Location of the site: (a) River Tenryu and its fluvial plain, ○: gauging station (Nakanomachi, Kakezuka). △: weather station (Iwata). (b) Satellite optical image of the study area, the river’s mouth, (Ikonos-2 satellite, acquisition time: 4 October, 2008, 10:54). (c) Time-averaged radar image (average of instantaneous images collected during 11:00 to 11:17 of 4 October, 2008). A river plume front is extending from the sand bar. Breaker zone is formed at the shoal of the river mouth.