集水區流水下切動力模型的量化分析

A Quantitative Analysis for the Stream Incision Power Model of the River Watershed

李準勝(Chun-Sheng Lee) ； 蔡龍珆(Louis L. Tsai)

《中華水土保持學報》 40卷3期 (2009/09) Pp. 1-18

https://doi.org/10.29417/JCSWC.200909_40(3).0001

摘要

由於板塊構造活動速率相當緩慢，人類歷史的記載是無法反應長時距的變化，而構造地形指標具有反應較長時距構造運動特徵的性質，所以本研究以流水下切動力模型爲基礎，利用凹曲度（θ:代表地貌特徵）和標準化陡度（k(下標 sn):代表地盤抬昇程度）兩個構造地形指標來探索中台灣造山運動帶的構造地形特徵。本研究結果顯示，中央山脈東西兩側的θ指標整體平均值分別爲0.950和0.713，反應在地形地貌上所呈現兩側的不對稱性，由k(下標 sn)值往下游呈現漸增的趨勢與岩性條件下的反應漸減趨勢是相反的，以及近50~60年的平均降雨量亦或是流量對於k(下標 sn)指標的反應是沒有明顯的關聯性。本研究認爲岩性和近50~60年的氣候特徵並不是控制河流演化的重要因子，大地構造運動才是主因。由中央山脈東西兩側地區的整體log(k(下標 sn))平均值幾乎是趨於相同的數值，來說明中臺灣的造山運動帶是呈現一個均衡穩定的狀態。最後本研究得到四個分區的大地構造活動性趨勢爲西部麓山帶地區＞雪山山脈地區＞中央山脈東翼地區＞中央山脈西翼地區。

關鍵字

流水下切動力模型 ； 凹曲度θ指標 ； 標準化陡度k(下标 sn)指標

並列摘要

Since plate movement is considerably slow, human history record is too short to register landscape change for such a long time scale. However, longitudinal river profile can display watershed landscape characteristics. The purpose of this study is to explore the implication in evolution of tectonic geomorphology for the orogeny of Central Taiwan by using concavity (θ) index and normalized steepness (k(subscript sn)) index base on the stream power model. The result of this study indicates that the whole average of the concavity (θ) index are 0.950 and 0.731 which respond to asymmetric form for east and west sides of Central Range. The normalized steepness (k(subscript sn)) index is expected to be decreased on the condition of resistance of rock stratum, but the result of this study exhibits an opposite trend. Moreover, the average precipitation in the past 50~60 years and the flow versus the normalized steepness (k(subscript sn)) index exhibit no remarkable relationship. This study suggested that the control factor of stream evolution is tectonic movement, not the resistance of rock stratum and climate in the past 50~60 years. In addition, the whole average of normalized steepness (k(subscript sn)) index for two sides of Central Range are similar, which implies a steady orogeny state for Central Taiwan. Finally, Western Foothills Belt possessed the strongest tectonic movement, followed by Hsuehshan Range Belt, Eastern Backbone Range Belt and Western Backbone Range Belt.

並列關鍵字

Stream Incision Power Model ； Concavity θ index ； Normalized Steepness k(subscript sn) index