MODELLING OF SEDIMENT ROUTING IN COLD AND SNOWY REGION WITH PARTICULAR REFERENCE TO FREEZING AND THAWING

Abstract

The sediment control throughout the watershed is regarded as one of indispensable tools from the environmental viewpoint of landscape managements in the watershed. The purpose of this paper is to develop the previously-proposed sediment routing model into the framework which can predict the sediment runoff in spring and early summer in cold and snowy region on the basis of the effects of freezing and thawing on both the rainfall runoff and sediment runoff. The model proposed in this paper was applied to the Kuchoro river catchments whose large amount of yielded sediment has a considerable influence on the landscape of Kushiro Mire. Comparing the features of sediment runoff in spring with that in autumn may indicate the possibility that the coarser pore by frost and thaw suppresses the occurrence of surface flow and subsequently reduces the surface erosion, while the decrease in soil strength increases the sedimentoutflow due to riverbank erosion.