Two-dimensional river bed configuration analysis of the Hii River and diversion channel flood in September 2013

The Hii River in Shimane Prefecture is well known as a typical Japanese sandy riverbed and it flows into Lake Shinji. During flood, water level of Lake Shinji is kept rather high because water level difference between the lake and Japan Sea is very small. The backwater at the river mouth considerably increases the water level upstream. To reduce the flood risk, a diversion channel was constructed at 14.4 km from the river mouth in May, 2013. The diversion channel was operated during the flood of September 2013. The measured volume of sand transported to the diversion channel from the Hii River was about 26,000 m³. Therefore it is very important to get the detailed information of the bedload transport process around the inlet of the diversion channel. Two-dimensional numerical analysis was carried out and it was noticed that the volume of sand was well simulated by the numerical analysis.