Better Flood Forecast System Coming to Central Texas in 2016

Come May 2016, turbocharged forecasts capable of faster updates as conditions change will be used to predict flooding on Central Texas rivers, an innovation expected to give emergency managers more lead time to prepare for problems downstream.

“What if you were the emergency manager for any particular town in Texas and you knew 6, 8, 10 hours out that you were going to have flooding on a particular creek, how much flooding there would be and the probability?” said Harry Evans, the former chief of staff for the Austin Fire Department, part of a team working on the project. “You would be really empowered to warn the public and order additional rescue resources.”

The National Weather Service, with a team of academic researchers led by University of Texas professor David Maidment, are putting the final touches on the souped-up forecasting system, has been presented at a University of Texas seminar last week.

Using supercomputers and high resolution imaging, the new system can be run every hour, forecasting 15 hours ahead of possible flooding across 784 locations in and along rivers and creeks in Travis and Hays counties. How long will it take to forecast across the Central Texas locations and 2.7 million other spots across the United States? Just 10 minutes, according to preliminary runs at UT.

Currently the weather service conducts forecasts on just six locations in Travis and Hays, and can take up to an hour to run the forecast model, especially for large rivers like the Brazos, Colorado, and Trinity when data such as rain levels and river flows are constantly changing during storms.

The science behind those forecasts hasn’t changed dramatically for two decades.

For areas like Central Texas – known as Flash Flood Alley – where catastrophic floods since 2013 have killed about two dozen people and caused tens of millions of dollars in damage, the new and long overdue system will be critical for first responders who value every bit of time to prepare.

“To be honest, it is a game changer. It is advanced scientists with advanced computing power. There’s a lot of hope of what this model can deliver that can enhance the National Weather Service,” Greg Waller of the West Gulf River Forecast Center in Fort Worth told the Austin American-Statesman.

At UT, Maidment has been working on the new forecasting infrastructure for the last decade but first proposed it last year to the National Water Center _ the hydrology branch of the National Weather Service. He says he was spurred by the Halloween floods of 2013 as he watched forecast tools fail hundreds of residents who lost their homes, and the three who were killed in the Onion Creek area of Southeast Austin.

“This is not a problem that Austin, Hays County or Wimberley has to carry alone,” Maidment said. “It is setting up a much better system than the past.”

Of the 784 points that will be included in the forecasts, 110 of them will be in Onion Creek and 130 in the Blanco River upstream from Wimberley. Currently, there is only one point at each location. Having more forecast points allows weather officials to get a more precise idea of how certain parts of a river or creek will flood.

Using laser imaging, the system will also generate land images 400 times clearer than the existing system. Knowing the terrain of the land can determine the potential depth of flooding at specific points, among other information.

The new system won’t replace the current forecast modeling system. Waller said the current system allows for more human interaction to catch errors.

When the new system launches next year, the National Water Center will work like the National Hurricane Center, forecasting flooding from creeks and rivers.

Currently, 13 river centers do that job. Some river basins, like Central Texas, are harder to monitor than others, because of their topography and their soil types.

Despite the promise of faster and more numbered forecasts, the new system will have limitations.

One complication is that there aren’t enough rain gauges to measure rain levels on land and water levels across rivers and creeks. They can read the wrong measurements or fail during strong storm surges as demonstrated by the Halloween 2013 and the recent Memorial Day floods.

Gov. Greg Abbott declared a statewide emergency last week to ask for $3 million to pay for more gauges.

“With models, you sometimes say garbage in, garbage out. With any model, that is still one vulnerability that we will have. We will still have to make sure that the data going in is good data,” said Paul Yura, warning coordination meteorologist with the service’s Austin-San Antonio office.

“It will definitely be a great tool to have, but it is still a tool. There is still going to be the need for people to send in ground truth reports. This type of observation will still be key piece to the warning process.”