筏子溪河床穩定分析之研究

Analysis of Riverbed Stability in Fa-Tzu River

王傳益(Chuan-Yi Wang) ； 施漢鵬(Han-Peng Shih) ； 顏順益(Shun-Yi Yen) ； 鄭人豪(Jen-Hao Cheng) ； 呂其倫(Chi-Lun Lu)

《水保技術》 5卷2期 (2010/04) Pp. 69-82

https://doi.org/10.30040/JSWCT.201004.0002

摘要

筏子溪爲烏溪重要支流，由於臨近台中市人口稠密區、工業區及科學園區，因此筏子溪之河床穩定與否，對於台中都會區具有極高重要性。本研究以河川分層概念，探討河川型態與其變化歷程。透過水理輸砂數值模式NETSTARS，模擬不同重現期距洪峰流量下之河床演變，針對筏子溪各河段之河床穩定性及河道整體沖淤進行分析，進而提出治理對策，以供相關單位未來河川治理之參考。
研究結果顯示，筏子溪整體橫向穩定性不佳，尤其以斷面3~23（台鐵橋上游至高速公路橋）間爲相對不穩定區段，而中上游段之橫向穩定相對較佳，主要受地形或堤防限制影響，河道橫向之變化較小。槽量分析方面，主深槽大致擺盪於谿線上，堤防基礎無立即之危險。在各重現期距流量下，筏子溪於高速公路橋（累距7,770~7,816 公尺）上游河床大致呈現沖刷，下游則呈現淤積之趨勢。此外，高速公路橋下游河段，河床變動隨重現期距流量之增加而加大，由沖淤互現狀態轉爲淤積狀態。因此，未來於高速公路上游需注意河床刷深造成堤防基礎破壞問題，需考量加深堤防基礎；下游則需注意河床淤積造成洪水位抬升問題，需考量增加通水斷面。

關鍵字

筏子溪 ； 河床穩定性 ； 槽偏量 ； 谿線

並列摘要

The Fa-Tzu River is the major tributary of the Wu River. The riverbed stability of Fa-Tzu River highly influences the development of Taichung City as it locates near the metropolitan area of Taichung City. In this study, the stream classifications concept was applied to analyze river characteristics and discussed the river morphologic change. A numerical model NETSTARS was used to simulate the hydraulics and sediment transport of river under different return period discharges in order to analyze the riverbed stability and the trend of scour. Based on the results proper regulation methods can be proposed a served as a reference for relevant engineers in the future.
The results showed that the traverse stability of Fa-Tzu River sections is not good, especially for the reach upstream of railway to expressway bridge. The upper and middle reaches showed better transverse stability because of the landform or levee restriction. The horizontal variation of channel trough-line generally shifted near the thalweg, and the levee foundation is not in danger immediately. In addition, riverbed deposition occurred upstream of the expressway bridge and scour occurred downstream of the expressway bridge scour under flow discharges with different return periods.
Riverbed variation increases with an increase of the flow discharge downstream of expressway bridge. Furthermore, riverbed changed from scour and deposition condition to purely deposition condition. Therefore, the upstream scour trend and downstream water rises trend need to be taken care in the future. The suggested regulation methods are to deepen the foundation of levee upstream of expressway bridge, and to increase the cross sectional areas for the downstream reach.

並列關鍵字

Fa-Tzu River ； Riverbed Stability ； Horizontal Variation of Channel Trough-Line ； Thalweg