Erosion-induced momentum production and system acceleration govern landslide mobility

Erosion can fundamentally alter landslide acceleration through the produced momentum. However, existing analytical landslide velocity models do not account for the energy dissipation associated with erosion-induced system acceleration. Here, I present a novel, complete dynamical velocity model for erosive landslides that incorporates two intrinsically coupled mechanically essential processes: erosion-induced acceleration and mobility booster through the net momentum production. This coupling is established analytically by formulating a simple equation for landslide velocity with erosion and deriving its elegant exact solution. I demonstrate that these two processes jointly govern the mobility of erosive landslides. My model applies to both non-deformable and deformable landslides, a key advantage, as erosive landslides are inherently deformable. The newly introduced booster velocity, defined as the ratio of erosion-induced acceleration to the mobility booster rate, provides the first precise mechanical criterion for determining landslide mobility: the lower the booster velocity, the higher the landslide mobility, a phenomenal understanding. This criterion incorporates all governing mechanisms: erosion rate, energy generator, and resulting acceleration. Remarkably, this result becomes possible only when erosion-induced acceleration is considered. However, contrary to prevailing perceptions, erosion-rate alone is insufficient to determine landslide mobility, irrespective of its magnitude. The model ascertains that accurate simulation of landslide dynamics requires accounting for erosion-induced reductions in frictional energy dissipation and inertia, alongside system acceleration, as these mechanisms collectively control landslide mobility. Neglecting erosion-induced reduced-inertia leads to physically inconsistent predictions and can substantially underestimate landslide mobility, potentially resulting in catastrophic consequences for people and infrastructure in landslide-prone mountain slopes and valleys.