RELATION BETWEEN FORMATION PROCESS OF FORMER RIVER CHANNELS OF THE CHIKUMA RIVER AND SEDIMENTARY STRUCTURES AND LOCATIONS OF FOUNDATION LEAKAGE

Abstract

 Locations of foundation leakage at the levee toe can be identified by the creation of landform classification maps. This map explains the processes of former river channels form, and classifies former river channels into old ones and new ones. Investigations on the soil compositions and permeability coefficients of former river channels and flood plains clarified that former river channels are associated with locations where water pressure is relatively high. With regard to how the locations of former river channels and levees are related to foundation leakage, it was found that foundation leakage with sand boiling tended to occur at levees situated about 200m off former river channels.