The Nile River in eastern Africa is the longest river in the world and has a large delta. The Amazon River and Mississippi River also have large deltas. River deltas make good farmland, as does the land along rivers, called flood plain. This land is called flood plain because it is low and easily flooded when a river overflows its banks. Floodwaters carry soil and other particles and leave them on the flood plain.
Floods can be good for the flood plain, but they also can be damaging.
Many towns are built along rivers, too. When a river floods, it can damage homes and businesses in these towns. People have built levees and dams to prevent floodwaters from reaching their towns. Levees are high banks built along rivers that keep them from overflowing. Dams are structures built on rivers that control the flow of water.