"Rivers Forming" graphic from National Geographic.

The Hydrology of Tree-Like Figures on the Desert

I came across this aerial photo by National Geographic and was compelled to post on the hydrology of how such a stunning river would develop.

Dendritic drainage structures originate from sheet flow – downslope movement of water as a thin sheet – which converges or diverges on an uneven surface. Where convergence occurs the water develops more power (mass x velocity), which mobilizes sediments. This erosion deepens the channels, concentrating even more water and new rills develop as water flows into the deepening rill. The watershed boundary seen between the main branches of this stream will eventually close in to a narrow ridge as headward expansion progresses. Erodability of the surface is the critical factor explaining differences in drainage structure given comparable conditions of slope, permeability and climate. Patterns like these are typical where there are clayey soils, little vegetation, and concentrated precipitation. Drainage density is the sum of stream length divided by drainage area and provides a measure of how efficiently the landscape can transport water, therefore you can expect a very quick, response to rain events in streams like these.

It always amazes me the how beautiful and articulate nature can be.

Photograph courtesy Adriana Franco/National Geographic Your Shot.

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