Morphological index of nick points in Shimen watershed

• Main Authors: Jhy-Wei Ferng, 馮智偉
• Other Authors: Su-Chin Chen
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/94993067570343324716

博士 === 中興大學 === 水土保持學系所 === 98 === Oblique arc-continent collision in the period of Penglai orogeny made the Taiwan mountain belt develop landscape of three evolution stages of post-steady-state (north Taiwan, collapsing range), steady-state (central Taiwan) and pre-steady-state (south Taiwan, growing range). Analysis of stream-power erosion model shows linear form in the S-A plot and fittings of bedrock profiles are mainly the exponential functions in the steady-state range. The north boundaries of the steady-state range are near the Lanyang river (east Taiwan) and Taan river (west Taiwan), and the south boundaries are near the Lele river (east Taiwan) and Laonung river (west Taiwan). Moreover, the S-A plots in the ranges of north and south Taiwan show concave and convex forms, respectively, and fittings of bedrock profiles are both logarithmic. Distribution of hypsometric integral (HI) in Taiwan reflects the uplift sequence of the Taiwan orogenic belt. The Central Range with higher HI uplifted earlier than the Eastern Coastal Range and the Western Foothills. In the Western Foothills, higher HI in the north district once implies that the north district uplifted earlier than the south district. Due to aggradation process, the plain areas that uplifted most presently have high HI contrarily. Pattern of HI in the Western Coastal Plain also shows that the passive indentation of the Peikang High has exerted crustal deformation not only to the oblique propagating fold-and-thrust units in the Western Foothills but also to the recent sediments in the Coastal Plains. The hypsometric curve and the altitude frequency distribution reflect the landscape evolution stages and the residual mass distribution of drainage basin, respectively. In the plain areas, the hypsometric curves of the alluvial plains are S-shaped and the altitude frequency distribution concentrate in median altitude, but the hypsometric curves of the structural subsidence basins or plains are concave and the altitude frequency distribution concentrate in low altitude. In the western foothills, the hypsometric curves are concave and the altitude frequency distribution concentrate in low altitude. Due to continuous uplift process, the HI of the western foothills will increase, the hypsometric curves will gradually develop to S-shaped, and the altitude frequency distribution will finally concentr ate in median altitude. Moreover, hypsometric curves of some high uplift rate areas, such as Linkou, Houli, Huko and Tainan tablelands, are convex and quite similar to the young IV age of the Strahler model. In the central range, due to the balance of uplifting and erosion, the hypsometric curves are all S-shaped and the altitude frequency show normal distribution. In the eastern coastal range, the hypsometric curves are concave and the altitude frequency distribution concentrate in low altitude, and are very similar to the hill areas in the western foothills. Beside, increasing or decreasing of HI caused by some local but young anticline or syncline shows that HI could be a good tool for detecting local variations of subsurface structures