Estimation of Long-Term Biomass Level in Riparian Zone of the Nakagawa River Using Satellite Images

Abstract

 Recently, with global warming, sudden torrential rains exceeding 100 mm/h have occurred frequently, and it has been pointed out that the risk of flooding is increasing. In the first-class rivers in Japan, the environment of the river channel has been changing due to the overgrowth of plants in recent decades, and there is a concern that the flow function will deteriorate due to the increase in roughness and the contraction of the river channel. To create an appropriate logging plan that satisfies the two purposes of environment and disaster prevention, it is necessary to understand the secular change in the amount of biomass and fully discuss the effects of both sides. There is no long-term transition data. Therefore, this study aimed to estimate the long-term (about 30 years) changes in the amount of biomass using satellite images. By estimating the amount of biomass from collected vegetation samples and the normalized difference vegetation index, we quantified long-term changes in the amount of biomass in the offshore land, which is the basis of these discussions.