Wetlands and aquatic habitats on Central Texas Gulf coast barrier and delta complexes (Matagorda Island, Matagorda Peninsula, and Colorado River Delta) are dominated by estuarine emergent wetlands (salt and brackish marshes), which in 2001 encompassed 11,257 ha in the study area and represented 67 percent of the vegetated wetland and aquatic classes (marshes, mangroves, and seagrass beds). Among other mapped classes, seagrass beds are most abundant at 4,607 ha, followed by tidal flats (2,289 ha), Gulf beaches (1,124 ha), palustrine marshes (857 ha), and mangroves (112 ha). Historically, losses and gains in habitats have occurred throughout the study area, but the overall trend in vegetated wetlands is one of net gain, as revealed by slight increases in estuarine marshes of about 500 ha from the 1950's through 2001. However, the total area of tidal flats decreased by about 1,840 ha since the 1950's.

Analysis of habitat distribution by geographic subarea reveals local differences in historical trends. There were systematic net losses of estuarine marshes on east Matagorda Peninsula but net gains on the Colorado River Delta, west Matagorda Peninsula, and Matagorda Island. Losses on east Matagorda Peninsula were due primarily to submergence of marsh vegetation on the downthrown side of active faults that intersect marshes and to erosion of the Gulf and bay shorelines. Movement along active faults has apparently accelerated rates of relative sea-level rise, which have exceeded rates of marsh vertical accretion. As a result, several hundred acres of marsh has been submerged and replaced by open water on the downthrown side of faults. Net marsh gains on the Colorado River Delta were due to delta progradation on its west side, although marshes were lost because of erosion on its east side. A net increase of estuarine marshes on west Matagorda Peninsula was due largely to deposition of washover fans by Hurricane Carla in 1961 that became the sites on which new marshes had developed by 1979. Losses in tidal flats might be explained partly by a rise in relative sea level, causing the flats to be replaced by other habitats, such as open water, seagrass beds, and marshes.

The object of this research, funded by the National Oceanic and Atmospheric Administration through the Coastal Management Program and administered by the General Land Office of Texas, was to determine wetland status and trends and probable causes of trends along the Central Texas coast, using recent and historical aerial photographs supported by field surveys. Current wetland distribution (status) was determined by interpreting and digitizing wetlands on color infrared (CIR) photographs taken in 2001. Historical distribution was based on photographs taken in the 1950's and 1979 and on historical GIS maps obtained from the U.S. Fish and Wildlife Service (USFWS).