Evaluating the Effectiveness of Green Roads for Runoff Control

Abstract

Green roads can be incorporated into low-impact development (LID) practices to reduce the risk of flood disasters by collecting rainfall and reusing it as irrigation water for vegetation near the roads. In this study, an elevated expressway in Taichung, a city in central Taiwan, was selected to evaluate the performance of LID facilities; the storm water management model (SWMM) was applied with real site dimensions to compute possible runoff hydrographs and compare different real rainfall event scenarios. The runoff reductions from infiltration ponds, infiltration swales, rain barrels, and ecoponds were ranked. The results showed that the annual runoff reduction was 43.5–54.5%, and all LID facilities collected 5,365 m3 of runoff. Finally, three actual rainfall events in 215 were simulated to determine drainage efficiency. The SWMM results showed that the elevated expressway LID facilities would have effectively reduced the flooding risks for those three actual rainfall events. Moreover, the performance of runoff reduction rate during slow rains with a long duration was higher than the performance under heavy rains with a short duration.