a delta is formed by sediment depositing at the mouth of a river by water fanning out
mississippi_river_delta is branching_or_bird_foot_delta. delta is geological_formation. delta is not geological_formation. delta is not alluvial_sediment. river is flowing_body_of_water. delta is alluvial_sediment. mississippi_river_delta is not branching_or_bird_foot_delta. delta is flow_path. stream is body_of_water. stream is small_body_of_flowing_water.