Abstract: The water storage capacity of saturated green roof substrates is defined as the maximum water content, which is important for evaluating the effect of rainfall detention. In this research, ceramics particles, peat, and coal cinder were selected to design the substrate of green roof by adjusting the combinations and mixing proportions. The influences of substrate thickness, rainfall intensity, and substrate type on the effect of rainwater detention were investigated through artificial rainfall experiments. Results suggest that thickness and rainfall intensity have no effect on the maximum water content in the presence of the same substrate. But with the increase of substrate thickness, the total capacity of water detention grows, and the delay time of runoff also extends; while when rainfall intensity increases, the delay time of runoff shortens. As for different substrates, the maximum water content of substrates of large total porosity is large correspondingly; and the water retention capacity is related with the coefficient of non-uniformity of substrate particles, which means that more even particles lead to lower water retention capacity.

Key words: green roof, maximum water content, retention effect, delayed runoff, rainwater retention