Discerning the relative importance of Tectonic vs Climatic Controls on Topography from River Profile Analysis

The competing influence of climate and tectonics drive landscape change. However, separating the relative importance of tectonics and climatic control on the morphology and evolution of Earth’s present-day topography is challenging; climate and tectonics covary, their spatiotemporal scales differ, and geomorphic observations can be inconclusive. Longitudinal river profile analysis has long been used in geomorphology to evidence the influence of tectonics or climate on topography. However, such analysis often requires making limiting assumptions about the spatiotemporal variations in tectonic, climatic and geological conditions experienced by a river network. Here we present a novel river profile network analysis that is less dependent on limiting assumptions, and leverages different measures of river profile concavity. River profile concavity is the rate at which a river network’s slope decreases downstream. We acknowledge an apparent concavity, which reflects the present-day observed geometry, and an inherent concavity, which is the expected concavity of a river network under idealized conditions (all other forcing being equal). Results from numerical modelling show that the differences between the inherent and apparent concavity can be used to extract information about the relative importance of climate and tectonics in shaping river profiles. Applying these results to Taiwan, we demonstrate that the regional pattern of rock uplift, not precipitation, exerts the most significant influence on present-day river profiles. Taken together, these results overcome previous challenges in river profile analysis for deciphering climate vs. tectonic controls on landscape morphology and evolution.