Scale-Free Structure of Surface-Water Connectivity Within a Lowland River-Floodplain Landscape

Abstract

Lowland rivers regularly flood and create complex inundation patterns where energy and matter are exchanged between landscape patches over a dynamic network of surface-water connections. Scale-freeness of networks for phenomena in many disciplines have been studied with mixed results. Here we present the first documented example of a (roughly) scale-free network of surface-water connections within a river-floodplain landscape. We accomplish this by simulating 23 inundation maps across the historical range of flows for the Mission River in Texas. We then analyze the topology of the surface-water connections between the river and two habitat patch types. Results show that surface-water connectivity is scale-free for ≥64% of simulated flows (≥70% for flows with floodplain inundation). Moreover, the dynamic surface-water connections meet five of the six conceptual criteria of scale-free networks. Our findings indicate that river-floodplain landscapes are self-organizing toward scale-free surface-water connections among patches that optimizes energy and matter exchange.