Historic Flooding in Texas Hill Country/Highland Lakes

[Wolf BrotherParticipant]

Hi,
I live in the Greater Austin Metropolitan area. About a month ago the Highland Lakes Watershed and the Hill country was primed for flooding. We received a good amount of rain that while it wasn’t enough to flood, it did leave the ground saturated.

Then 2 weeks or so ago, we started getting rain. As of 4 days ago most of the Llano and middle Colorado Rivers watersheds have received from a foot to a foot and a half of rain. I did the math, 1 foot of rain over the several hundred square miles of watershed equaled 3 to 4 Trillion gallons of water falling as rain onto already saturated soil.

Lake Bucannan (The first flood control lake in the Highland lakes chain) went from 78% to 104% full. MOST of the increase in 2 days.
Lake Travis (The last flood control lake in the Highland lakes chain) went from about 67% to 140% full. Most of the 31 foot increase in depth came in 2 days. The Llano river watershed does not empty into Lake B. Lake Travis topped out setting a new 5th highest level of full.

With the sudden rapid rise – homeowners and those who keep boats in marinas were caught unawares so we were treated to numerous pictures of boats, boatdocks, other junk being swept down over the various dams in the lake chain. (Highland lakes consist of several constant volume lakes and 2 flood control lakes.

Due to the amount of silt in the water (and I suspect years of the Austin City Council spending money NOT on infrastructure) the 3 water purification plants are only able to produce about 1/3 of the amount of needed treated water so for the FIRST TIME EVER Austin is in a Boil Water alert phase.

We have water, we just have to boil it. Within 1 hour of that announcement, ALL stores who sold bottled water – were out.

NOW we have Willa that looks primed to pump more moisture from SW to NE over the same area that has been saturated for the past month. So we may be getting even more rain.

Will keep you folks updated.

[HomesteadingMamaParticipant]

Thanks for info. Looking forward to updates.

Stay safe.

[Wolf BrotherParticipant]

Yesterday (10/25) there was this bright orb in the sky, hurt my eyes to look at it.

The rain happened, not anywhere near bad enough to add to the flood.

Lake Buchanan is being opened to recreation today. My understanding is none of the other lakes are.

Lake Travis is around 130% full. 4 floodgates remain open. High, fast moving water on all the lakes beyond due to the floodgate operation. (Those lakes are constant volume so they’re passing the water right on thru them.) The expectation is WITHOUT FURTHER RAINS, the floodgates will remain open until early November. Lake Travis is falling at 2 feet/day. Since it’s 30+ feet overfull the math says 15 more days to get down to 100% full.

The water is so full of silt and muck that the 3 water plants are at 33% capacity.
Intake water,
clean intake filters,
intake water,
clean intake filters. You get the idea.

For the first time EVER, Austin water customers are under a boil water notice.
Monday AM (10/22). Within 2 hours after the notice, ALL stores who sell bottled water had sold out.

We had plenty of water but I went ahead and did the drill to show the wife just how big of a PITA it is.

Now ALL the stores has LOTS and LOTS of water but people are not buying like they did.

[Wolf BrotherParticipant]

Yesterday, 11/8/2018, the final open floodgate, of the 4 that were open to help control the historic flood I wrote about above, closed.

Flood operations on Lake Travis ended roughly 6 days short of 2 full months of continuous flood control operations. While some people would argue with me, mainly those who built in the flood overflow areas of the lakes, we got off pretty light.

There was a bridge on Ranch Road 2900 over the Llano river, it was designed to withstand a 50 year flood. This one was historic, maybe a 1000 year flood. A local news crew was filming a “look at all the water and debris in the Llano River” segment with that bridge in view behind the reporters left shoulder when the bridge went away. It went from the “Wow! Look at the water to a WOW!!!!! The BRIDGE JUST WASHED AWAY!!!!” segment.

Basically, the two flood control dams did what they were designed to do, fill up, over fill into the flood areas, and release the water slower than the flood would. It did cause the rivers and constant volume lakes to have flood water in the more common flood areas but it did not get as bad as it has in the past. So the people who had boats and structures in those areas lost stuff.

The City of Austin was lucky in that the rains did not fall much on the Onion Creek floodplain, NOR on the Shoal creek area in Austin. SO the City itself did not have flood issues like it has in the past.

[Author]

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