October marked the two-year anniversary of the 2015 Halloween flood that placed large areas of Austin underwater, and two months since the city dodged major flooding from Hurricane Harvey.
Flash floods prompted by heavy rainfall were the major contributors in the four disaster declarations from 2013-16 that resulted in loss of life and more than $100 million in damage in Austin.
The three major creeks in Northwest Austin—Bull, Walnut and Little Walnut—are a part of the 100-year flood plain, according to the Watershed Protection Master Plan. A 100-year flood plain is an area that the Federal Emergency Management Agency calculates has a 1 percent chance of flooding in one year—or a 26 percent chance of flooding over the lifetime of a 30-year mortgage.
Flash floods occur when heavy rainfall forces creek and rivers to overflow, according to the National Oceanic and Atmospheric Administration. Experts at the NOAA consider flash floods the most dangerous flood variety because they combine the power of a flood with “incredible speed” and can occur with no warning.
The geography of the state of Texas makes it vulnerable to some of the heaviest rainstorms in the world, according to data from the Flood Safety Education Project. Travis County sits in an area of Central Texas nicknamed “Flash Flood Alley”—one of the most flash-flood prone areas in North America, according to Austin’s Office of Homeland Security and Emergency Management.
Lisa Hardeman and her husband, Stephen, 25-year residents of Spicewood Springs Road in Northwest Austin, said they have seen their share of floods over the roadway’s low-water crossings that obstruct their drive to and from home.
On the night of the Memorial Day flood in 2015, Lisa Hardeman said she estimates the creek rose 7 feet in an hour, flowing over her deck, about 2 feet lower than the threshold of the house, which sits on 7.5- and 9-foot-tall steel stilts overlooking Bull Creek.
“I’d never seen it do that. Quite honestly, I just started praying,” she said.
At that point, she said it was too late to higher ground.
“Spicewood Springs Road was a river, and there was 3-4 feet of water. It was just under the mailbox,” she said.
That is when she called the police.
“They were going to try to get a boat from [Loop] 360 to go upstream to try to get me, but I knew no boat could go upstream. It was torrential,” she said.
Although she survived the experience unscathed, Lisa Hardeman said it made her more vigilant about evacuating her home during heavy rainfalls.
“Even though we’ve been here 25 years, so many different things can affect how quickly the creek floods that we never became lackadaisical. But I was a little over-confident until we had the [Memorial Day] flooding,” she said.
‘A very disheartening situation’
Matt Hollon, manager of the Watershed Protection Department’s Planning Division, said although the city is naturally prone to flash floods, early planning mistakes exacerbated the vulnerability in some areas of the city.
When Austin first received its flood plain maps from FEMA in the late 1970s, Hollon said mapping technology was in its early stages. A combination of misunderstanding of what could be built in a flood plain and lack of rules led to poor planning decisions.
“[The maps] weren’t delineated properly, and development occurred in unsuitable areas,” Hollon said. “It was a very disheartening situation.”
This led to the development of thousands of properties, including Lisa Hardeman’s home on Spicewood Springs Road, within the 100-year flood plain.
Some 1,981 structures lie within the Barton, Bull, East and West Bouldin, Little Walnut, Shoal, Waller and Walnut creek watersheds’ 100-year flood plains, as detailed in the 2016 Watershed Protection Master Plan. The city estimates 773 of those structures would be flooded in a 100-year storm.
Hollon said a majority of these structures were built between the 1960s and 1980s, before the city had a comprehensive understanding of its flood plain regulation. Development within the flood plains has plateaued since the city’s flood plain ordinance went into effect in 1983.
Protecting Northwest Austin
Northwest Austin residents and city officials are working on several initiatives to curb damage in areas that flood frequently.
Barrington Oaks-based Realtor Mary Battaglia helped a group of Northwest Austin residents negotiate the sale of their frequently flooded homes.
On April 17, City Council approved buyouts on Charing Cross and DK Ranch roads. The four homes were located in an area with outdated storm drains, city officials said.
Because replacing old drainage infrastructure throughout Austin is an expensive undertaking—estimated at a price tag close to $1 billion citywide—city staff determined the most cost-effective plan of action was to buy the houses, convert the land into a park and offer to relocate residents to homes of the same size and value in the area.
Battaglia said the residents she spoke with were pleased with the outcome.
“I was out there saying, ‘I don’t want them to give you less than what we think we can get you here in this area,’” Battaglia said. “[The city was] very good about the program and what they offered. Really, I was impressed.”
The watershed protection department is also working on other initiatives in Northwest Austin to help mitigate flooding, including improving storm drainage systems on Whispering Valley Drive and West Cow Path in the Angus Valley neighborhood as well beginning a study of flooding on Jollyville Road.
Dangers of low-water crossings
Among the most dangerous aspects of flash floods are low-water crossings, areas where floodwaters commonly eclipse the roadway. Hollon said 75 percent of Austin’s water fatalities occurred at low-water crossings. The watershed protection master plan counts 1,866 low-water crossings in Austin, 65 of which fall within Northwest Austin’s three main watersheds.
Low-water crossings pose a significant challenge for Northwest Austin residents who live on Spicewood Springs or use it as a shortcut from US 183 to Loop 360. There are seven low-water crossings on Spicewood Springs alone located in the Bull Creek 100-year flood plain.
Lisa Hardeman said the culverts of the low-water crossings near her house often get jammed with downed trees, sticks and other debris that accumulate either because of flooding or general buildup over time. The more blocked the culverts are, the more quickly the low-water crossings accumulate water.
Requesting the removal of debris from these culverts is not a simple task because Spicewood Springs is a Travis County road within Austin’s extraterritorial jurisdiction outside the city limits. Lisa Hardeman said many residents are still unsure who is responsible for debris removal on the roadway.
Austin can provide monitoring, patrols and safety equipment, but it is Travis County’s responsibility to clear the culverts and perform road maintenance, city and county officials said.
Citywide solutions
In 2016, Austin’s Flood Mitigation Task Force provided 11 recommendations to City Council on how to better prepare the city for inevitable flooding.
One of those recommendations, Hollon said, proposed by the watershed protection department through CodeNEXT—the ongoing overhaul of the city’s land development code—relates to redeveloping regulations for large multifamily and commercial projects.
“We’ve had this no-harm rule for a long time,” Hollon said. “Folks have not been piling on and adding to the problems, but they haven’t really started to chip away and reverse the trend and try to improve it.”
Reem Zoun, a supervising engineer for the city of Austin, said CodeNEXT could change flood-mitigation requirements for redeveloping properties that have 100 percent impervious cover, such as a parking lot.
“The proposed code is that you will be required to mitigate for that 100 percent impervious cover that you have for the impact that it is already causing,” Zoun said.
The rules around flood plain development have also tightened significantly since the 1980s, but the city is still working to rid itself of the unregulated development of the past. Hollon said since 2012 the number of structures within the 100-year flood plain that the city expects to be inundated with water has dropped nearly 25 percent, from 2,380 structures to 1,816.
District 7 Council Member Leslie Pool said public education regarding the area’s vulnerability to flooding is a major component of hazard mitigation.
“People forget; policies erode; and the significant concerns that people have get dulled over time if the circumstances don’t repeat themselves or if it doesn’t happen to you,” Pool said. “If you have not been affected by flooding, you don’t have the level of awareness and sensitivity to how destructive and dangerous flooding is.”
But when it comes to the forces of Mother Nature, Pool said there is “very little” society can do. Hollon agrees.
“We’re really just trying to make sure we’re prepared, and if a Harvey hits, we would do as well as we can,” Hollon said. “It’s going to take years because all of these [flood-mitigation] projects are expensive. But we’ve got to start.”
