City of Houston

Infrastructure Design Manual Chapter 9 Stormwater Design and Water Quality Requirements

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Chapter 9 (07-01-2022) clearly states City of Houston municipal design criteria, Atlas 14 IDF coefficients for 2–500 year events, Rational/HCFCD/Clark/NRCS/Malcolm hydrology, HouStorm software, first 1/2-inch WQ treatment, and LID BMP list. Complements HCFCD criteria but is an independent city IDM chapter, not a state manual adoption. A 3-year rainfall frequency is defined in 9.1.04.R but has no Table 9.1 intensity coefficients, so it was omitted from the return-period array. Pipeline excerpt repair removed 3 unlocated citation(s).

Fields not found in document: document_metadata.version_or_edition, document_metadata.adoption_or_effective_date, document_metadata.last_revised_date

Other manuals in Texas: City of Amarillo, City of Arlington, City of Austin, City of Beaumont / Jefferson County Drainage District No. 6, City of Brownsville, City of College Station, City of Corpus Christi, City of Denton, City of El Paso, City of Fort Worth, City of Frisco, City of Garland, City of Grand Prairie, City of Killeen, City of Laredo, City of Lubbock, City of McAllen, City of McKinney, City of Mesquite, City of Pasadena, City of Pearland, City of Plano, City of Round Rock, City of San Antonio, City of Waco, Dallas / North Central Texas (iSWM), Harris County, Tarrant County, Texas, Texas Commission on Environmental Quality

Document Metadata

Jurisdiction level

City

“Drainage criteria administered by the City of Houston and complemented by Harris County and the Harris County Flood Control District (HCFCD)”
Section 1, 9.1.02.A, Page 9-2

State

Texas

“Infiltration report of soil testing, signed and sealed by a Professional Engineer licensed in the State of Texas”
Section 1, 9.1.04.O, Page 9-7

Version / edition

Not found in document

No evidence cited

Adoption / effective date

Not found in document

No evidence cited

Last revised date

Not found in document

No evidence cited

Relationship to state manual

independent

“Drainage criteria administered by the City of Houston and complemented by Harris County and the Harris County Flood Control District (HCFCD)”
Section 1, 9.1.02.A, Page 9-2

Design Criteria

Design storm return periods (years)

2-year, 5-year, 10-year, 25-year, 50-year, 100-year, 500-year

“Table 9.1 – Rainfall Intensity Coefficients ... 2-year ... 5-year ... 10-year ... 25-year ... 50-year ... 100-year ... 500-year”
Section 2A, Table 9.1, Page 9-11

Water quality volume method

At a minimum, permanent stormwater quality BMPs for new development and significant redevelopment must treat the first 1/2 inch of runoff (except as noted in the Stormwater Quality Guidance Manual or Minimum Design Criteria); LID features may also store/treat a water quality volume (WQv).

“At a minimum, the system must be designed to treat the first 1/2 inch of runoff, except as noted in the SWQGM or the MDC.”
Section 9, 9.9.01.C.3, Page 9-46

Peak flow calculation method(s)

Rational Method (drainage areas up to 200 acres; storm sewer projects up to 640 acres), HCFCD H&H Manual methodology (areas greater than 640 acres), Clark Unit Hydrograph Method (dynamic hydrograph modeling), NRCS Dimensionless Unit Hydrograph (detention volume / static conditions), Malcolm's Small Watershed Method (detention volume / static conditions)

“Rational Method: The Rational Method will be used to estimate peak flows for individual drainage areas up to 200 acres in size, and for project areas up to 640 acres in size.”
Section 2A, 9.2.01.B.2.a, Page 9-12

Hydrologic/hydraulic software

HouStorm

“HouStorm shall be used to perform 2-year and inlet design analysis and design of storm drainage systems”
Section 2A, 9.2.01.A, Page 9-10

Approved BMP categories

Bioretention, Infiltration Trenches, Porous Pavement / Porous Paver Systems, Vegetated Swales (dry and wet), Green Roof, Hard Roof, Rain Barrels, Detention ponds / stormwater detention basins

“Low Impact Development (LID) techniques that are considered acceptable for achieving detention are Bioretention, Infiltration Trenches, Porous Pavement, Vegetative Swales, Green Roof, Hard Roof, and Rain Barrels.”
Section 2A, 9.2.01.H.3.j, Page 9-31