Properties of dune topographic state space for six barrier islands of the U.S. southeastern Atlantic coast

Barrier island dunes are postulated to exhibit two states, or stability domains. In this model, transitions between domains can exhibit irreversibility. However, these transitions may also be bistable, whereby the topography of either domain can develop at a location. To infer evidence for these dynamical properties and link them to dune topography, statistical mapping of dune topographic state space was undertaken for six barrier islands of the southeastern U.S. Atlantic coast. Topographies for three to four plots per island were constructed from airborne LiDAR data. Elevation in each was quantified in terms of descriptive statistics, spatial autocorrelation and landscape patch structure. The state space derived from ordination of these data was not primarily structured by the domain model. Instead, positive and negative relief defined the major axis of topographic variability. Only the plot topographies intermediate of these extremes in relief and contained within a smaller window of elevations resembled those of the two-state model. Their emergence along the second axis of variability was correlated with the spatial autocorrelation of elevation and geographic factors related to wave and tidal energy. Topographies suggestive of irreversibility and bistability were distinguishable based on their position in state space relative to these two domains regions.