Revealing the physics of sediment ploughing by geophysical mass flows: Depth-averaged approach

Abstract

Ploughing is an erosion mechanism where the dam-like front of a geophysical flow shovels sediments along its path to increase its runout. Ploughing is commonly reported in the field. However, the physics of ploughing remain missing in hazard assessments tools owing to the difficulties of simulating the competing effects between erosion and deposition. In this study, 2D non-depth-averaged (non-DA) simulations are used to elucidate the physics of ploughing induced by erosion and deposition. A closure model for erosion and deposition is then developed and implemented into a depth-averaged (DA) framework to facilitate practical simulations for routine hazard assessments. Both the 2D non-DA and DA models are based on the Smoothed Particle Hydrodynamics (SPH) method. The new DA model is evaluated with experimental data and shown to be able to simulate the competing effects of erosion and deposition, which causes flow momentum gain and loss, respectively. The new DA framework is proven to be able to simulate the effects of ploughing, which has been a long-standing limitation of DA models.