Alluvial deposits are layers of sediment, such as sand, silt, and clay, that are transported and deposited by flowing water, typically in rivers and streams. These deposits often accumulate in floodplains, riverbanks, and deltas, where the water slows down and loses its ability to carry heavier materials. These sediments are important for agriculture, as they enrich the soil with nutrients. Regions with significant alluvial deposits, like the Ganges River in India or the Mississippi River in the United States, often support fertile farmland and diverse ecosystems due to the rich resources found in these deposits.