Hillslope evolution by nonlinear creep and landsliding: An experimental study

Landscape evolution models are widely used to explore links between tectonics, climate, and hillslope morphology, yet mecha- nisms of hillslope erosion remain poorly understood. Here we use a laboratory hillslope of granular material to experimentally test how creep and landsliding contribute to hillslope erosion. In our experimental hillslope, disturbance-driven sediment transport rates increase nonlinearly with slope due to dilation-driven gran- ular creep, and become increasingly episodic at steep slope angles as creep gives way to periodic landsliding. We use spectral analysis to quantify the variability of sediment flux and estimate the slope- dependent transition from creep to landsliding. The power spec- trum of sediment flux steepens with hillslope gradient, exhibiting fractal 1/f scaling just below the creep-landsliding transition. By evolving the experimental hillslope under fixed base-level boundary conditions, we demonstrate how disturbance-driven transport gen- erates hillslope convexity. The transient evolution is consistent with numerical predictions derived from a recently proposed nonlinear transport model, as initially steep hillslopes are lowered rapidly by landsliding before slopes decay slowly by creep-dominated transport.