Matthew Hiatt, Willem Sonke, Elisabeth Addink, Wout M. van Dijk , Marc van Kreveld, Tim Ophelders, Kevin Verbeek, Joyce Vlaming, Bettina Speckmann, Maarten G Kleinhans 

Automatic and objective extraction of channel networks from topography in systems with multiple interconnected channels, like braided rivers and estuaries, remains a major challenge in hydrology and geomorphology. Representing channelized systems as networks provides a mathematical framework for analyzing transport and geomorphology. In this paper, we introduce a mathematically rigorous methodology and software for extracting channel network topology and geometry from digital elevation models (DEMs) and analyze such channel networks in estuaries and braided rivers. Channels are represented as network links, while channel confluences and bifurcations are represented as network nodes. We analyze and compare DEMs from the field and those generated by numerical modeling. We introduce a metric called the sand function that characterizes the volume of deposited material separating channels to quantify the spatial scale attributed to each link. Scale asymmetry is observed in the majority of links downstream of bifurcations, indicating geometric asymmetry and bifurcation stability. The length of links relative to system size scales with sand function scale to the power of 0.24-0.35, while the number of nodes decreases against system scale and does not exhibit power-law behavior. Link depth distributions indicate that the estuaries studied tend to organize around a deep main channel that exists at the largest scale while braided rivers have channel depths that are more evenly distributed across scales. The methods and results presented establish a benchmark for quantifying the topology and geometry of multi-channel networks from DEMs with an automatic and objective tool.