Results and findings from 15 years of sustainable urban storm water management

In accordance with the latest German regulations, the basic idea of the project "Sustainable Urban Storm Water Management", funded by the Trier University of Applied Sciences, Germany, is to restore the natural water balance in urban areas to avoid the widely recognized disadvantages of runoff from impervious surfaces. To improve the components of such concepts and their hydro logical simulation approaches, a one-family house in Western Germany was monitored in this respect over 15 years (1998-2012). It comprised a green roof, as well as storm water infiltration and utilization. Measurements included precipitation and runoff. This data set was used for calibration of storm-runoff model approaches with increasing complexity and for simulation of hydrological green roof performance under different climate conditions (local and Mediterranean). Also, a long-term simulation using differing arrangements was conducted, e.g. linkage of additional storm water from a pitched concrete roof to the green roof. The investigations revealed that the most relevant model component in hydrological green roof simulation is the calculation of the evapotranspiration process. Some results could be checked against values from German regulations. The most relevant practical findings are that the green roof proved itself to be an excellent "filter" for the storm water utilization tank and that the linkage between a pitched roof section and the green roof proved its worth providing additional water supply for the vegetation in rain-scarce periods, as well as a retention facility during heavy storm events.