多方式特性法模式應用於動床主支流之研究

Abstract

本研究以李氏(1992)、Yeh et al.(1995)所發展之非均質多方式特性法模式為主要架構，沿著物理擾動軌跡積分求解N個床質粒徑百分組成、斷面水深、平均流速及底床高程等，為一結合演算法，在理論基礎上較貼近物理現象。為了能應用於天然河川系統，將本模式擴充至具有模擬主支流之功能，並考慮內部邊界條件的問題，採用水位相等之概念來處理。本研究先引用台大顏清連教授等(1988,1990)發表之實驗案例，設計一主支流渠道進行模擬，以及採用民國八十五年筏子溪水工模型試驗資料，進行不同頻率年洪水之定量流模擬。在河川案例模擬方面，收集大漢溪及三峽河流域之斷面資料，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值比較，檢驗本模式於天然河川之適用性，由模擬結果顯示，與新海橋實測水位之峰值相當接近；此外，藉由模擬河道沿程之底床變化，了解底床受到洪水量較大之颱洪所造成之影響。

This study is based on the non-uniform sediment multimode characteristics model developed by Li (1992) and Yeh et al. (1995). The proposed model is a coupled model, in which along the physical perturbation-wave trajectories the N bed-meterial size fractions, flow depth, velocity, and bed elevation can be solved simultaneously. In order to be applied to the natural river systems, this model was expanded to simulate the confluence flows while considering the issues of the internal boundary conditions, which is dealt with by using the concept of equal water elevations. This research quotes the experimental results done by Professor Yen et al. (1988, 1990) as a case study to design a confluence channel and carry out simulation, and uses the experimental data of Fatzu Creek’s Projrct model (1996) to carry out the flood simulation of different frequency years. In the river simulations data was collected at the sections of Tahan and Sanxia Rivers and classified into mainstream and tributary stream, respectively. In order to examine the suitability of this model being applied in natural rivers, simulations of the events of floods during typhoon seasons were carried out, in which the results were compared with the data collected from the Hsinhai bridge station. According to the simulated results, the simulated peak stages at the Hsinhai bridge are close to the observed values. In addition, it can be seen that the bed elevation changes of the river are mainly affected by the larger typhoon floods.