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Estimation of sediment yield during storms based on soil and watershed geomorphology characteristics
|Authors: ||Chi-Cheng Yang|
|Contributors: ||NTOU:Department of Harbor and River Engineering|
sediment yield;sediment travel time;instantaneous unit sedimentgraph;sediment concentration rating curve
|Issue Date: ||2011-06-30T07:55:07Z
|Abstract: ||當大量降雨落在坡陡流急之集水區時，常造成嚴重土壤沖蝕情形，因泥砂的沖蝕及運移過程相當複雜，致使暴雨期間流域內之土壤沖蝕量並不容易估算。本研究建立一計算暴雨時期泥砂產量之物理方法，應用土壤與集水區地形特性，求得各級序漫地流階段與渠流階段的泥砂運行時間解析解，據以建立地貌瞬時單位泥砂歷線模式，隨時間分佈的泥砂量是瞬時超量降雨所形成，因此地貌瞬時單位泥砂歷線為超量降雨強度與泥砂運移率之函數，此模式不再受限於瞬時單位歷線理論的線性假設。 暴雨事件之泥砂產量可經由降雨強度與瞬時單位泥砂歷線褶合積分而得，研究中選取美國密西西比州之Goodwin試驗集水區以及台灣大安溪流域卓蘭集水區水文紀錄資料，作為模式測試驗證，研究結果顯示，模式計算之泥砂產量與集水區實測紀錄甚為相近。此外，為探討泥砂濃度率定曲線特性，研究中藉由設定不同的泥砂運行時間，進而產生Williams (1989)所述的五大類泥砂濃度率定曲線，即單一值線、順時針迴圈、逆時針迴圈、單一直線加迴圈，以及8字形迴圈；故逕流運行時間與泥砂運行時間之關係，為影響遲滯迴圈型態的重要因素。本研究所建立之地貌瞬時單位泥砂歷線模式，能考慮沖蝕過程之動態效應，因此在水資源規劃等相關領域，可採用本模式計算集水區泥砂產量。|
Concentrated rainfall usually results in serious soil erosion on steep hillslopes. Since the itinerary of the eroded sediment is complicated, estimating watershed erosion during storms is practically difficult. A physically-based approach for sediment yield estimation during storms was proposed in this study. By using soil and watershed geomorphologic information, analytical solutions for sediment travel time in different orders of overland areas and channels were derived to develop a geomorphologic instantaneous unit sedimentgraph (GIUS) which showed the temporal distribution of sediment discharge resulting from an instantaneous rainfall excess input. The resultant GIUS was a function of the rainfall excess intensity and sediment delivery ratio. The linearity restriction of the unit hydrograph theory was relaxed. Sediment yields during storm events were calculated by convoluting rainfall intensities with the proposed GIUS, which had been verified by using data from Goodwin Creek Experimental Watershed in the United States and Ta-An-Chi Watershed in Taiwan. The simulated and the measured sediment yields were in good agreement for the test storms. The sediment-concentration rating curves generated by the proposed model were further investigated to fit the 5 categories of sediment-concentration rating curves classified by Williams (1989) as single-valued line, clockwise loop, counterclockwise loop, single line plus a loop, and figure eight. The results demonostrated that the hysterestic loop is dominated by the relation between the watershed runoff travel time and sediment travel time. The proposed physical model can account for the hydrodynamic effect in the erosion process. It was considered a promising application for sediment yield estimation in the field of water resources design.
|Appears in Collections:||[河海工程學系] 博碩士論文|
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