Water Cooler 10/20/2018 – Open Thread – Austin Area Flooding

All the rain here in the Austin area made the Formula 1 weekend so miserable that I have time to write today’s Water Cooler after all. This got some brief national coverage earlier in the week, but it’s an on-going disaster of major proportions.

I’ll give some quick background and one eye-popping figure followed by some amazing videos.

The Highland Lakes
After major Colorado River flooding nearly a century ago, a series of dams were built, both to avoid flooding and to maintain the water supply. The image on the front of this two-page Lower Colorado River Authority (LCRA) overview shows how it all works.

Last weekend
Austin weather in the summer is easy to predict. If you guessed high 100 low 75 rain 0 for the 100 or so days between Memorial Day and Labor Day you’d be pretty close on probably 85 of them. The rest of the year is a crapshoot however. This past week was a good example. It was 90 degrees last Sunday afternoon before an overnight cold front dropped it to the 40s Monday morning and it didn’t hit 50 degrees again until Wednesday. That same system brought rain – a lot of it.

A mind-boggling number
During such events, the LCRA has to decide how many floodgates to open on which dams to minimize the overall flooding. Some of the lakes are “passthrough”, where all water coming in has to go out, and others can vary widely in their depth.

Lake Travis sits just above Austin and is one whose depth fluctuates. Thanks to the rain and even more so to the dam releases further up the chain, Lake Travis rose 36 feet in 3 days. It seems impossible to believe but it’s an unbelievable amount of water.

And now a few short videos
The most common one anyone outside Austin probably saw was this bridge getting wiped out on the Llano River. I don’t know how far it normally sits above the water.

At some point Monday and into Tuesday morning, water was pouring over the Max Starke Dam in Marble Falls. There was 8″ to 12″ of rain in 48 hours in that area.