Dammed If They Do, Dammed If They Don’t
The Conundrum of the Buffalo Bayou Dams
Why so much water for so long in Buffalo Bayou?
May 26, 2016
The water in the normally empty reservoir had dropped only a few feet by the time we stood on the earthen dam looking down at the dark, opaque blue-gray surface. After almost a month, the rippling water below was still some twenty-three feet deep, and extended as far as we could see along the thirteen-mile long dam and far into the thousands of acres of flooded woods.
It had taken only a little more than twenty-four hours for the rains that began on April 18 to fill the vast flood control reservoirs in west Houston with a record amount of water: a total of more than 206,000 acre feet, a massive amount of water. Imagine 206,000 acres covered in a foot of water. Enough to cover more than eight times the acreage of both reservoirs to a depth of one foot. That much water would take an estimated four weeks to drain, according to reports at the time.
But that was only if there was no more rain. There was more rain, and it was taking much longer. The reservoirs, vast wooded parks with recreational facilities and nature paths, are still draining. As of May 24, the combined total of the two reservoirs was still about 90,000 acre-feet, down to a little less than half.
And Buffalo Bayou was still flowing high and fast, higher and faster for longer than ever before. Property owners upstream had flooded and property owners downstream who had hoped for more moderate flows were instead seeing long-standing trees falling into the fast-flowing stream, banks eroding, sediment collecting, debris causing water to back up onto their property.
Why was this happening and is there a way out of it?
How Old Is Buffalo Bayou? Where Does It Come From?
Geology Lessons on the Bayou
March 27, 2016
Want to learn about the geology and natural history of Buffalo Bayou?
Save Buffalo Bayou is partnering with professional geologist Tom Helm, who also happens to be an outstanding naturalist and river guide, to offer floating classes on the geology of our 18,000-year-old mother bayou.
Paddle with Tom on a two-hour canoe trip down Buffalo Bayou and see some of our Pleistocene natural history right here in the middle of Houston. Learn all about the formation of the bluffs and sandstone rocks during the last ice age. See examples of depositional environments and fluvial processes. Find out why the banks are sandy and how sand moves downstream, why the river looks the way it does, and much more.
Where, When, Cost
The classes start at the Woodway boat launch in Memorial Park and float past the park and the Hogg Bird Sanctuary, through the historic natural area targeted for destruction by the Harris County Flood Control District. Multiple stops will be made along the way to examine features of interest.
The schedule depends on class size. One to four persons can be scheduled any day of the week, usually with no more than 48 hours’ notice. Groups larger than four persons (up to 30 persons maximum) are accepted only on weekends. These larger weekend groups need to schedule at least one month in advance.
Cost is $50 per person, which includes canoe and equipment, and light refreshments at the end. Discounts are available for academic faculty and students.
Note that the classes will be not take place if the flow of Buffalo Bayou is greater than 300 cubic feet per second (as measured by the Piney Point USGS gauge). At water levels above this, the sandstones are mostly obscured. If a trip is cancelled due to high water, students have the option of rescheduling or receiving a full refund.
For more information, contact Tom Helm.
Some Things We Learned Already: Why Mud Stinks
We floated with Tom recently for a preview of the geology class. Among the things we learned is why some of the mud stinks. The mud and the sand are filled with layers of organic matter, leaves mostly, and as the organic matter decomposes, it smells like … decomposing stuff. But it also builds soil for future vegetation. This process produces the mysterious oily sheen that you see floating on top of the mud sometimes.
We also learned to tell mud from sand from silt. (Hint: it’s a matter of the size of the grains.) Tom showed us how geologists rub the mud between their thumb and fingers to feel the size of the grains.
We studied the patterns in the sand, watched the grains of sand moving in the water, and learned about eddies and sediment deposition and transport. We saw a lot of animal tracks.
We learned to put the constantly changing bayou in the context of its natural process.
In every outthrust headland, in every curving beach, in every grain of sand there is the story of the earth.
― Rachel Carson
No Changes in Operation of Buffalo Bayou Dams
Release Rates May Be Looked At in Future
March 13, 2016
It was a dark and stormy night. Thunder boomed and heavy rain pelted the roof as a small group of us sat nervously in the middle of the rising Addicks Reservoir in far west Houston listening to the district commander of the Army Corps of Engineers tell us Addicks and Barker dams are safe.
Flanking Col. Richard Pannell last Wednesday, March 9, was a panel of officials from the Corps’ Galveston District office, as well as representatives from the Harris County Flood Control District and Granite Construction, the company awarded the $71.9 million contract to replace the leaky conduits in the 70-year-old earthen dams. The audience was a small crowd of about thirty hardy citizens who had braved the heavy traffic and heavy rain and managed to find the Bear Creek Community Center in the middle of a dark, wet forest despite the wrong address in the Corps’ public notice.
Col. Pannell made a thorough and convincing presentation of the history of the dams, the current problems, and what is being done about them. Among other work, the conduits in the two dams will be entirely replaced by new conduits in separate locations. This process will take about three years. He emphasized that the dams were in no immediate danger of failing and explained that the dams are labeled “extremely high risk” because of the potential consequences to Houston, the nation’s fourth most populous city, in the unlikely event that the dams failed.
Dams Operating Normally Despite Leaks
There were several questions about the capacity of the dams and the impact of repairs on the rate of future releases of water impounded behind the dams. The pattern of extended high releases and rapid drops has been criticized for damaging property on the bayou and killing trees and vegetation that control erosion.
After the enormous Memorial Day storm last year, the Corps began releasing impounded stormwater at 3000 cubic feet per second (cfs) for the first time. Normally the release rate is limited to 2000 cfs as measured by the Piney Point gauge. The Corps does not release water from the dams during a rain event, and the high releases began on June 1 and continued for ten days, finally dropping on June 12. The banks were already saturated from the storm, and the damage from the extended high flow was plainly visible up and down the bayou.