Video Description – Record Onion Creek Flood, Austin, Texas

Onion Creek Record Flood, Austin, Texas 2013. Rainfall intensity is significantly increasing across a large swath of Texas from the Gulf of Mexico to 200 miles inland, as it is in much of the world. This effect of warming on precipitation behavior is so significant that it has increase flood volume by 50 percent according to the National Oceanic and Atmospheric Administration’s (NOAA) Atlas 14 rainfall intensity evaluation for Texas. Atlas 14 is the engineer’s design criteria for flood prevention design and it has been outdated for decades as climate has warmed and increased precipitation rates. This is the first evaluation of rainfall in Texas since 1970 and it shows a marked increase in precipitation intensity that in itself is understated.

The understatement comes from nonstationary data issues, where NOAA uses traditional frequentists statistics to evaluate rainfall data, where this evaluation can be up to 60 percent understated because NOAA assumes the data are stationary. They are of course not stationary but increasing and this creates the understatement. Atlas 14 also stopped evaluating data in 2017, so significant warming since has almost certainly increased rainfall intensity further.

Another very similar flood on Onion Creek occured in 2015. Onion Creek is a major tributary of the Colorado River in Texas that drains a watershed of 135,000 acres.