Relationships between alluvial fans, channel steepness and drainage area in the Andean piedmont, Colombia.

Mountain regions and their foreland basins sustain a set of landforms (e.g., floodplains, fluvial terraces, and alluvial fans) that are sensitive to climatic and tectonic changes. The variation of these factors can change the rates of incision and aggradation in river valleys and trigger the propagation of the imbalance signal along with the river profile, transforming the local relief. Geomorphic indices (e.g., the normalized channel steepness index, ksn) highlight river profile and slope gradient changes. In order to advance the knowledge about the dynamics of the foreland regions, a central question emerged: Are larger fans more related to basins with high stream power (ksn) or to drainage area? To answer this question, we mapped alluvial fans and used Ksn indices to identify significant variations in stream power along the basins that constitute the headwaters of the Guaviare River, in the Eastern Cordillera of Andes, Colombia. The alluvial fans were mapped using visual interpretation of Landsat imagens and digital elevation models from Coopernicus DEM (30 m resolution). The ksn index and drainage area of basins upstream of the alluvial fan apex were quantified using TopoToolBox package. Results will be present in the conference. FAPESP Grant (#2020/11047-1)