EPA Stormwater Management Model Climate Adjustment Tool

As part of President Obama’s Climate Action Plan Climate Resilience Toolkit, the U.S. Environmental Protection Agency (EPA) released the Climate Adjustment Tool (CAT) for EPA’s Stormwater Management Model - a downloadable online stormwater simulation model. The Climate Adjustment Tool allows engineers and planners to evaluate the performance of water infrastructure while considering future climate change projections, such as more frequent high-intensity storms and changes in evaporation rates of seasonal precipitation. The tool can help to determine the benefits of resiliency decisions in order to reduce local economic burden and protect communities.

The new CAT tool is a simple to use software utility that applies monthly climate adjustment factors onto historical precipitation and temperature data to consider potential impacts of future climate on stormwater. The new tool will enable users to add climate projections based on the Intergovernmental Panel on Climate Change’s climate change scenarios to existing simulations to determine the quality of water traveling through traditional infrastructure - a system of gutters, storm drains, pipes, channels, collection tanks and storage devices. The tool also has the ability to model the performance of green infrastructure practices, including permeable pavement, rain gardens, and green roofs. Engineers and planners are able to accurately represent any combination of traditional and green infrastructure practices within an area to determine their effectiveness in managing stormwater and combined sewer overflows in their community.

The Stormwater Management Model (SWMM), first released in 1971, models hydrology and hydraulics to simulate the movement of water through the landscape and into and through sewer systems. It has had numerous updates over the years, including the addition of a green infrastructure module in 2010 to simulate the integration of green infrastructure practices into a community’s stormwater management plan. SWMM is widely used throughout the world and considered the “gold standard” in the design of urban wet weather flow pollution abatement approaches, and allows users to include any combination of low impact development/green infrastructure controls to determine their effectiveness in managing stormwater and sewer overflows.

To assist planners and environmental managers the EPA has developed additional tools, including:

The EPA’s National Stormwater Calculator: a tool that can be used by homeowners, landscapers, and developers to estimate the amount of rainwater and frequency of runoff on a specific site based on local soil conditions, land cover, historic rainfall records, and climate change scenarios.

The EPA’s Climate Resilience Evaluation and Awareness Tool (CREAT): a tool that assists drinking water and wastewater utility owners and operators understand potential climate change threats and assess the related risks.


If you have any trouble accessing the website link above, please find here an archived page. You may find this has limited use.  https://web.archive.org/web/20161224234052/https://www.epa.gov/water-research/storm-water-management-model-swmm


Publication Date: February 13, 2015

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