The City of Houston has recently adopted new storm detention requirements to their Infrastructure Design Manual that are effective April 1.
The City of Houston’s Redevelopment & Drainage Taskforce, which the GHBA has participated on since its creation in 2018, was tasked with considering and reviewing the new proposed rates. Due to requirements from Harris County to be eligible to participate in future flood control bond projects, it was necessary for the City to meet the same threshold for detention rates that the County had previously adopted by December 31. However, the City abandoned their evaluation process and adopted the new criteria on January 4 without final review or discussion with the taskforce or development stakeholders.
There are still more questions than answers as to how this will be put into practice. The GHBA will continue to work with our stakeholder partners, city staff and Houston City Council Members to convey our concerns, address our questions and develop a path forward. We will keep the GHBA membership updated on those efforts as we move towards April.
Brief summary of the proposal:
- For Single family residential (SFR) lots of less than or equal to 7,500 SF:
a. If the Impervious area is less than or equal to 65%, No detention is required.
b. If the Impervious area is over 65%, Detention Requirement = [0.75 acre-feet per acre of impervious cover surface in excess of 65%]
- For lots of less than or equal to 7,500 SF but using Shared Driveway:
Detention Requirement = [0.75 acre-feet per acre of impervious cover surface in excess of 65%] + [0.75 acre-feet per acre] x [Area of shared driveway]
- For lots over 7,500 SF but less than 1 acre:
Detention Requirement = [0.75 acre-feet per acre of impervious cover surface]
- For tract size over 1 acre but less than less than or equal to 20 acres:
Detention volume will be required at the acre-feet per acre of disturbed area that results in impervious surface as depicted by the chart in the supplement.