Hydrologic Numerical Models Meeting the Minimum Requirement of National Flood Insurance Program

National Models

Local Models

Other Models

No Longer Accepted Models

Engineers, surveyors, floodplain managers and FEMA mapping partners will benefit in viewing this page to understand the current nationally accepted hydrologic models that meet National Flood Insurance Program (NFIP) minimum requirements for flood hazard mapping.

Disclaimers

This website lists models, where the compliance with the requirements of 44 CFR 65.6(a)(6) has been previously demonstrated for use in FEMA flood hazard studies and/or mapping efforts. The lists include models that professional engineers can use to perform engineering analysis and mapping for flood insurance studies, however a model’s inclusion on this list does not indicate whether its approval or certification is current as to any other governmental agency. Professional engineers are ultimately responsible for the appropriate application and accuracy of the results.
FEMA is not responsible for technical support or accuracy of the results and has not evaluated the technical soundness of the models independently.
This list cannot be used as a marketing tool explicitly or implicitly anywhere.
FEMA updates its list as necessary, however, the accuracy of this list is not guaranteed. It is highly recommended that model selection is discussed with FEMA before undertaking or initiating any analysis intended to be submitted to FEMA.
FEMA provides this list for reference only and, in doing so, does not endorse any non-federal products, companies or services. If you believe that any information provided on this page is inaccurate, please contact FEMA at 1-877-FEMA MAP (1-877-336-2627).

Current Nationally Accepted Hydrologic Models

Hydrologic Models: Determination of Flood Hydrographs

Single Event

Program: HEC-RAS 6.0.0 AND UP (MAY 2021)

Developed By

U.S. Army Corps of Engineers (USACE)

Available From

Water Resources
Support Center
U.S. Army Corps of Engineers
Hydrologic Engineering Center
609 Second Street
Davis, CA 95616-4687

Public Domain

Yes

Comments

The River Analysis System is able to model spatially and time varying precipitation and infiltration to 2D flow Areas, Storage areas, and between 1D cross sections. Three infiltration methods are available; Initial and Constant Loss method and the SCS method, and Green and Ampt method.

Calibration runs against available gage or other study data should be used wherever possible to validate model output.

Program: Gridded Surface Subsurface Hydrologic Analysis (GSSHA) Version 1.43 and up (Sept. 2006)

Developed By

U.S. Army Corps of Engineers (USACE)

Available From

U.S. Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory
3909 Halls Ferry Rd.
Vicksburg, MS 39180

Public Domain

Yes

Comments

GSSHA is a spatially explicit, physics based hydrologic model that can simulate a wide range of runoff mechanisms, including infiltration-excess and saturation-excess runoff, snow melt, storm and tile drains, groundwater exfiltration and discharge, lakes (including non-draining lakes such as prairie potholes), detention basins, culverts and weirs.

GSSHA also includes the ability to simulate time and space varying head boundary conditions, making it suitable in many coastal watershed applications. GSSHA has been applied from jungle rainforests to the permafrost basins of Alaska, from the desert southwest to the Florida Everglades as well as in urban storm surge flooding simulations in New Orleans and New York City.

More information can be found on the GSSHA Wiki webpage.

Program: HEC-HMS 1.1 and up (Mar 1998)

Developed By

U.S. Army Corps of Engineers (USACE)

Available From

Water Resources
Support Center
U.S. Army Corps of Engineers
Hydrologic Engineering Center
609 Second Street
Davis, CA 95616-4687

Public Domain

Yes

Comments

The Hydrologic Modeling System provides a variety of options for simulating precipitation-runoff processes. It now includes snowmelt and interior pond capabilities, plus enhanced reservoir options.

Calibration runs should be used wherever possible to determine model parameters.

Program: MIKE (2009 SP4)

Developed By

DHI Water & Environment

Available From

DHI Water & Environment Inc.
141 Union Blvd Ste. 320
Lakewood, CO 80228

Public Domain

Comments

Simulates flood hydrographs at different locations along streams using unit hydrograph techniques. Three methods are available for calculating infiltration losses and three methods for converting rainfall excess to runoff, including SCS Unit hydrograph method.

Calibration or verification to the actual flood events highly recommended.

Program: National Weather Service FLDWAV Computer Program

Developed By

National Weather Service (NWS)

Available From

Hydrologic Research Laboratory
Office of Hydrology
National Weather Service (NWS), NOAA
1345 East-West Highway
Silver Spring, MD 20910

Public Domain

Yes

Comments

FLDWAV program, developed by the National Weather Service (NWS), is a generalized flood routing program with the capability to model floodflows through a single stream or a system of interconnected waterways.

National Weather Service FLDWAV Computer Program

Program: PondPack v.8 (May 2002) and up

Developed By

Bentley Systems

Available From

Bentley Systems
685 Stockton Drive
Exton, PA 19341

Public Domain

Comments

The program is for analyzing watershed networks and aiding in sizing detention or retention ponds. Only the NRCS Unit Hydrograph method and NRCS Tc calculation formulas are acceptable. Other hydrograph generation methods or Tc formulas approved by state agencies in charge of flood control or floodplain management are acceptable for use within the subject state.

Calibration or verification to the actual flood events highly recommended.

SWMM 5 Version 5.0.005 (May 2002) and up

Developed By

U.S. Environmental Protection Agency

Available From

Water Supply and Water Resources Division
U.S. Environmental Protection Agency

Public Domain

Yes

Comments

SWMM 5 provides an integrated environment for editing study area input data, running hydrologic simulations and viewing the results in a variety of formats. These include color-coded drainage area and conveyance system maps, time series graphs and tables, profile plots and statistical frequency analyses.

Calibration or verification to the actual flood events highly recommended.

Program: WinTR-20 3.30.1 (September 2022) and Up

Developed By

U.S. Department of Agriculture, Natural Resources Conservation Service

Available From

U.S. Department of Agriculture, Natural Resources Conservation Service

Search “TR-20”

Public Domain

Yes

Comments

The TR-20 computer model has been revised and completely rewritten as a Windows based program. It is storm event surface water hydrologic model applied at a watershed scale that can generate, route and combine hydrographs at points within a watershed.

Calibration runs preferred to determine model parameters.

Program: WinTR-55 2.00.0 (July 2022) and Up

Developed By

U.S. Department of Agriculture, Natural Resources Conservation Service

Available From

U.S.Department of Agriculture, Natural Resources Conservation Service

Search “TR-55”

Public Domain

Yes

Comments

The new WinTR-55 uses the WinTR-20 program as the driving engine for analysis of the hydrology of the small watershed system being studied.

Program: XP-SWMM 8.52 and up

Developed By

Innovyze formally known as XP Solutions

Available From

Innovyze
6720 SW Macadam Avenue, Suite 150
Portland, OR 97219

Public Domain

Comments

Model must be calibrated to observed flows, or discharge per unit area must be shown to be reasonable in comparison to nearby gage data, regression equations or other accepted standards for 1% annual chance events.

Calibration or verification to the actual flood events highly recommended.

Program: XPStorm 10.0 (May 2006)

Developed By

Innovyze formally known as XP Solutions

Available From

Innovyze
6720 SW Macadam Avenue, Suite 150
Portland, OR 97219

Public Domain

Comments

XPStorm has the same stormwater modeling capability as the XP-SWMM program.

Calibration or verification to the actual flood events highly recommended.

Single Event

Program: Gridded Surface Subsurface Hydrologic Analysis (GSSHA) Version 1.43 and up (Sept. 2006)

Developed By

U.S. Army Corps of Engineers (USACE)

Available From

U.S. Army Engineer Research and Development Center Coastal and Hydraulics Laboratory
3909 Halls Ferry Rd.
Vicksburg, MS 39180

Public Domain

Yes

Comments

More information can be found on the GSSHA Wiki webpage

Program: HSPF 10.10 and up (Dec 1993)

Developed By

U.S. Environmental Protection Agency,
U.S. Geological Survey

Available From

Center for Exposure Assessment Modeling
U.S. Environmental Protection Agency
Office of Research and Development
Environmental Research Laboratory
960 College Station Road
Athens, GA 30605-2720

Public Domain

Yes

Comments

Calibration to actual flood events required.
Water Resources Application Software

Program: HEC-HMS 3.0 and up (Dec 2005)

Developed By

U.S. Army Corps of Engineers (USACE)

Available From

U.S. Army Corps of Engineers
Hydrologic Engineering Center
609 Second Street
Davis, CA 95616-4687

Public Domain

Yes

Comments

The Hydrologic Modeling System (HMS) includes two different soil moisture models suitable for continuous modeling, one with five layers and one with a single layer. Two approaches to evapotranspiration are provided and snowmelt is available.

Calibration to actual flood events is required.

Program: MIKE 11 RR (2009 SP4)

Developed By

DHI Water & Environment

Available From

DHI Water & Environment Inc.
141 Union Blvd Ste. 320
Lakewood, CO 80228

Public Domain

Comments

The Rainfall-Runoff Module is a lumped-parameter hydrologic model capable of continuously accounting for water storage in surface and sub-surface zones. Flood hydrographs are estimated at different locations along streams. Calibration to actual flood events is required.

Program: PRMS Version 2.1 (Jan 1996)

Developed By

U.S. Geological Survey

Available From

U.S. Geological Survey
12201 Sunshine Valley Drive
Reston, VA 22092

U.S. Geological Survey
P.O. Box 25046,
Mail Stop 412
Denver Federal Center
Lakewood, CO 80225-0046

Public Domain

Yes

Comments

PRMS is a modular-designed, deterministic, distributed-parameter modeling system that can be used to estimate flood peaks and volumes for floodplain mapping studies.

Calibration to actual flood events required.

The program can be implemented within the Modular Modeling System that facilitates the user interface with PRMS, input and output of data, graphical display of the data and an interface with GIS.

Locally Accepted Hydrologic Models

Hydrologic Models: Determination of Flood Hydrographs

Single Event

Program: AHYMO S4 (Aug. 1997)

Developed By

Albuquerque Metropolitan Arroyo Flood
Control Authority, Anderson-Hydro

Available From

Anderson-Hydro

13537 Terragon Drive, NE
Albuquerque, NM 87112

Public Domain

Yes

Comments

Flood hydrographs at different locations along streams.

Only accepted for usage and the default parameters in the model applicable within New Mexico.

Information on the AHYMO S4 model

Program: Colorado Urban Hydrograph Procedure (CUHPF/PC) V1 (May 1996 and May 2002) and V2 (September 2016 and October 2019)

Developed By

Denver Urban Drainage and Flood Control District

Available From

Denver Urban Drainage
and Flood Control District
2480 West 26th Avenue, Suite 156-B
Denver, CO 80211

Public Domain

Yes

Comments

Flood hydrographs at different locations along streams. Hydrographs are routed using UDSWM2-PC (a modified version of the Runoff Block of EPA's SWMM).

Only accepted for usage and the default parameters in the model applicable within the Denver, Colorado, metro area.

Program:FLO-2D v. 2007.06 and 2009.06

Developed By

Jimmy S. O'Brien

Available From

FLO-2D Software, Inc.
P.O. Box 66
Nutrioso, AZ 85932

Public Domain

Comments

Runoff excess is computed by distributed hydrological parameters. Surface runoff routing is based on the non-linear dynamic wave approximation of the momentum equation. Applicable to watersheds with flows characterized as dispersed surface runoff instead of concentrated channel flow.

An integrated river and floodplain model. A flood routing hydrologic and hydraulic model with urban detail features, sediment transport, mudflow, and groundwater modeling

Please review 'Guidance for Flood Risk Analysis and Mapping for Alluvial Fans, November 2016. Coordination with the Regional Office is required. Calibration to actual flood events is required.

Only accepted for usage within Mohave County, Cochise County, Pima County, Pinal County, and Maricopa County, Arizona and Lyon County, Nevada.

PROGRAM:FLO-2D Pro

Developed By

Jimmy S. O'Brien

Available From

FLO-2D Software, Inc.
P.O. Box 66
Nutrioso, AZ 85932

Public Domain

Comments

Only accepted for usage within Mohave County, Cochise County, Pima County, Pinal County, and Maricopa County, Arizona.

Program: StormWise (formerly ICPR4)

Developed By

Streamline Technologies, Inc.

Available From

Streamline Technologies, Inc.
1135 East State Road 434
Suite 3002
Winter Springs, FL 32708

Public Domain

Comments

Hydrology, integrated 1-D/2-D surface hydraulics, and 2-D groundwater model.

Only accepted for usage within the State of Florida; County of Georgetown, South Carolina; City of Lubbock, Texas; and the Cities of Lafayette and Martinsville, Indiana

Program: INFOWORKS ICM (INTEGRATED CATCHMENT MODELING) V.8-SERIES AND V. 10.5 AND UP

Developed By

Innovyze

Available From

Innovyze
6720 SW Macadam Avenue Suite 150
Portland, OR 97219

Public Domain

Comments

Hydrology and integrated 1-D/2-D surface hydraulics.

Only accepted for usage within Santa Clara County, California and New York, New York.

Program: TUFLOW Software Suite

Developed By

BMT Group Ltd

Available From

BMT Group Ltd
Level 8
200 Creek Street
Brisbane
4000
Australia

Public Domain

Comments

1D network and 2D fixed grid based software for simulating flood and tidal flow. Only accepted for usage within Ventura County, California.

Program: VCRat 2.6 (Dec. 2008)

Developed By

Ventura County Watershed Protection District

Available From

Ventura County Watershed Protection District
800 S. Victoria Ave.
Ventura, CA 93009

Public Domain

Yes

Comments

The VCRat model is based on the Modified Rational Method (MRM) and calculates a hydrograph of runoff at all subarea collection points within the watershed, combines hydrographs from each subarea, and routes the combined hydrograph through the channel system.

Manual and the training materials are available from the District.

Only accepted for usage within the Ventura County, California area.

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More Nationally and Locally Accepted Models

Numerical Models No Longer Accepted

Please visit the Numerical Models No Longer Accepted by FEMA for NFIP Usage page for a list of unaccepted models.

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