{{orphan|date=February 2026}} {{Short description|Stormwater modeling software}}

'''GIFMod''' ('''Green Infrastructure Flexible Model''') is a free, open-source computer program for simulating the hydraulic and water quality performance of green infrastructure and other stormwater management practices.<ref name="massoudieh2017">{{cite journal |last1=Massoudieh |first1=Arash |last2=Maghrebi |first2=Mahdi |last3=Kamrani |first3=Babak |last4=Nietch |first4=Christopher |last5=Tryby |first5=Michael |last6=Aflaki |first6=Sassan |last7=Panguluri |first7=Srinivas |title=A flexible modeling framework for hydraulic and water quality performance assessment of stormwater green infrastructure |journal=Environmental Modelling & Software |volume=92 |pages=57–73 |year=2017 |doi=10.1016/j.envsoft.2017.02.013 |doi-access=free |pmid=32523421 |pmc=7286434}}</ref> Developed at the Catholic University of America in collaboration with the United States Environmental Protection Agency (EPA), GIFMod is included in the EPA's Green Infrastructure Modeling Toolkit.<ref name="epa_toolkit">{{cite web |title=Green Infrastructure Modeling Toolkit |url=https://www.epa.gov/water-research/green-infrastructure-modeling-toolkit |publisher=United States Environmental Protection Agency |access-date=2026-02-19}}</ref>

== Overview ==

GIFMod enables users to construct models of various low-impact development (LID) practices, including bioretention systems, permeable pavement, infiltration basins, constructed wetlands, green roofs, and wet ponds.<ref name="massoudieh2017"/> The software uses a block-and-connector architecture in which spatial features such as surface water ponds, soil layers, and drainage pipes are represented as "blocks," while the interfaces between them are represented as "connectors."<ref name="massoudieh2017"/>

The hydraulic module solves a combination of the Richards equation, kinematic and diffusive wave equations, Darcy's law, and other user-provided flow models. GIFMod also includes modules for particle transport and reactive transport of water quality constituents, allowing users to simulate processes such as sorption, sedimentation, filtration, and user-defined biochemical transformations.<ref name="massoudieh2017"/>

GIFMod includes both deterministic and probabilistic inverse modeling capabilities for parameter estimation. The deterministic approach uses a genetic algorithm, while the stochastic approach employs Bayesian inference through Markov chain Monte Carlo methods.<ref name="massoudieh2017"/>

== Development ==

GIFMod was developed by researchers at the Catholic University of America and the EPA's National Risk Management Research Laboratory.<ref name="epa_inventory">{{cite web |title=A Flexible Modeling Framework For Hydraulic and Water Quality Performance Assessment of Stormwater Green Infrastructure |url=https://cfpub.epa.gov/si/si_public_record_report.cfm?Lab=NRMRL&dirEntryId=339415 |publisher=EPA Science Inventory |access-date=2026-02-19}}</ref> The foundational paper describing the framework was published in ''Environmental Modelling & Software'' in 2017.<ref name="massoudieh2017"/> The software is written in C++ and is available as both a console application and a graphical user interface version.<ref name="massoudieh2017"/>

The source code is hosted on GitHub under the EPA's organizational account.<ref>{{cite web |title=USEPA/GIFMod |url=https://github.com/USEPA/GIFMod |publisher=GitHub |access-date=2026-02-19}}</ref>

== Reception and use in research ==

An independent review of bioretention modeling tools published in ''Environmental Modelling & Software'' identified GIFMod and HYDRUS as the only two models that use the Richards equation for determining infiltration under variably saturated conditions, noting this as an advantage over tools that rely on simpler approximations.<ref name="lisenbee2021">{{cite journal |last1=Lisenbee |first1=Whitney A. |last2=Hathaway |first2=Jon M. |last3=Burns |first3=Matthew J. |last4=Fletcher |first4=Tim D. |title=Modeling bioretention stormwater systems: Current models and future research needs |journal=Environmental Modelling & Software |volume=144 |article-number=105146 |year=2021 |doi=10.1016/j.envsoft.2021.105146 |doi-access=free}}</ref>

A review in ''WIREs Water'' on the catchment-scale effects of green infrastructure listed GIFMod among several modeling tools used to quantify the local and sewershed-level effects of low-impact development practices in urban settings.<ref name="golden2018">{{cite journal |last1=Golden |first1=Heather E. |last2=Hoghooghi |first2=Nahal |title=Green infrastructure and its catchment-scale effects: an emerging science |journal=WIREs Water |volume=5 |issue=1 |article-number=e1254 |year=2018 |doi=10.1002/wat2.1254 |doi-access=free |pmid=29755726 |pmc=5907509}}</ref>

Researchers at the University of Hong Kong used GIFMod to model stepped bioretention cells for slopes, concluding that the software was well suited for simulating systems with multiple cells and complex pipe configurations.<ref name="chen2022">{{cite journal |last1=Chen |first1=Boji |last2=Chui |first2=Ting Fong May |title=Optimal design of stepped bioretention cells for slopes |journal=Journal of Hydrology |volume=614 |article-number=128526 |year=2022 |doi=10.1016/j.jhydrol.2022.128526}}</ref>

A subsequent review in the ''Journal of Hydrology'' compared bioretention modeling approaches and discussed GIFMod's calibration performance, noting Nash-Sutcliffe efficiency values ranging from 0.68 to 0.86 for log-transformed hydrographs in field applications, while also observing limitations in its representation of underdrain and internal water storage configurations.<ref name="lisenbee2022">{{cite journal |last1=Lisenbee |first1=Whitney A. |last2=Hathaway |first2=Jon M. |last3=Winston |first3=Ryan J. |title=Fine scale hydrologic modelling of bioretention using DRAINMOD-urban: Verifying performance across multiple systems |journal=Journal of Hydrology |volume=615 |article-number=128663 |year=2022 |doi=10.1016/j.jhydrol.2022.128663}}</ref>

An independent study on nitrogen removal in bioretention basins noted that GIFMod was among the few available tools capable of process-based water quality modeling for green infrastructure, in contrast to widely used models that rely on approximate representations of biochemical processes.<ref name="wang2021">{{cite journal |last1=Wang |first1=Jia |last2=Chua |first2=Lloyd H.C. |last3=Shanahan |first3=Peter |title=Modeling and designing for nitrogen removal in bioretention basins |journal=Environmental Modelling & Software |volume=145 |article-number=105206 |year=2021 |doi=10.1016/j.envsoft.2021.105206}}</ref>

The Mid-Atlantic Regional Integrated Sciences and Assessments (MARISA) program, supported by the National Oceanic and Atmospheric Administration, lists GIFMod as a water modeling tool in its data tools inventory.<ref name="marisa">{{cite web |title=GIFMod |url=https://www.midatlanticrisa.org/data-tools/water-model-tool/items/gifmod.html |publisher=MARISA |access-date=2026-02-19}}</ref>

The National Fish and Wildlife Foundation has also listed GIFMod as a resource for pollution prevention calculations in green infrastructure planning.<ref name="nfwf">{{cite web |title=Pollution Prevention Calculators |url=https://www.nfwf.org/sites/default/files/2021-04/lisff-2021-pollution-prevention-calculators.pdf |publisher=National Fish and Wildlife Foundation |access-date=2026-02-19}}</ref>

The Sustainable Infrastructure Tools Navigator, an independent resource for infrastructure planning, lists GIFMod as a tool for evaluating urban stormwater and green infrastructure performance.<ref name="sitn">{{cite web |title=Green Infrastructure Flexible Model (GIFMod) |url=https://sustainable-infrastructure-tools.org/tools/green-infrastructure-flexible-model-gifmod/ |publisher=Sustainable Infrastructure Tools Navigator |access-date=2026-02-20}}</ref>

== See also ==

* Storm Water Management Model (SWMM) * Green infrastructure * Bioretention * Richards equation * Environmental modeling

== References == {{reflist}}

== External links ==

* {{Official website|https://gifmod.com/}} * [https://www.epa.gov/water-research/green-infrastructure-modeling-toolkit EPA Green Infrastructure Modeling Toolkit] * [https://github.com/USEPA/GIFMod Source code on GitHub]

Category:Environmental science software Category:Hydrology models Category:Stormwater management Category:Software using the GNU General Public License Category:Free software programmed in C++