Influences of time scale on green stormwater infrastructure’s effect on suspended solids in urban rainfall runoff

Abstract To investigate the influences of time scale on green stormwater infrastructure’s (GSI) effect on suspended solids (SS) in urban rainfall runoff, the control effect of GSI on SS in rainfall runoff was systematically explored based on three aspects of time scale – event, seasonal, annual. The Sponge City pilot area of Beijing, China, was selected as the study area. The results showed that under the condition of same rainfall duration and rainfall recurrence period, reduction of SS mass gradually decreased with the backward movement of rainfall peak. With regard to rainfall with small recurrence period, rainfall duration had little effect on the control effect of GSI. When the recurrence period was 10 yr and rainfall duration was 1, 2, and 3 h, the effect of GSI on SS percent reduction was 15.7%, 17.3%, and 19.1%, respectively, reflecting rainfall duration effect. Besides, with the extension of antecedent dry period, GSI effect on SS reduction first increased and then leveled off in the same recurrence period. In terms of seasonal change, the GSI effect on SS reduction showed high percent reduction in spring and winter (up to 45.5%), followed by autumn, with the lowest percent reduction in summer. On the annual time scale, GSI presented the strongest control effect in dry years (up to 45.0%), followed by normal years, and weakest in wet years.