Abstract
Several projects in the Sacramento San Joaquin River Delta has been proposed in the form of tidal marsh restoration, which is an environmental hydromodification to allow for a more natural tidal wetland on existing shorelines. There are many planned projects for this region, but there are four specific separate tidal marsh hydromodification projects that are the most developed and engineered: the Chevron Point Tidal Marsh restoration on Twitchell Island, Meins Landing Tidal Habitat Restoration Project, Dutch Slough Tidal Habitat Restoration, and the McCormack Williamson Tract Breaching and Restoration Project. Models currently exist for all but the Chevron Point Tidal project. All of the remaining projects have been modeled on an individual basis, meaning these specific proposed projects usually never take into account any addition or other tidal projects working concurrently, as far as modeling attempts. In order to gain a better understanding of how these potential projects could hydraulically interact as a “system” after construction, the projects should be modeled together to determine the absolute hydraulics of the entire Delta system as a whole. An existing state of the art model developed by Aquaveo and the United States Army Corps of Engineers, the Adaptive Hydraulics Model (ADH), of the Sacramento San Joaquin River Delta was obtained and utilized for the proposed tidal marsh modeling. The ADH model utilized hydraulic and hydrologic data collected from various sources and calibrated to simulate a normal water year with one 50-year storm event. Elevation data for the proposed tidal marsh projects was collected using GPS technology on site (for Chevron Point) or extracted from the Delta Lidar data collected in 2007. To connect these new data points with the bathymetry found in the existing model, breaches were created in the model at each of the four projects, each approximately 50-100 meters in length. After various failed running attempts and debugging, the existing ADH model of the Sacramento San Joaquin River Delta was successfully altered to include the four tidal marsh restoration hydromodification project sites. Water depth and water velocity (both direction and magnitude), and the water surface elevation was calculated for the entire area of each project and successfully simulated a 2520 hour event under normal water year conditions. Several observation points were established for each of the projects, where water depth and velocity data was collected and compared amongst each of the project sites and some previous model results. The resulting average water depths were between 0.64 and 2.28 meters, and the average velocities were between 0.02 and 0.12 meters per second. These results were compared to several other previous model study results, with average water depths were between 0.75 and 0.91 meters, and the average velocities were at 0.09 meters per second. It was determined that the four different sites modeled together or separately would produce similar hydraulic numerical results.