Bottom topography and roughness variations as triggering mechanisms to the formation of sorted bedforms

A new model is presented that addresses the occurrence of sorted bedforms on inner shelves of coastal seas. These features consist of alternating bands of coarse and fine grains, with small topographic undulations. We show that inherent feedbacks between alongshore currents, sea waves, bottom topography and roughness variations result in the emergence of morphological patterns, similar to the observed bed features. We find that two modes are amplified which display different characteristics, yielding a possible explanation to the diversity exhibited by sorted bedforms in the field. The results illustrate that both roughness variations and bottom topography influence the generation of sorted bedforms.