Abstract
Coastal boulders transported inland by marine hazards, such as tsunamis and storms, are commonly found worldwide. Studies on the transport process of coastal boulders contribute to the understanding of a wide range of phenomena such as high-energy flow events, fluid-structure interaction, and coastal sediments. Consequently, it is crucial to understand how boulders move, but even more important to determine the instability condition for boulder transport. The hydrodynamic formulas including drag and lift coefficients are widely used to predict the incipient motion of boulders while few studies are conducted to evaluate the capability of these formulas. Recently, a series of laboratory experiments carried out at the Hydraulic Engineering Laboratory (Italian acronym LIDR) of the University of Bologna, Italy, revealed that boulders can start moving when the flow height and flow velocity are lower than the theoretical threshold computed by hydraulic formulas. In this paper, we use a numerical shallow water model to reproduce these freely available laboratory data with the aim of testing the capability of the model in capturing the main evolution of the process, and of casting new light on the instability condition of coastal boulders.
Highlights
Coastal boulders are regarded as the consequence of extreme marine events, and many imply tsunami events [1,2]
The experimental flows were generated by opening a gate of a water tank with initial water level in the tank sweeping a range sufficiently large to cover a reasonable interval of flow velocities and heights
The numerical model was found to reproduce quite well the propagation time of the bore in the flat portion of the flume, with discrepancies only found in the flume sector closer to the gate, that is in the region of bore formation, which do not affect the analysis
Summary
Coastal boulders are regarded as the consequence of extreme marine events, and many imply tsunami events [1,2]. Parallel laboratory tests were implemented to study boulder transport [21] The essence of these numerical models was to describe the flow-boulder interaction by coupling a shallow water model for flow dynamics and an analytical model for the block. Gradually more sophisticated studies have been carried out to figure out the dynamic process of boulder transport, investigations are still needed to verify the accuracy and capability of the existing numerical models and to better understand the basic physical process. On the basis of the experiments on the incipient motion of boulders impacted by water flows conducted by Bressan et al [22], the aim of this paper is to explore the performance of the shallow water equations in predicting the flow properties (depth and velocity) and to improve our understanding of boulders mobilization. Considerations on the capabilities of our numerical model to predict block mobilization are done in the last section of the paper
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
