New computation method for flood flows and bed variations in a low-lying river with complex river systems

摘要

The lower Shinanogawa River has the complex river system, which is comprised of several tributaries, branched rivers and a no embankment area (see Fig.l). In the record-breaking flood observed in 2011, large inflows from the Ikarashigawa River and Kariyatagawa River caused backward flows to the upstream around the confluences and large inundation in the no embankment area. Flood flows and bed variations in such a complex river system have not been studied so far.