process monitoring are needed for future holistic management of the Galveston Bay System to be 
successful. 
Introduction 
The State-owned submerged lands of Texas include about 1.4 million acres of the inner contin¬ 
ental shelf extending about 10.3 miles offshore in the Gulf of Mexico and 1.5 million acres of bays, 
estuaries and lagoons. Peripheral to these inland bay waters are about 1.1 million acres of marshes 
and other wetlands. 
The Galveston Bay System is one of seven major bays and estuaries along the Texas coast. It 
contains four major related bays (Figure 1.1); the center of the system is located at approximately 
29 30' N and 94 42' W. The two principal water bodies are Galveston Bay at the outflow of the San 
Jacinto River and Trinity Bay at the outflow of the Trinity River. Buffalo Bayou, a tributary of the San 
Jacinto River, and Clear Creek have moderate-sized drainage basins contributing freshwater inflow 
to Galveston Bay. East Bay lies landward of Bolivar Peninsula and receives minor freshwater inflows 
from the drainage of Oyster Bayou, a small stream. West Bay is located landward of Galveston Island, 
a barrier island, and receives minor inflow from Chocolate Bayou. Southwest and landward of Follets 
Island are Bastrop and Christmas Bays, which are comparatively small and essentially isolated from 
all water sources except tidal exchange. The Intracoastal Waterway enters East Bay at its easternmost 
location, traverses the southern limits of the bay system behind the barriers, and exits the system 
through the westernmost shore of Christmas Bay. 
Only two tidal inlets permit significant tidal circulation between the brackish water of the bay 
system and the marine water of the Gulf of Mexico. Bolivar Roads is the major inlet through which 
international ships travel to the Port of Houston. San Luis Pass is a minor but important inlet for tidal 
exchange, and both commercial and sport fishing boats use the inlet daily. Rollover Pass, a manmade 
cut through Bolivar Peninsula, provides minor tidal circulation at the eastern end of East Bay. 
The Galveston Bay System is large, encompassing about 340,000 acres (600 square miles) of areal 
extent, and has a simple geometry. Except for spoil banks and oyster reefs, the bay floor is generally 
flat and regular. It is very shallow, having a maximum depth of about 12 feet (Figure 1); Trinity Bay 
is mostly less than 10 feet deep. East Bay is less than 8 feet deep, and West Bay is less than 6 feet deep. 
Extreme vertical exaggeration of a bay profile is necessary to illustrate bay geometry and changes in 
elevation. Gulf Coast bays are all very shallow compared with most bays in the United States. 
The terrain about the Galveston Bay System has subdued topography and low relief. The coastal 
plain slopes gently gulfward less than 1 foot per mile, forming a gentle incline at the land-water 
contact. Bay shorelines may be marshes or small beaches composed solely of shell, sand or mud, or 
more commonly a combination of these sediments. Because of the small gradient of the coastal lands, 
a sea-level rise of a few feet can flood the coastal zone inland for many miles. Along some segments 
of the bay shore, wave-cut bluffs more than 8 feet high occur locally. 
Geology 
The geology of the Galveston Bay System and environs strongly reflects a dynamic geologic 
province. Dynamic in this sense does not mean active seismically (subject to earthquakes) but does 
denote slow, continuous processes reflecting sedimentation, subsidence, faulting and erosion, as 
well as catastrophic changes caused by hurricanes. 
Geologic Framework 
The Galveston Bay System is a small part of the northern Gulf Coast Basin, a large area of 
sedimentary deposition lying between Mexico and Florida. The basic structural and stratigraphic 
framework of the basin was established in the late Triassic and Jurassic (1), when the North American 
plate separated from the African and South American plates. During early rifting, the principal 
deposits were Triassic red beds. Soon after, the basin became isolated, and water inflow was 
restricted, resulting in the deposition of thick evaporite sections dominated by salt. A major salt basin 
underlies the Houston Embayment and is the source of local salt domes that produce salt, sulfur, and 
oil and gas. 
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