Climatic controls on the stream network topology

Stream networks are striking expressions of how Earth’s hydraulic cycle shapes topography, yet the degree to which different geomorphological processes are visible in their ramified structure remains debated. Here we analyzed 18,030 river networks across the contiguous United States as mapped by the high resolution National Hydrographic Dataset, measuring the Tokunaga parameter c, which characterizes the degree of side-branching, in order to quantify the stream networks' topologies. We find that stream networks with more side branches tend to occur in wetter climates while channel networks in arid regions are less "feathered". As side branches tend to be steeper than the main channel, the aridity-induced dependence of slope ratio identified in recent studies may indicate inherent topological differences between stream networks in arid and humid regions. Such climatic signatures in the planform morphology of stream networks may help to better understand landscape evolution on the continental scale, and may also hold clues for the climatic history of other planetary bodies such as Mars or Titan.