The U.S. Environmental Protection Agency (EPA shared details for a webinar Aug. 23, 2017. The EPA Tools and Resources Webinar on the National Stormwater Calculator (SWC) will be 3 to 4 p.m. and is suitable for state environmental and health agencies, tribes, local governments, communities, stakeholders and others interested in learning about reducing storm water runoff.
Storm water discharges continue to cause impairment of the nation’s water bodies. In order to reduce impairment, EPA has developed the SWC to help support local, state, and national storm water management objectives and regulatory efforts to reduce runoff through infiltration and retention using green infrastructure practices as low impact development (LID) controls.
The primary focus of the SWC is to inform site developers on how well they can meet a desired storm water retention target with and without the use of green infrastructure. It also can be used by landscapers and homeowners. The SWC is a Windows-based desktop program that requires an Internet connection. A mobile web application version that will be compatible with all operating systems will be released this fall.
An LID cost-estimation module within the application allows planners and managers to evaluate LID controls based on comparison of regional and national project planning level cost estimates (capital and average annual maintenance) and predicted LID control performance. Cost estimation is accomplished based on user-identified size configuration of the LID control infrastructure and other key project and site-specific variables. This includes whether the project is being applied as part of new development or redevelopment and if there are existing site constraints.
The SWC allows users to consider how runoff may vary based both on historical weather and potential future climate conditions. To better inform decisions, it is recommended that the user develop a range of SWC results with various assumptions about model inputs such as percent of impervious surface, soil type, sizing of green infrastructure, as well as historical weather and future climate scenarios. Please check with local authorities about whether and how use of these tools may support local storm water management goals.