| Summary: | 碩士 === 國立高雄師範大學 === 地理學系 === 91 === The whole Chenyulan drainage basin is located in the Nan-tou County with two tributaries named the Hoshe and Salihsian rivers on its upper reaches. This study tries to understand：（1） the correlation of river terraces between the mainstream and the tributaries ;（2）the effect factors of landscape evolution processes in the whole drainage basin and what it.
According to the correlation and 14C dating, we found that the river terraces in the Chenyulan drainage basin can be mainly divided into four evolution periods with the law of down-cut and superposition, and the same with its two tributaries. In the first period, due to highest alluvial fan terrace sediments aggradated between Sin-shan and Wang-shan of the mainstream in the past 9000 yr. BP, the mainstream moved to the east. In the second period, terrace sediments widely aggradated along the mainstream in the past 4000 yr. BP. However, in the Sa-li-hsian River, terrace sediments started to aggradate until 2000 years ago. According to the rock terrace that appeared on the upper reaches and the sediment layer that relatively thinner than that in the first and second periods, the river processes tend to intermittent down-cut and episodic aggradation in the third and forth periods. All terrace sediments in the Chenyulan drainage basin are wedge aggradation.
The landscape evolution is triggered by the climate change and the tectonic uplift. River responds would become very complex under various resistances environment caused by many different geomorphologic forms. In system specifications, although reaches along the Chenyulan River express a different characteristic forms due to spatio-temporal sensitivity, we still found that evolution of the whole stream always inherited a certain sequence of the formative events. Thus, in the time-space context, this character makes the terraces in the Chenyulan drainage basin becoming a landscape mosaics.
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