What regions around a river are normally known for the fertile ground?

The regions normally known for the fertile ground around a river are called floodplains or river valleys.

Floodplains are formed when a river overflows its banks and deposits sediment on the surrounding land. This sediment is rich in nutrients, which makes the soil very fertile. Floodplains are often used for agriculture because of their high soil quality.

River valleys are also known for their fertile soil. River valleys are formed when a river carves out a deep channel in the earth's surface. The sediment that is deposited in river valleys is also rich in nutrients, which makes the soil very fertile. River valleys are often used for agriculture because of their high soil quality.