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Chapter 3. Controlling Urban Runoff 217 

1 Appendix 1A: Methods and Tools for Controlling Stormwater 

2 Runoff (Quantity and Quality) 

1 

3 This appendix describes various methods, including guidance manuals, and tools for controlling 

4 stormwater runoff. This appendix includes: 

5 1A.1 Methods and Manuals 

6 1A.2 Complex Models 

7 1A.3 Simpler Models (largely spreadsheet-based or online) 

8 A.1.1 Methods and Manuals 

Nationally-Applicable LID Design Methods and Manuals 

Prince George’s County, Maryland, Low-Impact Development Design Strategies: An Integrated 

Design Approach, EPA 841-B-00-003, 2000. 

Prince George’s County, Maryland, Low-Impact Development Hydrologic Analysis, EPA 841-B00-002, 2000. www.epa.gov/nps/lid

U.S. EPA, Stormwater Best Management Practices Design Guide, Office of Research and 

Development, EPA/600/R-04/121, Volumes 1-3 (121, 121A, 121B), September 2004. 

www.epa.gov/nrmrl/pubs/600r04121/600r04121.htm

Center for Watershed Protection Urban Subwatershed Restoration Manual Series 

(www.cwp.org/Store/usrm.htm) 

Center for Watershed Protection Managing Stormwater in Your Community: A Guide for 

Building an Effective Post-Construction Program

(www.cwp.org/Resource_Library/Center_Docs/SW/pcguidance/Manual/PostConstructionManual.pdf)

Water Environment Research Foundation (WERF). Decentralized Stormwater Controls For 

Urban Retrofit And Combined Sewer Overflow Reduction

www.werf.org/AM/Template.cfm?Section=Search&Template=/CustomSource/Research/

ResearchProfile.cfm&ReportId=03-SW-3&CFID=2715758&CFTOKEN=75805127

WERF. Critical Assessment of Stormwater Treatment and Control Selection Issues. In 

Publication. 

Geosyntec Consultants and Wright Water Engineers. Urban Stormwater BMP Performance 

Monitoring. 2009. www.bmpdatabase.org/MonitoringEval.htm 

The Low-Impact Development Center, www.lowimpactdevelopment.org; several LID manuals 

9 
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Chapter 3. Controlling Urban Runoff 218 

Federal Facility Design Manuals 

Technical Guidance on Implementing the Stormwater Runoff Requirements for Federal Projects 

under Section 438 of the Energy Independence and Security Act, USEPA, 2009, EPA 841-B-09-

001, December 2009, www.epa.gov/owow/nps/lid/section438 

U.S. Naval Facilities Engineering Command, Low Impact Development, Draft, Unified Design 

Criteria, UFC 3-210-10, October 2004. www.wbdg.org/ccb/DOD/UFC/ufc_3_210_10.pdf

U.S. Department of Housing and Urban Development, The Practice of Low Impact Development, 

2003, www.huduser.org/portal/publications/destech/lowImpactDevl.html 

U.S. Army Corps of Engineers. Low Impact Development for Sustainable Installations: 

Stormwater Design and Planning Guidance for Development within Army Training Areas. 

Public Works Technical Bulletin 200-1-62. October 2008. 

1 

Transportation-focused LID Design Methods and Manuals 

Low Impact Development Center, Inc., 2006, GeoSyntech Consultants, University of Florida, 

Oregon State University, Evaluation of Best Management Practices for Highway Runoff Control, 

Report N. 565 for National Cooperative Highway Research Program (NCHRP), Project 25-20 

(1). http://onlinepubs.trb.org/Onlinepubs/nchrp/nchrp_rpt_565.pdf

2 

Example State/Local Design Manuals and Resources (also refer to individual practice fact 

sheet references) 

The Chesapeake Stormwater Network. Baywide BMP Design Specifications. 

www.chesapeakestormwater.net/baywide-design-specifications2 

Pennsylvania. Stormwater BMP Manual. 2006. 

www.elibrary.dep.state.pa.us/dsweb/View/Collection-8305 

Delaware. Standards & Specifications for Green Technology BMPs. 2005. 

www.dnrec.state.de.us/DNREC2000/Divisions/Soil/Stormwater/New/GT_Stds%20%26%20Spe

cs_06-05.pdf 

District of Columbia. Stormwater Guidebook. 

http://ddoe.dc.gov/ddoe/frames.asp?doc=/ddoe/lib/ddoe/stormwaterdiv/2009.05.07_SWM_Table

_of_Contents.pdf 

North Carolina Coastal Federation, www.nccoast.org, resources on implementing LID to protect 

shellfish beds and coastal beaches. 

U.S Fish and Wildlife Service, Bayscapes, U.S Fish and Wildlife Service, Bayscapes, 

www.fws.gov/ChesapeakeBay/Bayscapes.htm

3 
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Chapter 3. Controlling Urban Runoff 219 

BMP Performance Information 

Water Environment Research Foundation. International Stormwater BMP Database. 

www.bmpdatabase.org 

EPA. Urban BMP Performance Tool. www.epa.gov/npdes/urbanbmp 

Center for Watershed Protection. National Pollutant Removal Performance Database. 

www.cwp.org/Resource_Library/Controlling_Runoff_and_Discharges/sm.htm 

1 

Source Control and Pollution Prevention Manuals 

U.S. EPA National Management Measures to Control Nonpoint Source Pollution from Urban 

Areas Office of Oceans, Wetlands and Watersheds, EPA-841B-05-004, December 2005 

(www.epa.gov/owow/nps/urbanmm/) 

US EPA The Use of Best Management Practices (BMPs) in Urban Watersheds, Office of 

Research and Development, EPA/600/R-04/184, September 2004. 

Center for Watershed Protection Urban Subwatershed Restoration Manual Series, Volume 

8,Pollution Source ControlPractices, February 2007 (www.cwp.org/Store/usrm.htm) 

Managing Storm Water Runoff to Prevent Contamination of Drinking Water and Managing 

Highway Deicing to Prevent Contamination of Drinking Water. Steve Ainsworth, USEPA 

2 1A.2 Complex, LID-capable Models 

3 Publicly Publically-available models appropriate for evaluating LID practices include: 

4 • EPA’sU.S. EPA's Storm Water Management Model, version 5 (SWMM5), 

5 • EPA’sU.S. EPA's Hydrologic Simulation Program - FORTRAN model (HSPF), and 

6 • U.S. Army Corps of Engineers, Hydrologic Engineering Center – Hydrologic Modeling 

7 System (HEC-HMS) 

8 • Western Washington’s Hydrology Model, version 3 (WWHM3). 

9 • University of Wisconsin, Civil & Environmental Engineering Department, Water 

10 Resources Group - RECARGA 

11 The following summarizes these complex, LID-capable models: 

12 U.S. EPA's Storm Water Management Model, version 5 (SWMM5) 

13 EPA’sThe US EPA Storm Water Management Model (SWMM) is a dynamic rainfall-runoff 

14 simulation model used for single event or long-term (continuous) simulation of runoff quantity 

15 and quality from primarily urban areas. SWMM5 divides the water balance process into four 

16 compartments: (1) atmosphere (precipitation); (2) land surface (divides precipitation into 

17 infiltration, storage, or runoff; (3) groundwater; and (4) transport (pipe and channel flow, as well 
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Chapter 3. Controlling Urban Runoff 220 

1 as storage). It can perform both single event and long-term continuous simulation using 

2 precipitation data recorded at hourly or less intervals. These inputs can be supplemented with 

3 monthly evaporation data and daily temperature readings. Different hydraulic routing techniques 

4 are available to manage from simple to complex routing conditions. Infiltration can be simulated 

5 using Horton, Green-Ampt, or Curve Number techniques. These techniques vary in complexity 

6 and the availability of the parameters used for their estimation. They can take into account initial 

7 soil moisture conditions, hydraulic conductivity, soil moisture capacity, and its regeneration. 

8 Separate accounting is provided for runoff from pervious areas and impervious areas, and routing 

9 of runoff from one area over another is possible. SWMM5 can simulate pollutant build-up, 

10 washoff, and treatment, although these capabilities are not needed to determine predevelopment 

11 hydrology comparisons. 

12 SWMM5’s advantages are that it uses physically-based process models and input parameters 

13 wherever possible, it can model any number of storage- or infiltration-based BMPs, it contains 

14 robust procedures for routing runoff flow, and it allows models to be built to any level of spatial 

15 detail needed to provide the most accurate water balance for a site. A disadvantage is that it does 

16 not currently have the capability to model some BMPs the employ infiltration, storage, and/or 

17 flow routing in combination with one another (such as infiltration ponds and vegetated swales). 

18 This model has been in use since 1971, and has since undergone several major upgrades since its 

19 inception, including expansion of LID applications in 2009. The following applications are 

20 discussed in the 2009 manual: 

21 1. Post-Development Runoff. 

22 2. Surface Drainage Hydraulics. 

23 3. Detention Pond Design 

24 4. Low Impact Development 

25 5. Runoff Water Quality. 

26 6. Runoff Treatment 

27 7. Dual Drainage Systems. 

28 8. Combined Sewer Systems. 

29 9. Continuous Simulation 

30 The model and supporting documentation are available at 

31 www.epa.gov/ednnrmrl/models/swmm/index.htm. 

32 U.S. EPA’s Hydrological Simulation Program Fortran (HSPF), and WinHSPF 

33 WinHSPF has broad capabilities for hydraulic, hydrologic, and water quality modeling. BMPs 

34 are modeled as either “reaches” that can represent channels or areas of storage, or as “pervious 

35 land”. WinHSPF can be used for a single rain event or continuous simulation. In WinHSPF, only 

36 the “pervious land” module can be used for infiltration. Infiltration can vary with time as soil 
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Chapter 3. Controlling Urban Runoff 221 

1 moisture conditions change, and spatial variability in infiltration rates can be addressed. The 

2 advantages of WinHSPF include the very broad capabilities for simulating infiltration, surface 

3 runoff, groundwater movement, evaporation and evapotranspiration, snowmelt, and for water 

4 quality parameters, including temperature (a requirement of Section 438). Another advantage is 

5 that it has been incorporated into BASINS, an EPA model that takes advantage of the capabilities 

6 of GIS and other systems. 

7 Disadvantages of WinHSPF are its complexity and its limited routing capability compared to 

8 SWMM5. 

9 It is the only comprehensive model of watershed hydrology and water quality that allows the 

10 integrated simulation of land and soil contaminant runoff processes with in-stream hydraulic and 

11 sediment-chemical interactions. The user must input continuous rainfall records to drive the 

12 runoff model. Additional records of evapotranspiration, temperature, and solar intensity can be 

13 imported for more accurate results. A large number of model parameters can be specified 

14 although default values are provided where reasonable values are available. The result of this 

15 simulation is a time history of the runoff flow rate, sediment load, and nutrient and pesticide 

16 concentrations, along with a time history of water quantity and quality at any point in a 

17 watershed. 

18 The model and supporting documentation are available for download at 

19 www.epa.gov/ceampubl/swater/hspf. 

20 HEC-HMS 

21 HEC-HMS replaces HEC-1 by building on the original capability of simulating precipitation22 runoff and routing processes. HEC-HMS added capabilities for distributed modeling and 

23 continuous simulation. HEC-HMS includes a broad selection of models for representing rainfall 

24 distributions, computing runoff volume (i.e. different selections of infiltration and losses 

25 algorithms), for modeling direct runoff (overland flow and interflow); baseflow in a stream; and 

26 channel flow. It is capable of modeling either event-based or continuous simulations. 

27 HEC-HMS uses three major components in analyzing a hydrologic system: 

28 1. Basin model – user-entered data on basin data, including losses characteristics and 

29 connectivity. 

30 2. Meteorological model – user-entered data on rainfall, snowmelt, and evapotranspiration 

31 rate. 

32 3. Control specifications – user-entered calculation intervals 

33 Precipitation considerations include areal and temporal distribution, and use of radar data. 

34 Evapotranspiration and precipitation are represented in the soil-moisture accounting (SMA) 

35 model and enables modeling of the drying of the watershed, or otherwise movement of water, 

36 between rainfall events for continuous modeling. A five-layer model is used: canopy, surface, 

37 soil, upper groundwater, and lower groundwater. Alternatively, there is a deficit-constant method 

38 that simplifies to a one-layer model for soil. HEC-HMS divides surfaces into either directly 

39 connected impervious areas or pervious surfaces. Losses on the pervious surfaces include 
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Chapter 3. Controlling Urban Runoff 222 

1 interception, infiltration, storage (consisting of canopy, surface, soil-profile, and groundwater), 

2 evaporation and transpiration. 

3 HEC-HMS is widely used for simulating distributed infiltration controls, particularly when 

4 interactions with streams (with potentially varying baseflows or flash-flows) or input into 

5 subsequent river analysis is desired, via HEC-RAS. HEC-HMS also includes extensive elements 

6 for modeling engineered structures in management systems for reservoirs, dams, pumps, and 

7 other structures. 

8 This model is available for download at

9 www.hec.usace.army.mil/publications/pub_download.html

10 WWHM3 

11 WWHM3 is the third edition of the Western Washington Hydrology model developed for 

12 Washington State Department of Ecology, with input parameters unique for that region. The 

13 model is built on a continuous simulation HSPF platform and can model the entire hydrological 

14 cycle for multiple years. The purpose of the WWHM3 is to size stormwater control facilities to 

15 mitigate the effects of increased runoff (peak discharge, duration, and volume) from proposed 

16 land use changes that impact natural streams, wetlands, and other water courses. WWHM3 also 

17 uses an “LID Scenario Generator” to show the mean annual distribution of stormwater into 

18 surface runoff, interflow, groundwater, and evapotranspiration. Using the LID Scenario 

19 Generator, the user can change land use combinations to optimize performance. In addition to 

20 LID Scenario Generator, the user can explicitly model various LID practices, including green 

21 roofs. 

22 The software has been used to develop stormwater systems for the 19 counties in western 

23 Washington State and is designed to comply with the CWA (NPDES Phase I and II), the 

24 Endangered Species Act and State and local stormwater regulations. More information can be 

25 found at 

26 www.ecy.wa.gov/Programs/wq/stormwater/wwhmtraining/wwhm/wwhm_v3/index.html. 

27 RECARGA 

28 The RECARGA model was developed by the University of Wisconsin Civil & Environmental 

29 Engineering Department Water Resources Group to provide a design tool for evaluating the 

30 performance of bioretention facilities, raingarden facilities, and infiltration basins. Individual 

31 facilities with surface ponding, up to 3 distinct soil layers and optional underdrains can be 

32 modeled under user-specified precipitation and evaporation conditions. The model continuously 

33 simulates the movement of water throughout the facility (ponding zone, soil layers and 

34 underdrains), records the soil moisture and volume of water in each water budget term 

35 (infiltration, recharge, overflow, underdrain flow, evapotranspiration, etc.) at each time step and 

36 summarizes the results. The results of this model can be used to size facilities to meet specific 

37 performance objectives, such as reducing runoff volume or increasing recharge, and for 

38 analyzing the potential impacts of varying the design parameters. Information is available at 

39 http://dnr.wi.gov/runoff/stormwater/technote.htm. 
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Chapter 3. Controlling Urban Runoff 223 

1 1A.3 Simpler Models 

2 The following summarizes several simpler, spreadsheet-based or online, models: 

3 Virginia Runoff Reduction Method Spreadsheets 

4 The “Runoff Reduction Method” is a system that incorporates site design, stormwater 

5 management planning, and BMP selection to develop the most effective stormwater approach for 

6 a given site. The method relies on a three-step compliance procedures that includes 1) applying 

7 site design practices to minimize impervious cover, grading and loss of forest cover, 2) apply 

8 runoff reduction practices, and 3) computer pollutant removal by selected BMPs. Two 

9 spreadsheets have been developed, one for new development and one for redevelopment projects 

10 that allow the designer to see whether the phosphorus load reduction has been achieved by the 

11 application of runoff reduction practices. www.dcr.virginia.gov/lr2f.shtml

12 LID Quicksheet 1.2 

13 Developed by the Milwaukee Metropolitan Sewerage District (MMSD), LID Quicksheet 1.2 is a 

14 calculation spreadsheet that has been developed to provide a practical way to calculate how the 

15 use of particular low impact development practices affect the stormwater detention volume 

16 required under Chapter 13. The LID practices included in the Quicksheet are rain gardens, rain 

17 barrels, green roofs, cisterns, and permeable pavement. The intent of the Quicksheet is to allow 

18 the designer to evaluate the effect of LID practices on reducing the volume of traditional 

19 stormwater detention. Information on LID Quicksheet 1.2 is available in Appendix L at: 

20 http://v3.mmsd.com/manuals.aspx. 

21 Emeryville Stormwater Sizing Calculator 

22 The City of Emeryville, California developed this spreadsheet-based calculator to determine the 

23 proper size of stormwater treatment devices for new development projects. The spreadsheet 

24 includes 7 tables each targeted to a specific type of stormwater treatment information. The tool 

25 uses user-defined drainage area and types to calculate the required facility size for the area. It 

26 also calculates the amount of shortfall in metered detention areas, bioretention basins, lowered 

27 planter strips, flow-through planter boxes, and bioretention swales. The tool can help track 

28 treatment capacity excess and shortages so that parcel areas can be redistributed if there is a 

29 shortfall. This tool along with others can be accessed at 

30 http://cfpub.epa.gov/npdes/greeninfrastructure/modelsandcalculators.cfm. 

31 Capitol Region Watershed District (Twin Cities, MinnesotaMN), Volume 

32 Reduction Worksheet

33 : This spreadsheet includes formulas for volume reduction practices. Volume credits are 

34 provided for seven different types of practices. www.capitolregionwd.org/permit_forms.html
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Chapter 3. Controlling Urban Runoff 224 

1 The Center for Neighborhood Technology Green Values Calculator (GVC) 

2 The GVC compares green infrastructure performance, costs, and benefits to conventional 

3 stormwater practices at both development-site and neighborhood scales. The tool provides a 

4 quantified analysis of green infrastructure environmental benefits including reduced runoff 

5 volume and groundwater recharge. Users can specify site data in a custom run or use several 

6 templates for typical urban and suburban scenarios. A number of “green interventions” can be 

7 selected and used to calculate financial and hydrologic reduction data. Hydrologic reductions 

8 include lot-level goals for peak and total discharge, desired total site peak discharge, total 

9 detention required, and average annual discharge. The GVC is maintained by The Center for 

10 Neighborhood Technology and can be accessed at http://greenvalues.cnt.org. 

11 SELECT 

12 The System Effectiveness and Life-cycle Evaluation of Costs Tool (SELECT) is a simple 

13 planning-level tool that enables a stormwater manager to examine the effectiveness of alternative 

14 scenarios for controlling stormwater pollution and the whole-life cost associated with each 

15 scenario. SELECT uses a long-term record of hourly rainfall which it translates into runoff using 

16 a runoff coefficient that is related to the effective imperviousness of the catchment. This runoff is 

17 introduced to the BMP (which include a number of common BMPs, including permeable 

18 pavement, wetlands, and swales). If there is capacity in the BMP, the runoff is captured; if the 

19 BMP is full, the runoff is discharged untreated to the receiving waters. The model calculates total 

20 outflow as the sum of what is treated and what is not. 

21 This tool was developed for the Water Environment Research Foundation (WERF) by a team 

22 including ACR, LLC, the University of Utah, and Colorado State University and uses Microsoft 

23 Excel as an interface. SELECT is currently only available to WERF subscribers. More 

24 information, including how to become a WERF subscriber and download the tool, can be found 

25 here www.werf.org/select. 

26 Upper Neuse Site Evaluation Tool (SET) 

27 The Upper Neuse Site Evaluation Tool (SET) is a spreadsheet-based tool developed by Tetra 

28 Tech, Inc. for the Upper Neuse River Basin Association. It was designed to aid in the assessment 

29 of development plans and available BMPs to achieve regional water quality objectives. The SET 

30 can also be used to compare the costs of stormwater BMP systems and estimate the cost savings 

31 for reducing impervious surfaces within a site design. The most recent version of the SET can be 

32 found at www.unrba.org/set. 

33 The SET has two functioning components – the Hydrology/Pollutant Component for assessing 

34 water quality impacts of development, and the Cost Component for assessing the costs of BMPs 

35 and other infrastructure. The Hydrology/Pollutant Component requires user-controlled targets for 

36 nutrient loading, an optional target for sediment loading, and targets for peak flow for storage of 

37 runoff during the type of storm events most likely to cause downstream channel erosion. Data 

38 entry includes general site data, land use, drainage areas and BMP information. Various BMPs 

39 can be tested to find a combination that meets the targets. The Cost Component allows a user to 
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Chapter 3. Controlling Urban Runoff 225 

1 compare the costs of stormwater BMP systems and estimate the cost savings for reducing 

2 impervious surfaces within a site design 

3 Rainwater Harvester Computer Model 

4 North Carolina State University developed a computer model to assist in determining the 

5 appropriate cistern size for a given situation. The model uses rainfall data and anticipated usage 

6 to establish cistern inputs and outputs and provides a cost summary and usage statistics in a 

7 report form. Version 2.0 includes an improved interface, reduced calculation times, an interactive 

8 graph of cistern levels, and the ability to save and load model inputs. Also, the website also 

9 includes a quick online calculator that provides an overview of the benefits of a water harvesting 

10 system for homeowners. www.bae.ncsu.edu/topic/waterharvesting/model.html