Crevassing of an inland dune during the 1998 flood in upper Vistula river valley (South Poland)

Krewasowanie środlądowej wydmy w dolinie gornej Wisly podczas powodzi w 1998 roku A relatively small flood in April 1998 inundated stream valleys draining the Tarnow Plateau. The flood water of one of these streams crevassed a dune. An elongated crevasse, an irregular-shaped transport zone and a crevasse splay were formed as a result. The crevasse splay consisted o f several lobes, which were separated by crevasse channels. Minor fans formed at the channel outlets. All this forms were the result o f rapid processes of erosion and accumulation. The dominant lithofacies in the crevasse splay sediments were fine and medium sand with horizontal (bottomset) and low-angle (topset) stratification. Trough and planar cross-stratified medium- and coarse-grained sands appear in the middle part o f the vertical sequence. Most o f these sediments were laid down in a high-energy environment of a sheet flow. The phase o f vanishing flow left ripple marks, encountered in the highest part o f the distal splay.