City of Columbus

Stormwater Drainage Manual

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June 2025 Columbus SWDM. Explicit WQv rainfall depth equation is deferred to OEPA CGP / Rainwater and Land Development Manual rather than restated as a single Columbus-only formula in Section 3.3. No named proprietary modeling package is mandated (methods are specified). Manual text: effective August 26, 2025. Pipeline excerpt repair removed 1 unlocated citation(s).

Fields not found in document: design_criteria.required_hydrologic_hydraulic_software, document_metadata.version_or_edition

Other manuals in Ohio: City of Akron, City of Cincinnati, City of Cleveland, City of Dayton, City of Toledo, City of Youngstown, Ohio, Ohio Department of Transportation (ODOT)

Document Metadata

Jurisdiction level

City

“Columbus Stormwater Drainage Manual June 2025 / Division of Sewerage and Drainage”
Cover / headers

State

Ohio

“Ohio EPA Construction General Permit / Rainwater and Land Development Manual”
Section 3.3 / Definitions

Version / edition

Not found in document

No evidence cited

Adoption / effective date

2025-08-26

“Effective August 26, 2025, the 2024 Stormwater Drainage Manual and the 1994 Erosion”
Preface / Effective date

Last revised date

2025-06

“Stormwater Drainage Manual List of Updates June 2025”
List of Updates

Relationship to state manual

independent

“The design criteria provided in this section are in addition to the criteria detailed in the Ohio Construction General Permit and the Ohio Rainwater and Land Development Manual.”
Section 3.3

Design Criteria

Design storm return periods (years)

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

“Type II 24-Hour Distribution Rainfall (in) Frequency: 100-yr 50-yr 25-yr 10-yr 5-yr 2-yr 1-yr”
Table 2-3

Water quality volume method

Post-construction stormwater quality controls sized to the Water Quality Volume (WQv) and Water Quality Flow (WQf) per Section 3.3 / 6.2.9, using Ohio EPA Construction General Permit post-construction criteria and Ohio Rainwater and Land Development Manual methods (more stringent of OEPA vs Columbus criteria applies). Combined-sewer discharges are exempt from Section 3.3 water quality controls unless separation/redirection is planned. Extended detention example: release 50% of WQv in 8 hours and 100% of WQv per design tables.

“All runoff from development sites shall be directed to one or more stormwater quality controls designed according to: 1. Appropriate currently effective Ohio EPA Authorization for Stormwater Discharges Associated with Construction Activity… 3. Appropriate currently effective Ohio Rainwater and Land Development Manual, and 4. Criteria provided in Section 3.”
Section 3.3.1.1

Peak flow calculation method(s)

Rational Method (peak flows; up to 200 acres), USGS Regression Equations (streams; ~17–2600 acres), NRCS (SCS) Curve Number Method (peak flows up to 640 acres), Approved hydrograph methods (required for detention design and downstream analysis), Critical storm method for quantity control (Table 3-1): release ≤ critical storm at ≤ 1-year predevelopment peak; 100-year post ≤ 10-year predevelopment peak, SCS Type II 24-hour design storm hyetograph (Table 2-3) with NOAA Atlas 14 Central Ohio IDF

“The City allows three methods for calculating stormwater runoff peak flows: 1. The Rational Method… 2. USGS Regression Equations… 3. The Natural Resources Conservation Service (NRCS… Curve Number method…”
Section 2.2.1

Hydrologic/hydraulic software

Not found in document

No evidence cited

Approved BMP categories

Dry detention pond, Wet detention pond, Constructed wetland / shallow constructed wetland, Parking lot storage, Infiltration basin, Vegetated filter strips, Underground detention system, Permeable pavement, Bioretention facilities (GI), Sand/media filter

“Infrastructure Surface Controls Dry Detention Pond ● ● • OEPA CGP/Supplements • Columbus SWDM Wet Detention Pond ● ● • OEPA CGP/Supplements • Columbus SWDM Constructed Wetland ● ● • OEPA CGP/Supplements • Columbus SWDM Shallow Constructed Wetland ● ● • OEPA CGP/Supplements •”
pp. 109–110