| Summary: | 碩士 === 國立成功大學 === 水利及海洋工程學系 === 89 === A catchment is usually delineated as many subbasins by using Geographical Information System (GIS) before HEC-HMS is applied. The problem how many subbasins should be delineated is always faced for users. If the size of subbasin is too large, the spatial herterogeneity can not be considered. On the contrary, it is more difficult to process the spatial data for too many subbasins. The objective of the study is to apply cluster analysis for catchment delineation, and investigate whether SCS curve number (SCS CN) method is appropriate for estimation of direct runoff in Taiwan. The Zhuo-Kou river, a tributary of Kaoping Creek, is chosen for case study. In the cluster analysis, value of curve number, surface slope and the specified rain gauges weighting for each subbasin are used as clustering variables. It is found that a catchment can be efficiently delineated by using cluster analysis if the network of river system is further taken into account. “Median curve number” from eight storm events is defined to estimate the direct runoff. The analysis results conclude that the CN values from tables derived by SCS are suitable for the study area, but the total 2-day antecedent rainfall depth may be more appropriate to determine antecedent moisture condition.
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