Storm
Water Management Model (SWMM)
Description:
Available through the EPA, SWMM is a dynamic rainfall-runoff
simulation model. It can be used for single event or long-term
(continuous) simulation of runoff quantity and quality from
primarily urban areas. The runoff component of SWMM operates
on a collection of subcatchment areas that receive precipitation
and generate runoff and pollutant loads. The routing portion
of SWMM transports this runoff through a system of pipes,
channels, storage/treatment devices, pumps, and regulators.
SWMM tracks the quantity and quality of runoff generated within
each subcatchment, and the flow rate, flow depth, and quality
of water in each pipe and channel during a simulation period
comprised of multiple time steps.
Capabilities:
SWMM is used in many sewer and stormwater studies worldwide.
Tpical applications include:
• Design and sizing of drainage system components for
flood control
• Sizing of detention facilities and their appurtenances
for flood control and water quality protection
• Flood plain mapping of inflow and infiltration on
sanitary sewer overflows
• Generating non-point sources pollutant loadings for
waste load allocation studies
• Evaluating the effectiveness of BMP’s for reducing
wet weather pollutant loadings
The SWMM program accounts for several hydrologic processes
that produce runoff from urban areas including time-varying
rainfall, evaporation of standing surface water, snow accumulation/melting,
rainfall interception from depression storage and infiltration
of rainfall into unsaturated soil layers.
Limitations:
Basic Inputs:
• Subcatchment slope, size, and soil properties
• Conduit (pipe) materials, sizes, routing characteristics,
pump locations, pumping rates, etc
• Precipitation details
Basic Output:
• Runoff quantity and quality, groundwater flow, conveyance
system flow and water quality
• System-wide variables like air temperature, total
rainfall, snow depth, evaporative losses, dry weather inflow,
groundwater inflow
• Node variables like hydraulic head, water volume held
in storage, surface flooding, pollutant concentrations after
any treatment applied at the node
How to Run the Model:
To model stormwater runoff over a study area, the basic steps
to follow are:
1. Specify a default set of options and object properties
to use. These include the subcatchment properties (area, width,
slope), ID labels for the different conduits and nodes that
will be created, and routing methods for flows within the
conduits
2. Draw a network representation of the physical components
of the study area
3. Edit the properties of the objects that make up the system,
such as conduit diameter, conduit material, pumping rates,
and other characteristics of the conduit system.
4. Select a set of analysis options. There exist a number
of different analysis methods and options including setting
different time steps, chosing an infiltration model (Horton,
Green-Ampt, Curve Number), routing method, and flow units,
among others.
5. Run a simulation
6. View results of the simulation
Developer: SWMM was developed by the United States Environmental Protection Agency with assistance from the consulting firm CDM, Inc. The EPA maintans a model website which contains additional information on this and other models.
Faculty Contact: Sri Rangarajan
Application: Currently used in E4350, Planning & Management of Urban Hydrologic Systems
