Austin is already ahead of Houston in its approach to stormwater runoff, and it may be about to extend its lead. The Texas capital is working on a rewrite of its building code that, if passed by the city council next year, would require that most rain be absorbed where it falls instead of running off and causing problems elsewhere.
Letting rain soak in where it falls has two advantages, says a report released Monday by three nonprofit groups. First, it lessens flooding. Second, it reduces the pollution of streams that results when stormwater runoff picks up pollutants from parking lots, roads, and other surfaces. Rain that soaks into the ground is naturally cleansed by the soil, plant roots, and organisms as it percolates into the water table.
The latest draft of Austin’s new code strengthens the city’s rules for stormwater, which originated in the 1990s with a citywide effort to protect the water quality of a beloved swimming hole known as the Barton Springs Pool.
Here’s what Brian Zabcik, a clean water advocate at Environment Texas, one of the organizations behind the new report, wrote in an email:
“A new provision in the Water Quality section will require new developments and redevelopments to retain a minimum amount of stormwater onsite by using green infrastructure. The minimum amount is defined as the amount of rainfall in 95% of all storms. In practical terms, this will translate into retaining from a half-inch to one-and-a-quarter inches of rain, depending on the amount of impervious cover on the property. The current code only requires developments to detain and filter pollutants out of stormwater, which can then be drained off-site. Retention means that features have to allow the water to soak into the ground, evaporate into the air, be absorbed into plants, or be stored in tanks for later on-site building use.”
Contrast Austin with Houston, its larger neighbor to the east, where pell-mell growth exacerbated the flooding that occurred in August. No amount of good planning would have prevented Houston from suffering mightily when Hurricane Harvey struck the Gulf Coast and then hung around as a tropical storm, dumping a year’s worth of rainfall in a few days. But experts said Houston had made itself more vulnerable by paving over vast stretches of land, leaving the water with nowhere to go except into people’s homes.
In September, Environment Texas released a Texas Stormwater Scorecard of the state’s biggest cities that gave Austin the highest grade, 90 percent, followed by San Antonio, 65 percent; Fort Worth, 60 percent; Houston, 50 percent; and Dallas, 40 percent. It cited Houston’s “longstanding preference for gray stormwater infrastructure”—the gray referring to concrete, as in dams and sluices, as opposed to green, as in vegetation.
Austin’s new code covers more than stormwater. It would promote denser development close to downtown and discourage sprawl. While that might be good for the environment, it’s unpopular with some Austin residents who fear that building up rather than out would destroy the character of the city, whose unconventional motto is Keep Austin Weird. So the stormwater rules could fall victim if the city council rejects the overall code. One purpose of the report by Environment Texas and others is to build support for the proposed code.