The purpose of BAHM is to provide a visually-oriented interactive tool to optimally size stormwater control facilities (both water quantity and water quality) to mitigate the stormwater and water quality impacts of land use changes on local streams and rivers. It can also be used to review of development plans for compliance with stormwater regulations, promote sustainable development practices, and educate the engineering community and public on the impacts of land use changes.
WWHM3 gives the user greater modeling flexibility and options. Version 2 was limited to drainages of less than half a square mile (320 acres) because of the lack of a conveyance feature (natural channel or pipe). This limitation does not apply to WWHM3; with Version 3 the user can model entire watersheds of unlimited size as long as they are contained within a single county or use the time series element to transfer flows from one county to an adjacent county.
Specific changes and additions in Version 3 include: