綠屋頂降雨截水公式之建立

Abstract

由於綠屋頂之植物及土壤介質均可截留雨水，因而可降低逕流減少雨水系統負載。唯目前國內外尚未有適當方法可供推估綠屋頂截水能力，故本研究收集及參考目前國內外已建立之截水公式，並依據實驗結果及相關理論建立出適合台灣環境之綠屋頂截水公式，供評估台灣綠屋頂在不同條件下降雨截水效益。本研究亦探討不同降雨型式、介質厚度、介質特性與植栽等因子於綠屋頂截水能力之影響，分析綠屋頂在降雨期間介質含水率及其底部滲漏與表面逕流隨時間變化之情況，且為了有效率模擬綠屋頂之截水能力，本研究除了改善先前座台，亦重新建立一30cm*30cm實驗小座台，利於截水實驗時更換不同介質、厚度及植物等設置條件。此外，由於預期研究期間自然降雨事件數量有限，亦改善之前建置之降雨模擬器模擬不同降雨強度，於截水實驗搭配小實驗座台，以便於針對不同截水因子分析綠屋頂截水能力並驗證所收集及建立公式之適用性。所建立之含水差異係數法及含水率推估法於驗證組驗證結果之R平方值分別為0.9118及0.8655，誤差分別在1.2%-48.4%及0.1%-46.7%間，推估自然雨準確性最佳可達為2.7%及40.7%。而所收集方法以迴歸統計法結果最佳，R平方值為0.9244，誤差在0.5%-22%間，推估自然雨準確性在15.8%-69.7%之間。

Green roofs can reduce both the runoff from rainfall events and the loading on storm sewers, because their plants and soil media can retain precipitation. However, a proper method for estimating the detention capability of a green roof is so far not available. Therefore, this study reviewed various rainfall detention equations and developed several equations for evaluating the detention capability under different conditions. This study investigated the effects of several essential factors such as rainfall intensity, soil depth and water content in soil, on the rainfall detention capability. For effectively analyzing the performance of a green roof, other than improving previous experiment platforms, this study also designed a 30cm*30cm experimental platform and improved the previous rainfall simulator for the new platform to simulate different rainfall events. Data measured from the experimental platforms are used to calibrate and verify the parameters of various rainfall detention equations. The verification results show that the R-squared values for the water content deviation coefficient equation and the moisture estimation equation are 0.9118 and 0.8655, respectively. And the differences between measured and equation estimated valued range between 1.2%-48.4% and 0.1%-46.7%, respectively, and the differences for real rainfall events range between 2.7% and 40.7%. For other evaluated equations, the regression equation performs the best. Its R-squared value is 0.9244, and the difference from measured values is about 0.5%-22%, while the differences for real rainfall events range between 15.8% and 69.7%.