Stormwater Atlas

hydrology.software

Approved Hydrologic and Hydraulic Software

Tools commonly required or accepted for sizing and flood routing.

ReviewedPrevalence 32%~194 manuals tagged14 citationsModel: heuristic+editorial
Provisional practice synthesis for discussion — not a design manual or adopted regulation. Controlling state, regional, and MS4 criteria apply when more stringent. Verify citations against the linked jurisdiction manuals.

Practice

Manuals rarely mandate a single product. They more often list acceptable tools that implement approved methods and can export reviewable inputs and outputs. Named families in the atlas frequently include HEC-HMS, EPA SWMM, HydroCAD, and HEC-RAS for open-channel or floodplain checks.

Software allow-list posture (capability, not a mandated product)

Draft national guidance grounded in atlas practice — not a design manual or adopted regulation.

Capability needSuggested national guidanceAtlas note
Event / watershed hydrologyAccept tools that implement approved methods and export reviewable inputs/outputs (e.g. HEC-HMS class)29% of manuals with software lists (22)[1,3,5,9,11]
Urban runoff / LID continuousAccept SWMM-class tools where continuous or multi-event simulation is required17% of manuals with software lists (13)[6,9,10,11,13]
Site detention / pond routingAccept HydroCAD-class or equivalent tools used by the review agency21% of manuals with software lists (16)[2,4,5,8,11]
Open channel / floodplainAccept HEC-RAS-class tools for conveyance and floodplain checks when required13% of manuals with software lists (10)[3,6,7,9,12]
Submittal hygieneRequire version disclosure and native input files with the drainage report — do not mandate a single brandAtlas lists named tools; product mandates are uncommon

Guidance

  1. 6.1Editorial

    Treat software as an allow-list of capabilities, not a single mandated product.[1,2,3,4]

  2. 6.2Field-verified

    Accept tools that implement approved hydrologic methods and export reproducible inputs and outputs (HEC-HMS, SWMM, HydroCAD, and HEC-RAS class tools are frequently named).[1,2,3,4]

  3. 6.3Editorial

    Require version disclosure and native input files with drainage-report submittals.[1,2,3,4]

Open questions

Prescribe versus allow-list posture. How to handle proprietary and cloud-only tools in public-records submittals.

References

Numbered footnotes for guidance clauses and atlas notes. Field-verified entries come from structured atlas evidence; corpus-pattern entries are keyword-matched excerpts.

  1. [1]AlaskaAlaskaField-verifiedSection 3.2, page 3-5
    “A partial list of hydrologic modeling software accepted by some Alaskan municipalities includes the following: ILLUDAS TR55-1986 WinTR553 WinTR20 SCS HEC-HMS”
  2. [2]ConnecticutConnecticutField-verifiedPage 55, 59, 190
    “hydrologic analysis software such as WinTR-55... HydroCAD or similar software... TR-20... USGS and New Jersey Department of Environmental Protection Hantush Groundwater Mounding Spreadsheet”
  3. [3]MinnesotaMinnesotaField-verifiedChapter 8, Table 8.1 Modeling Tool Selection
    “TR-55 (original or DOS) ... HEC-1 ... HEC-HMS ... WinTR-20 (or TR-20) ... WinTR-55 ... HEC-RAS”
  4. [4]New York StateNew YorkField-verifiedPage 1.5
    “These data can be imported into HydroCAD, USDA NRCS TR20, and other computer models”
  5. [5]New York StateNew YorkField-verifiedSection 4.9
    “Hydraulic and hydrologic modeling software, such as USDA NRCS TR20, HydroCAD, Pond Pack, StormCAD, Hydraflow, and Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) and others, shall be used”
  6. [6]PennsylvaniaPennsylvaniaField-verifiedPage 2-65
    “HEC-RAS, International River Interface Cooperative (iRIC), or other software capable of performing a sediment transport analysis.”
  7. [7]VermontVermontField-verified2-14
    “The models TR-55 and TR-20 (or approved equivalent) will be used for determining peak discharge rates”
  8. [8]Charlotte-MecklenburgNorth CarolinaField-verifiedChapter 1, Section 1.3, Page 7
    “The City will typically use HEC software to verify designs submitted by the development community. In addition, the City may check designs using HydroCAD and StormCAD. Designers may use any software tools that are based on the methods described in this manual.”
  9. [9]City of ChesapeakeVirginiaField-verifiedp. 5
    “25-yr. 7.0” 50-yr. 8.17” 100 9.44” C. Acceptable methods for runoff analysis are tabulated below: Model Major Sys. Minor Sys. Hydrologic Hydraulic Water Quality Hydrology Software HEC-GeoHMS X X HEC-HMS X X TR-55 X TR-20 X Pond Pack X X X WMS X X Watershed Modeling X X Hydrauli”
  10. [10]District of ColumbiaDistrict of ColumbiaField-verifiedAppendix H, Section H.4
    “HEC-1, WinTR-55, TR-20, and SWMM Computer Models”
  11. [11]City of DetroitMichiganField-verifiedChapter 4, Table 4-5, Page 4-9
    “Rational Method, EPA SWMM, HydroCAD, StormCAD, or other DWSD-approved model... NRCS Curve Number Approach, EPA SWMM, HEC-HMS, TR-55, TR-20, HydroCAD, StormCAD, or other DWSD-approved model”
  12. [12]County of Los AngelesCaliforniaField-verifiedSection 6.3, Page 6-3
    “LACPW developed a hydrologic calculator (HydroCalc)... Use of this program is encouraged”
  13. [13]City of MinneapolisMinnesotaField-verifiedSection 4.3.1.6, Page 26
    “The hydrologic and hydraulic models accepted by the City of Minneapolis include: HydroCAD; XP-SWMM”
  14. [14]City of ChesapeakeVirginiaCorpus patternpages 5-5
    “Minor Sys. Hydrologic Hydraulic Water Quality Hydrology Software HEC-GeoHMS X X HEC-HMS X X TR-55 X TR-20 X Pond Pack X X X WMS X X Watershed Modeling X X Hydraulic Software HEC-GoeRAS X X HEC-RAS X X WSPRO X X EPA SWMM X X X X X FHWA HY-8 (Culver”
  15. [15]MinnesotaMinnesotaCorpus patternpages 189-189
    “infall-runoff simulation, reservoir & channel routing HEC-1 Medium No Yes -- -- HEC-HMS Medium Yes Yes -- -- WinTR-20 (or TR-20) Medium No Yes -- -- WinTR-55 Low No Yes -- -- HydroCAD Medium No No -- -- Hydraulic Models water surface profile deter”
  16. [16]IdahoIdahoCorpus patternpages 70-70
    “ogram—Fortran (HSPF), Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS), and Storm Water Management Model (SWMM). EPA’s National Stormwater Calculator, released in 2012, uses the SWMM modeling engine combined with an interactive m”
  17. [17]City of DetroitMichiganCorpus patternpages 104-104
    “or hydrograph routing software (i.e. EPA SWMM, proprietary SWMM-based software, HEC-HMS, TR-20, HydroCAD, StormCAD, or similar) must be used. The Modified Rational Method employs a series of trapezoidal shaped hydrographs created from different st”
  18. [18]PennsylvaniaPennsylvaniaCorpus patternpages 488-488
    “ever, other available models for this approach include: HydroCAD, PondPack, EPA SWMM or other SWMM packages, TR-20, TR-55 and TR-55 based computer models, WinSLAMM, and others. DEP recommends to utilize a model with the most appropriate hydrolo”
  19. [19]City of MinneapolisMinnesotaCorpus patternpages 41-41
    “ment should be used. Table 4-2 Parameter guidance Precipitation HydroCAD and XP-SWMM Design storm events for HydroCAD and XPSWMM See Table 4-3: City of Minneapolis design storm events—rainfall frequency depth [24-hour storm event] P8 precipitat”
  20. [20]City of PortlandOregonCorpus patternpages 101-101
    “Method, NRCS’s TR-55, the Army Corps of Engineers’ Hydrologic Modeling System (HEC-HMS) or HEC-1, or the Environmental Protection Agency’s Storm Water Management Model (EPA-SWMM). If sizing using continuous simulation, a minimum of 20 years of Po”
  21. [21]New York StateNew YorkCorpus patternpages 50-50
    “rmCAD, Hydraflow, and Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) and others, shall be used to extract rainfall frequency and duration data, for the project location, to create intensity-duration-frequency (IDF) curves, and”
  22. [22]PhiladelphiaPennsylvaniaCorpus patternpages 228-228
    “urve Number Method Any Moderate to high Yes (smaller sites) NRCS, TR-55, TR-20, HEC-HMS Infiltration loss models Constant Loss Any Moderate to high Yes (smaller sites) HEC-HMS Green-Ampt Any High No EPA SWMM, HEC-HMS Horton Any High No EPA SWMM PW”
  23. [23]City of LawrenceKansasCorpus patternpages 18-18
    “he SWMM program is also available from the U.S. EPA Water Research website. The HEC-HMS and TR-55 packages are also available through the US Army Corps of Engineers Hydrologic Engineering Center Software website. 2. Acceptable manual methods shall”
  24. [24]City of ColumbusOhioCorpus patternpages 171-171
    “alculation, or using a computer model able to compute backwater curves, such as HEC-RAS or U.S. EPA SWMM. Demonstrate that the water elevation resulting from the 100-year storm event does not encroach into proposed or existing residential dwelling”

Supporting jurisdictions

11 jurisdictions cited in this section (outline tags ~194 manuals; full atlas has ~299).

chesapeake-vamn-state-2008idaho-bmp-catalogdetroit-mipa-stateminneapolis-mnportland-orny-statephiladelphia-palawrence-kscolumbus-oh