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Rainfall Runoff Model for Green Roof
|Authors: ||Hsu, Shih-Jiun|
|Contributors: ||NTOU:Department of Harbor and River Engineering|
Green Roof;Stormwater Management;Rainfall-Runoff Model;Low Impact Development;urban flood mitigation
|Issue Date: ||2017-05-24T08:39:48Z
|Abstract: ||近年來都市化嚴重，不透水面積取代了原有的綠地，綠地面積大量減少，造成都市淹水的情況日益嚴重，而傳統都市排水的方式面臨挑戰，新的思維「低衝擊開發」開始被重視，屋頂綠化也是低衝擊開發的項目之一。 國內屋頂綠化應用在都市雨洪削減的研究相對較少，因此本研究的目的即是建立屋頂綠化之降雨逕流模式，模式採用短期的物理模式，以Green-Ampt入滲模擬屋頂綠化的水文機制，考慮屋頂綠化系統之截留、入滲、土壤含水量、排(保)水板蓄水量，再以逕流公式計算，判斷當降雨發生時，逕流是否產生。並應用實際值進行參數校正，再以Microsoft Office Excel軟體編寫計算程式，建立降雨逕流模式。 本研究於海洋大學河工二館頂樓架設屋頂綠化試驗場址，試體表面積為3.2平方公尺，採用薄層綠化型式，傾斜角度1%，介質厚度約20公分，植栽種類選用假儉草。試驗期間為2014年1月至6月，量測屋頂綠化逕流量，並利用氣象觀測儀器，記錄雨量、風速、日照、溫度等氣象數據。選定七場降雨事件，利用其中三場事件進行參數檢定，將檢定過後的參數帶入其餘四場事件供為驗證使用，將其繪製成圖表，並利用敏感度分析起始含水量和水力傳導度對模式的影響程度。 結果顯示，水力傳導度所影響的是土壤內水分的速率，不會影響到逕流量，起始含水量是降雨發生前土壤內所含的水量，為影響逕流量的主要參數；驗證模擬結果和實際量測流量進行比較，尖峰流量平均誤差約為2.2%，總逕流量平均誤差為1.1%；若是未施作屋頂綠化與本研究實際量測流量比較，實際量測的尖峰流量可以達到88.1%的削減，總逕流量則可以達到88.9%的削減。由研究結果顯示，本研究建立之模式可以進行流量的計算，屋頂綠化可以降低尖峰流量及逕流削減。|
The great mass of green land in urban areas has been turned into impermeable pavement due to rapid urbanization in recent years. It has disturbed the urban hydrologic system resulting in urban flood problem which can’t be solved by traditional methods such as building storm water sewerage system, building detention/retention ponds, etc. Therefore, the new wave of Low Impact Development (LID) techniques have been advocated in recent years in US and other western countries to mitigate non-point source pollutants and storm water in urban areas. Green roof is one of the techniques used in LID but research in the effectiveness in flood mitigation is rare in Taiwan The purpose of this study is to establish a hydrologic model to simulate the relationship between rainfall and runoff for green roof. The model is an event and physical model. Interception of plant, Green Ampt infiltration mechanism, media properties, storage capacity of drainage board, and other parameters have been considered in the model. Major parameters in the model are calibrated by observed data. The calculation procedures of the model are programmed using Microsoft Office Excel language. In the study, an experimental extensive type green roof with surface area of 3.2 m2 (L=2.0m x W=1.6 m), 1% in slope angle, 20cm of medium depth, covering with plant named Eremochloa Ophiuroides is set up on the roof of No. 2 Building, Department of Harbor and River Engineering, National Taiwan Ocean University. Also a meteorological station is set up near the green roof for measuring climatic data including rainfall, wind speed, radiation, and temperature. Observation period started from January 2014. Seven rainfall events are measured to the end of June 2014. Three events are for parameters calibration and four for verification. The sensitivity analysis is carried for two major parameters (initial moisture content and hydraulic conductivity). Results show that hydraulic conductivity will only influence the moving speed within medium not runoff and initial moisture content is the major influential factor to runoff. In the verification, average difference for peak flow between measured and simulated values is 2.2% and 1.1% for average total runoff volume. If we compare the hydrologic condition between before and after green roof is set up, peak flow is reduced 88.1% and 88.9% for total runoff volume. The model established in this study can effectively describe the rainfall-runoff relationship. Also green roof has significant effectiveness in mitigating storm water for low return period rainfall.
|Appears in Collections:||[河海工程學系] 博碩士論文|
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