National Stormwater Calculator (SWC)

The National Stormwater Calculator (SWC) is a tool for computing site-specific stormwater runoff based upon local soil conditions, land cover and precipitation records.

Model Information
For more information about this model, go to
Spatial Resolution
Spatial resolution is on the magnitude of single sites and can be as specific as square feet
Temporal Resolution
The resulting time series of rainfall and runoff are aggregaed into daily amounts.
The calculator’s primary focus is informing site developers and property owners on how well they can meet a desired stormwater retention target.
Intended User
practitioner, decision maker
Model Type
decision making
Inclusion of Climate Change
The SWC allows users to consider how runoff may vary based on historical weather and potential future climate conditions. 
Geographic Region
Data Requirements
all data sets built in
Source Code Availability
closed source
Computational Burden
Scenario Modeling
scenarios by hand only
Coding Language
GUI, C/C++
Operating System
not applicable
Mathematical Approach
deterministic, simulation
Maintenance Plan
Date of Last Known Update
not available
User Manual
go to documentation at