Hydraulic Simulation for Calcasieu Lake Area With Small Rivers Using an Immersed Boundary Method

Abstract

Abstract Coupled one-dimensional and two-dimensional hydraulic models using an immersed boundary method (IBM) was developed and implemented for a simple flooding case in a previously published study [1]. In this study, the IBM model was applied for simulations on a real geographical location, which was the Calcasieu Lake and its surrounding area in Southwest Louisiana. The simulation area ranges from the city of Lake Charles on the northern region to Gulf of Mexico on southern region, and two National Wildlife Refuges (NWR) on the east and west regions to the Calcasieu Lake. Calcasieu Lake is the major part of the wetland ecosystem, a simple change in the natural state of the lake, i.e. the change in the water surface elevation or flooding, can have a drastic impact on the ecosystem of its surrounding areas. The flooding to the wetlands is mainly through small rivers connected to the lake. In order to study the effects of coastal flooding to the wetlands, the IBM 1D-2D coupled model was implemented in the simulation package. The main purposes of this study are to: 1) determine the appropriate number of immersed boundary points to be used for this simulation, 2) validate the IBM model using an actual geographical region. Due to the lack of measurement in the small rivers, the validation was conducted by comparing simulated results from IBM model to the results from two non-IBM approaches (i.e., manually carved rivers and no rivers). Data obtained from NOAA and USGS were used for the boundary conditions for the 2D hydraulic model. During the first phase of study, the results from the higher number of immersed boundary points came close to each other which suggested that higher number of immersed boundary points are more precise for calculation. The final comparison of water surface elevation and velocity magnitude proved the accuracy and validity of the simulation package.