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Abstract

With advancements in the efficiency and accuracy of investigation techniques and equipment, remote sensing technologies have been widely used to investigate river conditions. Quantifying the morphology along a river channel was difficult before airborne laser altimetry technology, light detection and ranging (LiDAR), was introduced, facilitating the collection of high-resolution, highly accurate topographical data. This study adopted airborne LiDAR data for analyzing and recognizing riverbed morphology. The roughness index was defined as the standard deviation of a residual topography. A variable moving-window was used to derive a smoothed digital elevation model (DEM). According to the roughness index, the residual topography was the difference between the original and smoothed DEMs. Roughness data derived from different reaches of a predisaster riverbed were compared with data derived from a postdisaster riverbed. The experimental results showed that the upper reaches exhibited higher roughness values than did the lower reaches. Thus, the relief of the postdisaster riverbed surface was near the derived smoothed relief. Such characteristics were reflected in the major differences evaluated through slope measurements in the riverbed morphological analysis; the position of the peak value changed after the disaster. An integrated plane-wise fluvial circumstance of a river watershed area was rapidly and accurately constructed, and this study concluded that these remote sensing techniques are vital in facilitating traditional surveys for regional investigations.

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