4 ms·

During the height of the storm the spillways came in use (due to so much water). That happened at 108 feet and the top of the dam was 118. This happened in spit

During the height of the storm the spillways came in use (due to so much water). That happened at 108 feet and the top of the dam was 118. This happened in spite of the engineers releasing water for hours. Had they not done this those dams would have catastrophically failed. https://www.washingtonpost.com/news/post-nation/wp/2017/08/28/houston-releases-water-from-two-dams-in-attempt-to-prevent-uncontrolled-overflow/?utm_term=.9fb755c1e1aa https://www.washingtonpost.com/news/post-nation/wp/2017/08/2... The person you are replying to should make fewer assumptions about the work of engineers outside of their domain.

liberte82 9y ago
I still don't understand how water can raise an extra 10 feet over the spillway. Isn't a bathtub only as high as its lowest side?
- snowwrestler 9y ago
  Inflow minus outflow rates determine the height of a reservoir. On the upstream side you have a big river basin. On the downstream side, pipes and a spillway. If the basin is catching a lot of rain, you'll need all the pipes and spillway to keep up with the inflow. That's part of the dam's design.
- hexane360 9y ago
  The spillways can only transport so much water. If inflow is greater than that, you can build up above that point. Even a fast moving channel 10 feet deep is dwarfed by the flux of water that can be deposited by a heavy storm over a large area. Edit: for some concrete numbers, the reservoir was rising 0.5 ft/hr!! For reference, it appears the Addicks Reservoir has an area of 26,000 acres around this depth. That's 157,300 ft^3/s of inflow. Outflow was only 4,000 ft^3/s! Edit 2: Here's a visualization: http://i.imgur.com/usZAici.jpg http://i.imgur.com/usZAici.jpg
- ars 9y ago
  It can happen if water is entering the lake faster than it can exit. That's why a river can crest much higher than the water lower than it - it's a dynamic level, not a static one.
- tajen 9y ago
  It also just takes a wave (due, for example, to terrain movement) to go overboard and it drastically erodes the crest of the dam, starting a chain reaction between erosion of the crest and more water going through.

liberte82 9y ago

I still don't understand how water can raise an extra 10 feet over the spillway. Isn't a bathtub only as high as its lowest side?

snowwrestler 9y ago
Inflow minus outflow rates determine the height of a reservoir. On the upstream side you have a big river basin. On the downstream side, pipes and a spillway. If the basin is catching a lot of rain, you'll need all the pipes and spillway to keep up with the inflow. That's part of the dam's design.
hexane360 9y ago
The spillways can only transport so much water. If inflow is greater than that, you can build up above that point. Even a fast moving channel 10 feet deep is dwarfed by the flux of water that can be deposited by a heavy storm over a large area. Edit: for some concrete numbers, the reservoir was rising 0.5 ft/hr!! For reference, it appears the Addicks Reservoir has an area of 26,000 acres around this depth. That's 157,300 ft^3/s of inflow. Outflow was only 4,000 ft^3/s! Edit 2: Here's a visualization: http://i.imgur.com/usZAici.jpg http://i.imgur.com/usZAici.jpg
ars 9y ago
It can happen if water is entering the lake faster than it can exit. That's why a river can crest much higher than the water lower than it - it's a dynamic level, not a static one.
tajen 9y ago
It also just takes a wave (due, for example, to terrain movement) to go overboard and it drastically erodes the crest of the dam, starting a chain reaction between erosion of the crest and more water going through.