This discussion paper is a preprint. It is a manuscript under review for the journal Earth Surface Dynamics (ESurf).
Lithology and orographic precipitation control river incision in the
tropical Andes
Benjamin Campforts1,2,Veerle Vanacker3,Frédéric Herman4,Matthias Vanmaercke5,Wolfgang Schwanghart6,Gustavo E. Tenorio2,7,Patrick Willems8,and Gerard Govers2Benjamin Campforts et al. Benjamin Campforts1,2,Veerle Vanacker3,Frédéric Herman4,Matthias Vanmaercke5,Wolfgang Schwanghart6,Gustavo E. Tenorio2,7,Patrick Willems8,and Gerard Govers2
1Research Foundation Flanders (FWO), Egmontstraat 5, 1000 Brussels, Belgium
2Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200E, 3001 Heverlee, Belgium
3Earth and Life Institute, Georges Lemaître Centre for Earth and Climate Research, University of Louvain, Place Louis Pasteur 3, 1348 Louvain-la-Neuve, Belgium
4Institute of Earth Surface Dynamics, University of Lausanne, CH-1015 Lausanne, Switzerland
5Université de Liège, Département de Géographie, Clos Mercator 3, 4000 Liège, Belgium
6Institute of Earth and Environmental Sciences, University of Potsdam, Germany
7Facultad de Ciencias Agropecuarias, Universidad de Cuenca, Campus Yanuncay, Cuenca, Ecuador
8Department of Civil Engineering – Hydraulics Section, KU Leuven, Kasteelpark 40 box 2448, 3001 Leuven, Belgium
1Research Foundation Flanders (FWO), Egmontstraat 5, 1000 Brussels, Belgium
2Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200E, 3001 Heverlee, Belgium
3Earth and Life Institute, Georges Lemaître Centre for Earth and Climate Research, University of Louvain, Place Louis Pasteur 3, 1348 Louvain-la-Neuve, Belgium
4Institute of Earth Surface Dynamics, University of Lausanne, CH-1015 Lausanne, Switzerland
5Université de Liège, Département de Géographie, Clos Mercator 3, 4000 Liège, Belgium
6Institute of Earth and Environmental Sciences, University of Potsdam, Germany
7Facultad de Ciencias Agropecuarias, Universidad de Cuenca, Campus Yanuncay, Cuenca, Ecuador
8Department of Civil Engineering – Hydraulics Section, KU Leuven, Kasteelpark 40 box 2448, 3001 Leuven, Belgium
Abstract. Process-based geomorphic transport laws enable to assess the impact of rainfall variability on bedrock river incision over geological timescales. However, isolating the role of rainfall variability on erosion remains difficult in natural environments in part because the variability of rock strength and its resistance to incision are poorly constrained. Here, we explore spatial differences in the rate of bedrock river incision in the Tropical Andes. The Ecuadorian Andes are characterized by strong rainfall gradients due to orographic precipitation sourced in the Amazon basin. In addition, the tectonic configuration has generated a profound lithological heterogeneity. The relative role of either these controls in modulating river incision on millennial time scales, however, remains unclear. Using 10Be catchment-wide erosion rates, meteorological and hydrological data, as well as data on bedrock erodibility, we provide quantitative constraints on the importance of rainfall variability and lithological variations. Explicit incorporation of rock erodibility in river incision models predicated on the stream power equation enables us to identify a first order control of lithology on river incision rates. Rainfall variability based on a spatially and temporally explicit hydrological dataset and a stochastic-threshold river incision model explain regional differences in river incision that cannot be attributed to topographical and/or lithological variability.
In this contribution, we explore the spatial determinants of bedrock river incision in the tropical Andes. The model results illustrate the problem of confounding between climatic and lithological variables, such as rock strength. Incorporating rock strength explicitly into river incision models enables us to clarify the role of rainfall variability in controlling river incision rates.
In this contribution, we explore the spatial determinants of bedrock river incision in the...