How Are Floodplains Formed?
The Center for Earth and Environmental Science describes that floodplains are formed as rivers erode their own banks. Floodplains are the flat lands that lie adjacent to a river; they encompass the area that floods when the river's water level rises. As the river flows, it washes material downstream. When a flood occurs, this material is resuspended in the water and added to the floodplain.