How is a flood plane formed?

Answer 1

A 'young' river will flow more or less straight and relatively quickly. As it cuts down throught the land it levels out and flows more slowly. Now that it's slower it cannot keep in suspension some of the mud which was in it and this settles out a bit. This will raise the bottom of the river bed and the river will get shallower. At times it will flow over the banks and the areas each side will have mud deposietd from this almost still water. This process builds up a plain which is known as a flood plain.