| 摘要: | 集水區的測高曲線積分值可用來推論地形演育的程度，但必須留意積分值同時也受到尺度效應之影響。台灣位處歐亞板塊及菲律賓海板塊斜向聚合之環境，地形演育的程度在北部、中部及南部各有不同，因此適合用來驗證集水區隨地形演育變化的測高性質。本研究使用由5公尺網格數值模型(DEM)概略化的10公尺DEM做高程值分析，選取山區以侵蝕及搬運作用為主的集水區作為新的小尺度分析單元，稱為侵蝕主導單元（erosion-dominant unit），希望藉由此操作去掉平原以及河道兩旁堆積區的影響，使測高曲線的分析回歸其針對侵蝕為主地區的基本假設。
根據前人研究，台灣北部、中部及南部分別歸屬為垮塌山脈（collapsing mountain）、成熟山脈（mature mountain）以及成長山脈（growing mountain）。本研究在中央山脈稜線以西的山區，分北、中、南，各選取一集水區為代表樣區做細部的分析，先就三個尺度探討尺度相依特性。最後在北、中、南各選取兩個集水區，以最有代表性的尺度做更進一步分析，討論在不同山脈成熟程度下測高曲線的特徵及其與地形演育階段的關係，並與前人在中央山脈稜線以西山區的研究結果做比較。
本研究認為在水保局所使用之次集水區尺度，以介於100至200平方公里之面積尺度下，集水區測高曲線型態可以區別不同山脈演育程度，並且支持Ohmori（1993）提出之測高曲線循環。另外侵蝕主導單元作為新的小尺度分析單元，其在地質上的意義更貼近集水區演育的基本假設，並且在此尺度下更容易直接以測高曲線積分值分布看出集水區受侵蝕作用後所呈現的地貌。
;Hypsometric integral of drainage basin can be used to infer the landscape evolution stage, but caution must be taken that it is significantly influenced by scale dependency. Locating at oblique convergence boundary, mountain belt of Taiwan results in different phases of geomorphological development, which is suitable for illustrating different hypsometric characteristics of drainage basins. In this study we used 10meter-DEM which reduced from 5meter-DEM to process elevation analysis. We choose erosion and transportation dominating watersheds for study, so that the effect of deposition along channels and flat land can be minimized. The raised new small scale analytical units we call it erosion-dominant unit. In this condition, the hypsometric analysis can carry out under the original assumption of erosion dominating background.
According to previous studies, the northern, central, and southern segments of Taiwan mountain belt are differentiated as collapsing mountain, mature mountain, and growing mountain, respectively. To investigate scale dependency, we select three representative drainage basins from each segment of the western mountain belt and do detailed analysis. At last, we pick two drainage basins from each segment and do analysis in the most representative scale, to discuss distinct hypsometric characteristics through different stage in mountain belt. In addition, I compare my result with the result of previous studies in western Central mountain range.
The sub-basin scale, which SWCB used, with area between 100 and 200 square kilometers, can be used to distinguish different mountain evolution stages, and to support Ohmori′s cycle of hypsometric curve. In addition, taking erosion-dominant unit as the new small scale analytical unit, its geological signification is more conforming to original hypothesis of drainage basin evolution cycle. With this scale, we could recognize the details of landscape evolution stage at each drainage basin through the use of hypsometric integral value distribution. |
