気候変動と土地利用変化を考慮したダム開発の河川水文や地形への影響評価

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The purpose of this study is to develop an empirical method that can quantitatively predict riverbed changes caused by dams based on observation data obtained over a wide area, and to clarify whether the magnitude of the impact of dams on the downstream riverbed changes with climate change. The Godavari River in India, where there are many large dams and where hydrological data are available, was selected as the target area.In Saigon, Kumhari, Nowrangpur, etc., the results agreed well with those predicted by existing analytical methods, while in Dhalegaon, Bamini, Jagdalpur, etc., the results suggested a short cycle of erosion and recovery of the riverbed, contrary to the results of analytical methods.The results of reproducing, predicting, and evaluating the riverbed changes by applying past climatic conditions and future climate change scenarios showed that the model can adequately represent the riverbed changes. As for the future projections, the results showed that it is necessary to use several CMIP5 models to make appropriate projections, considering the uncertainty.Even if warming is moderate, dam construction is expected to increase the rate of riverbed erosion under climate change, and rapid warming is expected to increase the frequency of floods and further accelerate erosion.These results are significant not only because they show that the empirical model of this study is capable of making appropriate predictions, but also because they quantitatively show how dam construction will affect the riverbed under warming conditions.