Modeling Seasonal Sediment Dynamics and Landscape Evolution in a Marly Badland Catchment, Draix‐Bléone Critical Zone Observatory, SE France

Badlands are sensitive components of the Earth's surface where weathering, erosion and transport processes can be observed on human timescales. Within the Draix‐Bléone Critical Zone Observatory (CZO) in SE France, both water and sediment fluxes and their climatic drivers have been recorded for >35 yrs, making it an ideal natural laboratory to develop a landscape‐evolution model (LEM) for badland evolution calibrated with field data. The aim of this study is to develop an LEM that reproduces the intra‐annual sediment‐flux variability observed in the Draix‐Bléone CZO, in particular the transition from transport‐limited to supply‐limited conditions that occurs during summer, and the associated hysteresis between rainfall and sediment fluxes. The model predicts soil thickness and sediment export at monthly timescales, providing a potential link between “classical” LEMs that pertain to long (≫1 yr) timescales and event‐scale models. Sediment supply is limited in the model by winter sediment production induced by frost‐cracking. We include the impact of rainfall intensity, identified as the main trigger of sediment mobility both on hillslopes and in streams, to reproduce the dynamics of the transport‐limited regime. Parameter calibration is performed using average annual sediment‐export and seasonal soil‐depth data in specific compartments of the catchment. The progressive increase in model complexity leads to the identification of a minimum number of process laws needed to reproduce the observed badland dynamics. Our model constitutes an important first step toward modeling observed annual morphologic changes in badlands and more accurately predicting badland evolution in the context of anthropogenic climate change.