River deposits are materials that are left behind by rivers as they flow. Alluvium, which is seven letters long, is a type of sedimentary material that is composed of clay, SILT, sand, and gravel. SILT, which is five letters long, is a type of soil that is composed of fine particles. SEDIMENTS, which is nine letters long, are solid particles that are transported by water, air, or ice. Silts, which is four letters long, are fine-grained soils that are composed of clay and SILT particles. Deltas, which is six letters long, are landforms that are formed when a river splits into several branches before it reaches the sea.