ASSESSMENT OF CHANGES IN STREAMFLOW DUE TO GLOBAL WARMING AND EVALUATION OF SEVERAL ADAPTATION MEASURES IN RIVERS IN TOYAMA PREFECTURE

Abstract

 In recent years, flood disasters have become more frequent and larger in scale due to increased precipitation caused by global warming. In order to reduce the flood damage, several flood control methods and countermeasures are being undertaken throughout the entire basins. In Toyama Prefecture rivers, vegetation is found to be thriving in the river channels, and the vegetation management of the rivers is expected to have the effect of reducing water levels during the flood event. In addition, the rice paddy field dams are expected to have a rainfall storage effect due to the high land use of rice fields in the Toyama prefecture. In this study, we evaluated the effects of vegetation management in the rivers and rice paddy dams on the future flow rate of the rivers in Toyama Prefecture. The effect of vegetation management of the rivers on the Oyabe River, where vegetation thrives, was an average reduction of 0.2 m in water level, assuming a 4°C rise in the future. The rice paddy field dam was effective in the Oyabe River, where paddy land use is high, and the water level decreased by an average of 0.93 m when the rice paddy field dam application rate was 100% and by 0.44 m when the application rate was 50%, assuming a 4°C rise in the future climate.