What are the drainage requirements in Austin?
With the increased urbanization of Austin, storm events will continue to pose a greater threat of introducing the effects of flooding unless an effective way of controlling the rainfall runoff is established and maintained. In an effort to ensure that no future developments will result in further flooding impacts, the City of Austin has implemented various development standards regarding drainage. A guidebook published as the Drainage Criteria Manual, or “DCM,” contains information on design principles and practices that help control post-development runoff. The requirements presented in the DCM apply throughout the entire incorporated city as well as into its jurisdictional extraterritorial district.
The Mueller Southwest Greenway Pond was designed by BIG RED DOG Austin President Brad Lingvai.
The requirements of the DCM are based on utilizing historical rainfall data and the amount of impervious cover on a site to determine stormwater peak runoff rates, which can be calculated for the 2, 10, 15, and 100-year frequency storms. These calculated amounts of runoff are required to not cause any increased inundation of buildings or roadway surfaces. This is achieved by sizing street curbs, gutters, and inlets to intercept and convey the flows safely away from the development through an engineered storm drain system contained within either the public right of way or a drainage easement.
One important drainage requirement to consider is the regulation of peak flows from the site. A development that increases the amount of impervious cover, by adding additional areas of paved material such as asphalt or concrete, will also increase the peak runoff rate. To alleviate this issue, either on-site or off-site detention will be required, or depending on if the site meets certain guidelines, the developer can seek to pay a fee and participate in the Watershed Department’s Regional Stormwater Management Program (RSMP).
For more information on the City of Austin’s drainage requirements you can access the DCM and all of the city’s other Technical Criteria Manuals .
Have questions about this blog post or Austin’s drainage requirements? Feel free to contact me at (512) 669-5560 or by email at [email protected]