Topographic signature of badlands landscapes

 

As part of the earth's dynamic systems, badland landscapes are chiefly generated by the interaction between bedrock weathering, climate seasonality, and the controversial contribution of the hillslope and fluvial erosion processes. Although contemporary definitions clearly point out that badland initiation is a function of overland-flow-dominated gully channels, gravitational processes-dominated mass movements, and subsurface processes-driven piping, the following related questions remain to be tackled regarding their topographic position in the landscape: (1) Are the badland landforms signature of hillslope or fluvial erosion domain? (2) How do climate and regional settings (i.e., macro landforms, homogenous or heterogenous lithologies, etc.) influence the topographic position of badlands? To address these questions, we have selected climatically distinct badlands from different continents where; digital elevation models are available: Utah and South Dakota (USA), Upper Llobregat and Murcia (Spain), Northern Apennines and Basilicata (Italy), Mediterranean and Plateau – Margin Transition Badlands (Turkey), and Southern Taiwan. The badland boundaries were visually inspected and manually digitized based on diagnostic morphologic indicators. We have utilized the slope and drainage area relationship by using a 5m digital terrain model to identify topographic thresholds at TopoToolbox, a MATLAB-based software for topographic analysis. Preliminary results show that most badland areas occupy a maximum of 10⁴ to 10⁵ m² contribution area in the landscapes. Although contribution areas relatively represent uniform thresholds in the sites, the local gradient (S), which is proportional to the contribution area, tends to be higher in the sub-humid mountainous badlands (Upper Llobregat, Northern Apennines) and wet tropical SW Taiwan than in semi-arid badlands (Basilicata, Murcia). We conclude that the topographic signature of badlands in the context of the sub-catchment scale may depict an appropriate instance of a transitional domain from a diffusive erosional process to a fluvial erosion process. Our findings may serve as a foundation for a better understanding of the classification and automatic detection of badland landscapes, also known as erosional hot spots.

This study has been produced benefiting from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) through grant 118C329 and TUBITAK 2214-A International Research Fellowship Programme.