Quote:
Originally Posted by Psychoma
Only looking at Google Maps if something ever happened looks like would stay off to the east of Houston, but just a random glance at maps opinion. Looking at photos of Lake Houston dam looks like this type of dam has water normally flow over the top across it (don't know this type of dams design name). So it would be the type of dam where you wouldn't want water to go over the banks and then go around the dam which would cause the overtopping effects that are detrimental to dam integrity. Lake Conroe dam that feeds Lake Houston started an 8,120 cubic ft/second release early today to help lower that lake. Barker & Addicks on the W side of Houston are planning releases with Addick starting at 2aCDT tonight(early Monday) w other maybe 24hrs later, both feed into Buffalo Bayou. Those two dams will start flooding the neighborhoods behind them where its so full starting Monday even with the release (see here for links to maps and news confernce on release: abc13.com. Don't know what actions they took or not but dam owners should have taken steps to lower water levels before these predicted rains came..........
This argument is actually why there's ongoing debate on how to better classify hurricanes. Hurricane Categories are soley based on wind speed, yet dangers from hurricanes include tornadoes, flooding, surge, etc etc with water accounting for 75% of all deaths. And categories cover zero of those other effects (surge is higher the higher the cateogry but danger/height not reflected in category rating). |
Thanks for scoop. I think Conroe is not the problem.
I realize what I am talking about is extremely unnerving so let me first say this is all speculation.
This said I created a small model of incoming flows to Lake Houston.
Level is now 47.33 feet and all spill ways appear to be open.
There is the main spillway which is like 3160 feet long and is about 41 feet above sea level.
The dam overflows at 60 feet.
This means 3160*(60-41)=60,000 square feet of area to allow flow out at best.
There also are two gates 18*20.5 ft for another 738 ft2. Total available area for out flow=60,738 ft2.
At an average flow of 10ft/sec, total discharge would reach roughly 600,000 ft3/sec.
Okay let's look at maximum in flow.
The watershed feeding into Lake Houston is over 2828 square miles. All of it is saturated and most upstream reservoirs are full already. Conroe is specifically full and releasing.
Now suppose it continues to rain and in flows equal 1" per hour for each of the 2828 square miles.
2828*5280*5280/12/3600 = 1.8 million ft3/sec
A small average rainfall of 1/2" per hour is 900,000 ft3/sec and would also eventually cause a problem.
The reservoir has buffer capacity to handle surge flows. This means total levels must rise from current 47 ft to 60 ft to over top the dam.
The area of the reservoir is 10,160 acres. If we assume this is a fixed area, then the reservoir has room for 5.3 billion ft3 of water.
All that acts as a buffer.
Is it possible to know how much excess water is flowing into Lake Houston? Actually yes. We can look at the rate of rise.
If we look at most current data for today, 15 minutes ago the level was 47.33 ft. 2 hours 15 minutes ago it was 46.97. In a two hour period the lake rose 0.36 ft.
0.36 ft spread out of 10,160 acres is 146 million ft3.
This means 146 million more ft3 of water entered the lake than went over the spillway. Per hour this is about 70 million per hour.
At rate of rise 0.36 ft per hour doesn't mean the dam will over top in 13ft/0.36ft/hr 36 hours.
Two factors are involved. The higher the level goes the more the lake drains. On the other hand the more it rains the greater the inflow to the reservoir and the shorter the time.
Conclusion: It is entirely within mathmatical reason to anticipate the Lake Houston dam can be over topped.
Houston! We may have a problem.
To keep an eye on water level see:
https://waterdatafortexas.org/reserv...vidual/houston
You can also look at one of the river guages for the feed into the lake at this link. As of this post it stands at 60 ft. Before the rains started it was 42.5 ft
https://waterdata.usgs.gov/tx/nwis/u...ate=2017-08-27
PPS Level this past hour now 47.75 and rise if 0.42 ft/hour. Rain is winning.
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