Galveston Bay is an estuary located in Southeast Texas near the Houston-Galveston area. In this wonderfully complex system, freshwater inflows from rivers, bayous and streams mix with salty water from the Gulf of Mexico. This mixing provides a unique environment that houses indigenous coastal plants and offers a nutrient rich arena that nurtures juvenile marine organisms such as shrimp, oysters, crabs, and numerous fish.
Galveston Bay is the largest and most biologically productive estuary in Texas, and sits adjacent to one of most heavily urban, industrialized areas in the nation. Approximately 4.5 million people reside in the five counties surrounding Galveston Bay (Brazoria, Chambers, Galveston, Harris, and Liberty Counties), making the Houston metropolitan area the fourth most populous in the nation. That figure represents over 75 percent of Texas' coastal population! While the western side of Galveston Bay is occupied by the urban metropolis, the eastern side remains largely rural.
Galveston Bay, its bayous, and diverse natural features make this region geographically unique, afford an array of recreational opportunities, and play an essential role in maintaining our quality of life. It is composed of four major sub-bays: Galveston, Trinity, East and West Bays. While Galveston Bay's combined area is 384,000 acres or 600 square miles, it is very shallow; averaging only 7 feet. It is surrounded by 232 miles of shoreline. Extending inland from this shoreline and the shorelines of the bay's tributaries, is 33,000 square miles of land that we call the Galveston Bay watershed.
Natural processes operating over geologic time created Galveston Bay and continue to slowly modify the Bay today. The two upper bays, Galveston and Trinity, were formed approximately 4,500 years as many modern estuaries are, through the drowning of river valleys as sea levels rose after the last Ice Age. The two lower bays, East and West Bay, are coastwise lagoons that were segregated from gulf waters by the linear barrier system, which developed around 4,000 years ago as sea level reached near present levels. East Bay formed as a result of Bolivar Peninsula; West Bay formed landward of Galveston Island.
Although natural processes are at work modifying the Bay, the most visible changes have come at the hands of humans.
See more information on Galveston Bay geography in Chapter Five of The State of the Bay and in GBEP Partner Resources.