Inverse maximum gross bedform-normal transport 1: How to determine a dune-constructing wind regime using only imagery

Abstract

It has been a goal of aeolian science to use bedforms as indicators of local and regional sediment transport and atmospheric circulation, but even with the application of the rule of maximum gross-bedform normal transport (MGBNT), the underdetermined nature of the problem has precluded its application in all but the most simple cases. We present a method to apply the rule of MGBNT and its inverse (IMGBNT) from analysis of aeolian dune crestlines derived from aerial imagery. Although the solutions to IMGBNT analysis are non-unique, the possible transport vectors influencing bedform morphology can often be constrained by making inferences regarding bedform type (e.g., transverse, oblique, or longitudinal), resultant drift direction, and the ratio of transport vector magnitudes. The technique is demonstrated on the Great Sand Dunes, located in Colorado, USA. This dune field has a wide array of dune morphologies; eight crestline sets were identified and mapped. IMGBNT analysis and the subsequent constraint of possible solutions suggests that transport vectors from the southeast and southwest, with a SE:SW transport ratio of ∼1:2, produce oblique north–south oriented dunes that dominate the main dune field. These results compare favorably with MGBNT analysis of meteorologic measurements from three stations located adjacent to the Great Sand Dunes, which predict dune types and orientations similar to those observed in their vicinity.