Dr. Helen Willemien Dow (maiden name: Beeson)

River networks dissect much of Earth's surface into drainage basins. Erosional instabilities arising from competition between advective and diffusive processes can explain why headwaters branch, but the mechanics linking larger scale network branching with evolution towards a characteristic river basin shape are poorly constrained. 

​

Horton hypothesized that incipient networks formed down gradient on an inclined, planar surface have an unequal distribution of drainage area such that larger basins erode more rapidly and widen at the expense of adjacent streams with lower erosion rates.

​

We map channel steepness and analyze basin topology and geometry in simulated and real landscapes with a large range in spatial scale (0.1 -1000 km) but with similar inclined, planar surfaces at the time of incipient network formation. We document that the evolution from narrow rill-like networks to dendritic, leaf-shaped river basins follows from initial drainage area differences between catchments. These serve as instabilities that grow, leading to divide migration, stream capture, lateral branching and network reorganization.