The following information was summarized from the American Rivers website:

How do floods help the stream?

Floods are a natural process which helps maintain the health of the river.  Just as fire is essential in a forest or prairie, flooding is essential to the river ecosystem.  Various plant species are adapted to the flooding conditions; thriving on periods of wet or semi-dry conditions.  Additionally, floods cue many fish species to begin their spawning migrations.

Floods also help to form habitat.  The energy associated with a flood can be very powerful.  Eroding banks and creating side channels and islands.  In doing so, they also create places for animals to live, hide, and feed.

Floods also help plants and animals migrate to new areas downstream.  They can also clear away old vegetation, helping the understory grow.

Why are floodplains important?

Natural stream channels have an associated adjacent land area called a floodplain.  These adjacent areas are periodically inundated by flood waters and serve a variety of functions.

  • temporarily store water
  • help to dissipate energy
  • filter nutrients
  • allow for infiltration
  • provide important habitat
  • create recreational opportunities

Studies have shown that floodplain size is directly related to the overall health of a stream 

Floodplains absorb and store flood waters, reducing velocity and allow for the slow release to the stream.
They also improve water quality, plants within the floodplain filter sediments and pollutants.  Floodplain trees and plants also help to anchor the river banks preventing erosion and providing shade to reduce water temperatures.  Leaves which fall into the water are broken down by aquatic insects and other organisms.  Providing the basis for the river’s food chain.  As stated above, floodplains provide fish and wildlife the places they need to feed and reproduce.

The Federal Emergency Management Agency (FEMA) has been involved in management efforts for many years and has mapped many floodplain areas.  However, unmapped, headwater or intermittent streams have historically not been viewed as areas of importance.  These areas are becoming increasingly more significant as a direct result of their elimination.

As more and more land is developed, floodplain encroachment occurs more frequently, resulting in cumulative impacts to the downstream areas.  Healthy floodplain areas create a vegetated transition zone between rivers and upland habitats, providing shelter, food, and migration corridors for river wildlife.

For More Information on Floodplains:      ODNR Floodplains Main Page