The impact of landslides on sediment dynamics, fluvial bedrock incision and steady-state topography

Abstract:

Landslides are the main source of sediment in most mountain ranges while rivers act as conveyor belts, evacuating landslide-derived sediment. The dynamic interplay between landslide sediment delivery, fluvial transport, and river incision into bedrock controls the pace of landscape evolution and mediates relationships among tectonics, climate, and erosion.

Here, we evaluate the impact of landslides on sediment dynamics using HyLands, a novel Landlab component that is designed to numerically simulate both landslide activity and sediment dynamics following mass failure. The hybrid nature of the model is in its capacity to simulate both erosion and deposition at any place in the landscape. This is achieved by coupling an existing, mass conservative, model for channel incision (SPACE) with a new component simulating rapid, stochastic mass wasting and subsequent sediment redistribution (landsliding).

We first illustrate the functionality of HyLands to capture fluvial dynamics ranging from detachment-limited to transport-limited configurations. We then apply the model to a portion of the Namche-Barwa region in Eastern Tibet and compare simulated and observed landslide magnitude-frequency and area-volume scaling relationships. Next, we illustrate the relevance of explicitly simulating landsliding and sediment dynamics over longer timescales for landscape evolution in general and river dynamics in particular. We further demonstrate how the interplay between landslide sediment delivery and fluvial dynamics can result in the formation of autogenic knickpoints and epigenetic gorges. Finally, we show how landslides strongly alter steady state topography and how positive feedbacks between landslide sediment delivery and fluvial incision limit topographical relief.