Onion Creek flood: tougher flood gauges installed 7 months later

AUSTIN (KXAN) – More than seven months after the deadly Onion Creek flood, the federal agency that watches creek and river levels is installing more sturdy gauges, meant to better withstand powerful floodwaters.

US Geological Survey crews were out in the tiny, creekside community of San Leanna in Travis County (pop. 384) on Thursday where one of the gauges washed away Oct. 31. The replacement gauge over the Twin Creeks Bridge is 15 feet higher than the old one and housed on a sturdy metal frame. It is also on the opposite side of Onion Creek where floodwaters are less likely to reach.

KXAN photographer Julie Karam is dwarfed beside the new 'hardened' USGS water height gauge at Twin Creeks.
KXAN photographer Julie Karam is dwarfed beside the new ‘hardened’ USGS water height gauge at the Twin Creeks Bridge.

Even the sensitive equipment that measures water flow and height and transmits that data via satellite and other means is positioned high up inside its locked metal box housing.

On the morning of Oct. 31, during ongoing heavy rain, the 12-year-old gauge at Twin Creeks Road washed away about 3 a.m. as an already swollen Onion Creek quickly rose beneath the 30-foot high bridge. Water poured over the gauge anchored to an arch support and eventually over the two-lane bridge itself.

A second gauge downstream at US Highway 183 would also stop working about 30 minutes later, and was offline for more than five hours before USGS crews could replace and repair damaged equipment.

During that time crews took manual readings using a wired weight lowered from the bridge to the top of the rushing, debris-filled water. Readings done every 15 minutes at the height of the rainstorm were then texted or emailed to USGS hydrology supervisors and emergency operations staff in Travis County.

“We didn’t realize how much people were truly depending on (the gauge), especially emergency manager-types for large floods,” said Joe Capesius, a hydrologist with USGS. He was out at Twin Creeks on Thursday as the new gauge was being welded into place.

Capesius said in the last five year, USGS has ‘hardened’ many of its water height gauges in flood-prone areas of the nation, including in Central Texas’ flash flood alley.

When the Twin Creeks gauge was first installed in 2002, it was primarily meant to measure low (drought) water flows and water quality, Capesius said. It was not constructed to withstand massive flows of floodwater that could easily overwhelm and destroy the gear inside the locked metal box.

“Most of your flow is at low stages,” Capesius said. “But sometimes gauges get put in for one purpose and people realize ‘oh, we can use this information for other purposes.’ Sometimes when you’re using it for purposes for which it’s not designed, things can happen like you saw here (at Twin Creeks).”

Several miles downstream, Onion Creek homeowner Chris Rubs said it has been a long wait for the replacement gauges, but worth the peace of mind.

“It’s always better late than never,” Rubs conceded. “So we can at least have some notice next time. Hopefully it never happens again, but in case it does, (the gauges) will be for the benefit of the neighborhoods.”

A USGS spokesperson told KXAN in an email it took a little more than seven months to get to this point because of the amount of planning and research involved.

“(We wanted) to make sure we were making the best hardening choices for each site. This involved gauge design, site selection, purchasing, and making pieces that are used in gauge construction,” wrote Jennifer LaVista. “The City of Austin (and Travis County) also reviewed our decisions as appropriate.”

“Although this process takes time, it is important that each decision is carefully considered so that we can produce the best product possible,” LaVista added.

Wave of destruction

The floods destroyed hundreds of homes and damaged many others. The county and city are in the process of buying out some of those most affected.

Even now, seven months after the surge of water, signs of the event are everywhere in Onion Creek – from fading water marks on limestone facades, to large, neon green markings spray-painted on some garage doors, indicating a destroyed, unoccupied home.

One departed homeowner had even added a personal message: ‘Bye’ in red spray paint.

Many of those modest, but once-comfortable properties will be bulldozed and returned to parkland in this 30-year-old community.

Rubs just moved back from a rental property to his single story home that was badly flood-damaged in October, but salvageable. For now, he and his wife and two small dogs are living in their RV parked in the driveway while large-scale renovations to walls, electrical and plumbing are completed.

Other USGS gauges slated for hardening

The USGS is installing similar hardened water height gauges this week at:

  • Onion Creek and Hwy 183 in Travis County
  • Williamson Creek in Southwest Austin
  • Shoal Creek at 12th Street in Austin

There are plans to install other water height gauges in Williamson County to monitor flows in the Upper Brushy Creek basin.

The cost of the four Travis County installations to the USGS is $82,620.

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