不同輸砂公式對河道沖淤影響之研究

Abstract

動床數值模式於應用時，須引用輸砂經驗公式來推估輸砂量，但不同經驗式仍各有其適用範圍及優缺點，且影響河道之沖淤情形。本研究係以陳氏(2002)發展之一維動床顯式有限解析法模式(EFA)為基礎，再加以擴充數條輸砂公式，並透過比較底床沖淤模擬值來找出不同輸砂公式對河道沖淤變化之影響，進而討論不同輸砂公式應用時之差異性與準確性。 於模擬案例方面，採用Suryanarayana (1969)實驗室案例之動床實驗渠槽進行沖刷與淤積模擬分析；而天然河川水系之應用方面，以頭前溪為模擬對象，進行颱洪事件模擬，評估不同輸砂公式於天然河川之適用性及準確度。根據數值模擬之結果，選用不同輸砂公式對底床沖淤量與沖淤趨勢有頗大之影響。

When using the mobile-bed numerical modeling, sediment transport formulas is required to compute the capacity of sediment transport. However each of these formulas has its own range of applications and advantages to influence river bed change. This study extends on Chen’s (2002) 1-D finite analytic mobile-bed model (EFA) to expands several sediment transport formulas. The results of the numerical simulations could be used to compare the river bed change resulted from using different sediment transport formulas. Further discussion is carried out on the variation and the accuracy of these results. With regard to the case studies for the simulations, the Suryanarayana’s (1969) mobile-bed experimental data are adopted to simulate the scour and deposition. In addition, Touchien River is chosen as a case study for the evaluation of the suitability and accuracy of these sediment transport formulas in the simulation of the flood events resulted from typhoons in the natural river system. According to the results of these numerical simulations, the use of various sediment transport formulas would significantly affect the amount and the tend of scour and deposition of the river bed.