September 23-24

Hurricane Harvey

Flooding impacts in connection with the Reservoirs

Facts relating to ongoing flooding conditions in connection with the Addicks and Barker reservoirs are developing rapidly. Please contact the U.S. Army Corps of Engineers hotline, 800-452-9488, for the most current information. 

> US Army Corps of Engineers' News Releases
> US Army Corps of Engineers' Inundation Animation
> US Army Corps of Engineers' Press Conference, September 4, 2017

> HOW TO GUIDE

> Addicks Reservoir Ground Elevation (32x40)
> Barker Reservoir Ground Elevation (32x40)

> Addicks Reservoir Water Levels
> Barker Reservoir Water Levels

 > Enlarge Map

FLOODING IMPACTS in connection with the RESERVOIRS

UPSTREAM behind the reservoirs

Pools behind the U.S. Army Corps of Engineers' Addicks and Barker reservoirs began rising on August 25, in response to rainfall over the upstream watersheds. Reservoir pools rise when the stormwater inflow rate exceeds the stormwater release rate. When the reservoir gates are closed, no stormwater is released.

Reservoir gates were opened on August 28, releasing stormwater into Buffalo Bayou. Reservoir pools continued to rise due to tremendous inflow rates from bayous draining into the reservoir, although stormwater releases mitigated the rate of rise. Stormwater releases into Buffalo Bayou have not and will not increase flooding behind (or upstream of) the reservoirs. Pools in both reservoirs were at or near their peaks as of August 30.

Rising water in the reservoirs has resulted in widespread flooding of streets and homes upstream. These elevated pool levels could impact surrounding areas behind the dams for several weeks to months. If you are unsure whether you live close enough to the reservoirs to experience impacts from rising pool levels within the reservoir in connection with Hurricane Harvey, here is a list of adjacent subdivisions. It is meant to be comprehensive but it may not be complete.

DOWNSTREAM along Buffalo Bayou

The U.S. Army Corps of Engineers initiated stormwater releases from the reservoirs on August 28. Some streets and homes downstream of the reservoirs flood when the combined release rate from the reservoirs exceeds approximately 4,000 cubic feet per second. 

> Current Release Rates and Pool Levels 

Please contact the U.S. Army Corps of Engineers hotline, 800-452-9488, for the most current information. The map below estimates downstream inundation associated with this controlled release and assuming no additional rainfall. Inundation may vary due to runoff downstream of the reservoirs and adjustments to the controlled release rate by the Corps. Current inundation levels may persist for several days.

> Buffalo Bayou Inundation Scenarios, August 30, 2017

While the Corps owns and operates the reservoirs, the Harris County Flood Control District is in daily communication with the Corps on the level of stormwater in the reservoirs, and on the release rates from the reservoirs into Buffalo Bayou.

A note on uncontrolled releases around the Addicks Reservoir Dam

WHEN...

  • Heavy rains and in-flowing stormwater cause pool levels in the Addicks and Barker reservoirs to reach a certain level, and
  • Controlled releases from the reservoir outlets into Buffalo Bayou are unable to compensate for this increase

 …THEN uncontrolled stormwater can spill over the concrete-armored spillways at the ENDS of the two dams into areas outside the reservoirs. (see map above)

This type of uncontrolled release has been relatively minor during Harvey. Rising stormwater in the Addicks Reservoir began spilling around the north end of the Addicks dam August 28, near the intersection of North Eldridge Parkway and Tanner Road. Uncontrolled releases are NOT EXPECTED around the south end of the Addicks dam, and are NO LONGER EXPECTED around the Barker Reservoir dam.

While the Corps’ design of the reservoirs anticipated this type of event, it is the first time this has happened in the 70-plus-year history of the dams. It is also the first time that homes upstream of the reservoirs have flooded from rising water in the reservoirs.

The stormwater spilling around the ends of Addicks Reservoir first impacted the Twin Lakes on Eldridge and Lakes on Eldridge subdivisions, which are also located near the intersection of North Eldridge Parkway and Tanner Road on the north side of the Addicks Reservoir. Other areas along the east side of the Addicks Reservoir will also see additional stormwater.

Addicks and Barker reservoirs were built in the 1940s to prevent flooding of downtown Houston and the Houston Ship Channel. The Corps is continuously monitoring the structural integrity of the dams, including the ends of the dams. This work includes balancing the flow of stormwater into the reservoirs with releases through the reservoir outlets. This effort must take into account Hurricane Harvey's historic rains, the resulting high water levels in both the reservoirs and along Buffalo Bayou -- all of which can cause flooding -- and the need to build capacity in the reservoirs in case of further rainfall.

  • Rising reservoir pools can spread outside of government-owned land into neighborhoods adjacent to the reservoir, causing flooded streets and homes. This is already occurring.
  • Higher-than-normal releases from the reservoirs can contribute to flooding on Buffalo Bayou. These “surcharges” are already occurring, as is flooding.
  • Uncontrolled stormwater going around the end of the Addicks dam is of concern in connection with protecting structural integrity.

Both ends of each dam include concrete-armored spillways. Stormwater escaping around the ends of the dams is considered preferable to water overtopping the reservoir dam itself. However, controlled flows from reservoir outlets are considered preferable to uncontrolled flows, both for the integrity of the dams and the potential impacts to adjacent neighborhoods and downstream areas along Buffalo Bayou.

Outlet gates at the Addicks and Barker dams are releasing record levels of stormwater that has been stored in the reservoirs in response to Harvey’s historic rainfall in Harris County. These additional releases have resulted in out-of-banks flooding in neighborhoods along Buffalo Bayou, the receiving bayou from the two federal reservoirs.

Addicks and Barker reservoir levels will start to lower slowly with the releases. Creeks and channels that flow into the reservoirs are also ponding water at the same level as the reservoirs, but will start to recede as the reservoirs lower. Adjacent stormwater detention basins will do the same. All levels will decrease as the reservoir levels are reduced.

About Addicks and Barker Reservoirs

Addicks and Barker reservoirs are located near the intersection of I-10 and State Highway 6, in an area considered to be in the upper watershed of Buffalo Bayou. They provide flood damage reduction along Buffalo Bayou downstream of the reservoirs and through the center of the City of Houston. But like much of our national infrastructure, Addicks and Barker have been around a long time. The Corps continually inspects all of its dams nationwide under its Dam Safety Program, a program that shows our commitment to protecting lives, property and the environment by ensuring that all dams are designed, constructed, operated and maintained as safely and effectively as possible. The Corps' Dam Safety Program provides a framework to ensure that both short- and long-term solutions are studied and applied and helps to ensure public safety for our local communities.