Research Project Full Title: Building the Trinity River Delta Hydrodynamic Model
Principal Investigator(s): Assoc. Professor Ben R. Hodges (PI); Assoc. Professor Paola Passalacqua (Co-PI)
Researchers: Zhi Li
Sponsor(s): Texas Water Development Board
This study will make use of the prior development of a gridded topographic model developed for the TWDB under prior contract #1600011928. The gridded topography will be used with the Frehd-C hydrodynamic model to build the Trinity Delta Hydrodynamic Model (TDHM) as a tool for environmental flows decision support.
The complexity of the flow paths through the Trinity River and its connected bayous and delta make it challenging for TWDB to effectively quantify environmental flow impacts. This area is roughly defined as south of County Road 442, 8 miles south of Dayton that is hydrologically and hydraulically connected to lakes Anahuac, Dutton, Lost, and Old River through a network of channels and marshes. It is impractical to monitor all the pathways through the system, so the most effective timing and quantities of water delivered for environmental flows is difficult to evaluate. A hydrodynamic model can provide a means of evaluating water impacts and understanding the effects of different environmental flow management strategies. Building such a model requires careful attention to the model representation of the flow paths and the ability of the model to effectively handle the inundation and drying of wetlands and marshes with tides and varying inflows. A similar model has been previously developed for the Nueces River Delta, and has proved valuable in estimating effects of different fresh water inflow management strategies.
Information developed using the model will lead to improvements of the inflow datasets driving the TWDB’s Galveston Bay hydrodynamic and salinity transport model. Additionally, this study will provide more information to the Trinity San Jacinto Basin and Bay Area Stakeholder Committee and the Texas Commission on Environmental Quality for quantitatively evaluating existing environmental flow standards for Galveston Bay.
In the prior study the LIDAR data for the Trinity River Delta was developed into a gridded topography for hydrodynamic modeling. We tested the Fine Resolution Environmental Hydrodynamic Model (Frehd) and the SUNTANS model for use with the high-resolution topography. The Frehd model proved to slow to run, and the unstructured grid tessellation of the SUNTANS model proved impractical for the system. To overcome these problems, we created a version of Frehd in the C programming language (Frehd-C) that can run on parallel computers and is efficient for modeling the Trinity delta system. In this study, we will use the Frehd-C model with the topography previously developed to build and test the TDHM.