Session3: Environmental Hydraulics
Title: RIPARIAN MICROTOPOGRAPHY OF SHONAI RIVER BY APPLYING POLE-CAMERA METHOD
Ryosuke Akahori
Currently, structures from motion-multi view stereo (SfM-MVS) techniques are widely used and considered to be among the most powerful tools for capturing the surface topography of riparian environments. Majority of the original images processed using the SfM-MVS technique are acquired through unmanned aerial vehicles (UAVs) because of their portability and operational feasibility. However, the current legal environment for UAV operation has globally changed due to security reasons, and restricted areas for UAV operation are expected to consistently expand hereafter. In this study, an alternative method to capture images for the SfMMVS is proposed, in which a remote-controlled camera mounted on top of a 7-m telescopic pole is used, referred to as the pole-camera method. We applied the proposed method during our field observations of the Shonai River, located in Japan, to investigate the evolution of microtopography and the riparian herbaceous vegetation in a specific reach of this river. High-resolution digital surface models (DSM) were produced as a result of SfMMVS by applying images obtained using the proposed method, and then investigating the comparisons between the surface elevations. The accuracy of the resulting DSM was evaluated through a comparison of these models with the results from the RTK-GNSS survey data. It was confirmed that the proposed method could provide a sufficiently accurate DSM. The DSM was applied to the topography data of a numerical calculation to reproduce the local flow structures around the vegetation patches. The results demonstrated the advantages of using such precise topography information.