Deformation of a modern alluvial plain

The alluvial plain of the Waal River (The Netherlands), over 4000 m2, showed large flow-lobe like structures after it had fallen dry following floodings. The upstream-directed parabola-shaped folds had mutual distances from < 1 m to about 10 m and amplitudes of up to a few decimeters. The deformation is ascribed to a rare coincidence of hydrological, topographic, and weather conditions. Local high-energy currents developed opposite to the main river current direction, dragging the top layer along over several meters. A drilled section indicates that no true detachment plane but rather a detachment zone is present. Similar structures formed under comparable conditions have not been described previously in the literature.