To quantify the effect that roof slope has on green roof rainwater runoff was analyzed from 6 sedum green sloped roof platforms constructed at 3 slopes(50%, 30%, flat) and 2 soil thickness(5cm, 10cm). A comparison between the response of an impervious roof (runoff coefficient C=1) and a green-roof has been carried out. Two rain events(123.3mm, 27.5mm) were analyzed for quantifying for runoff reduction and delaying the initial time of runoff. The results are as follows.
1) The corresponding reduction of runoff for 123.3mm rainfall were 45.0%, 48.0%, and 56.0% for the 50%, 30%, and flat slopes of 10cm soil thickness. runoff diminishes as slope decreases.
2) The corresponding reduction of runoff for 123.3mm rainfall were 44.6%, 41.0%, and 28.5% for the 10cm, 5cm and 0cm of soil thickness of 50% slopes. runoff diminishes as soil thickness increases, indicating that these greened slopes reduced runoff compared to traditional roof.
3) The corresponding elapsed time of runoff for 27.5mm rainfall were 2hour 36minutes, 1hour 36minutes, and 1minute for the 10cm, 5cm and 0cm of soil thickness of 50% slopes, the elapsed time of runoff diminishes as soil thickness decreases.
4) The corresponding elapsed time of runoff for 27.5mm rainfall were 1hour 36minutes, 1hour 50minutes, and 4hour 44minutes for the 50%, 30%, and flat slopes of 5cm soil thickness, the elapsed time of runoff diminishes as slope increases.