A Study of Erosional Morphology in the Toukoshan Conglomerate Area - Three Cases in Central Taiwan

• Main Authors: Po-Yu Chang, 張伯宇
• Other Authors: Jiun-Chuan Lin
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/81111032729563498011

博士 === 國立臺灣大學 === 地理環境資源學研究所 === 91 === In the exposed area of conglomerates those are highly permeable, whether surface runoff erosion plays the critical role in the growth of drainage network and the spatial variation of dissection intensity is deserve to be discussed. In this thesis, the eastern flank of the Chukou Hill, Ninety-nine Peaks and Hoyanshan in central Taiwan, where the Toukoshan Conglomerate is exposed, are selected as study cases. They are divided into six sub-units for the purpose of analysis and investigation. Morphometric analysis, correlation analysis and field observation of slope processes are conducted to examine the relative importance between surface runoff erosion and the other processes and find the significant environmental variables those influence the variation of drainage densities among sub-units. Many morphometric attributes of ravine and ravine network suggest although the influence of surface runoff erosion exits, it is not the dominant process in the formation of ravine network in all research areas. Seepage erosion is more relatively importance for ravine development in the eastern flank of the Chukou Hill. In these sub-units situated at Ninety-nine Peaks and Hoyanshan, the domination of seepage erosion is in need of further identification. Among the environmental variables considered in this thesis, stratigraphic structure is the only one which has significant correlation with the drainage density in statistics. The higher drainage densities exist in the sub-units where conglomerate overlies an impermeable bed or contain discontinuous layers of sandstone or mudstone. They are more advantageous to the operation of seepage erosion in geological conditions. It implies the spatial variation of drainage densities among sub-units could be explained by the relative intensity of seepage erosion. The result of field observation of slope processes supports this conclusion.