Numerical modelling of boulder transport during extreme flow events

Abstract:

Extreme events, such as tsunamis or storm surges, can cause great damage and dramatic changes to the coastline. Meanwhile, these high-energy events can also transport large grain size sediments (i.e., boulders), which can potentially be preserved in the geological record and used to study flow dynamics during these extreme events. Recent boulder transport modelling mostly focuses on clear water flow with steady flow conditions. Obviously, topography and other sediment transport processes have been ignored before in previous researches. Before the tsunami wave reaches the coastline, the flow can erode a massive amount of sediments from shallow marine environments. The flow velocity and direction will change significantly due to the topography, and the flow density will also increase with more deposits carried in the flow. Our research aims to establish a new sediment transport model to explore the boulder transport mechanisms under different flow conditions and topographies. Our model includes three different boulder transport modes (sliding, suspension, and rolling) and tracks the boulder movement processes in idealized and real topographic as well as flow conditions. Finally, we combine our boulder transport model with GeoClaw, which is a depth-averaged tsunami model to study the flow inundation and boulder deposits on Anegada, British Virginian Islands.