OBSERVATION OF SEDIMENT PROCESSES OF A FLOOD EVENT AT THE RIVER MOUTH OF TENRYU, JAPAN WITH X-BAND RADAR AND IN SITU MEASUREMENTS

摘要

A flood event in July 2010 at the river mouth of Tenryu, Japan was observed with a land based X-band radar and in situ measurements. Radar images were collected hourly for more than 72 hours from the beginning of the flood and processed to time averaged images. Variations of velocity components, turbidity and water temperature were measured at the bottom of approximately 1.5 km offshore of the river mouth at depth of XX m. With the X-band radar, migrations of undulations in the river channel bottom to the downstream were observed, which were moving faster when the water level gradient increased between the river and sea. At the same time, several sharp intermittent rises were observed in turbidity and water temperature, which were nearly in-phase with increase of water level gradient. These are suggesting that flood flows traveled down along the slope with sediments when river bed revolution was active at the periods when the water level difference between the river channel and sea increased.