Articles | Volume 4, issue 1
Research article
15 Jan 2016
Research article |  | 15 Jan 2016

Tectonic geomorphology at small catchment sizes – extensions of the stream-power approach and the χ method

S. Hergarten, J. Robl, and K. Stüwe

Abstract. Quantitative tectonic geomorphology hinges on the analysis of longitudinal river profiles. The model behind almost all approaches in this field originates from an empirical relationship between channel slope and catchment size, often substantiated in the form of the stream-power model for fluvial incision. Significant methodological progress was recently achieved by introducing the χ transform. It defines a nonlinear length coordinate in such a way that the inherent curvature of river profiles due to the increase of catchment sizes in the downstream direction is removed from the analysis. However, the limitation to large catchment sizes inherited from the stream-power approach for fluvial incision persists. As a consequence, only a small fraction of all nodes of a digital elevation model (DEM) can be used for the analysis. In this study we present and discuss some empirically derived extensions of the stream power law towards small catchment sizes in order to overcome this limitation. Beyond this, we introduce a simple method for estimating the adjustable parameters in the original χ method as well as in our extended approaches. As a main result, an approach originally suggested for debris flow channels seems to be the best approximation if both large and small catchment sizes are included in the same analysis.

Short summary
Longitudinal river profiles are increasingly used for unraveling the tectonic history on a regional scale. In the last years, the introduction of the so-called chi transform brought significant technical progress, but this method is still limited to the domain governed by fluvial erosion covering only a small part of the surface. Here we present and compare extensions of the method towards smaller catchment sizes where hillslope processes or debris flows significantly contribute to erosion.