Greens Bayou

Greens Bayou


Drainage Area Watershed Population Open Stream Miles Primary Streams
212 Sq. Miles 607,601 (2020 Census Data) 308 Miles Garners Bayou
Greens Bayou
Halls Bayou
Reinhardt Bayou

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 from west to east before turning south and flowing 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. (Learn more about efforts in Halls Bayou here)

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, making it one of the more populous watersheds in the county.

Like much of Harris County, the Greens Bayou watershed is flood prone. The high-density development in the area combines with significant floodplains to cause high damages during frequent flood events. Much of the development in the watershed occurred prior to our current understanding of floodplains and restrictions on building in the floodplains.

The Flood Control District has projects in progress across the watershed, building on decades of investment in the area. Presently, more than $115.7 million are allocated to the Greens Bayou watershed, including bond program, partnership and Flood Control District funds, and all projects listed in the 2018 Bond Program have been initiated. As of April 2021, six stormwater detention basins are either complete or in construction in the mid-reach section of the watershed alone.


Flooding of homes and businesses along Greens Bayou and its tributaries has occurred numerous times in the last two decades, with devastating flood levels throughout the watershed brought on by Tropical Storm Allison in 2001 and Hurricane Harvey in 2017. During Hurricane Harvey, Greens Bayou had more flooded homes than any other watershed except Brays Bayou, representing almost 16 percent of the home flooding in Harris County.

Significant floodplains and high-density development have combined to cause high damages during frequent flood events. Most of the watershed is highly developed, though some large areas between U.S. 59 and I-10 remain undeveloped. Construction of new residential and commercial developments is expected to continue in the northern and western regions of the watershed. Additionally, storm surges can influence flooding levels along the lower 10 miles of the watershed.

Approach to Flood Risk Reduction

Areas of Focus

After the devastation of Tropical Storm Allison in 2001, the Flood Control District began an aggressive approach to flood risk reduction efforts in Greens Bayou. Our work in the watershed builds on decades of investment in the area, and includes:

  • Upstream Greens Bayou: The U.S. Army Corps of Engineers Galveston District and the Flood Control District have completed the Greens Bayou Federal Flood Risk Management Project in the upper stretch of Greens Bayou. This project included approximately 3.7 miles of channel conveyance improvements and the construction of the Antoine Stormwater Detention Basin.
  • Mid-Reach Greens Bayou: From there, we turned our resources to the mid-reach portion of Greens Bayou, where six regional stormwater detention basins are either complete or currently in construction. These projects are estimated to reduce the risk of flooding for 4,500 structures in the Atlas 14 1% AEP (100-year) floodplain.
  • Lower Greens Bayou: Flood Control District teams are now studying the lower section of the watershed to investigate potential projects in coordination with community leaders who are part of a project workgroup.

Located just south of Beltway 8, near the confluence of Greens Bayou and Garners Bayou, the Flood Control District implemented the first wetlands mitigation bank in Harris County. The mitigation bank provides compensating wetlands credits for projects that cannot avoid disturbing wetlands and qualify for credits. The wetlands bank and reaches of the bayou that pass through dense woodlands and support diverse wildlife habitats. Downstream of I-10, the channel flowline is below mean sea level and this reach of the bayou is tidally influenced.

Bond Funded Projects

In August 2018, Harris County voters approved a $2.5 billion bond program for flood risk reduction projects. Many of these projects incorporate partner funding to maximize local benefits. Learn more about the 2018 Bond Program.

Partnership Funding

Partnership funding is a foundational component of the 2018 Bond Program and is a vital piece of the equation in Greens Bayou. The Flood Control District has submitted applications and is awaiting a response on nearly $395 million in partnership funds through direct allocations, grant money and loans from partners at the federal, regional, state and local levels. Learn more about the Flood Control District’s approach to partnership funds.

Project Photos

Greens Bayou: In Greens Bayou alone, there are more than more than $57 million in active construction projects that have been initiated since the 2018 Bond Election. Several other projects are in various stages of the project lifecycle. Learn more about the project lifecycle here

Watershed FAQs

Greens Bayou Watershed

Partnership Funding

Learn more

Flood Damage Reduction Tools

Learn more

Home Buyout Program

Learn more

Sign Up for News

Stay informed

Projects in Greens Bayou Watershed

Active Projects in Greens and Halls Bayou Watersheds