高屏溪谷與潮州斷崖沖積扇的地形學研究

Abstract

Kaoping valley and Chaochou fault are lecated the southwestern part of Taiwan Island. With conspicuous fault scarps and abundant debris supply, alluvial fans are developed well in this area. There are 38 fans with area over 0.1 km each, 22 of them are distributed in the Laonung valley, 8 of them in Nantzuhsien valley, and the rest are in the piedmont along the Chaochou fault scarps. In the valley, most of the fans have been undercut to be composit fans. The fact of the fan head trench shifting down could reveal that the down cutting rate of stream channel is greater than the uplift rate of mountain area. By product-moment correlation, some fan variables are correlated closely, such as fan area has a significant relation with length, width, slope and roundness of sediments. Based on the discriminant analysis, the precipitation, geological period, the stream length, hypsometric integral and relief ratio are the dominating factors to the existence of the fan. By factor analysis, drainage area, uplift rate, relief ratio, geology of drainage basin, drainage length and evolution stage of fan are the main factors influencing the fan morphology. From the relation between fan and drainage basin, the evolution of the fan of the Nantzuhsien valley and Chaochou fault can be interpreted by the equillbrium model.