Incorporating LID Modeling Methods into Existing Analysis Procedures

Client: Milwaukee Metropolitan Sewerage District
Grant Date: 2002-2003

In order to provide communities within the Milwaukee Metropolitan Sewerage District (MMSD) service area with a simple approach to the hydrologic analysis of LID sites, the LID Center adapted the NRCS unit hydrograph method (TR-20) in a way that accounts for the cumulative effect of distributed retention storage within a drainage area. In response to user-specified amounts of bioretention, permeable pavement, etc., a spreadsheet displays changes in the runoff hydrograph and the estimated amount of detention that is still needed to achieve the regulatory peak runoff requirements. Stakeholder meetings were scheduled throughout the project to ensure that the final version of the software and its documentation would encourage the use of LID and meet the professional needs of stormwater plan reviewers as well as land development engineers.