When do the new TxDOT Houston District drainage criteria become effective?

The new drainage criteria became effective July 1, 2025, with a 3-month transition period through September 2025 to help developers and engineers adapt to the new requirements.

What projects require coordination with TxDOT Houston District Hydraulics Section?

Projects greater than 10 acres, sites with offsite contributing areas larger than 5 acres, projects with design complexities requiring modeling software, and any projects using routing software for detention analysis must schedule pre-design meetings with TxDOT Houston District Hydraulics Section.

TxDOT Houston Releases New Drainage Criteria for Development Projects

Q: What is the simplified detention volume methodology for small projects?

For projects 1-2 acres, the detention volume requirement is 0.85 acre-feet per acre of disturbed area. Projects ≤1 acre can use a maximum 6-inch restrictor with specific head constraints and simplified documentation requirements.

JRH Engineering & Environmental Services, Inc.
2 hours ago
6 min read

TxDOT Houston Releases New Drainage Criteria for Development Projects – What You Need to Know

As the premier provider of civil engineering, structural engineering, and environmental engineering services in North Carolina, Florida, and Texas, JRH Engineering & Environmental Services is committed to keeping our clients informed about critical regulatory changes that impact development projects.

The Texas Department of Transportation (TxDOT) Houston District has released updated drainage criteria effective July 1, 2025, introducing significant changes that will affect how developers approach drainage design and permitting across the region.

Understanding the New Drainage Criteria Framework

The revised TxDOT Houston District Permits Drainage Design Guidelines represent a comprehensive overhaul of drainage requirements for typical site developments that share frontage with TxDOT and propose discharge to TxDOT right-of-way.

These new drainage criteria emphasize engineering judgment and site-specific analysis while maintaining TxDOT's primary mission of protecting the traveling public from roadway flooding impacts.

Key Principle Changes

The updated guidelines clarify that TxDOT's parallel drainage systems are not intended to provide drainage infrastructure for new development.

Instead, the primary purpose of TxDOT's drainage infrastructure is to limit the severity and duration of flood events to facilitate safe driving and minimize traffic disruption caused by flooding.

This fundamental principle shapes all aspects of the new drainage criteria.

Simplified Detention Volume Methodology for Small Projects

One of the most significant changes in the new drainage criteria is the introduction of a simplified detention volume methodology for smaller development projects.

The guidelines now categorize projects into distinct tiers with tailored requirements:

Mini Development Sites (≤1 acre)

For projects equal to or less than 1 acre without any offsite contributing area, the new criteria establish a streamlined approach:

Detention volume requirement: 0.85 acre-feet per acre of disturbed area
Restrictor sizing: Maximum 6-inch diameter with specific head constraints
Simplified documentation: Use of standardized TxDOT Houston District Drainage Summary Table

Small Development Sites (1-2 acres)

Projects greater than 1 acre but less than or equal to 2 acres follow similar simplified procedures:

Detention volume requirement: 0.85 acre-feet per acre of disturbed area
Allowable discharge determination: Based on TxDOT As-Built plans or simplified calculation methods
Roadside ditch discharge: 2 cubic feet per second per acre calculation method

Medium Development Sites (2-10 acres)

Projects in the 2-10 acre range require more comprehensive analysis using:

Malcom's Small Watershed Hydrograph Method for detention volume calculations
Detailed existing and proposed conditions analysis including time of concentration calculations
Comprehensive drainage area mapping and peak flow computations

Mandatory Requirements for Projects Over 10 Acres

The new drainage criteria establish mandatory coordination requirements for larger and more complex projects.

Development sites greater than 10 acres must now comply with enhanced oversight provisions:

Pre-Design Coordination Requirements

Projects exceeding 10 acres must schedule a meeting with TxDOT Houston District Hydraulics Section (email: HOU_HYD_Permits@txdot.gov) prior to beginning drainage impact analysis. This requirement also applies to projects with:

Offsite contributing areas larger than 5 acres
Design complexities requiring modeling software
Any routing software usage for detention/impact analysis

Approved Modeling Software

The new criteria restrict acceptable routing software to specific platforms:

HEC-HMS
XP-SWMM
EPA-SWMM
HEC-RAS (when applicable)

Mandatory Drainage Reports

For projects over 10 acres, drainage reports must be submitted prior to plan submittal and conceptual review must be completed before proceeding with detailed design.

This represents a significant shift toward proactive review and coordination.

The 3-Month Transition Period

TxDOT Houston District has implemented a 3-month transition period to help developers and engineers adapt to the new drainage criteria.

During this period, which began July 1, 2025, the department will provide additional guidance and support to ensure smooth implementation.

Transition Support Measures

Technical assistance for interpreting new requirements
Guidance on documentation requirements and submission procedures
Clarification meetings for complex projects
Flexibility in interpretation while industry professionals adapt to new standards

Implementation Timeline

July 1, 2025: New criteria become effective
July-September 2025: Transition period with enhanced support
October 1, 2025: Full enforcement of all requirements

Updated Technical Requirements and Methodologies

The new drainage criteria introduce several technical updates that engineering professionals must understand:

Rational Method Parameters

The guidelines specify required parameters for Rational Method calculations:

Time of concentration: Natural Resources Conservation Service (NRCS) Method
Rainfall intensity: TxDOT NOAA Atlas 14 coefficients (Partial Duration Series only)
Runoff coefficients: Updated Table 1 values with specific land use categories

Small Watershed Method Implementation

For medium development sites, the criteria mandate use of Malcom's Small Watershed Hydrograph Method with specific equations for:

Hydrograph development: Time to peak and discharge calculations
Detention volume determination: Maximum cumulative difference between existing and proposed conditions
Five-minute time increments for hydrograph analysis

Restrictor Design Standards

The new criteria establish specific requirements for restrictor design:

Orifice equation parameters: Coefficient of discharge values from Harris County Flood Control District standards
Location requirements: Restrictors must be entirely within private property
Head limitations: Maximum allowable head constraints based on restrictor type

Enhanced Documentation and Submission Requirements

The updated drainage criteria significantly expand documentation requirements for all project types:

Civil Drawing Set Requirements

All submissions must include comprehensive documentation:

Boundary survey maps (signed and sealed by Texas RPLS)
Existing and proposed drainage area maps with flow directional arrows
Detention pond cross-sections with labeled elevations and groundwater information
Restrictor details with complete specifications and calculations

Drainage Checklist Compliance

A comprehensive drainage checklist must be completed and submitted with all permit applications. This checklist covers:

Pre-design verifications including diversion analysis
Hydrologic and hydraulic calculations with all supporting documentation
Grading and drainage plans with required details and specifications

Environmental and Regulatory Compliance

The new drainage criteria emphasize environmental protection and regulatory compliance:

Stormwater Pollution Prevention

All projects must include Stormwater Pollution Prevention Plans (SWPPP) with:

Erosion control measures appropriate for site conditions
Sediment control practices to protect TxDOT right-of-way
Pollution prevention protocols for construction activities

Jurisdictional Coordination

The criteria acknowledge that other jurisdictional entities may have more stringent requirements and place responsibility on the Development's Engineer to coordinate with all applicable agencies.

Practical Implementation Guidance

To ensure successful compliance with the new drainage criteria, developers and engineers should consider the following recommendations:

Early Planning Strategies

Engage early with TxDOT Houston District Hydraulics Section for projects over 10 acres
Conduct preliminary drainage analysis before finalizing site layouts
Coordinate with multiple jurisdictions to identify the most restrictive requirements

Professional Engineering Requirements

Licensed Texas Professional Engineer must prepare and seal all drainage plans
Engineering judgment must be applied to prevent impacts to TxDOT drainage systems
Conservative solutions should be considered when multiple jurisdictions have conflicting requirements

Quality Assurance Measures

Complete drainage checklist before submission
Verify all required documentation is included in civil drawing sets
Ensure compliance with both TxDOT and local jurisdiction requirements

Official Resources and Contact Information

For the most current information regarding the new drainage criteria, developers and engineers should reference the official TxDOT Houston District resources:

Primary Documentation

Drainage Design Guidelines for Typical Projects (Revised July 1, 2025)
Drainage/Hydraulics Checklist (Revised July 1, 2025)
Pump Discharge Criteria (Revised July 1, 2025)

Contact Information

Email: HOU_HYD_Permits@txdot.gov
As-Built Plan Requests: HOU_PlanRequest@txdot.gov
Website: https://www.txdot.gov/about/districts/houston-district/contractor-information.html#drainage

Additional Resources

TxDOT NOAA Atlas 14 Coefficients: Available through official TxDOT spreadsheet
Houston District Standards: https://www.dot.state.tx.us/hou/specinfo/specs.htm
Bridge Standards: https://www.dot.state.tx.us/insdtdot/orgchart/cmd/cserve/standard/bridge-e.htm

Looking Forward: Compliance and Success

The implementation of TxDOT Houston District's new drainage criteria represents a significant evolution in how development projects must approach stormwater management and drainage design.

These changes emphasize the importance of early coordination, comprehensive analysis, and professional engineering judgment in creating drainage solutions that protect both development investments and public safety.

Key Success Factors

Proactive planning and early coordination with TxDOT Houston District Hydraulics Section
Comprehensive documentation meeting all checklist requirements
Professional engineering expertise in navigating complex regulatory requirements
Quality assurance throughout the design and submission process

Future Considerations

As the new drainage criteria become fully implemented, developers can expect:

Streamlined processes for compliant projects
Enhanced predictability in permitting timelines
Improved coordination between jurisdictions
Better protection for both development and public infrastructure

Conclusion

The TxDOT Houston District's new drainage criteria effective July 1, 2025, represent a comprehensive update designed to improve the efficiency and effectiveness of drainage design for development projects.

With simplified methodologies for smaller projects, mandatory coordination requirements for larger developments, and enhanced documentation standards, these changes will significantly impact how civil engineers approach drainage design in the Houston area.

As the premier provider of civil engineering, structural engineering, and environmental engineering services in North Carolina, Florida, and Texas, JRH Engineering & Environmental Services is fully prepared to help clients navigate these new requirements successfully.

Our experienced team of licensed professional engineers understands the intricacies of TxDOT regulations and can provide the expertise needed to ensure compliance while maintaining project efficiency and cost-effectiveness.

For developers and engineers working in the TxDOT Houston District, the key to success lies in understanding these new requirements, planning appropriately, and working with experienced professionals who can navigate the complexities of modern drainage design.

The 3-month transition period provides an opportunity to adapt to these changes, and those who prepare thoroughly will be best positioned for continued success in this evolving regulatory environment.