We demonstrate that landscapes with more planar initial conditions tend to have lower mean junction angles. Geomorphic processes on alluvial piedmonts result in especially planar initial conditions, consistent with a correlation between junction angles and the presence/absence of Late Cenozoic alluvial deposits and the constraint imposed by the intersection of planar approximations to the topography upslope from tributary junctions. We caution against using junction angles to infer paleoclimate.

Many Earth surface processes are controlled by the spatial pattern of surface water flow. We review commonly used methods for predicting such spatial patterns in digital landform models and document the pros and cons of commonly used methods. We propose a new method that is designed to minimize those limitations and show that it works well in a variety of test cases.