So far, Addicks and Barker have been taking in a lot of water as Harvey continues to hurl rain down on the area. Considering the history of these two systems of dams and reservoirs built on the northwestern end of Houston, that could be cause for concern.
The dams, owned and operated by the U.S. Army Corps of Engineers, were completed in 1945 and 1948 respectively to protect downtown Houston from catastrophic flooding by blocking some of the water that would otherwise come gushing down Buffalo Bayou, increasing the flooding of the already overwhelmed waterway running through the heart of Houston.
These systems of dams and reservoirs function as dry reservoirs, meaning the dams stay wide open and water is allowed to flow freely until the heavier rains roll in, according to the Corps. The city has a system of highly sensitive flood gauges and once those gauges hit "critical levels" the dam safety officer orders the floodgates closed and the dams begin top fill up.
The thing is, in 2009 the dams were dubbed to be in "extremely high risk of catastrophic failure". Since then the Corps has taken bandaid approaches, including filters to control seepage, more lighting and an emergency power system, to prevent a full-on collapse of either dam while waiting on the slow process of getting more permanent and expensive measures put in place, as the Houston Press has previously reported.
Since then the Corps has been working on this issue and they worked in advance of Harvey to get ready for the storm.
As Harvey began to churn toward the Texas Gulf Coast, the dams were in the middle of a $75 million upgrade that started in 2016 and construction workers just finished building a pair of coffer dams, watertight enclosures pumped dry to permit construction work below the waterline. The Corps also laid in plenty of basic flooding supplies, like sandbags and such, to make sure they had everything they could on hand to do their best to prevent some of the flooding.
The dams are designed to hold about 410,000 acre-feet of water, but 20 inches of rain amounts to more than 1.8 million acre-feet of water, and so far, Houston has received more than 22 inches of water in August 2017, making it the wettest month on record, according to the Harris County Flood Control District.
Not all of that rain is being handled by Addicks and Barker (there are 22 watersheds across Harris County) but the dams have still been taking in a ton of water since the Corps ordered both dams closed at 8 p.m. on Friday.
While the dams initially taking on the water, the Corps made it clear that if Barker or Addicks rose to a certain level they would release the water rather than risk losing either dam entirely.
On Saturday, the Fort Bend County Office of Emergency Management issued a warning about Barker Reservoir, reporting that the U.S. Army Corps of Engineers was expecting water levels in the reservoir to rise to "record levels", exceeding the previous levels of the Tax Day Floods by several feet.
Local residents in Fort Bend were advised that when the elevation of the water reaches 95 feet in the reservoir, water will then begin to flow out of government land into the Cinco Ranch and Canyon Gate areas located within its western boundaries, according to a release.
The U.S. Army Corps of Engineers reported that the water levels within the Barker Reservoir in northeast Fort Bend County was beginning to impact residential roads within the reservoir in Fort Bend County on Sunday afternoon. (In other words, it looks like Barker hit the 95-foot marker and the Corps had to release some water, though we're still waiting on the Corps to confirm this. We'll update as soon as we hear back.)
Residents near Barker were warned not to drive on roads in Canyon Gate and east Cinco Ranch, roads east of South Mason Road, particularly in the area south of Westheimer Road and east of Grand Parkway since it is expected the water will rise backwards from the reservoirs. The Corps also warned people in the Fort Bend area to stay off Grand Parkway (aka State Highway 99).
“It is critical now that residents in the western portion of the reservoir pay close attention to the developing situation there, and have a plan to keep yourself, your families and your pets safe,” said Fort Bend County Judge Robert Hebert in a release. “Corp of Engineer predictions indicate that water could soon rise to levels that will enter structures in those areas.“
The Addicks reservoir has risen to about 97 feet so far, according to Corps statistics. As the reservoir levels rose up on Sunday Harris County Flood Control warned roadways running through the reservoir are expected to go underwater and that neighborhoods immediately adjacent to Addicks on the western and northern boundaries could face flooded streets and homes.
While this sounds pretty lousy, keep in mind that this is what Addicks and Barker were designed to do, to help keep water out of the center of Houston. Despite the massive amount of water the reservoirs are taking on, both structures are apparently handling the pressure up to this point.
However, there's still a lot more rain in the forecast as Tropical Storm Harvey continues to play out and it remains to be seen if the dams will keep up the good work. As the rain comes down and the reservoirs fill up, that water is still going to have to go somewhere. (Though admittedly at this point, if you live near these dams, you probably know that.)
The U.S. Army Corps of Engineers has confirmed they are releasing water from both Addicks and Barker to reduce the risk to the Houston area from Sunday evening through at least Monday morning.
Col. Lars Zetterstrom, Galveston District commander, stated that while the structures what they were designed to do, the Corps has to release water to take some of the pressure off the dams. He noted that it is likely the water will go over uncontrolled spillways at the ends of both dams, starting around the northern end of Addicks dam and both ends of Barker.
Roads within the Addicks and Barker areas will be flooded and closed until the water subsides, and some structures (it’s unclear how many at this point) will “impacted” which seems to be a slightly nicer way of saying a bunch of homes near these two reservoirs are about to see more water.