An algorithm for objective analysis of grainflow morphology

Authors: Pei Zhang*, Department of Geography, The University of Alabama
Topics: Coastal and Marine
Keywords: Dune migration, Sediment transport, Aeolian geomorphology, Terrestrial Laser Scanning, Digital Elevation Model
Session Type: Virtual Paper
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Grainflows produce temporary geomorphological signatures on the slipfaces of aeolian dunes, and are a fundamental agency by which dunes migrate. The purpose of this study is to present an algorithm to objectively and efficiently delineate grainflow boundaries by processing Digital Elevation Models (DEMs) in Matlab and ArcGIS. Grainflows can be identified by analyzing temporal changes in slipface elevation, and the morphology can be extracted by defining the boundary that encloses the area of movement. The method allows large numbers of grainflows to be quickly and objectively delineated and extracted from LiDAR data. The process avoids the subjective nature of manual measurement, thereby improving commensurability of different grainflow regimes in both terrestrial and extraterrestrial environments. The algorithm is presented here in the context of analyzing grainflows and related processes on the slipfaces of dunes, but it is applicable over the broader scope of other forms of slope failure and geophysical flows, such as avalanches, snowslides, landslides, and debris flows. The method was tested on a set of 117 DEMs, and 1621 grainflows were delineated and the volumes of sand moved were analyzed with this method by finding and fitting an appropriate probability distribution function. The results (P = 0.42) indicate that logarithmically transformed accretion volumes fit a 3-parameter Weibull distribution with the parameters of shape = 5.54, scale = 6.40, and lower threshold = 5.06.

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