Situated about 15 miles (24 kilometers) west of Galveston, Texas, West Bay Bird Island is one of the few naturally formed islands in Galveston Bay. Leased and managed by the Audubon Society, the island supports a rookery of birds including reddish egrets, great egrets, Forster’s terns, black skimmers, roseate spoonbills, and tricolored herons.
Over the years, the island has suffered severe erosion, caused in part by the migration of a tidal channel and sea level rise.
In 2003, the Texas General Land Office retained Mott MacDonald to help protect the island from further erosion and restore its marsh habitat. We collected bathymetric and topographic data to develop preliminary and final engineering designs, prepare permit documents, and perform numerical modeling of tide-induced, wind-induced, and wave-induced hydrodynamics.
To pinpoint the primary causes of erosion, we performed a geomorphologic analysis using historical aerial photos, historical sedimentological data, and previous hydrodynamic evaluations of the San Luis Pass area.
Mott MacDonald evaluated various shoreline protection alternatives using these criteria:
- Capital construction cost
- Maintenance cost
- Natural resource impacts
- Impacts on navigation
Numerical modeling was used to determine the ability of each alternative to perform as desired, and a design for the selected alternative was created.
In 2006, construction was completed on an innovative solution using a dredged relief channel to divert flow away from the island. About 66,700 cubic yards (51,000 cubic meters) of sandy material was dredged from a channel approximately 1,500 feet (457 meters) long and used to create new habitat and a protective bar about 600 feet long (183 meters) adjacent to the island.
The project created about 4.9 acres (2 hectares) of bird nesting habitat, 10.8 acres (4.4 hectares) of intertidal marsh, and 2.1 acres (0.8 hectares) of high marsh. It protected an additional 14.1 acres (5.7 hectares) of intertidal marsh and one acre of tidal sand flat. The result is a larger and more sustainable environment for birds and other wildlife.