Geography of Houston
Houston, the most populous city in the Southern United States, is located along the upper Texas Gulf Coast, approximately 50 miles (80 km) northwest of the Gulf of Mexico at Galveston. The city, which is the ninth-largest in the United States by area, covers 601.7 square miles (1,558 km2), of which 579.4 square miles (1,501 km2), or 96.3%, is land and 22.3 square miles (58 km2), or 3.7%, is water.
Houston is located in the Gulf Coastal Plain biome, and its vegetation is classified as temperate grassland. Much of the city was built on marshes, forested land, swamp, or prairie, all of which can still be seen in surrounding areas.
The city's topography is very flat, making flooding a recurring problem for its residents. The city stands about 50 feet (15 m) above sea level—the highest area within city limits being 90 feet (27 m). However, subsidence, caused by extensive groundwater pumping and resource extraction, has caused the elevation to drop 10 feet (3.0 m) or more in certain areas. As a result, the city turned to surface water sources for its municipal supply, creating reservoirs such as Lake Houston and Lake Conroe (of which Houston owns two-thirds interest).
Houston has four major bayous passing through the city: Buffalo Bayou, which runs into downtown and the Houston Ship Channel; and three of its tributaries: Brays Bayou, which runs along the Texas Medical Center; White Oak Bayou, which runs through the Heights and near the northwest area; and Sims Bayou, which runs through the south of Houston and downtown Houston. The ship channel goes past Galveston and into the Gulf of Mexico.
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