臺灣主要流域之河川型態及其野溪界點判定評估

Assessing River Morphology and Torrent Division Point of Main Basins in Taiwan

朱芳儀(Fang-Yi Chu) ； 吳俊毅(Chun-Yi Wu) ； 安軒霈(Shiuan-Pei An) ； 林仕修(Shih-Hsih Lin) ； 陳樹群(Su-Chin Chen)

《中華水土保持學報》 49卷3期 (2018/09) Pp. 178-186

https://doi.org/10.29417/JCSWC.201809_49(3).0005

摘要

本研究由河川型態的角度來探討臺灣的河川流域特性，進行綜合性比較並歸納野溪特性，據此評估判定野溪界點之可行性。選取臺灣26個主要流域作為研究區域，由流域形狀與河川縱剖面可發現當流域形狀偏圓，圓度值0.35以上，水系橫向發展空間越大，下游會形成數條較高級序的主流，河川縱剖面呈現多分支狀；而形狀狹長，圓度值0.2以下則反之，其縱剖面較為單一化。臺灣主要流域中超過河段平均高程500 m的一級河其坡度約7%以上，集水區面積約200到400 ha；二級河坡度則在4%以上，集水區面積約1000至2000 ha；透過現場勘查、航照衛星影像可驗證符合以上條件之一、二級河具有野溪之特徵。故本研究將野溪初步定義為河段平均坡度大於4%，且集水區面積小於2000 ha之溪流，判別野溪除上述條件初步判識外，需再進行細部勘驗。而該定義可作為野溪界點判定評估的初步基準，未來可進一步與河川治理界點劃分之範圍進行探討及研究。

關鍵字

河川型態 ； 水系縱剖面 ； 野溪特性 ； 河川級序

並列摘要

This study analyzed the fluvial morphological characteristics of river basins in Taiwan. Torrent characteristics were comprehensively compared and summarized, and the feasibility of torrents division point was assessed. The study area included 26 primary basins in Taiwan. The shape of the basins and the longitudinal profile of the rivers were analyzed. The results showed that when the basin shape is almost circular with an Rc of 0.35 or more, the transverse development space of the drainage is larger. Numerous higher stream orders are available in the downstream. By contrast, the basin shape is long and narrow, the longitudinal profile is relatively simple when Rc is 0.2 or less. When reach elevation is higher than 500 m, the slope of the first order streams in primary basins in Taiwan is higher than 7%, and the watershed area is 200-400 ha. Furthermore, the slope of the second order streams is higher than 4%, and the watershed area is 1000-2000 ha. On the basis of field investigation, aerial photograph, and satellite imagery, the first and second order streams were verified as possessing torrent characteristics. Therefore, the average reach slope and watershed area of the torrent was primarily defined to be higher than 4% and less than 2000 ha, respectively. In addition to the aforementioned conditions, distinguishing torrents must be verified using field surveys. Moreover, our definition can be applied to determine the torrent division point and to compare it against a range of river division points in the future.

並列關鍵字

River morphology ； longitudinal profile of drainage ； torrent characteristic ； stream order