Water Resources Research Act Program

Details for Project ID 2014DC160B

Developing a chance-constraint framework for optimization of long-term hydraulic performance of green roofs

Institute: District of Columbia
Year Established: 2014 Start Date: 2014-03-01 End Date: 2015-02-28
Total Federal Funds: $14,918 Total Non-Federal Funds: $40,161

Principal Investigators: Arash Massoudieh, Pradeep Behera

Project Summary: The main role of low impact development (LID) practices in the context of sustainable urban stormwater management is to reduce the volume and the peak flow rate of stormwater hydrographs. In Washington, DC, which is serviced by combined sewer system (downtown core ) and separate sewer systems, during heavy storms a large portion of storm runoff and municipal wastewater can flow into Anacostia and Potomac Rivers through combined sewer outfalls. This has a substantial adverse effect on the water quality of these receiving waters. So it is extremely important to reduce the stormwater during heavy storms. The use of green roofs is one of the ways that is being encouraged by the city for the reduction of the storm runoff volume and delaying peak flow rate. One of the issues facing the use of green roof and some other low impact practices is that although they capture a large portion of runoff during low intensity and duration events, their capacity may be filled up during high intensity or duration precipitation events and therefore their effectiveness during large events may be diminished. So it is important to evaluate the effectiveness of various designs of green roofs over large time scales considering the local climate and precipitation patterns. Using the grant provided through DC WRRI, we have been collecting long-term data on precipitation, temperature, humidity, runoff from green roofs and soil humidity using six pilot green roofs since May of 2013 (Horgan, Berry et al. 2013) . The six green roofs have been planted with different vegetation and also have been constructed using different soil depths. We have also developed a detailed mechanistic model of green roofs equipped with a deterministic and a Bayesian parameter estimation capability for simulation of green roofs. The goal of this research will be to use the data collected so far to estimate the parameters of the mechanistic model and then using the estimated parameters to evaluate the long term performance of green roofs in DC area using meteorological data in the past 60 years.