The role of hydrodynamic impact force in subaerial boulder transport by tsunami-Experimental evidence and revision of boulder transport equation

摘要

The hydrodynamic impact contributes to the initiation of subaerial boulder transport by tsunamis and tsunami-like flows. Here, we consider two approaches to modelling this impact force-hydrostatic and hydrodynamic-and assess the suitability of each in boulder transport models. The model proposed, solved as an ordinary differential equation, eliminates the need to assume a conservative value of flow acceleration. Introducing the hydro-dynamic impact force reduces, by almost 45%, the recognised overestimation of threshold flow velocity in simple hydrodynamic models for boulder transport. By contrast, including the hydrostatic impact force reduces the overestimation by less than 10%. We found the new model consistent with the results of simple flume experiments. In these experiments, three rectangular limestone blocks of 27-70 cm~3 in subaerial pre-transport setting condition were subjected to tsunami-like flow by sudden opening of a sluice gate.