Field Investigation for Morphodynamic of River Mouth Bar Using UAV and RTK-GNSS

A field investigation was carried out to observe changes in a river-mouth sand bar on the Tenjin River in Tottori prefecture, Japan. Topographic surveys were conducted using a real-time kinematic-global navigation satellite system (RTK-GNSS), unmanned aerial vehicle (UAV), and radio-controlled (RC) boat from July 2015 to March 2019. From these measurement data, the characteristics of the deformation of the sand bar tip in the opening of the river mouth and the relation between the river mouth bar and sea bottom changes were analyzed, and the validity of an alternative survey technique using RTK-GNSS, UAV and RC boat was confirmed. During the period of the field investigation, the sand bar was flushed away by a typhoon attack, and the recovery process of the river-mouth bar was investigated by RTK-GNSS and UAV surveys.