THE IMPACT OF TOPOGRAPHY AND GEOLOGY ON THE SEDIMENTS IN THE UPSTREAM OF THE KAO-PING CATCHMENT

摘要

River morphology,river flow,and river transport capacity are closely related to the supply of sediment. This study examined the catchment sediment transport,accumulation,and balance for the Kao-Ping River basin in southern Taiwan during Typhoon Morakot in 2(X)9 and Typhoon Fanapi in 2010,using the sediment generation index (Ip) and sediment transportation index (IR) derived from the sediment balance relationship. For both of these indicators,this study selected different control factors,including topographical factors (slope,aspect,river width and slope,riverbank slope,and friction angle),rainfall factors,and collapse ratio. The impact of these factors was then analyzed using GIS software analysis and multivariable analysis. The results indicated that the great quantities of sediment accumulation created in catchments during Typhoon Morakot had gradually moved to the middle and lower reaches of the river two years later when Typhoon Fanapi struck,suggesting that sediment movement accumulation had already gradually reached a state of balance. However,areas of severe accumulation still exist. If humanadministered or dredging methods for resolving sediment accumulation are not considered,a secondary disaster could be induced by a heavy typhoon or a heavy rainstorm.