Aeolian dune-field patterns arise from interactions (collisions) between dunes within a set of boundary conditions. Over time, patterns evolve toward fewer, larger, and more-widely spaced dunes, allowing dune spacing to be used as a proxy for dune-field maturity. In this work, the spatial density of dune interactions was measured in dune fields with mean dune spacings of 25 m to 4 km in order to study how this parameter varies with scale. Results demonstrate that the density of interactions in fields of linear and crescentic ridge dunes follows statistically distinct, but parallel, trends, and the relationship between dune spacing and interaction density can be modeled as an inverse quadratic function. When parameterized in non-dimensional terms, these two curves collapse to a constant, and the relative spatial density of interactions (termed the interaction index) does not change with spacing. This implies that interactions are drivers of pattern development at all scales of pattern coarsening. Disparate interaction indices for crescentic and linear dunes derive from the dynamic behavior of the dune morphologies. These morphologies reflect wind regime and sediment supply, and are largely independent of other boundary conditions.

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