Louisiana Chenier Plain Regional Hydrodynamic and Salinity Numerical Model

Abstract

This paper describes a coupled one-and two-dimensional hydrodynamic and salinity transport model developed for the Chenier Plain along the southwestern Louisiana coast. The Louisiana Chenier Plain encompasses the coastal zone and marshes from Freshwater Bayou west of Vermilion Bay to Sabine Lake near the Texas-Louisiana border. Over the years, man-made changes to the regional circulation patterns have caused documented land loss, increased salinities, marsh deterioration, impacts on seasonal inundation patterns and drainage potentials, and greater vulnerability to storm surges. Alterations include the construction of several large and deep artificial ship channels, numerous dredged access canals to enhance navigation, the Gulf Intracoastal Waterway, and the presence of roadways disrupting the natural hydrology of the marsh. The 500m x 500m MIKE21 grid represents the lakes, marshes, and a portion of the near-shore Gulf of Mexico, covering an area greater than 10,800 square kilometers. The natural and man-made system of inland waterways, encompassing 128 channels spanning across 1400 kilometers are represented through the one-dimensional model MIKE11. The numerical model has been validated through water-level, salinity and velocity measurements. It is noteworthy that the model incorporates real-time hydraulic structure operations. The model compared well with the field measurements. The Root Mean Square Error for the water level and salinity was in the range of 5 to 8 cm and 3 to 7 parts per thousand, respectively. The model predicts water levels, discharges, depth-averaged velocities, and salinities across the Chenier Plain. The validated model will be used as a tool to evaluate proposed restoration and management strategies.