Towards a process-based classification of delta morphology via quantification of shoreline structure

Delta shoreline structure has long been hypothesized to encode information on the relative influence of fluvial, wave, and tidal processes on delta formation and evolution, however analyses and comparisons of deltaic shorelines have typically been qualitative or utilized relatively coarse quantitative metrics. We ask whether robust quantification of shoreline structure would enable mapping of delta shorelines to a physically-based space in which the relative influence of the different processes could be compared, as has recently been done using a sediment budget approach. To explore this question, we analyze Landsat-derived shorelines from more than 40 deltas across the globe. Since the shorelines exhibit variability on scales ranging from tens of meters to kilometers, we propose a multiscale characterization of shoreline structure by mapping the shorelines to univariate series and using spectral analysis techniques to distinguish shoreline variability across a range of spatial scales within and across deltas. We observe distinct classes of deltas, which we attribute to the different processes driving deposition in these systems. The analysis suggests the potential towards a quantitative, process-based classification of delta morphology via shoreline structure.