The movement of isolated boulders on tidal flats by ice floes

The ability of ice floes to move isolated boulders on tidal flats by flotation and by pushing and (or) rolling them along the bed is considered in the standard format of sediment movement (entrainment, transport, and deposition). Analysis shows that flotation competence depends on ice thickness and floe size, and is sufficient to transport most of the boulders reported from eastern Canadian tidal flats. However, a limiting factor in the transportation of large boulders by this mode is likely to be the entrainment mechanism. Analysis of movement of grounded boulders by lateral ice thrust shows that, on both deformable and non-deformable beds, rolling rather than sliding will occur. Rolling competence depends on floe size, ice roughness, the ice–rock coefficient of friction, and current and (or) wind strength. Resistance to movement is a function of the embedment ratio and bed properties. Rolling could account for most of the observed short-distance transport of large boulders.