Environmental considerations relating to operation and maintenance of the Texas Gulf Intracoastal Waterway

James, Wesley P.
Giesler, Steven
DeOtte, Robert
Inoue, Masamichi
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Texas A&M University, Sea Grant Program

This study aims to identify potentially adverse environmental factors, other than dredging, associated with the operation and maintenance of the Texas Gulf Intracoastal Waterway. Field sampling was conducted along the waterway in January, May, and August 1975 to ascertain background water and sediment quality. To study the flow between Galveston Bay and Sabine Lake, a numerical model study was conducted of this reach of the waterway. Satellite imagery was used in the Lower Laguna Madre to study the circulation patterns and sedimentation rates. The following conclusions and recommendations were developed. Conclusions: 1. The Intracoastal Waterway can transport water, pollutants, aquatic plants and animals from one river system to another. 2. The waterway and normal operational activities in the waterway did not appear to be a major source of pollutants but elevated concentration of nutrients and metals were usually associated with freshwater inflow. 3. In shallow, open-bay reaches of the waterway, the current patterns adjacent to the channel can have significant effect on the shoaling rate. 4. The Intracoastal Waterway and associated dredged material islands have the potential of modifying circulating patterns and salinity levels in the bays and estuaries. Recommendations: 1. a feasibility study should be conducted for constructing a control facility in the reach between Sabine Lake and Galveston to limit flows and to contain hazardous materials in the event of an accidental discharge. 2. Additional field studies should be conducted along the Neches River, Brazos River, Caney Creek, Colorado River, and Arroyo Colorado to define the source of the nutrients and metals entering the waterway. 3. Detailed hydrological and ecological studies should be conducted at several locations in land-cut areas to evaluate the impact of the existing waterway on the groundwater and surface hydrology. 4. Studies should be conducted on promoting bottom vegetation in shallow bays. 5. Current patterns in adjacent shallow bays should be considered when planning modification to the waterway. 6. Model studies should be conducted of proposed waterway modifications in shallow bays to optimize circulation patterns, control salinity levels, and reduce maintenance dredging.

227 pgs.
navigational channels, ship canals, environmental factors, dredging, sedimentation, maintenance, water circulation, water quality, satellite sensing