Monitoring Hydromorphological Changes in Meandering Rivers via
Multi-Temporal UAV-Based Measurements
Abstract
Unmanned Aerial Vehicle (UAV) based Structure-from-Motion (SfM)
techniques have renovated 3D topographic monitoring of earth surface,
offering low-cost, rapid and reliable data acquisition and processing.
Multi-temporal models of the river environment can be produced by
autonomous operation in order to determine erosion, subsidence,
landslide, soil transport and surface deformation in the riverbeds.
Herein, the acquisition of repeated topographic surveys helps us to
characterize the flow regime and to monitor the sediment dynamics. This
study presents the hydromorphological changes of the meandering
structures by using UAV-generated point clouds and Digital Surface
Models (DSMs) produced by SfM at different times in the Büyük Menderes
Basin located in the western part of Turkey. The processing of the data
obtained with the flights were made in January and June 2018 at selected
three meander locations with the highest visible changes according to
the long-term satellite imageries. Especially, riverbank erosion along
the river was determined by digitizing the edges and volumetric
calculations of the eroded/deposited sediments derived from UAV-based
measurements. In addition to the periodic volumetric differences of the
meander structures, the differences in volumetric comparison methods for
the same meander structures have been evaluated. Ultimately, the
sediment profiles were extracted along the river banks at the selected
part of the meanders and the amount of deposited sediments were
determined to increase in a range between 1.5% and 3.3% of the total
sediment. In conclusion, it is estimated that UAVs will be used instead
of conventional photogrammetry aircraft in many future projects,
considering the data production times and costs in large areas. Further,
various digital cameras and sensors can be mounted on UAVs in order for
examining the sediment effect on the health and productivity of plants
in agricultural areas around the meanders.