Active rivers can significantly alter their features within the channel, in the riparian zone and across the neighboring floodplain. However, accurate monitoring of extensive river channel morphodynamics using ground-based survey techniques can be challenging because of the need to access all locations across the site and the sparse point measurements that are obtained, and satellite remote sensing may not be appropriate when the river channel width and rate of change are below the spatial resolution of available imagery. However, unmanned aerial system (UAS) provides the opportunity to gain timely and high-resolution datasets quantifying river channel changes, bank erosion, point bar, and island development, and even bathymetric variations in clearwater conditions, but more studies are needed to assess their overall accuracy. In this chapter, introduction to the key advances and challenges of using UAS methods in fluvial geomorphology is given, with a special focus on the survey design, horizontal and vertical channel changes, granulometry, and bathymetry.