Climate’s influence on topography encoded in stream network topology and geometry

Abstract Stream networks express how Earth’s hydrologic cycle is embedded within its three-dimensional topography. In a planar view, a stream network’s morphology is often described by its topological connectivity and branching geometry. Although these two characteristics are naturally connected, they have mostly been studied independently, leaving their co-evolution poorly understood. Here, we analyze how the topology and geometry of 17,021 5th-order real-world river networks across the contiguous United States are shaped by climate and topography. We found that ~73% of these networks show topological self-similarity in their branching patterns. Stream networks with more side-branching tend to have wider network-averaged branching angles. Surprisingly, our analysis reveals that the climate dependence of network topology observed in other studies is mainly mediated through the climate dependence of topographic and geometric metrics, such as branching angles and channel slope ratios between pairs of incoming tributaries. These findings demonstrate the co-evolution of topography, network topology, and network geometry under the joint impact of landscape evolution and climatic forcing.