abyssal plain aeolian processes alluvial fan base level bay mud beach beach cusps biorhexistasy bioswale braided river calcite clay climate decantation depth-slope product desert eolianite erosion exner equation fluid dynamics forest fossil glacier gravel bar holocene karst topography lake lake geneva levee loess madagascar moraine ocean oceanic trench oxbow lake particle size plateau regolith river delta san lorenzo river sand sea sediment transport sedimentary basin sedimentary depositional environment sedimentary rock settling shear stress shifting cultivation silt slash and burn stream bed surface runoff till turbidite turbidity vegetation waterfall