Numerical Modeling of Hydrodynamics, Waves, and Salinity in Matagorda Bay and Ship Channel, Texas

The U.S. Army Corps of Engineers (USACE) has recently completed a numerical modeling study of hydrodynamics, waves, and salinity for the proposed improvements to the Matagorda Ship Channel (MSC), Texas. The numerical modeling study investigates the impact to currents, waves, and salinity in Matagorda Bay from the proposed ship channel dimensions which are approximately 3 m (10 ft) deeper and 61 m (200 ft) wider. The modeling includes two historical hurricanes and three freshwater inflow conditions for high, medium, and low flow stages with representation of the present and future conditions of coastal boundary water surface elevation. Model results show the proposed ship channel dimensions will slightly increase flow efficiency and current magnitude in the bay. Water levels in the bay tend to increase slightly with proposed improvements and greater river inflow. The water level change in the bay is less sensitive in future condition with higher water level input than the present condition. The difference of salinity variations with and without channel improvements is small in Matagorda Bay, ordinarily less than 2 ppt. In the upper bay, the model minimum salinity becomes slightly greater with the proposed improvements. Higher salinity occurs more often in Matagorda Bay in future condition with higher water level than the present water level. The effect of the proposed ship channel dimensions to water surface elevations, current velocities, and salinities is overall small as compared to the present channel condition.