DELAY EFFECT OF RAINWATER DRAINAGE OF GREEN ROOF WATERPROOFING SYSTEM WITH SOIL AND LAWN LAYERS

Abstract

The effect of green roofs to delay rainwater drainage timing, which is expected to prevent the serious flood disaster in big cities at heavy rains, is studied. Delay times and quantities of drainage water were measured for various kinds and thickness of soil layers and various conditions of lawn grass at heavy rains. It was made clear that the relation between the drainage delay effect and the composition of the soil layer, and the effect of treatment of the lawn grass. The simulation program was furthermore developed on the basis of the measured results, and the method for estimating quantitatively the drainage delay effect of green roofs was proposed.