ANALYSIS OF WEATHERING DEGREE IDENTIFICATION BY CHEMICAL COMPOSITION FOR GRANIC BASIN

Abstract

 This study aimed to quantify and index the risk of geological weathering based on chemical composition using water quality in a watershed. We attempted to derive the risk by comparing the chemical composition and components of the baseflow in relation to the slope failure rate in granitic regions of the Japanese archipelago where mass movement due to heavy rainfall has occurred frequently in recent years. The study area included eight granitic areas, which were included in the previous studies, and data were compared for 64 basins. The main results show that the chemical composition of the granitoids is different depending on the formation age of the granitoids. The chemical reactions involved in weathering were different depending on the age, with Mg, Ca, and Sr in the Early Cretaceous and Fe in the Late Cretaceous and Middle and Early Jurassic showing a strong correlation with the rate of slope failure.