顯式有限解析法模式於動床主支流之研究

Abstract

一般情況下，河川水系常有主支流交匯之情形。因此對於交匯後河川流量、水深、底床之變化，應予以探討，以供河川整治及工程規劃之需。本研究係延續Hsu and Yeh’s (1996)一維有限解析法動床模式(Explicit Finite Analytic method, EFA)，發展擴充至具有模擬主支流渠道之功能。在交匯區內部邊界條件採用水位相等之概念來處理；在上、下游邊界處則根據流況給予流量或水位歷線。 由於動床主支流實驗案例甚為缺乏，故本模式採用Suryanarayana (1969)之均勻與非均勻沉滓動床實驗資料，假設另一條相同渠道作為支流匯入，進行含主支流渠道之沖刷與淤積模擬分析，以進行模式之測試。在天然河川水系方面，收集大漢溪及三峽河之斷面資料，以大漢溪為主流、三峽河為支流進行颱洪事件模擬，並與新海橋水位站之實測水位值比較，以檢驗本模式於天然河川之適用性。經由數模比較，顯示成果尚屬合理。

Under normal conditions, river systems often include junction and division flows. In order to rebuild and map out engineering plans for the river systems, one would have to probe into the research of the discharges, the depths and the changes of river channels after confluence. This study extends Hsu & Yeh’s (1996) 1-D finite analytic mobile-bed model (EFA), and expands it to incorporate the function of simulating the confluence flows. Equal stage at the region of confluence is adopted into the internal boundary condition; with the discharge or stage hydrograph specified at the upstream or downstream boundary according to the given flow characteristics. Due to the lack of experimental cases for mobile-bed confluence flows, Suryanarayana’s (1969) experimental data of uniform and non-uniform bed material are adopted. This model simulates the scour and deposition of the tributary, under the assumption that the simulated channel and the tributary are the same. In regard to the natural river system, the section data of Tahan Creek and Sanxia River are collected in which they are considered as the mainstream and the tributary, respectively. To test the suitability of this model in the natural river system, the simulation of the typhoon flood incident is carried out and the results are compared with the measuring value of the Hsinhai Bridge water level station. By way of this model simulates, the simulation results are satisfactory.