San Jacinto River

San Jacinto River

Watershed Overview

Drainage Area Watershed Population Open Stream Miles Primary Streams
487 Sq. Miles 235,740 (Harris County portion) 310 Miles San Jacinto River
Houston Ship Channel
Cotton Patch Bayou
East Fork San Jacinto River
Boggy Bayou
Patricks Bayou
Panther Creek

The San Jacinto River watershed is a very large watershed that originates well outside of Harris County. The San Jacinto River flows through much of eastern Harris County and joins with the Houston Ship Channel before flowing into Galveston Bay along the southeastern edge of the county. The watershed (within Harris County) extends through the cities of Houston, Galena Park, Pasadena, Deer Park, Baytown, Humble, La Porte, Morgans Point, Shoreacres, and Seabrook. The channels within the watershed drain all or part of Harris, Montgomery, Waller, Walker, Grimes, Liberty, and San Jacinto counties, for a total drainage area of approximately 4,500 square miles. In Harris County, the San Jacinto River watershed covers about 487 square miles and includes seven primary streams: The San Jacinto River, the Houston Ship Channel, Cotton Patch Bayou, East Fork San Jacinto River, Boggy Bayou, Patricks Bayou, and Panther Creek. 

There are about 310 miles of open streams within the watershed, including the primary streams and tributary channels. Based on the 2010 U.S. Census, the estimated population of the Harris County portion of the San Jacinto River watershed is 197,570. The San Jacinto River flows from its headwaters near Huntsville, through Lake Conroe and Lake Houston. Lake Houston was developed as a water supply reservoir and therefore does not provide significant storage during flood events. The Port of Houston Authority operates the Houston Ship Channel, which originates at the Turning Basin and follows the original alignment of Buffalo Bayou to the San Jacinto River. The Ship Channel continues through the San Jacinto River and San Jacinto Bay to Galveston Bay, which is the ultimate outfall for all drainage in Harris County.

Structural flooding has occurred in low-lying areas adjacent to the water bodies. However, water surface elevations in the Houston Ship Channel, the San Jacinto River and Galveston Bay are not affected by the flow from any single watershed. These waterways are tidally influenced and can be affected by storm surge.

Land Use

Various portions of the watershed are developing at different rates, with the largest increases occurring near Lake Houston and the Houston Ship Channel. The Ship Channel supports the Port of Houston, which is the third largest port in the world and can accommodate ocean-going vessels to the Turning Basin. A recent expansion of the channel has sparked new industrial growth in the area.


The San Jacinto River hosts a typical riverine ecosystem and contains reaches that are totally natural, as well as reaches with development encroaching to the water's edge. Lake Houston is heavily urbanized, although large areas of undeveloped property still exist in close proximity to the lake. The Houston Ship Channel is heavily industrialized and was created by extensive dredging and widening.

How Water Flows In The san jacinto river Watershed