Just because the area is in moderate drought doesn’t mean that won’t change, and it could happen quickly.
Hays County saw devastation twice in a span of six months four years ago, with Blanco River floods in May and October of 2015. Since then the county has made some major upgrades to early warning systems that were detailed Sept. 24 to the Commissioners Court. In the case of the May 2015 flood, officials have said the flow in the Blanco River was equal to that of the Mississippi.
The county’s flood warning system regularly monitors sites including10 dams, 27 low water crossings, 26 precipitation gauges and four cameras. Recent improvements funded by the Texas Water Development Board include five dams, four cameras and seven precipitation gauges just this year.
Jeff McInnis of the Office of Emergency Services began his presentation by reminding commissioners and members of the public that the county is situated “within Flash Flood Alley,” which stretches from Mexico to the Oklahoma border. “This is where a lot of storms set up,” he said – then added that the Balcones Escarpment plays a role too. While water in the Hill Country flows at very high velocities, on the downside of the escarpment it spreads out.
Hays County is home to more than 200 low water crossings as well as several watersheds – the county includes both the Colorado River Basin watershed (Barton and Onion creeks and the Pedernales River) and the Guadalupe/Blanco River Basin watershed (the Blanco and Upper San Marcos River and Bypass, Cottonwood, Plum and York creeks).
In addition to widespread river floods, the county has experienced “rain bombs” of nine or more inches in a localized area that can also cause problems, McInnis said. For example, a rain event near San Marcos in April 2017 filled one of that city’s five watershed dams installed on Sink and Purgatory creeks to capacity in just five hours.
Recent improvements include five dams, four cameras and seven precipitation gauges funded by the Texas Water Development Board this year.
The county’s flood warning system regularly monitors sites including 10 dams, 27 low water crossings, 26 precipitation gauges and four cameras, McInnis said.
The county’s website haysinformed.com tracks road crossings in real time, showing closed roads in red and open ones in green. That’s important, he said, not just for the public but for first responders. “It allows them to quickly respond,” he said placing barricades, which if obeyed save lives. “It’s a live map showing the water as it rises and falls.”
Pct. 4 Commissioner Walt Smith questioned whether instrumentation at low water crossings measure velocity, referencing vehicles that had been swept away at crossings. “The water wasn’t deep but people in those vehicles had no clue what the velocity was (when) the crossings weren’t closed or they ignored warning signs.”
McInnis said velocity is reflected in discharge rates, usually given in cubic feet per second (cfs).
Information collected by Hays County is shared with the National Weather Service which then puts the data out and “plugs it into” local forecasts.
County residents can sign up for site-specific early warnings through their phones by visiting warncentraltexas.org.
