Moving beyond the Galloway diagrams for delta classification: Connecting morphodynamic and sediment-mechanistic properties with metrics of delta channel network topology and dynamics

Abstract:

Delta channel networks self-organize to a variety of stunning and complex patterns that carry the signature of their climatic and hydro-morphodynamic forcings (e.g., river, tides and waves) and the mechanistic properties of their sediment (e.g., particle size, cohesiveness). Recently, we presented a rigorous framework based on spectral graph theory to study delta channel networks from a topologic (channel connectivity) and dynamic (flux exchange) perspective for advancing our understanding of deltas as complex systems [Tejedor et al., 2015a,b]. The framework enhances the quantitative comparison of deltas and seeks to replace the still qualitative diagrams [Galloway, 1975; Orton and Reading, 1993] by relating the controlling physical mechanisms of delta formation to the spatial patterns they create. Here we examine one controlling factor of river dominated delta evolution, namely the sediment cohesiveness. To explore the dependence of the delta channel network topo-dynamic complexity on sediment composition, we have simulated delta channel networks using a hydro-dynamic model (Delft3D) with varying sediment parameters. The results of our analysis show how complexity metrics are able not only to capture the variability in the delta network structure, but also to quantify the increase of complexity when the sediment composition transitions to coarser grains.