河川洪水位演算模式之研究

Abstract

本研究主要目的是結合運動波模式及動力波模式，建立河川洪水位演算模式，以掌握河川水體的即時水位變化趨勢。過去有關河川演算之研究中，其上游邊界大都採用觀測流量，下游邊界則為觀測水位，而本研究則是以上游觀測水位做為上游邊界條件，以避免水位-流量率定曲線轉換之誤差。 本研究首先在較陡坡河道，以即時觀測水位配合運動波模式進行數值演算，作為動力模式的上游邊界；而動力模式方面，則以緩變量流理論為基礎，配合非線性四點完全隱式差分法所建立。最後，將兩模式銜接，完成河川洪水位演算模式。 為測試模式之可行性，首先將模式應用於人工渠道，以三角歷線進行模擬；此外，亦將模式應用於蘭陽溪流域，利用賀伯颱風及安珀颱風進行模擬，進行牛鬥橋及蘭陽橋洪水位的演算，經由模擬結果顯示，本模式在人工渠道及天然河川皆能反映洪水來臨時之流況變化。

In order to simulate the flood stage variation for the flood mitigation in the typhoon season, a flood stage routing model was developed with combining the kinematic wave model and dynamic wave routing model. In most of study, discharges at gauge stations were used as the upstream boundary conditions, and water stage as the downstream boundary condition. To avoid the errors of discharge the rating curve at the gauge station, this paper adopts water stage specifying in the model as the upstream boundary condition. First, flood stage was routed by using kinematics model in the upstream steep channels. The calculated stage at the downstream is taken as upstream condition for the dynamic routing model. The dynamic routing model is based on the one-dimensional continuity and momentum equations which were discritized by a four-point implicit finite-difference method. In order to test the feasibility of this model, a triangular hydrograph in artificial watercourse was simulated and compared. Finally, the model was applied to the Lan-yang Creek to calculate the water stages of the Niu-Tou bridge and the Lan-yang bridge for the typhoon events in the past. The result shows that the proposed model can be used to simulate the dynamic variations of unsteady flows for the artificial watercourses as well as natural watercourses.