Characteristics of backflow in Iwaki river mouth

Saltwater flow characteristics in the mouth of the Iwaki River were investigated. The flow of water at the river mouth was highly dependent upon the water level of the coastal lake located immediately upstream, then the speed of the flow was calculated in highly accuracy by using the water level changes of the lake. Conditions in the river mouth are also markedly affected by tidal fluctuations, and the discharge of the fluctuation flow reaches to 200m3/s. Flow characteristics in the reaches river mouth were modeled and comparisons of calculations with measurement in the field revealed good agreement for periodicity and magnitude of flow rates. Incoming and outgoing water velocities reached 50 cm/s, which was sufficiently strong to transport the coastal drift that has entered in the river channel from near the shoreline back into the ocean. Backflow was lowest in April due to snowmelt, increasing in July due to the relative decrease in precipitation.