Why are floodplains and river deltas usually very fertile?

Floodplains and river deltas are typically very fertile due to the regular deposition of nutrient-rich sediments during flooding events. When rivers overflow their banks, they spread sediments across the landscape, enriching the soil with minerals and organic matter. Additionally, the constant flow of water helps maintain moisture levels, supporting diverse plant life. This combination of nutrient availability and optimal growing conditions makes these areas highly productive for agriculture.