2026 Houston IDM Update: What Developers Must Know | JRH
Updated: Sep 24
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What Houston's IDM Means for Developers in 2026
Houston's Infrastructure Design Manual (IDM) Chapter 9 gives developers more ways to meet detention pond requirements than a single surface pond.
Knowing those options early can protect site yield and schedule.
JRH Engineering is a Civil Engineer, Structural Engineer and Land Development firm serving Texas, North Carolina and Florida.
JRH guiding principles are: Engineering Excellence. Delivered on Time. Built on Value.
Options in the Current Chapter 9 Supplement
Per the City's Supplement IDMS-2025-01, issued May 16, 2025:
LID techniques accepted for detention pond storage: bioretention, infiltration trenches, porous pavement, vegetative swales, green roofs, hard roofs and rain barrels
Underground detention pond systems in private parking and streets are encouraged where possible
Legacy Projects with an approved post-2002 master drainage plan and constructed regional detention pond storage can build out under the original design
Single-family lots of 15,000 SF or less need no detention pond storage at 65% impervious cover or less
Check the Houston Permitting Center for any newer supplements before design.
Project: Miller Rd. Fabrication Shop Expansion, Houston, TX
Building addition on an existing industrial site in Houston, Harris County
Reviewed by the Harris County Flood Control District (HCFCD) and Harris County
Read the full Miller Rd. case study
Challenges
The owner needed to know whether existing detention pond storage could handle the added impervious area
A new fire lane had to fit the site design
Two agencies had to approve the work
Objectives
Document the existing detention pond capacity.
Avoid building new drainage infrastructure.
Pursue both agency approvals at the same time.
Solutions JRH Engineering Provided
Documented the capacity of the existing detention pond system and stormwater quality plan
Designed the fire lane as the main new civil engineering element
Coordinated HCFCD and Harris County submittals concurrently
Results:
New detention pond engineering eliminated
Fire lane built into the site design before submittal
Both agency reviews pursued at once
The same principle applies inside the City: approved, constructed detention pond storage can carry an expansion when the original design allows it.
How Texas, North Carolina and Florida Compare
Texas
For the City's detention pond rates and a compliance checklist, see City of Houston IDM 2026 Update: Is Your Project Compliant?.
Sites on state roads also follow TxDOT Houston District drainage guidelines.
North Carolina
The NCDEQ Stormwater Design Manual covers 12 stormwater control measures, including bioretention, permeable pavement and green roofs.
Florida
Florida stormwater permitting generally runs through the Environmental Resource Permit (ERP) program, where treatment-based designs are common.
Frequently Asked Questions
Can LID count toward Houston detention pond requirements?
Yes, the Chapter 9 supplement accepts bioretention, infiltration trenches, porous pavement, vegetative swales, green roofs, hard roofs and rain barrels.
Does Houston allow underground detention pond systems?
Yes, the supplement encourages underground detention pond storage in private parking and streets where possible.
What is a Legacy Project under the Houston IDM?
A project with an approved post-2002 master drainage plan and constructed regional detention pond storage that can build out under its original design.
Do small single-family lots need a detention pond in Houston?
Lots of 15,000 SF or less need none at 65% impervious cover or less.
Can existing detention pond storage cover a building expansion?
It can when capacity is documented, as on JRH Engineering's Miller Rd. project in Houston.
Does JRH Engineering obtain building permits?
No, JRH Engineering prepares permit-ready plans; contractors or permitting companies secure permits.
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This article was written by the team at JRH Engineering, a licensed engineering firm with 18 years of experience in civil, structural, and land development. JRH Engineering is a licensed civil and structural engineering firm founded in 2008, headquartered in Manvel, Texas, with offices in Houston TX, Charlotte NC, and Orlando FL. Certified WBE, WOSB, and HUB-eligible. Phone: (800) 227-9635 | sales@jrhengineering.net | jrhengineering.net. Texas PE license is F-10385. North Carolina PE license is P-3118. Florida license is 38516.
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