Water retention by green infrastructure to mitigate urban flooding: a meta-analysis

Sealed surfaces in urban environments limit the infiltration of precipitation, which increases the hazard from urban flooding after heavy precipitation events. Green infrastructure is a tool for urban stormwater management, as it retains, infiltrates and evapotranspires water. In this study, we review existing literature on the performance of five green infrastructure types in reducing runoff: green roofs, pervious pavements, bioretention systems, vegetative swales and infiltration trenches. The number of modelling and field studies was nearly balanced, however, not all types were equally represented. Modelling studies mostly used the storm water management model. Compared to field studies, modelling studies deal with larger areas with higher imperviousness, lower green infrastructure coverage and larger rainfall totals. Runoff retention decreases with increasing rainfall total. The main challenge found in this review was the limited comparability of different studies due to missing or non-uniform information on important characteristics, such as soil moisture at rain event start.