Expected flood map changes drive $22M increase in Travis bond budget

Travis County will spend an additional $22 million on its 2017 road and drainage bond projects in anticipation of expanding floodplains after a federal report predicted Texas will see more extreme rain in coming years than previously expected.

County commissioners on Tuesday unanimously approved raising the budget for Proposition A, which voters approved at $93 million, and boosted the amount the county will raise from nonvoter-approved bonds by about 10 percent, from about $95 million to about $105 million. Staffers told commissioners Tuesday they are working to identify funding sources for the increase and expect to present options to commissioners in December. Budget Director Travis Gatlin said the money will likely come from selling nonvoter-approved bonds.

County staffers said the change will not affect the expected five-year timeline for the bond projects.

The National Oceanic and Atmospheric Administration’s Atlas 14 report, the first of its kind in 50 years, redefined 25-year, 100-year and 500-year storms in Texas using climate records and historical rainfall data. In Austin, the new data show that a 100-year storm will bring closer to 13 inches of rain in some parts of Austin, similar to what has been expected of a 500-year storm.

The Federal Emergency Management Agency, as well as the city of Austin, Travis County and other local governments, will need to update floodplain maps to reflect the changes. In the meantime, the county will use the 500-year floodplain in place of the 100-year.

ATLAS 14'S LOCAL IMPACT: More extreme rain in Austin could change flood maps

County officials and climate experts have said the report will have widespread implications on urban planning, land development and engineering. Increasing the budgets for the 2017 bond projects is one of the first public effects since Atlas 14 was published in September.

"It is a cost increase. It's outside of our control, but it's within our grasp," County Judge Sarah Eckhardt said.

In addition to putting more of Travis County inside floodplain boundaries, the report means the county will have to spend more on infrastructure, particularly drainage. Those systems will need to be bigger and more plentiful to accommodate heavier rains, said David Greear, assistant public works director.

The budget adjustment represents about a 13 percent bump in the cost of Proposition A, which consists of roads, drainage, bridge, and bike and pedestrian projects, bringing the total to roughly $106 million. Commissioners didn't change the budgets for Proposition B, which includes $91.5 million in parks work not affected by the rainfall report.

ALSO READ: Travis County staff: 2017 bond projects behind schedule

Greear said the additional money will pay for larger detention ponds, more stormwater inlets and larger stormwater pipes. It will also fund higher and longer bridge spans, larger driveway culverts and wider ditches, he said.

County staffers last month told county commissioners that the increase would be about $31 million, but after further review and cost-cutting, they presented the revised $22 million proposal Tuesday.