When a flood plain is not flooded it may be good farm land
A floodplain is the flat area around a river that is covered in times of flood. A floodplain is a very fertile area due to the rich alluvium (fine sediment) deposited by floodwaters. This makes floodplains a good place for agriculture. A build-up of alluvium on the banks of a river can create levees, which raise the river bank.
Images for kids
Paraná River floodplain, at its confluence with the headstream of the Paranaíba on the right and the Verde River, near Panorama, Brazil
Gravel floodplain of a glacial river near the Snow Mountains in Alaska, 1902
This aggradational floodplain of a small meandering stream in La Plata County, Colorado, is underlain by silt deposited above a dam formed by a terminal moraine left by the Wisconsin Glacier.