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Floodwaters will flow through any breaches or swales in a natural levee. This channel flow will often scour the crevasse thus creating a much deeper channel. Although the transported sediment is predominately suspended material (silt and clay) and finer bed load (sand), much coarser material can be carried from deeper in the water column to the floodplain. As the velocity drops, the material is deposited in a small alluvial-type fan or splay away from the breach. The splay surface is characterized by distributaries, braided channels, or sheetwash features.
The grain size decreases away from the crevasse axis as the material aggrades on top of the splay and progrades toward the floodplain. The complex internal bedding is produced from many cycles of scour and fill. The structure is characterized by heterogeneity, multiple floodings, shallow-depth flow, and rapid sedimentation. Crevasse splays occur close to the channel.
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