Delaware Water Gap National Recreation Area - Flood Plains

Delaware Water Gap National Recreation Area by National Parks Service

River floodplains are the flatlands along a river that are naturally subject to the periodic inundation by the river.

When floodplains accept water from a flooding river, they diminish the force of water flow on the river's main stem and prevent damage downstream. (In the photo, the main stem of the river is the bright streak in the background behind the trees.) Water on floodplains has little or no flow, so it doesn't usually damage trees - which are adapted to survive occasional flooding - or erode soil, unless it is carrying chunks of ice. Also, because the water in a floodplain is not moving, it will deposit much of its sediment on the floodplain instead of carrying it downstream and depositing the sediment between larger gravel and naturally smooth rocks or "cobble" on the riverbed. This is important for fish, who use the spaces between cobblestones as a place for depositing eggs, and to aquatic insects, who hide and forage in these spaces.