河流縱剖面與構造地形指標之量化分析: 以濁水溪為例

Quantitative Analysis of Tecto-geomorphic Index and Longitudinal River Profile: A Case Study of Choushui River, Central Taiwan

廖智彥(Chien-Yen Liao)

指導教授 ： 蔡龍珆

國立中央大學/地球科學學院/應用地質研究所/碩士(2007年)

摘要

在集水區範圍內，構造地形及地貌特性能有效反應在河流剖面、集水面積、坡度等因子上。本研究針對濁水溪主流及12條支流縱剖面進行分析，藉由各因子的數化截取工作，進行基岩河流侵蝕模型、四種數學函數(線性、指數、對數、乘冪)擬合、Hack剖面、河流河段坡降指數(k’)以及標準化坡降指數(SL/k)等地形指標量化分析。本研究結果認為濁水溪流域經過百萬年時距的構造地形演育，影響的主要因子是構造抬升作用，而其分析結果異於Davis所謂河流均夷剖面的理論，其原因與台灣位處在歐亞板塊與菲律賓海板塊碰撞交界處的造山運動帶有關。從凹曲度(θ)所建置的經驗平均值(mean θ=0.47)與河流的擬合分析來看，濁水溪目前在侵蝕與抬升上，已屬均衡穩定狀態。河流坡降指數分析發現A區(上游段)河流與眉溪斷層相遇時，河流坡降指數皆明顯升高，眉溪斷層與EO(Eocene-Oligocene石英砂岩、硬頁岩, 眉溪砂岩等)緊鄰，局部分析雖無法精確了解岩性對坡降指數的影響，但就大範圍的標準化坡降指數而言，斷層對河流剖面的變化影響較為明顯。

關鍵字

河流坡降指數 ； 凹曲度 ； Hack剖面

並列摘要

River profile can reflect various geomorphic and landform characters of its drainage basin. This study is focused on the profile of the mainstream and 12 tributaries of the Choushui River. Four mathematical models(linear, exponential, logarithmic and power), Hack profile, S-L index(k’) and gradient index (SL/K) were examined for concavity studies of each profile. A quantitative landform analysis can thus be derived.
The results of this study illustrate that, after millions of years of tectonic evolution, the main factor to cause the landform of the drainage basin is tectonic uplifting, instead of what proposed by Davis’s graded river theory. This can be related to the location of Taiwan, which is right on the collision zone and orogenic belt of Eurasian Plate and Philippine Sea Plate.
According to its concavity index (mean θ=0.47), the Choushui River is close to a steady-state of erosion and uplifting at present. Furthermore, gradient index increases as each river meeting with Meishi Fault in district A( upper stream area). Although Meishi Fault is also outcropped with Eocene-Oligocene quartz sandstone and hard shale, the influence of lithology on gradient index is still under discussion. Therefore, in a large-scaled view of gradient index, tectonic fault exhibits a strong influence on river profile in the study area.

並列關鍵字

gradient index ； Hack profile ； concavity index

參考文獻

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