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{{alert|This site was recently updated and is undergoing review. Please submit comments to [mailto:mike.trojan@state.mn.us Mike Trojan at the MPCA]. Anticipated completion date is August, 2015.|alert-under-review}}
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{{alert|several proprietary software models are included in this discussion. Inclusion of these models does not represent an endorsement by the Minnesota Pollution Control Agency (MPCA)|alert-info}}
 
 
{{alert|several proprietray software models are included in this discussion. Inclusion of these models does not represent an endorsement by the Minnesota Pollution Control Agency (MPCA)|alert-info}}
 
  
 
Hydrologic, hydraulic, and water quality models all have different purposes and will provide different information. The tables shown at the bottom of this page summarize some of the commonly used modeling software and modeling functions and the main purpose for which they were developed (NOTE: the information in these tables can be downloaded as an [http://stormwater.pca.state.mn.us/index.php/File:Model_Matrix.xlsx Excel file]). The tables show the relative levels of complexity of necessary input data, indicate whether the model can complete a continuous analysis or is event based, list whether the model is in the public domain, and for hydraulic models indicate whether unsteady flow calculations can be conducted. For water quality models, the tables indicate whether the model is a receiving waters model, a loading model, or a BMP analysis model. The following definitions apply to the model functions.
 
Hydrologic, hydraulic, and water quality models all have different purposes and will provide different information. The tables shown at the bottom of this page summarize some of the commonly used modeling software and modeling functions and the main purpose for which they were developed (NOTE: the information in these tables can be downloaded as an [http://stormwater.pca.state.mn.us/index.php/File:Model_Matrix.xlsx Excel file]). The tables show the relative levels of complexity of necessary input data, indicate whether the model can complete a continuous analysis or is event based, list whether the model is in the public domain, and for hydraulic models indicate whether unsteady flow calculations can be conducted. For water quality models, the tables indicate whether the model is a receiving waters model, a loading model, or a BMP analysis model. The following definitions apply to the model functions.
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SWMM-Based Programs [http://www2.epa.gov/water-research/storm-water-management-model-swmm SWMM] is a hydraulic and hydrologic modeling system that also has a water quality component. Please see the full description above for more details on the model. The Storm Water Management Model (SWMM) was originally developed for the Environmental Protection Agency (EPA) in 1971. SWMM is a dynamic rainfall-runoff and water quality simulation model, primarily but not exclusively for urban areas, for single-event or long-term (continuous) simulation.  Version 5 of SWMM was developed in 2005 and has been updated multiple times since.  The Storm Water Management Model (SWMM) is a comprehensive computer model for analysis of quantity and quality problems associated with urban runoff. Both single-event and continuous simulation can be performed on catchments having storm sewers, or combined sewers and natural drainage, for prediction of flows, stages and pollutant concentrations. Extran Block solves complete dynamic flow routing equations (St. Venant equations) for accurate simulation of backwater, looped connections, surcharging, and pressure flow. A modeler can simulate all aspects of the urban hydrologic and quality cycles, including rainfall, snow melt, surface and subsurface runoff, flow routing through drainage network, storage and treatment. Statistical analyses can be performed on long-term precipitation data and on output from continuous simulation. SWMM can be used for planning and design. Planning mode is used for an overall assessment of urban runoff problem or proposed abatement options.  
 
SWMM-Based Programs [http://www2.epa.gov/water-research/storm-water-management-model-swmm SWMM] is a hydraulic and hydrologic modeling system that also has a water quality component. Please see the full description above for more details on the model. The Storm Water Management Model (SWMM) was originally developed for the Environmental Protection Agency (EPA) in 1971. SWMM is a dynamic rainfall-runoff and water quality simulation model, primarily but not exclusively for urban areas, for single-event or long-term (continuous) simulation.  Version 5 of SWMM was developed in 2005 and has been updated multiple times since.  The Storm Water Management Model (SWMM) is a comprehensive computer model for analysis of quantity and quality problems associated with urban runoff. Both single-event and continuous simulation can be performed on catchments having storm sewers, or combined sewers and natural drainage, for prediction of flows, stages and pollutant concentrations. Extran Block solves complete dynamic flow routing equations (St. Venant equations) for accurate simulation of backwater, looped connections, surcharging, and pressure flow. A modeler can simulate all aspects of the urban hydrologic and quality cycles, including rainfall, snow melt, surface and subsurface runoff, flow routing through drainage network, storage and treatment. Statistical analyses can be performed on long-term precipitation data and on output from continuous simulation. SWMM can be used for planning and design. Planning mode is used for an overall assessment of urban runoff problem or proposed abatement options.  
 
Current update of SWMM includes the capability to model the flow rate, flow depth and quality of Low Impact Development (LID) controls, including permeable pavement, rain gardens, green roofs, street planters, rain barrels, infiltration trenches, and vegetative swales
 
Current update of SWMM includes the capability to model the flow rate, flow depth and quality of Low Impact Development (LID) controls, including permeable pavement, rain gardens, green roofs, street planters, rain barrels, infiltration trenches, and vegetative swales
The SWMM program is available to the public. The proprietary shells, PC-SWMM, InfoSWMM, and Mike Urban, provide the basic computations of EPASWMM with a graphic user interface, additional tools, and some additional computational capabilities.
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The SWMM program is available to the public. The proprietary shells, [http://www.chiwater.com/Software/PCSWMM/ PC-SWMM], [http://www.innovyze.com/products/infoswmm/ InfoSWMM], and [http://www.mikepoweredbydhi.com/products/mike-urban Mike Urban], provide the basic computations of EPASWMM with a graphic user interface, additional tools, and some additional computational capabilities.
  
 
===XPSWMM===
 
===XPSWMM===
[http://xpsolutions.com/software/xpswmm/ XPSWMM] is a propriety model that originally began as a SWMM based program.  The model developer, XP Software Company has developed many upgrades that are independent of the USEPA upgrades to SWMM.  Because of these upgrades the two software platforms are no longer interchangeable.  XP SWMM does have a function that allows model data to be exported in SWMM format.  Comparison of model results between the two softwares will result in similar, but not identical, results.
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[http://xpsolutions.com/software/xpswmm/ XPSWMM] is a propriety model that originally began as a SWMM based program.  The model developer has developed many upgrades that are independent of the USEPA upgrades to SWMM.  Because of these upgrades the two software platforms are no longer interchangeable.  XP SWMM does have a function that allows model data to be exported in SWMM format.  Comparison of model results between the two softwares will result in similar, but not identical, results.
  
XP SWMM’s hydrologic and hydraulic capabilities includes modeling of floodplains, river systems, stormwater systems, BMPs (including green infrastructure), watersheds, sanitary sewers, and combined sewers.  Pollutant modeling capabilities include pollutant and sediment loading and transport as well as pollutant removal for a suite of BMPs. XP-SWMM is available from XP Solutions.
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XP SWMM’s hydrologic and hydraulic capabilities includes modeling of floodplains, river systems, stormwater systems, BMPs (including green infrastructure), watersheds, sanitary sewers, and combined sewers.  Pollutant modeling capabilities include pollutant and sediment loading and transport as well as pollutant removal for a suite of BMPs. XP-SWMM is available from [http://xpsolutions.com/software/xpswmm/ XP Solutions].
  
 
===WinSLAMM===
 
===WinSLAMM===
The Source Loading and Management Model is a stormwater quality model developed for the USGS by John Voorhees and Robert Pitt for evaluation of nonpoint pollution in urban areas. The model is based on field observations of infiltration practices, wet detention ponds, porous pavement, street sweeping and other source area and outfall control practices. The focus of the model is on small storm hydrology and particulate washoff. The [http://winslamm.com/ WinSLAMM] model may be obtained from PV & Associates. Local Wisconsin data files for input into SLAMM may be obtained from the U.S. Geological Survey.
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The Source Loading and Management Model is a stormwater quality model developed for the USGS by John Voorhees and Robert Pitt for evaluation of nonpoint pollution in urban areas. The model is based on field observations of grass swales, wet detention ponds, porous pavement, filter strips, cisterns and rain barrels, hydrodynamic settling devices, rain gardens/biofilters and street sweeping, as either other source area or outfall control practices. The focus of the model is on small storm hydrology and particulate washoff. The [http://winslamm.com/ WinSLAMM] model may be obtained from PV & Associates. Wisconsin data files for input into SLAMM may be obtained from the U.S. Geological Survey, and the model provides an extensive set of rainfall, runoff and particulate solids and other pollutant files developed from the [http://www.bmpdatabase.org/nsqd.html National Stormwater Quality Data Base] for most urban areas in the county.
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The graphical interface allows users to define both source area and drainage system stormwater control practices using a drag-and-drop interface, and the program and web site provides extensive program help and stormwater quality references.
  
 
===P8===
 
===P8===
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===BASINS===
 
===BASINS===
 
The [http://water.epa.gov/scitech/datait/models/basins/ Better Assessment Science Integrating Point and Nonpoint Sources (BASINS)] model is a multipurpose surface water environmental analysis system developed by the U.S. Environmental Protection Agency’s (EPA’s) Office of Water. The model was originally introduced in 1996 and has had subsequent releases in 1998 and 2001. BASINS allows for the assessment of large amounts of point and non-point source data in a format that is easy to use and understand. BASINS incorporates a number of model interfaces that it uses to assess water quality at selected stream sites or throughout the watershed. These model interfaces include:
 
The [http://water.epa.gov/scitech/datait/models/basins/ Better Assessment Science Integrating Point and Nonpoint Sources (BASINS)] model is a multipurpose surface water environmental analysis system developed by the U.S. Environmental Protection Agency’s (EPA’s) Office of Water. The model was originally introduced in 1996 and has had subsequent releases in 1998 and 2001. BASINS allows for the assessment of large amounts of point and non-point source data in a format that is easy to use and understand. BASINS incorporates a number of model interfaces that it uses to assess water quality at selected stream sites or throughout the watershed. These model interfaces include:
*QUAL2E: A water quality and eutrophication model
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*[http://www.epa.gov/ATHENS/wwqtsc/html/qual2k.html QUAL2E]: A water quality and eutrophication model
*WinHSPF: A watershed scale model for estimating in-stream concentrations resulting from loadings from point and non-point sources
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*[http://www.aquaterra.com/resources/hspfsupport/index.php WinHSPF]: A watershed scale model for estimating in-stream concentrations resulting from loadings from point and non-point sources
*SWAT: A physical based, watershed scale model that was developed to predict the impacts of land management practices on water, sediment and agricultural chemical yields in large complex watersheds with varying soils, land uses and management conditions over long periods of time.
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*[http://swat.tamu.edu/ SWAT]: A physical based, watershed scale model that was developed to predict the impacts of land management practices on water, sediment and agricultural chemical yields in large complex watersheds with varying soils, land uses and management conditions over long periods of time.
*PLOAD: A pollutant loading model.
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*[http://water.epa.gov/scitech/datait/models/basins/framework.cfm#models PLOAD]: A pollutant loading model.
  
 
===PONDNET===
 
===PONDNET===
The PONDNET model (Walker, 1987) is an empirical model developed to evaluate flow and phosphorous routing in Pond Networks. The following input parameters are defined by the user in evaluating the water quality performance of a pond: watershed area (acres), runoff coefficient, pond surface area (acres), pond mean depth (feet), period length (years), period precipitation (inches) and phosphorous concentrations (ppb). The spreadsheet is designed so that the phosphorous removal of multiple ponds in series can be evaluated.
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The [http://wwwalker.net/ PONDNET] model (Walker, 1987) is an empirical model developed to evaluate flow and phosphorous routing in Pond Networks. The following input parameters are defined by the user in evaluating the water quality performance of a pond: watershed area (acres), runoff coefficient, pond surface area (acres), pond mean depth (feet), period length (years), period precipitation (inches) and phosphorous concentrations (ppb). The spreadsheet is designed so that the phosphorous removal of multiple ponds in series can be evaluated.
  
 
===WiLMS===
 
===WiLMS===
The Wisconsin Lake Modeling Suite (WiLMS) is a screening level land use management/lake water quality evaluation tool developed by the Wisconsin Department of Natural Resources. It is a spreadsheet of thirteen lake model equations used to predict the total phosphorus (TP) concentration in a lake. TP loads can be entered either as point sources or by entering export coefficients for land uses. WiLMS can be downloaded for free at the Wisconsin DNR Web page.
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The [http://dnr.wi.gov/lakes/model/ Wisconsin Lake Modeling Suite (WiLMS)] is a screening level land use management/lake water quality evaluation tool developed by the Wisconsin Department of Natural Resources. It is a spreadsheet of thirteen lake model equations used to predict the total phosphorus (TP) concentration in a lake. TP loads can be entered either as point sources or by entering export coefficients for land uses. WiLMS can be downloaded for free at the Wisconsin DNR Web page.
  
 
===Bathtub===
 
===Bathtub===
Bathtub is an empirical model of reservoir eutrophication developed by the U.S. Army Corps of Engineers. Single basins can be modeled, in addition to a network of basins that interact with one another. The model uses steady-state water and nutrient balance calculations in a spatially segmented hydraulic network, which accounts for advective and diffusive transport and nutrient sedimentation.
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[http://wwwalker.net/bathtub/help/bathtub_overview.htm Bathtub] is an empirical model of reservoir eutrophication developed by the U.S. Army Corps of Engineers. Single basins can be modeled, in addition to a network of basins that interact with one another. The model uses steady-state water and nutrient balance calculations in a spatially segmented hydraulic network, which accounts for advective and diffusive transport and nutrient sedimentation.
  
 
===WASP===
 
===WASP===
WASP, Water Quality Analysis Simulation Program, is a model developed by the U.S. EPA to evaluate the fate and transport of contaminants in surface waters such as lakes and ponds. The model evaluates advection, dispersion, mass loading, and boundary exchange in one, two, or three dimensions. A variety of pollutants can be modeled with this program including nutrients, dissolved oxygen, BOD, algae, organic chemicals, metals, pathogens, and temperature.
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[http://www.epa.gov/athens/wwqtsc/html/wasp.html WASP], Water Quality Analysis Simulation Program, is a model developed by the U.S. EPA to evaluate the fate and transport of contaminants in surface waters such as lakes and ponds. The model evaluates advection, dispersion, mass loading, and boundary exchange in one, two, or three dimensions. A variety of pollutants can be modeled with this program including nutrients, dissolved oxygen, BOD, algae, organic chemicals, metals, pathogens, and temperature.
  
 
===SUSTAIN===
 
===SUSTAIN===
SUSTAIN (System for Urban Stormwater Treatment and Analysis Integration) was developed by the USEPA to assist stormwater professionals in developing and implementing plans for stormwater flow and pollutant controls on a watershed scale.  SUSTAIN contains seven modules that integrate with ArcGIS.  Hydrology, hydraulics, and pollutant loading are computed using EPASWMM, Version 5.  Sediment transport is based on HSPF.  Modules include:
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[http://www2.epa.gov/water-research/system-urban-stormwater-treatment-and-analysis-integration-sustain SUSTAIN] (System for Urban Stormwater Treatment and Analysis Integration) was developed by the USEPA to assist stormwater professionals in developing and implementing plans for stormwater flow and pollutant controls on a watershed scale.  SUSTAIN contains seven modules that integrate with ArcGIS.  Hydrology, hydraulics, and pollutant loading are computed using EPASWMM, Version 5.  Sediment transport is based on HSPF.  Modules include:
 
*Framework manager
 
*Framework manager
 
*BMP siting tool
 
*BMP siting tool
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===MIDS Calculator===
 
===MIDS Calculator===
The MIDS Calculator was developed by the MPCA as an Excel-based stormwater quality tool to predict the annual pollutant removal performance of low impact development (LID) BMPs.  The calculator will compute the volume reduction associated with infiltration practices plus the TSS and TP reductions for both LID and traditional BMPs, including permeable pavements, green roofs, bioretention, bioretention with underdrain (biofiltration), infiltration basin, tree trench, tree trench with underdrain, swale side slope, swale channels, swales with underdrains, wet swale, cistern/reuse, sand filter, constructed wetland and constructed stormwater pond.  
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The [http://stormwater.pca.state.mn.us/index.php/MIDS_calculator MIDS Calculator] was developed by the MPCA as an Excel-based stormwater quality tool to predict the annual pollutant removal performance of low impact development (LID) BMPs.  The calculator will compute the volume reduction associated with infiltration practices plus the TSS and TP reductions for both LID and traditional BMPs, including permeable pavements, green roofs, bioretention, bioretention with underdrain (biofiltration), infiltration basin, tree trench, tree trench with underdrain, swale side slope, swale channels, swales with underdrains, wet swale, cistern/reuse, sand filter, constructed wetland and constructed stormwater pond.
  
 
===STEPL===
 
===STEPL===
The Spreadsheet Tool for Estimating Pollutant Load (STEPL) was developed by the USEPA to calculate nutrient and sediment loads from different rural land uses and BMPs on a watershed scale.  STEPL provides a user-friendly interface to create a customized spreadsheet-based model in Microsoft (MS) Excel. It computes watershed surface runoff; nutrient loads, including nitrogen, phosphorus, and 5-day biological oxygen demand (BOD5); and sediment delivery. The annual sediment load (sheet and rill erosion only) is calculated based on the Universal Soil Loss Equation (USLE) and the sediment delivery ratio. The sediment and pollutant load reductions that result from the implementation of BMPs are computed using the known BMP efficiencies.
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The [http://it.tetratech-ffx.com/steplweb/models$docs.htm Spreadsheet Tool for Estimating Pollutant Load (STEPL)] was developed by the USEPA to calculate nutrient and sediment loads from different rural land uses and BMPs on a watershed scale.  STEPL provides a user-friendly interface to create a customized spreadsheet-based model in Microsoft (MS) Excel. It computes watershed surface runoff; nutrient loads, including nitrogen, phosphorus, and 5-day biological oxygen demand (BOD5); and sediment delivery. The annual sediment load (sheet and rill erosion only) is calculated based on the Universal Soil Loss Equation (USLE) and the sediment delivery ratio. The sediment and pollutant load reductions that result from the implementation of BMPs are computed using the known BMP efficiencies.
  
===Virginia Model===
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===[http://www.vwrrc.vt.edu/swc/Virginia%20Runoff%20Reduction%20Method.html Virginia Model]===
  
 
===USEPA National Stormwater Calculator===
 
===USEPA National Stormwater Calculator===
The National Stormwater Calculator is a tool developed by the USEPA for computing small site hydrology for any location within the U.S. (http://www.epa.gov/nrmrl/wswrd/wq/models/swc/). It estimates the amount of stormwater runoff generated from a site under different development and control scenarios over a long term period of historical rainfall. The analysis takes into account local soil conditions, slope, land cover and meteorology. Different types of low impact development (LID) practices (also known as green infrastructure) can be employed to help capture and retain rainfall on-site. Future climate change scenarios taken from internationally recognized climate change projections can also be considered.  The calculator’s primary focus is informing site developers and property owners on how well they can meet a desired stormwater retention target.
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The [http://www2.epa.gov/water-research/national-stormwater-calculator National Stormwater Calculator] is a tool developed by the USEPA for computing small site hydrology for any location within the U.S. (http://www.epa.gov/nrmrl/wswrd/wq/models/swc/). It estimates the amount of stormwater runoff generated from a site under different development and control scenarios over a long term period of historical rainfall. The analysis takes into account local soil conditions, slope, land cover and meteorology. Different types of low impact development (LID) practices (also known as green infrastructure) can be employed to help capture and retain rainfall on-site. Future climate change scenarios taken from internationally recognized climate change projections can also be considered.  The calculator’s primary focus is informing site developers and property owners on how well they can meet a desired stormwater retention target.
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===Autodesk Civil 3D===
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Autodesk Civil 3D includes additional software applications that allow you to perform a variety of storm water management tasks, including storm sewer design, watershed analysis, detention pond modeling, and culvert, channel, and inlet analysis. [https://knowledge.autodesk.com/support/civil-3d/learn-explore/caas/CloudHelp/cloudhelp/2019/ENU/Civil3D-UserGuide/files/GUID-F11FAAD6-F3D3-4FC7-8315-BF8329E5E35B-htm.html For more information, link here].
  
 
==Table summarizing models by model type==
 
==Table summarizing models by model type==
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{{:Summary of model information}}
 
{{:Summary of model information}}
  
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<noinclude>
 
==References==
 
==References==
 
*USEPA, 2009. [http://www.epa.gov/crem/library/cred_guidance_0309.pdf Guidance on the Development, Evaluation, and Application of Environmental Models].  Office of the Science Advisor, Council for Regulatory Environmental Modeling.
 
*USEPA, 2009. [http://www.epa.gov/crem/library/cred_guidance_0309.pdf Guidance on the Development, Evaluation, and Application of Environmental Models].  Office of the Science Advisor, Council for Regulatory Environmental Modeling.
 
*WEF, ASCE/EWRI. 2012.  [http://news.wef.org/wef-releases-design-of-urban-stormwater-controls-mop-23/ Design of Urban Stormwater Controls, WEF Manual of Practice No. 23]. ASCE/EWRI Manuals and Reports on Engineering Practice No. 87.  Prepared by the Design of Urban Stormwater Controls Task Forces of the Water Environment Federation and the American Society of Civil Engineers/Environmental & Water Resources Institute.
 
*WEF, ASCE/EWRI. 2012.  [http://news.wef.org/wef-releases-design-of-urban-stormwater-controls-mop-23/ Design of Urban Stormwater Controls, WEF Manual of Practice No. 23]. ASCE/EWRI Manuals and Reports on Engineering Practice No. 87.  Prepared by the Design of Urban Stormwater Controls Task Forces of the Water Environment Federation and the American Society of Civil Engineers/Environmental & Water Resources Institute.
  
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==Related pages==
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*[[Introduction to stormwater modeling]]
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*[[Available stormwater models and selecting a model]]
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*[[Detailed information on specific models]]
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*[[What is the pre-development condition]]
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*[http://stormwater.pca.state.mn.us/index.php/Minimal_Impact_Design_Standards Minimal Impact Design Standards]
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*[http://stormwater.pca.state.mn.us/index.php/Unified_sizing_criteria_section Unified sizing criteria]
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*[http://stormwater.pca.state.mn.us/index.php/Stormwater_pollutant_removal,_stormwater_credits Stormwater pollutant removal and stormwater credits]
  
<!--
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[[category:Models and calculators]]
TEXT BELOW IS FROM THE ORIGINAL STORMWATER MANUAL
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</noinclude>
Hydrologic, hydraulic, and water quality models all have different purposes and will provide different information. The table below summarizes some of the commonly used modeling software and modeling techniques and the main purpose for which they were developed. The table shows the relative levels of complexity of necessary input data, indicates whether the model can complete a continuous analysis or is event based, lists whether the model is in the public domain, and for hydraulic models indicates whether unsteady flow calculations can be conducted. For water quality models, the table indicates whether the model is a receiving waters model, a loading model, or a BMP analysis model.
 
 
 
{{:Modeling tool selection}}
 
 
 
The selection of a stormwater modeling tool is based on the modeling objectives and on the available resources. When evaluating the modeling objectives, the modeler should consider
 
*the type of information desired from the modeling effort;
 
*the specific conditions to be modeled;
 
*the required level of accuracy and reliability of the model; and
 
*the further use of the model and model results.
 
For example, estimating peak runoff rates is a different problem than estimating the peak elevation of a water body and could require the use of a different model. A model able to estimate phosphorus loading from a network of detention ponds may not be able to model the phosphorus loading from an infiltration pond.
 
<p>When evaluating the resources available, the modeler should consider
 
*the general limitations of modeling which include imperfect approximations of natural processes, uncertainty and variability in results, and uncertainty and error in the input parameters;
 
*availability of existing models used for site analysis;
 
*familiarity with the specific model; and
 
*modeling expertise available.</p>
 
 
 
==Hydrologic models==
 
Hydrologic models are used to estimate runoff volumes, peak flows, and the temporal distribution of runoff at a particular location resulting from a given precipitation record or event. Essentially, hydrologic models are used to predict how the site topography, soil characteristics, and land cover will cause runoff either to flow relatively unhindered through the system to a point of interest, or to be delayed or retained somewhere upstream. Many hydrologic models also include relatively simple procedures to route runoff hydrographs through storage areas or channels, and to combine hydrographs from multiple watersheds.
 
 
 
===Rational method===
 
The rational method is a simple calculation of peak flow based on drainage area, rainfall intensity, and a non-dimensional runoff coefficient. The peak flow is calculated as the rainfall intensity in inches per hour multiplied by the runoff coefficient and the drainage area in acres. The peak flow, Q, is calculated in cubic feet per second (cfs) as Q = CiA where C is the runoff coefficient, i is the rainfall intensity, and A is the drainage area. A conversion factor of 1.008 is necessary to convert acre-inches per hour to cfs, but this is typically not used. This method is best used only for simple approximations of peak flow from small watersheds.
 
 
 
===HEC-1===
 
[http://www.hec.usace.army.mil/software/legacysoftware/hec1/documentation/hec1user.pdf HEC-1] is a rainfall-runoff model developed by the U.S. Army Corps of Engineers. HEC-1 is a single storm event, lumped parameter model that includes several options for modeling rainfall, losses, unit hydrographs, and stream routing. The model is designed to simulate the surface runoff response of a river basin to precipitation by representing the basin as an interconnected system of hydrologic and hydraulic components. Each component models an aspect of the precipitationrunoff process within a portion of the basin. A component may represent a surface runoff entity, a stream channel, or a reservoir. Representation of a component requires a set of parameters which specify the particular characteristics of the component and mathematical relations which describe the physical processes. The result of the modeling process is the computation of stream flow hydrographs at the desired locations in the river basin. The upgraded version of this model is HEC-HMS.
 
 
 
===HEC-HMS===
 
[http://www.hec.usace.army.mil/software/hec-hms/ HEC-HMS] is a rainfall-runoff model developed by the U.S. Army Corps of Engineers to compute runoff hydrographs for a network of watersheds. The model evaluates infiltration losses, transforms precipitation into runoff hydrographs, and routes hydrographs through open channel routing. A variety of calculation methods can be selected including SCS curve number or Green and Ampt infiltration, Clark, Snyder or SCS unit hydrograph methods, and Muskingum, Puls, or lag routing methods. Precipitation inputs can be evaluated using a number of historical or synthetic methods and one evapotranspiration method.
 
 
 
===TR-20===
 
[http://www.nrcs.usda.gov/wps/portal/nrcs/detailfull/?ss=16&navtype=BROWSEBYSUBJECT&cid=stelprdb1042793&navid=140100000000000&pnavid=140000000000000&position=Not%20Yet%20Determined.Html&ttype=detailfull&pname=WinTR-20%20Watershed%20Hydrology%20%7C%20NRCS Natural Resources Conservation Service Technical Release No. 20] (TR-20): Computer Program for Project Formulation Hydrology was developed by the hydrology branch of the U.S.D.A. Soil Conservation Service in 1964. it was last updated in 2009.
 
 
 
WinTR-20 is a single event watershed scale runoff and routing model. It computes direct runoff and develops hydrographs resulting from any synthetic or natural rainstorm. Developed hydrographs are routed through stream and valley reaches as well as through reservoirs. Hydrographs are combined from tributaries with those on the main stream. Branching flow (diversion), and baseflow can also be accommodated. WinTR-20 may be used to evaluate flooding problems, alternatives for flood control (reservoirs, channel modification, and diversion), and impacts of changing land use on the hydrologic response of watersheds.
 
 
 
A new routine has been added to the program that allows the user to import NOAA Atlas 14 rainfall data for site-specific applications. The rainfall-frequency data will be used to develop site-specific rainfall distributions. The NOAA 14 text files for selected Eastern states are available in the Support Materials for downloading and use in WinTR-20 Version 1.11. The NOAA 14 text files and supporting GIS files are packaged in a zip file for each state.
 
 
 
===Win TR-55===
 
[http://www.cpesc.org/reference/tr55.pdf Technical Release 55] (TR-55; ''Urban Hydrology for Small Watersheds'') was developed by the U.S.D.A. Soil Conservation Service, now the Natural Resources Conservation Service (NRCS), in 1975 as a simplified procedure to calculate storm runoff volume, peak rate of discharge, hydrographs and storage volumes. In 1998, Technical Release 55 and the computer software were revised to what is now called WinTR-55. The changes in this revised version of TR-55 include: upgraded source code to Visual Basic, changed philosophy of data input, development of a Windows interface and output post-processor, enhanced hydrograph-generation capability of the software and flood routing hydrographs through stream reaches and reservoirs.
 
<p>WinTR-55 is a single-event rainfall-runoff small watershed hydrologic model. The model is an input/output interface which runs WinTR-20 in the background to generate, route and add hydrographs. The WinTR-55 generates hydrographs from both urban and agricultural areas at selected points along the stream system. Hydrographs are routed downstream through channels and/or reservoirs. Multiple sub-areas can be modeled within the watershed. A rainfall-runoff analysis can be performed on up to ten sub-areas and up to ten reaches. The total drainage area modeled cannot exceed 25 square miles. </p>
 
 
 
==Hydraulic models==
 
===HEC-RAS===
 
HEC-RAS is a river hydraulics model developed by the U.S. Army Corps of Engineers to compute one-dimensional water surface profiles for steady or unsteady flow. Computation of steady flow water surface profiles is intended for flood plain studies and floodway encroachment evaluations. HEC-RAS uses the solution of the one-dimensional energy equation with energy losses evaluated for friction and contraction and expansion losses in order to compute water surface profiles. In areas with rapidly varied water surface profiles, HEC-RAS uses the solution of the momentum equation. Unsteady flow simulation can evaluate subcritical flow regimes as well as mixed flow regimes including supercritical, hydraulic jumps, and draw downs. Sediment transport calculation capability will be added in future versions of the model. The HEC-RAS program is available to the public from the [http://www.hec.usace.army.mil/software/hec-ras/hecras-download.html U.S. Army Corps of Engineers].
 
 
 
===HEC-2===
 
HEC-2 is a rainfall-runoff model developed by the U.S. Army Corps of Engineers to compute steady-state water surface elevation profiles in natural and constructed channels. HEC-2 uses the standard step method for water surface profile calculations assuming that flow is one- dimensional, gradually varied steady flow. Subcritical and supercritical flow profiles may be evaluated.
 
<p>The water surface profile through structures such as bridges, culverts, weirs and other types of structures can be computed. The upgraded version of this model is HEC-RAS. The HEC-2 program is available to the public and can be downloaded from the [http://www.hec.usace.army.mil/software/legacysoftware/hec1/hec1-download.htm U.S. Army Corps of Engineers].</p>
 
 
 
===WSPRO===
 
WSPRO is a model for water surface profile computations developed by the U.S. Geological Survey. The model evaluates one-dimensional water surface profiles for systems with gradually varied, steady flow. The open channel calculations are conducted using backwater techniques and energy balancing methods. Single opening bridges use the orifice flow equation and flow through culverts is computed using a regression equation at the inlet and an energy balance at the outlet. The WSPRO program is available to the public and can be downloaded from the [http://water.usgs.gov/software/wspro.html U.S. Geological Survey].
 
 
 
===CULVERTMASTER===
 
CulvertMaster is a hydraulic analysis program for culvert design. The model uses the U.S. Federal Highway Administration Hydraulic Design of Highway Culverts methodology to provide estimates for headwater elevation, hydraulic grade lines, discharge, and culvert sizing. Rainfall and watershed analysis using the SCS Method or Rational Method can be incorporated if the peak flow rate is not known. CulvertMaster is a proprietary model.
 
 
 
===FLOWMASTER===
 
FlowMaster is a hydraulic analysis program used for the design and analysis of open channels, pressure pipes, inlets, gutters, weirs, and orifices. Mannings, Hasen-Williams, Kutter, Darcy-
 
Weisbach, or Colebrook-White equations are used in the calculations. FlowMaster is a proprietary model that can be obtained from [http://www.bentley.com/en-US/Products/FlowMaster/ Haestad Methods, Bentley Systems, Inc.]
 
 
 
==Combined hydraulic and hydrologic models==
 
 
 
===HydroCAD===
 
HydroCAD is a computer aided design program for modeling the hydrology and hydraulics of
 
stormwater runoff. Runoff hydrographs are computed using the SCS runoff equation and the SCS dimensionless unit hydrograph. For the hydrologic computations, there is no provision for recovery of initial abstraction or infiltration during periods of no rainfall within an event. The program computes runoff hydrographs, routes flows through channel reaches and reservoirs, and combines hydrographs at confluences of the watershed stream system. HydroCAD has the ability to simulate backwater conditions by allowing the user to define the backwater elevation prior to simulating a rainfall event. HydroCAD is a proprietary model and can be obtained from [http://www.hydrocad.net/ HydroCAD Software Solutions LLC].
 
 
 
===PondPack===
 
PondPack is a program for modeling and design of the hydrology and hydraulics of storm water runoff and pond networks. Rainfall analyses can be conducted using a number of synthetic or historic storm events using methods such as SCS rainfall distributions, intensity-duration-frequency curves, or recorded rainfall data. Infiltration and runoff can be computed using the
 
SCS curve number method or the Green and Ampt or Horton infiltration methods. Hydrographs are computed using the SCS Method or the Rational Method. Channel routing is conducted using the Muskingun, translation, or Modified Puls methods. Outlet calculations can be performed for outlets such as weirs, culverts, orifices, and risers. The program can assist in the determination of pond sizes. PondPack is a proprietary model that can be obtained from [http://www.bentley.com/en-US/Products/PondPack/ Haestad Methods, Bentley Systems, Inc.]
 
 
 
===SWMM-Based programs===
 
The Storm Water Management Model (SWMM) was originally developed for the Environmental
 
Protection Agency (EPA) in 1971 by Metcalf and Eddy, Inc., Water Resources Engineers, Inc. and the University of Florida. SWMM is a dynamic rainfall-runoff and water quality simulation model, primarily but not exclusively for urban areas, for single-event or long-term (continuous) simulation.
 
<p>The Storm Water Management Model (SWMM) is a comprehensive computer model for analysis of quantity and quality problems associated with urban runoff. Both single-event and continuous simulation can be performed on catchments having storm sewers, or combined sewers and natural drainage, for prediction of flows, stages and pollutant concentrations. Extran Block solves complete dynamic flow routing equations (St. Venant equations) for accurate simulation of backwater, looped connections, surcharging, and pressure flow. A modeler can simulate all aspects of the urban hydrologic and quality cycles, including rainfall, snow melt, surface and subsurface runoff, flow routing through drainage network, storage and treatment. Statistical analyses can be performed on long-term precipitation data and on output from continuous simulation. SWMM can be used for planning and design. Planning mode is used for an overall assessment of urban runoff problem or proposed abatement options. The SWMM program is [http://www2.epa.gov/water-research/storm-water-management-model-swmm available] to the public. The proprietary shells, XP-SWMM and PC-SWMM, provide the basic computations of EPASWMM with a graphic user interface, additional tools, and some additional computational capabilities. XP-SWMM is available from the [http://xpsolutions.com/Software/XPSWMM/ XP Software] company and PC-SWMM is available from [http://www.chiwater.com/Software/PCSWMM/ Computational Hydraulics International].</p>
 
 
 
==Water quality models==
 
Water quality models are used to evaluate the effectiveness of a BMP, simulate water quality conditions in a lake, stream, or wetland, and to estimate the loadings to water bodies. Often the goal is to evaluate how some external factor (such as a change in land use or land cover, the use of best management practices, or a change in lake internal loading) will affect water quality. Parameters that are frequently modeled include total phosphorus, total suspended solids, and dissolved oxygen.
 
 
 
===SLAMM===
 
The Source Loading and Management Model is a water quality model developed by John Voorhees and Robert Pitt for evaluation of nonpoint pollution in urban areas. The model is based on field observations of infiltration practices, wet detention ponds, porous pavement, street sweeping and other source area and outfall control practices. The focus of the model is on small storm hydrology and particulate washoff. Local data files for input into SLAMM may be obtained from the [http://wi.water.usgs.gov/slamm/ U.S. Geological Survey]. The SLAMM model may be obtained from [http://www.winslamm.com/ PV & Associates].
 
 
 
===P8===
 
[http://wwwalker.net/ P8] - Program for Predicting Polluting Particle Passage through Pits, Puddles & Ponds, is a physically-based model developed by William Walker to predict the generation and transport of stormwater runoff pollutants in urban watersheds. The model simulates runoff and pollutant transport for a maximum of 24 watersheds, 24 stormwater best management practices (BMPs), 5 particle size classes, and 10 water quality components. The model simulates pollutant transport and removal in a variety of BMPs including swales, buffer strips, detention ponds (dry, wet and extended), flow splitters, and infiltration basins (offline and online). Model simulations are driven by a continuous hourly rainfall time series. P8 has been designed to require a minimum of site-specific data, which are expressed in terminology familiar to most engineers and planners. An extensive user interface providing interactive operation, spreadsheet-like menus, help screens and high resolution graphics facilitate model use.
 
 
 
===BASINS===
 
The [http://water.epa.gov/scitech/datait/models/basins/index.cfm Better Assessment Science Integrating Point and Nonpoint Sources] (BASINS) model is a multipurpose environmental analysis system developed by the U.S. Environmental Protection Agency’s (EPA’s) Office of Water. The model was originally introduced in 1996 and has had subsequent releases in 1998 and 2001. BASINS allows for the assessment of large amounts of point and non-point source data in a format that is easy to use and understand. BASINS incorporates a number of model interfaces that it uses to assess water quality at selected stream sites or throughout the watershed. These model interfaces include:
 
* QUAL2E: A water quality and eutrophication model
 
* WinHSPF: A watershed scale model for estimating in-stream concentrations resulting from loadings from point and non-point sources
 
* SWAT: A physical based, watershed scale model that was developed to predict the impacts of land management practices on water, sediment and agricultural chemical yields in large complex watersheds with varying soils, land uses and management conditions over long periods of time.
 
* PLOAD: A pollutant loading model.
 
 
 
===PONDNET===
 
The [http://wwwalker.net/ PONDNET] model (Walker, 1987) is an empirical model developed to evaluate flow and phosphorous routing in Pond Networks. The following input parameters are defined by the user in evaluating the water quality performance of a pond: watershed area (acres), runoff coefficient, pond surface area (acres), pond mean depth (feet), period length (years), period precipitation (inches) and phosphorous concentrations (ppb). The spreadsheet is designed so that the phosphorous removal of multiple ponds in series can be evaluated.
 
 
 
===WiLMS===
 
The [http://dnr.wi.gov/lakes/model/ Wisconsin Lake Modeling Suite] (WiLMS) is a screening level land use management/lake water quality evaluation tool developed by the Wisconsin Department of Natural Resources. It is a spreadsheet of thirteen lake model equations used to predict the total phosphorus (TP) concentration in a lake. TP loads can be entered either as point sources or by entering export coefficients for land uses. WiLMS can be downloaded for free at the following Wisconsin DNR Web site:
 
 
 
===Bathtub===
 
[http://el.erdc.usace.army.mil/products.cfm?Topic=model&Type=watqual Bathtub] is an empirical model of reservoir eutrophication developed by the U.S. Army Corps of Engineers. Single basins can be modeled, in addition to a network of basins that interact with one another. The model uses steady-state water and nutrient balance calculations in a spatially segmented hydraulic network, which accounts for advective and diffusive transport and nutrient sedimentation.
 
 
 
===WASP===
 
[http://www.epa.gov/athens/wwqtsc/html/wasp.html WASP], Water Quality Analysis Simulation Program, is a model developed by the U.S. EPA to evaluate the fate and transport of contaminants in surface waters such as lakes and ponds. The model evaluates advection, dispersion, mass loading, and boundary exchange in one, two, or three dimensions. A variety of pollutants can be modeled with this program including nutrients, dissolved oxygen, BOD, algae, organic chemicals, metals, pathogens, and temperature.
 
 
 
SWMM-Based Programs
 
SWMM is a hydraulic and hydrologic modeling system that also has a water quality component.
 
Please see the full description above for more details on the model.
 
-->
 

Revision as of 12:22, 8 April 2020

Information: several proprietary software models are included in this discussion. Inclusion of these models does not represent an endorsement by the Minnesota Pollution Control Agency (MPCA)

Hydrologic, hydraulic, and water quality models all have different purposes and will provide different information. The tables shown at the bottom of this page summarize some of the commonly used modeling software and modeling functions and the main purpose for which they were developed (NOTE: the information in these tables can be downloaded as an Excel file). The tables show the relative levels of complexity of necessary input data, indicate whether the model can complete a continuous analysis or is event based, list whether the model is in the public domain, and for hydraulic models indicate whether unsteady flow calculations can be conducted. For water quality models, the tables indicate whether the model is a receiving waters model, a loading model, or a BMP analysis model. The following definitions apply to the model functions.

  • Rainfall-Runoff Calculation Tool: peak flow, runoff volume, and hydrograph functions, only. More complex modeling should utilize hydrologic modeling which incorporate rainfall-runoff functions.
  • Hydrologic: includes rainfall-runoff simulation plus reservoir/channel routing.
  • Hydraulic: water surface profiles, flow rates, and flow velocities through waterways, structures and pipes. Models that include Green Infrastructure typically also assess how the BMPs managage the water through inflow, infiltration, evapotranspiration, storage and discharge.
  • Combined Hydrologic & Hydraulic: rainfall-runoff results become input into hydraulic calculations.
  • Water Quality: pollutant loading to surface waters or pollutant removal in a BMP.
  • BMP Calculators: spreadsheets that predict BMP performance, only.

Defining Model Objectives and Selecting a Stormwater Model

Environmental modeling, including stormwater and water quality modeling, is complex given the purpose is to mathematically predict natural processes (USEPA, 2009). Models range from simple spreadsheets that predict a single process such as the runoff from a single storm, to complex simulations that predict multiple, inter-related processes including performance of multiple BMPs. A greater amount of uncertainty is inherent in the more complex models, which results in more complexity in model calibration (WEF, 2012). For example, estimating peak runoff rates is a different problem than estimating the peak elevation of a water body and could require the use of a different model. A model able to estimate phosphorus loading from a network of detention ponds may not be able to model the phosphorus loading from an infiltration pond.

Therefore it is important that modelers select a stormwater modeling tool that is based on both modeling objectives and available resources. The USEPA recommends that the first step in development of a model is to define the objectives (USEPA, 2009). When defining the modeling objectives, the modelers and decision-makers should consider the following (WEF, 2012):

  • Regulatory compliance: is the model required for regulatory compliance? Which models are accepted by the regulatory agency?
  • Hydrologic process: is the goal to model a single storm event or continuous rainfall? Should the model incorporate infiltration, evaporation, transpiration, abstraction, and other physical processes that reduce the volume of runoff? Is the model required to predict large storm events (for flood control), small storm events (for water quality predictions), or both?
  • Land use: is the model required for large rural/agricultural catchments or small urban catchments?
  • Area to be modeled: will the model be required to predict stormwater for individual blocks? Or is a larger catchment scale acceptable?
  • Intended use: is the intended use for planning purposes, engineering/design, or operational performance?
  • Model complexity: will a simple model be sufficient?
  • Modeler experience: what is the model-specific expertise of current staff? Is there budget to hire an expert?

The actual process of selecting a model is likely to be an iterative process of model evaluation, adjustments to objectives and/or costs, re-evaluation, and ultimately model selection. Potentially, modelers may select multiple models to meet the objectives of the study. For example one model may be best for hydrology and hydraulics, while another may be best for BMP performance. In these circumstances the modelers should investigate the ability of the models to be linked (USEPA, 2009).

Summary of Common Stormwater Models

The following section describes the most common stormwater models used by stormwater professionals. Use the hyperlinks for additional information on these models.

Rational method

The Rational Method is a simple hydrologic calculation of peak flow based on drainage area, rainfall intensity, and a non-dimensional runoff coefficient. The peak flow is calculated as the rainfall intensity in inches per hour multiplied by the runoff coefficient and the drainage area in acres. The peak flow, Q, is calculated in cubic feet per second (cfs) as Q = CiA where C is the runoff coefficient, i is the rainfall intensity, and A is the drainage area. A conversion factor of 1.008 is necessary to convert acre-inches per hour to cfs, but this is typically not used. This method is best used only for simple approximations of peak flow from small watersheds.

HEC-HMS

HEC-HMS is a hydrologic rainfall-runoff model developed by the U.S. Army Corps of Engineers that is based on the rainfall-runoff prediction originally developed and released as HEC-1. HEC-HMS is used to compute runoff hydrographs for a network of watersheds. The model evaluates infiltration losses, transforms precipitation into runoff hydrographs, and routes hydrographs through open channel routing. A variety of calculation methods can be selected including SCS curve number or Green and Ampt infiltration; Clark, Snyder or SCS unit hydrograph methods; and Muskingum, Puls, or lag routing methods. Precipitation inputs can be evaluated using a number of historical or synthetic methods and one evapotranspiration method. HEC-HMS is used in combination with HEC-RAS for calculation of both the hydrology and hydraulics of a stormwater system or network.

TR-20

Natural Resources Conservation Service Technical Release No. 20 (TR-20): Computer Program for Project Formulation Hydrology was developed by the hydrology branch of the U.S.D.A. Soil Conservation Service in 1964. It was recently updated to allow users to import Atlas 14 precipitation data available from NOAA.

WinTR-20 is a single event watershed scale runoff and routing (hydrologic) model that is best suited to predict stream flows in large watersheds. It computes direct runoff and develops hydrographs resulting from any synthetic or natural rainstorm. Developed hydrographs are routed through stream and valley reaches as well as through reservoirs. Hydrographs are combined from tributaries with those on the main stream. Branching flow (diversion), and baseflow can also be accommodated. WinTR-20 may be used to evaluate flooding problems, alternatives for flood control (reservoirs, channel modification, and diversion), and impacts of changing land use on the hydrologic response of watersheds. A new routine has been added to the program that allows the user to import NOAA Atlas 14 rainfall data for site-specific applications. The rainfall-frequency data will be used to develop site-specific rainfall distributions. The NOAA 14 text files for selected states are available in the Support Materials for downloading and use in WinTR-20 Version 1.11. The NOAA 14 text files and supporting GIS files are packaged in a zip file for each state.

Win TR-55

Technical Release 55 (TR-55; Urban Hydrology for Small Watersheds) was developed by the U.S.D.A. Soil Conservation Service, now the Natural Resources Conservation Service (NRCS), in 1975 as a simplified procedure to calculate storm runoff volume, peak rate of discharge, hydrographs and storage volumes in small urban watersheds. In 1998, Technical Release 55 and the computer software were revised to what is now called WinTR-55. The changes in this revised version of TR-55 include: upgraded source code to Visual Basic, changed philosophy of data input, development of a Windows interface and output post-processor, enhanced hydrograph-generation capability of the software and flood routing hydrographs through stream reaches and reservoirs. WinTR-55 is a single-event rainfall-runoff small watershed hydrologic model. The model is an input/output interface which runs WinTR-20 in the background to generate, route and add hydrographs. The WinTR-55 generates hydrographs from both urban and agricultural areas at selected points along the stream system. Hydrographs are routed downstream through channels and/or reservoirs. Multiple sub-areas can be modeled within the watershed. A rainfall-runoff analysis can be performed on up to ten sub-areas and up to ten reaches. The total drainage area modeled cannot exceed 25 square miles.

HEC-RAS

HEC-RAS is a river hydraulics model developed by the U.S. Army Corps of Engineers to compute one-dimensional water surface profiles for steady or unsteady flow. HEC-RAS is an updated version of HEC-2. Computation of steady flow water surface profiles is intended for flood plain studies and floodway encroachment evaluations. HEC-RAS uses the solution of the one-dimensional energy equation with energy losses evaluated for friction and contraction and expansion losses in order to compute water surface profiles. In areas with rapidly varied water surface profiles, HEC-RAS uses the solution of the momentum equation. Unsteady flow simulation can evaluate subcritical flow regimes as well as mixed flow regimes including supercritical, hydraulic jumps, and draw downs. Sediment transport calculation capability will be added in future versions of the model. The HEC-RAS program is available to the public from the U.S. Army Corps of Engineers. HEC-RAS utilizes the hydrologic results that are developed in HEC-HMS.

WSPRO

WSPRO is a hydraulic model for water surface profile computations developed by the U.S. Geological Survey. The model evaluates one-dimensional water surface profiles for systems with gradually varied, steady flow. The open channel calculations are conducted using backwater techniques and energy balancing methods. Single opening bridges use the orifice flow equation and flow through culverts is computed using a regression equation at the inlet and an energy balance at the outlet. The WSPRO program is available to the public and can be downloaded from the U.S. Geological Survey.

CULVERTMASTER

CulvertMaster is a hydraulic analysis program for culvert design. The model uses the U.S. Federal Highway Administration Hydraulic Design of Highway Culverts methodology to provide estimates for headwater elevation, hydraulic grade lines, discharge, and culvert sizing. Rainfall and watershed analysis using the SCS Method or Rational Method can be incorporated if the peak flow rate is not known. CulvertMaster is a proprietary model that can be obtained from Haestad Methods, Bentley Systems, Inc.

FLOWMASTER

FlowMaster is a hydraulic analysis program used for the design and analysis of open channels, pressure pipes, inlets, gutters, weirs, and orifices. Mannings, Hasen-Williams, Kutter, Darcy- Weisbach, or Colebrook-White equations are used in the calculations. FlowMaster is a proprietary model that can be obtained from Haestad Methods, Bentley Systems, Inc.

HydroCAD

HydroCAD is a computer aided design program for modeling the hydrology and hydraulics of stormwater runoff. Runoff hydrographs are computed using the SCS runoff equation and the SCS dimensionless unit hydrograph. For the hydrologic computations, there is no provision for recovery of initial abstraction or infiltration during periods of no rainfall within an event. The program computes runoff hydrographs, routes flows through channel reaches and reservoirs, and combines hydrographs at confluences of the watershed stream system. HydroCAD has the ability to simulate backwater conditions by allowing the user to define the backwater elevation prior to simulating a rainfall event. HydroCAD is a proprietary model and can be obtained from HydroCAD Software Solutions LLC.

PondPack

PondPack is a program for modeling and design of the hydrology and hydraulics of storm water runoff and pond networks. Rainfall analyses can be conducted using a number of synthetic or historic storm events using methods such as SCS rainfall distributions, intensity-duration-frequency curves, or recorded rainfall data. Infiltration and runoff can be computed using the SCS curve number method or the Green and Ampt or Horton infiltration methods. Hydrographs are computed using the SCS Method or the Rational Method. Channel routing is conducted using the Muskingun, translation, or Modified Puls methods. Outlet calculations can be performed for outlets such as weirs, culverts, orifices, and risers. The program can assist in the determination of pond sizes. PondPack is a proprietary model that can be obtained from Haestad Methods, Bentley Systems, Inc.

SWMM-Based programs (SWMM5, PC-SWMM, InfoSWMM, MikeUrban)

SWMM-Based Programs SWMM is a hydraulic and hydrologic modeling system that also has a water quality component. Please see the full description above for more details on the model. The Storm Water Management Model (SWMM) was originally developed for the Environmental Protection Agency (EPA) in 1971. SWMM is a dynamic rainfall-runoff and water quality simulation model, primarily but not exclusively for urban areas, for single-event or long-term (continuous) simulation. Version 5 of SWMM was developed in 2005 and has been updated multiple times since. The Storm Water Management Model (SWMM) is a comprehensive computer model for analysis of quantity and quality problems associated with urban runoff. Both single-event and continuous simulation can be performed on catchments having storm sewers, or combined sewers and natural drainage, for prediction of flows, stages and pollutant concentrations. Extran Block solves complete dynamic flow routing equations (St. Venant equations) for accurate simulation of backwater, looped connections, surcharging, and pressure flow. A modeler can simulate all aspects of the urban hydrologic and quality cycles, including rainfall, snow melt, surface and subsurface runoff, flow routing through drainage network, storage and treatment. Statistical analyses can be performed on long-term precipitation data and on output from continuous simulation. SWMM can be used for planning and design. Planning mode is used for an overall assessment of urban runoff problem or proposed abatement options. Current update of SWMM includes the capability to model the flow rate, flow depth and quality of Low Impact Development (LID) controls, including permeable pavement, rain gardens, green roofs, street planters, rain barrels, infiltration trenches, and vegetative swales The SWMM program is available to the public. The proprietary shells, PC-SWMM, InfoSWMM, and Mike Urban, provide the basic computations of EPASWMM with a graphic user interface, additional tools, and some additional computational capabilities.

XPSWMM

XPSWMM is a propriety model that originally began as a SWMM based program. The model developer has developed many upgrades that are independent of the USEPA upgrades to SWMM. Because of these upgrades the two software platforms are no longer interchangeable. XP SWMM does have a function that allows model data to be exported in SWMM format. Comparison of model results between the two softwares will result in similar, but not identical, results.

XP SWMM’s hydrologic and hydraulic capabilities includes modeling of floodplains, river systems, stormwater systems, BMPs (including green infrastructure), watersheds, sanitary sewers, and combined sewers. Pollutant modeling capabilities include pollutant and sediment loading and transport as well as pollutant removal for a suite of BMPs. XP-SWMM is available from XP Solutions.

WinSLAMM

The Source Loading and Management Model is a stormwater quality model developed for the USGS by John Voorhees and Robert Pitt for evaluation of nonpoint pollution in urban areas. The model is based on field observations of grass swales, wet detention ponds, porous pavement, filter strips, cisterns and rain barrels, hydrodynamic settling devices, rain gardens/biofilters and street sweeping, as either other source area or outfall control practices. The focus of the model is on small storm hydrology and particulate washoff. The WinSLAMM model may be obtained from PV & Associates. Wisconsin data files for input into SLAMM may be obtained from the U.S. Geological Survey, and the model provides an extensive set of rainfall, runoff and particulate solids and other pollutant files developed from the National Stormwater Quality Data Base for most urban areas in the county.

The graphical interface allows users to define both source area and drainage system stormwater control practices using a drag-and-drop interface, and the program and web site provides extensive program help and stormwater quality references.

P8

P8 - Program for Predicting Polluting Particle Passage through Pits, Puddles & Ponds, is a physically-based stormwater quality model developed by William Walker to predict the generation and transport of stormwater runoff pollutants in urban watersheds. The model simulates runoff and pollutant transport for a maximum of 24 watersheds, 24 stormwater best management practices (BMPs), 5 particle size classes, and 10 water quality components. The model simulates pollutant transport and removal in a variety of BMPs including swales, buffer strips, detention ponds (dry, wet and extended), flow splitters, and infiltration basins (offline and online). Model simulations are driven by a continuous hourly rainfall time series. P8 has been designed to require a minimum of site-specific data, which are expressed in terminology familiar to most engineers and planners. An extensive user interface providing interactive operation, spreadsheet-like menus, help screens and high resolution graphics facilitate model use.

BASINS

The Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) model is a multipurpose surface water environmental analysis system developed by the U.S. Environmental Protection Agency’s (EPA’s) Office of Water. The model was originally introduced in 1996 and has had subsequent releases in 1998 and 2001. BASINS allows for the assessment of large amounts of point and non-point source data in a format that is easy to use and understand. BASINS incorporates a number of model interfaces that it uses to assess water quality at selected stream sites or throughout the watershed. These model interfaces include:

  • QUAL2E: A water quality and eutrophication model
  • WinHSPF: A watershed scale model for estimating in-stream concentrations resulting from loadings from point and non-point sources
  • SWAT: A physical based, watershed scale model that was developed to predict the impacts of land management practices on water, sediment and agricultural chemical yields in large complex watersheds with varying soils, land uses and management conditions over long periods of time.
  • PLOAD: A pollutant loading model.

PONDNET

The PONDNET model (Walker, 1987) is an empirical model developed to evaluate flow and phosphorous routing in Pond Networks. The following input parameters are defined by the user in evaluating the water quality performance of a pond: watershed area (acres), runoff coefficient, pond surface area (acres), pond mean depth (feet), period length (years), period precipitation (inches) and phosphorous concentrations (ppb). The spreadsheet is designed so that the phosphorous removal of multiple ponds in series can be evaluated.

WiLMS

The Wisconsin Lake Modeling Suite (WiLMS) is a screening level land use management/lake water quality evaluation tool developed by the Wisconsin Department of Natural Resources. It is a spreadsheet of thirteen lake model equations used to predict the total phosphorus (TP) concentration in a lake. TP loads can be entered either as point sources or by entering export coefficients for land uses. WiLMS can be downloaded for free at the Wisconsin DNR Web page.

Bathtub

Bathtub is an empirical model of reservoir eutrophication developed by the U.S. Army Corps of Engineers. Single basins can be modeled, in addition to a network of basins that interact with one another. The model uses steady-state water and nutrient balance calculations in a spatially segmented hydraulic network, which accounts for advective and diffusive transport and nutrient sedimentation.

WASP

WASP, Water Quality Analysis Simulation Program, is a model developed by the U.S. EPA to evaluate the fate and transport of contaminants in surface waters such as lakes and ponds. The model evaluates advection, dispersion, mass loading, and boundary exchange in one, two, or three dimensions. A variety of pollutants can be modeled with this program including nutrients, dissolved oxygen, BOD, algae, organic chemicals, metals, pathogens, and temperature.

SUSTAIN

SUSTAIN (System for Urban Stormwater Treatment and Analysis Integration) was developed by the USEPA to assist stormwater professionals in developing and implementing plans for stormwater flow and pollutant controls on a watershed scale. SUSTAIN contains seven modules that integrate with ArcGIS. Hydrology, hydraulics, and pollutant loading are computed using EPASWMM, Version 5. Sediment transport is based on HSPF. Modules include:

  • Framework manager
  • BMP siting tool
  • Land simulation module
  • BMP simulation module
  • Conveyance simulation
  • BMP optimization
  • Post-processor

MIDS Calculator

The MIDS Calculator was developed by the MPCA as an Excel-based stormwater quality tool to predict the annual pollutant removal performance of low impact development (LID) BMPs. The calculator will compute the volume reduction associated with infiltration practices plus the TSS and TP reductions for both LID and traditional BMPs, including permeable pavements, green roofs, bioretention, bioretention with underdrain (biofiltration), infiltration basin, tree trench, tree trench with underdrain, swale side slope, swale channels, swales with underdrains, wet swale, cistern/reuse, sand filter, constructed wetland and constructed stormwater pond.

STEPL

The Spreadsheet Tool for Estimating Pollutant Load (STEPL) was developed by the USEPA to calculate nutrient and sediment loads from different rural land uses and BMPs on a watershed scale. STEPL provides a user-friendly interface to create a customized spreadsheet-based model in Microsoft (MS) Excel. It computes watershed surface runoff; nutrient loads, including nitrogen, phosphorus, and 5-day biological oxygen demand (BOD5); and sediment delivery. The annual sediment load (sheet and rill erosion only) is calculated based on the Universal Soil Loss Equation (USLE) and the sediment delivery ratio. The sediment and pollutant load reductions that result from the implementation of BMPs are computed using the known BMP efficiencies.

Virginia Model

USEPA National Stormwater Calculator

The National Stormwater Calculator is a tool developed by the USEPA for computing small site hydrology for any location within the U.S. (http://www.epa.gov/nrmrl/wswrd/wq/models/swc/). It estimates the amount of stormwater runoff generated from a site under different development and control scenarios over a long term period of historical rainfall. The analysis takes into account local soil conditions, slope, land cover and meteorology. Different types of low impact development (LID) practices (also known as green infrastructure) can be employed to help capture and retain rainfall on-site. Future climate change scenarios taken from internationally recognized climate change projections can also be considered. The calculator’s primary focus is informing site developers and property owners on how well they can meet a desired stormwater retention target.

Autodesk Civil 3D

Autodesk Civil 3D includes additional software applications that allow you to perform a variety of storm water management tasks, including storm sewer design, watershed analysis, detention pond modeling, and culvert, channel, and inlet analysis. For more information, link here.

Table summarizing models by model type

This table classifies common models by type of model. The information in this table can be download as an Excel file. Reference or links to any specific commercial product, process, or service by trade name, trademark, service mark, manufacturer, or otherwise does not constitute or imply endorsement, recommendation, or favoring by the Minnesota Pollution Control Agency.
Link to this table.

Model or tool Rainfall-runoff calculation tool Hydrologic model Hydraulic model Combined hydrologic and hydraulic Water quality model BMP calculator
TR-55 X
Rational method (equation) X
HEC-1 X
HEC-HMS X
Win TR-55 (or TR-20 DOS version) X
Win TR-55 X
HydroCAD X
HEC-RAS X X
HEC-2 X
WSPRO X
CulvertMaster X
Flow Master X
PondPack X
EPA SWMM X X
PC SWMM X X
Info SWMM X X
XPSWMM X X
MIKE URBAN (SWMM or MOUSE) X X
ICPR X
InfoWorks ICM X X
Mike 11 X
CivilStorm X
MODRET X
WINSLAMM X
P8 X
BASINS X
QUAL2E/QUAL2K X
WinHSPF X X
LSPC X X
SWAT X X
PLOAD X
PondNet X
WASP X
WMM X
WARMF X X
SHSAM X
SUSTAIN X X
Virginia Runoff Reduction Method X
MapShed X
MIDS calculator X
EPA National Stormwater Calculator X
SELECT X
Center for Neighborhood Technology Green Values National Stormwater Management Calculator X
Metropolitan Council Stormwater Reuse Guide Excel Spreadsheet X
MCWD/MWMO Stormwater Reuse Calculator X
North Carolina State University Rainwater Harvesting Model X
i-Tree Streets X
i-Tree Hydro X
RECARGA X
SELDM X
MIDUSS X
QHM X
WWHM X
HY8 X
Hydraulic Toolbox X
SMS X
GWLF-E X
EPD-RIV1 X
CE-QUAL-RIV2 X
CE-QUAL-W2 X
Autodesk Civil 3D X X X


Table summarizing information for different models

Summary of general information for models. The information in this table can be download as an Excel file (Note the links are not updated in the Excel file)
Link to this table.

Model or tool Input complexity Simulation type(s) Public domain Unsteady flow Type of water quality model Built-in BMPs TP TSS Volume Comment on use
TR-55 Low Event Yes Rainfall-Runoff Calculation Tools None No No Replaced by WinTR-55
Rational method (equation) Low Event Yes Rainfall-Runoff Calculation Tools None No No
HEC-1 Medium Yes Hydrologic Models None Replaced by HEC-HMS
HEC-HMS Medium Event or continuous Yes Hydrologic Models None No No
Win TR-55 (or TR-20 DOS version) Medium Event Yes Hydrologic Models None No No Propose to delete the TR-20 DOS version from the list
Win TR-55 Low Event Yes Hydrologic Models None No No
HydroCAD Medium Event No Hydrologic Models Detention ponds and storage chambers Yes Yes No It appears that HydroCAD can model ponds/storage and assess pollutant loadings, but not removal by BMPs
HEC-RAS Medium Event or continuous Yes Yes Receiving water, Hydraulic Models None Yes No
HEC-2 Medium Yes No Hydraulic Models None No No Replaced by HEC-RAS
WSPRO Medium Yes No Hydraulic Models None No No This is an old model and likely no longer used
CulvertMaster Low Event No No Hydraulic Models None No No
Flow Master Low Event No No Hydraulic Models None No No
PondPack Medium Event No No Detention ponds. PondPack can calculate first-flush volume and aid in designing for minimum drain time, but does not model pollutants No No No
EPA SWMM Medium/High Event or continuous Yes Yes Loading, Receiving Water (limited to first order decay) Low impact development BMPs including rain barrels, permeable pavers, vegetative swales, bioretention cells, infiltration trenches; traditional BMPs including detention basins, infiltration practices, wetlands, ponds. Yes Yes Yes
PC SWMM Medium/High Event or continuous No Yes Loading, Receiving Water (limited to first order decay) Low impact development BMPs including rain barrels, permeable pavers, vegetative swales, bioretention cells, infiltration trenches; traditional BMPs including detention basins, infiltration practices, wetlands, ponds. Yes Yes Yes
Info SWMM Medium/High Event or continuous No Yes Loading, Receiving Water (limited to first order decay) Low impact development BMPs including rain barrels, permeable pavers, vegetative swales, bioretention cells, infiltration trenches; traditional BMPs including detention basins, infiltration practices, wetlands, ponds. Yes Yes Yes
XPSWMM Medium/High Event or continuous No Yes Loading, Receiving Water (limited to first order decay) Rain gardens, green roofs, rain barrels, street sweeping, infiltration trenches, dry detention basins, wet ponds, swales, porous pavement, filter strips Yes Yes Yes
MIKE URBAN (SWMM or MOUSE) Medium/High Event or continuous No Yes Loading, Receiving Water (limited to first order decay) Low impact development BMPs including rain barrels, permeable pavers, vegetative swales, bioretention cells, infiltration trenches; traditional BMPs including detention basins, infiltration practices, wetlands, ponds. Yes Yes Yes
ICPR Medium Event No Ponds No No No Not believed to be a widely used model for stormwater/pollutant modeling
InfoWorks ICM High Event or continuous No Yes Yes Yes
Mike 11 Receiving water model
CivilStorm Medium Event No Yes Ponds, low impact development controls No No Yes
MODRET Not believed to be a widely used model for stormwater/pollutant modeling
WINSLAMM Medium Event/continuous for BMPs No BMP, Loading Grass swales, wet detention ponds, porous pavement, filter strips, cisterns and rain barrels, hydrodynamic settling devices, rain gardens/biofilters and street sweeping Yes Yes Yes
P8 Medium Event or continuous Yes BMP, Loading Detention ponds, infiltration basins, swales or buffer strips, and generalized devices Yes Yes Yes
BASINS Yes BASINS is a user interface to set up models in WinHSPF, SWAT, SWMM, PLOAD, and GLWF-E. These models are listed here separately.
QUAL2E/QUAL2K Medium Yes Receiving water None Yes Yes Receiving water model
WinHSPF High Event or continuous Yes Yes Loading, receiving water Nutrient management, Contouring, Terracing, Ponds, Wetlands; USEPA BMP Web Toolkit available to assist with implementing structural BMPs such as detention basins, or infiltration BMPs that represent source control facilities, which capture runoff from small impervious areas (e.g., parking lots or rooftops). Yes Yes Yes
LSPC High Event or continuous Yes Yes Loading, receiving water Though developed for HSPF, the USEPA BMP Web Toolkit can be used with LSPC to model structural BMPs such as detention basins, or infiltration BMPs that represent source control facilities, which capture runoff from small impervious areas (e.g., parking lots or rooftops). Yes Yes Yes
SWAT Medium/High Event or continuous Yes Yes Loading Model offers many agricultural BMPs and practices, but limited urban BMPs at this time. BMPs related to urban practices include detention basins, infiltration practices, vegetative filter strips, street sweeping, wetlands. Yes Yes Yes Limited use in urban areas
PLOAD Low Event Yes Loading User-defined practices with user-specified removal percentages Yes Yes No
PondNet Low Event Yes Loading Wet detention ponds Yes No Yes
WASP High Event or continuous Yes Receiving water None Yes Yes No Receiving water model
WMM Not believed to be a widely used model for stormwater/pollutant modeling
WARMF Event or continuous Yes Loading, receiving water
SHSAM Low Event No BMP Several flow-through structures including standard sumps, and proprietary systems such as CDS, Stormceptors, and Vortechs systems No Yes No
SUSTAIN Medium Event or continuous Yes Bioretention, cisterns, constructed wetlands, dry/wet ponds, swales, green roofs, infiltration basins, infiltration trenches, porous pavement, rain barrels, sand filters, filter strips Yes Yes Yes
Virginia Runoff Reduction Method Not believed to be a widely used model for stormwater/pollutant modeling
MapShed Medium Event Yes Loading, BMP Detention basins, vegetated buffer strips, stabilized streambanks, infiltration/bioretention, constructed wetlands, street sweeping Yes Yes Yes Region-specific input data not available for Minnesota but user can create this data for any region.
MIDS calculator Low Event Yes Green roof, bioretention basin (with and without underdrain), infiltration basin, permeable pavement, infiltration trench/tree box, dry swale, wet swale, sand filter, wetland, stormwater pond, user defined Yes Yes Yes
EPA National Stormwater Calculator Low Event or continuous Yes Disconnection, rain harvesting, rain gardens, green roofs, street planters, infiltration basins, porous pavement No No Yes
SELECT Low Event Yes Extended detention, bioretention, wetland basin, swale, permeable pavement, filter, and user-defined Yes Yes Yes
Center for Neighborhood Technology Green Values National Stormwater Management Calculator Low Event Yes Green roof, planter boxes, rain gardens, cisterns/rain barrels, native vegetation, filter strips, amended soil, swales, trees, permeable pavement No No Yes
Metropolitan Council Stormwater Reuse Guide Excel Spreadsheet Low Event Yes Computes storage volume for stormwater reuse systems No No Yes Uses 30-year precipitation data specific to Twin Cites region of Minnesota
MCWD/MWMO Stormwater Reuse Calculator Low Event Yes Computes storage volume for stormwater reuse systems No No Yes
North Carolina State University Rainwater Harvesting Model Not believed to be a widely used model for stormwater/pollutant modeling
i-Tree Streets Low Event Yes Trees No No Yes
i-Tree Hydro Low Event Yes Trees, watershed scale Yes Yes Yes NOTE: Beta version
RECARGA Low Event or continuous Yes Bioretention/rain garden and infiltration facilities No No Yes
SELDM Low Yes Stochastic Yes Not believed to be a widely used model for stormwater/pollutant modeling
MIDUSS Not believed to be a widely used model for stormwater/pollutant modeling
QHM Not believed to be a widely used model for stormwater/pollutant modeling
WWHM Not believed to be a widely used model for stormwater/pollutant modeling
HY8 Not believed to be a widely used model for stormwater/pollutant modeling
Hydraulic Toolbox Not believed to be a widely used model for stormwater/pollutant modeling
SMS Not believed to be a widely used model for stormwater/pollutant modeling
GWLF-E Replaced by MapShed
EPD-RIV1 Not believed to be a widely used model for stormwater/pollutant modeling
CE-QUAL-RIV2
CE-QUAL-W2 Receiving water model



References

Related pages