Assessing the runoff control performance of green road

The Huangjong elevated road in Taichung city was incorporated with low impact development (LID) practices, aiming to collect rainfall and reuse it as irrigation water for vegetation on the road surface. However, there was no monitoring plan to evaluate the LID performance. This study applied SWMM model (Storm Water Management Model) and the EPA calculation methods to quantify runoff reduction of this case. The results of SWMM model showed that the annual runoff reduction was 43.5~54.5%. The runoff reduction rate contributed from different LID types was ranked at infiltration ponds, infiltration swales, rain barrels, and ecopond. The required water conservation volume of this road was 2850 m₃, but the total LID practices collected 5365 m₃ runoff which was 1.9 times of the required volume. These LID practices cost 1% of the total budget of this road and turned out 50% runoff reduction, confirming that LID is economic efficient and effective practices.