City of Houston Detention Regulation Change

Dear Clients and Friends,

We have been monitoring the City’s proposed detention rate changes via our involvement with American Council of Engineering Companies (ACEC) Houston Chapter. We were informed that the proposed detention rate changes will become effective March 31, 2021.

If your project is already permitted or in for permit before March 31, you will be held to the current criteria.

If your project is submitted on or after March 31, you will be held to the new criteria, IDM Chapter 9 Detention Supplement, Storm Detention Requirements.

The new detention rates are on a sliding curve based on acreage and percent impervious cover, with the minimum rate being 0.75 ac-ft/ac increasing up to 0.95 ac-ft/ac if the tract is entirely impervious (most commercial developments). This represents a 50 to almost 100% increase over current detention rates and only applies to tracts 20 acres or less. Tracts over 20 acres will be subject to Harris County Flood Control District Criteria, which requires a minimum of 0.65 ac-ft/ac.

As always, feel free to reach out to of our WGA Team Members for more information or help with a specific site or question. If you are interested in setting up a short lunch and learn or presentation, please feel free to reach out to Jessy Deardurff at