Geometry of rivers strongly determined by movements in the earth’s crust

Rivers shape the landscape, but pinpointing the processes that determine the shape of rivers is a challenging puzzle. A new analysis of global climate, topography and tectonic data reveals that the course of rivers worldwide is largely determined by movements of the earth’s crust. The climate has far less influence than was thought. This discovery was made by a team of Swiss, American and Dutch researchers, including VU Amsterdam earth scientist Wouter Berghuijs.

04/12/2021 | 5:00 PM

Published today in the journal Nature Geoscience, their research shows how tectonic activity shapes the vertical geometry of rivers worldwide. The way in which the downstream slope of a river changes varies greatly from river to river. There are three basic variations: a river becomes steeper downstream, a river has a constant slope, or a river becomes less steep downstream. Most rivers become less steep downstream.

Merging datasets
A team of researchers, among them VU hydrology specialist Wouter Berghuijs, investigated the links between climate, tectonics and river profile shapes by merging a dataset of 350 thousand river segments with datasets drawn from climate and tectonics. The analysis shows how the vertical profile of rivers worldwide is strongly determined by spatial variations in the rising of the earth’s crust under the influence of tectonics. The more tectonic activity there is, the more the downstream slope of the river decreases.  

Climate has little influence
These new findings contrast with previous global analyses which suggested that climate played a greater role in river geometry. The new work reveals the climate effects previously studied to be far less important than tectonic activity. This means that the profiles of many rivers have remained largely unaffected by relatively rapid changes in climate, but instead reflect the slower dance of the earth’s crust.

Three possible river profiles
Overview of the three possible river profiles