Floodplains vary in size and consist of the floodway -- the main channel of the river or stream -- and the flood fringe which extends from the outer banks of the floodway to the enclosing valley walls. It is the distance between the floodway and the enclosing valley walls that determines the size of the floodplain or the lack of a floodplain. The main portion of the flood plain is an area of flat, level land, adjacent to the river or stream which is often created by the lateral movement of the water.
A floodplain experiences flooding when large amounts of water are discharged into the river or stream. This may occur naturally when the ground becomes saturated or when a large amount of rain falls in a short period of time, too quickly for it to be naturally absorbed. It may also occur when waters are funneled to the flood plain through stormwater management techniques.
Proper flood management is important in an urban environment. It increases property values. It saves lives. It prevents property damage. Properties that are exposed to flood risk decrease in value substantially. Because developments continue to be built near creeks and rivers, stormwater management is more important than ever. In these locations, it’s especially important to provide the water with easy routes to escape the area to prevent flooding, thereby shrinking the flood plain and increasing property values.
In a development plan, floodplains can be used for amenities such as parks and trails which are less vulnerable to the effects of flooding.