San Jacinto & Galveston Bay

San Jacinto & Galveston Bay

Watershed Overview

Drainage Area Watershed Population Open Stream Miles Primary Streams
20 Sq. Miles 235,740 (2020 Census Data) 24 Miles Little Cedar Bayou
Pine Gully

The San Jacinto Galveston Bay watershed is located at the southeastern edge of Harris County. The watershed primarily drains the area that includes La Porte, Morgans Point and portions of Pasadena. However, Galveston Bay is the ultimate outfall for all drainage in Harris County. The Galveston Bay watershed covers about 20 square miles and includes two primary streams: Little Cedar Bayou and Pine Gully. There are about 24 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 Galveston Bay watershed is 14,952.

Structural flooding has occurred in low-lying areas adjacent to the water bodies. However, water surface elevations in Galveston Bay are not affected by the flow from the bayou system. Water Surface elevations in Galveston Bay are tidally influenced and can be affected by storm surge.

Land Use

Much of the watershed has been developed, including several areas of significant industrial and pertrochemical activity. The watershed is adjacent to the Houston Ship Channel.


Galveston Bay supports a wide diversity of marine habitat and wildlife, including adjacent marshes and estuaries. Many areas within the watershed are considered environmentally sensitive.

Projects In san jacinto & galveston bay Watershed

The Harris County Flood Control District has a significant number of flood damage reduction projects occurring all over Harris County as part of its on-going Capital Improvement Program (CIP), Operations and Maintenance, and the 2018 Bond Program. Click the Project ID on the Map to learn about projects’ details. Some early-stage projects are not highlighted on the map. The map will be updated when projects advance or when more information becomes available.

Summary of Galveston Bay Watershed Plan

Published March 5, 2021

How Water Flows In San Jacinto & Galveston Bay Watershed