S. West Coast. Over the last few decades, a range of numerical models using different software platforms have been developed to study complex hydrodynamic and sediment-transport-related issues in the SFBD.  However, most of the previous models have limitations related to proprietary software, access for the research community for further development, limited support/maintenance, model extent, extreme value analysis methodology, and model schematizations. The models were not designed for ease of use or calibrated for high water level computations. Moreover, the computational expense was high and thus not cost-effective to utilize for the long-term hindcast applications critical to this effort.

Considering the need of the San Francisco Bay Community for a regional, public domain model that can be used with a high level of consistency around the Bay, the vision for the development of this model was initiated by U.S. Geological Survey, Alameda Flood Control District, and Deltares USA. 


The San Francisco Bay and Delta Model (SFBD) utilizes the open-source Delft3D-Flexible Mesh software to compute Dynamic Still Water Levels (SWLs) in San Francisco Bay and the Sacramento-San Joaquin Delta. SWL captures the effects of meteorological and fluvial forcing on the coastal water levels. The model covers the Delta up to the approximate upstream limit of tidal influence and extends seaward to the Pacific Ocean. The model has a relatively high grid resolution in the Bay (~100 m) and is designed for efficient still water level computations for hindcasting (Nederhoff et al., 2021) or forecasting purposes (Tehranirad et al, 2020).

The model excludes the impacts of wave setup and runup on the water level. The contribution of the wave-driven process in the Bay is generally limited. For example, for 75% of the analyzed points around the Bay, waves contribute less than 10% to the extremes compared to mean higher high water (MHHW). This means that the Total Water Level (TWL) relative to MHHW is 10% higher compared to extremes based on the hydrodynamic model computed SWL. More information on the importance of wave processes will be published soon. 


We refer to this new model schematization as San Francisco Bay and Delta – Still Water Level or SFBD-SWL.. The SFBD-SWL was developed by Deltares USA and U.S. Geological Survey through funding and technical support by Alameda County Flood Control District and the California Department of Water Resource and herby dedicated to the community to help support modeling consistency and uniformity for SLR and other coastal projects around the Bay.

The model performs well in terms of computed water levels. After minor calibration of the tidal constituents and bottom friction, water levels (tide and surge) within the Bay are well reproduced with errors smaller than 12 cm (or 5 inches). Efficient modeling is allowing for the brute force computation of a 70-year record of 1950-2019 and a reliable determination of extremes. The 70-year hindcast simulation was used to estimate extreme values of water levels and their matching return periods. Nederhoff et al. (2021) used the peak-over-threshold (POT) Generalized Pareto distribution (GPD) for the determination of extremes. The POT/GPD makes better use of the available modeled data but requires a high temporal resolution and was only used on the observation points of the model. For more information about the calibration/validation and determination of extremes, one is referred to Nederhoff et al., (2021) or the Download section below. 


Some typical applications of this new model and subsequent results:

  • Forecasting of water levels for making emergency-response decisions, infrastructure operations, and resource allocation;

  • Simulation of tidal water level across the SF Bay and Delta for current and future sea-level rise scenarios;

  • Assess the impact of planned flood protection scenarios across the SF Bay and Delta for extreme tidal and non-tidal events.


The software, the model, and its input conditions are publicly available. Third parties can run, amend, copy, and distribute this SFBD-SWL and other SFBD Community Models under Creative Commons Attribution-Share Alike 4.0 International License to meet the need for timely and best science. Available for download are the 1) the model input conditions for the water years (WY) 1951-2019; 2) processed model results for same time periods; 3) report and shapefile about extreme still and total water level across the SF Bay. 

1. Model setup for WY1951 - WY2019

Model grid, boundary conditions, and meteorological forcing for WY1951-2019.

2. Model results for WY1951 - WY2019

Processed model results for 1244 points across the SF Bay for WY1951 - WY2019.

3. Extreme value values for the Bay

Report and shapefile describing the analysis method and results for extreme still and total water level across the SF Bay.


When using one or more of the downloads, please include the following references. Moreover, please review the Terms of Use.

  • Nederhoff, K., Saleh, R., Tehranirad, B., Herdman, L., Erikson, L., Barnard, P. L., & van der Wegen, M. (2021). Drivers of extreme water levels in a large, urban, high-energy coastal estuary – A case study of the San Francisco Bay. Coastal Engineering, 170, 103984.

  • Tehranirad, B., Nederhoff, C.M., Herdman, L.M., and Erikson, L., 2021, Hydrodynamic model of the San Francisco Bay and Delta, California: U.S. Geological Survey,

  • Tehranirad, B., Herdman, L., Nederhoff, K., Erikson, L., Cifelli, R., Pratt, G., Leon, M., & Barnard, P. (2020). Effect of fluvial discharges and remote non-tidal residuals on compound flood forecasting in San Francisco Bay. Water (Switzerland), 12(9), 1–15.



Terms of Use

The data provided on this website is provided 'as-is' with absolutely no warranty whatsoever, whether express or implied, as to the accuracy, thoroughness, value, quality, validity, suitability, condition, or fitness for a particular purpose, nor as to whether the data or models are error-free, up-to-date, complete, or based on accurate or meaningful facts.   The data and models are provided on the condition that neither Deltares USA, Alameda Flood Control District, California Department of Water Resources, the U.S. Geological Survey nor the U.S. Government can be held liable for any damages resulting from the authorized or unauthorized use of the data. Any use of the data is at the user’s sole risk. This SFBD-SWL model is developed by Deltares USA and the U.S. Geological Survey and is sponsored by Alameda Flood Control District and California Department of Water Resources through the Integrated Regional Water Management Program. Parties developed the model with professional care based on the conditions of the mentioned contracts. The accuracy is subject to the contractual conditions and the usual assumptions and approximations made in mathematical modeling. Alameda Flood Control District © 2019-2021, use allowed under the terms of Attribution-ShareAlike 4.0 International

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