[H-GM04] [JJ] Geomorphology

[HGM04-04] Relationships between rainfall, water level fluctuation and landform change of riverbed since 2011 in Kamikochi region, the upper Azusa River, central Japan

*Hiroshi Shimazu¹ (1.Department of Geography, Faculty of Geo-Environmental Science, Rissho University)

Keywords:fluvial geomorphology, landform change, lateral erosion, rainfall, watar level fluctuation, Kamikochi

The purpose of this study is to discuss relationships between rainfall, water level fluctuation and landform change of riverbed in Kamikochi region, the upper Azusa River, central Japan. Based on ground surveying geomorphological maps of the observation area were made every year in summer season. Interval shooting cameras took photographs every 15 or 20 minutes interval. Rainfall data were obtained from AMeDAS Kamikochi station. Also section surveying performed every autumn season. The analyses of this study were performed using the data since 3 July 2011 when the cameras were set.
The rainfall event whose daily rain fall over 100 mm in the Baiu rainy season caused the bankfull discharge and the major landform change, which was channel migration. When the channel migration occurred, without gradual lateral move of channels, former channels were buried and/or narrowed with new main channels excavation. During the Baiu rainy season about 80mm of daily rainfall caused small landform changes, for example slight lateral erosion by channel move. Any landform changes were not occurred during under 50mm/day rainfall event in the Baiu rainy season and even about 100mm/day rainfall event after the Baie rainy season.