Predicting Hydrodynamics of a Proposed Multiple-Inlet System, Colorado River, Texas

This study investigates the hydrodynamics of a multiple-inlet system encompassing the lower Colorado River (CR) and the Gulf Intracoastal Waterway, Texas. The system includes two proposed new inlets, one connecting East Matagorda Bay to the Colorado River Navigation Channel (CRNC) and the other connecting West Matagorda Bay to the CRNC. If implemented, the resultant system would be comprised of three inlets in the near field (CR entrance and two proposed inlets) and three inlets in the far (regional) field (Mitchell's Cut in East Bay; Pass Cavallo and Matagorda Ship Channel in West Bay). Engineering questions concern stability of the various inlets, channel shoaling, and navigation safety. Alternative configurations of the proposed inlets are evaluated with the ADCIRC model, verified with measurements of water level and current velocity. It is found that the current in the CRNC becomes more ebb dominant with introduction of the new inlet to the East Bay, promoting navigation channel stability. In contrast, the current in the CRNC becomes flood dominant with introduction of the new inlet to the West Bay, which would alter the pattern of sediment deposition by promoting development of a flood shoal in the CRNC.