暴雨期間泥沙濃度率定曲線特性探討

Investigating the Characteristics of Sediment Concentration Rating Curves during Storms

10.29417/JCSWC.201009_41(3).0007

楊其錚(Chi-Cheng Yang)；李光敦(Kwan-Tun Lee)

泥沙濃度率定曲線 ； 泥沙運行時間 ； 逕流運行時間 ； 瞬時單位泥沙歷線 ； sediment concentration rating curve ； sediment travel time ； flow travel time ； instantaneous unit sedimentgraph

中華水土保持學報

41卷3期（2010 / 09 / 01）

265 - 275

繁體中文

降雨過程因逕流匯集作用，所以造成河川中流量的增加，而且因爲雨滴與漫地流對土壤表面的沖蝕作用，亦同時導致河川中泥沙濃度增加。Williams (1989)曾採用不同集水區實際量測資料，系統性地探討流量歷線與泥沙歷線間之關係，說明河道中泥沙濃度率定曲線之特性，並將之區分爲5大類，即單一値線、順時針迴圈、逆時針迴圈、單一直線加迴圈，以及8字形迴圈。本研究藉由新近發展的地貌瞬時單位泥沙歷線模式，詳細探討逕流歷線與泥沙歷線之關係，而後分析泥沙濃度率定曲線特性。研究中以美國密西西比州Goodwin試驗集水區爲例，藉中模式參數之設定，計算出不同的逕流運行時間與泥沙運行時間，而產生Williams (1989)所述泥沙濃度率定曲線的五大類型。研究結果顯示，當泥沙運行時間與逕流運行時間相等時，泥沙濃度率定曲線呈現單一值線關係；當泥沙運行時間小於逕流運行時間，泥沙濃度率定曲線呈現順時針迴圈關係；當泥沙運行時間大於逕流運行時間，泥沙濃度率定曲線呈現逆時針迴圈關係。而當集水區泥沙濃度率定曲線呈單一直線加迴圈或是8字形迴圈，則是不同階段水流與泥沙運行時間大小不一的複雜混合型態。

In rainstorm periods, overland flow will concentrate to channels resulting in the increasing of channel flow, and soil will also be eroded by rainfall impact and the shear force of the overland flow to increase sediment concentration in the channel flow. Williams (1989) examined the relationship between the flow hydrograph and sedimentgraph, and concluded that the sediment concentration rating curve can be classified into five categories: single-valued line, clockwise loop, counterclockwise loop, single line plus a loop, and figure eight. In this study, the Goodwin Creek Experimental Watershed, located in Mississippi, USA, was selected as a test site, and a newly developed geomorphologic instantaneous unit sedimentgraph model (GIUS) was used to simulate the flow and sediment hydrographs during storms. The five categories of sediment concentration rating curves cui be generated by assigning different model parameters. The results indicate when the flow travel time equals the sediment travel time, a single-valued rating curve can be generated. When the sediment travel time is less than the flow travel time, the rating curve will show a clockwise-loop shape. A counterclockwise-loop rating curve indicates the sediment travel time is larger than the flow travel time. If the sediment travel time is larger than the flow travel time in some specified runoff states and the sediment travel time is less than the flow travel time in other runoff states, then a single line plus a loop rating curve or a figure-eight rating curve will be found.