The Greens Bayou watershed is located in north Harris County and encompasses portions of the cities of Houston and Humble. The upper reach of Greens Bayou flows in an eastward direction and the lower reach flows southward into the Houston Ship Channel. The watershed covers about 212 square miles and includes four primary streams: Greens Bayou, Halls Bayou, Garners Bayou, and Reinhardt Bayou.
There are about 308 miles of open streams, including the primary streams and tributary channels. Based on the 2010 U.S. Census, the estimated population of the Greens Bayou watershed is 528,720.
Flooding of homes and businesses along Greens Bayou and its tributaries has occurred numerous times in the last two decades, with recent devastating flood levels throughout the watershed brought on by Tropical Storm Allison in 2001. Significant floodplains and high-density development have combined to cause high damages during frequent flood events. Additionally, storm surges can influence flooding levels along the lower 10 miles of the watershed.