Rivers have influence far beyond their banks. Many rivers naturally have spaces around them known as floodplains. This month’s edition of Nature At Work is all about these fascinating freshwater features. 

You might have noticed the water level in your local river getting higher after heavy rain, and lower after several days of no rain–the area of riverbank that is normally dry, but sometimes covered with water, is your river’s floodplain!

Via National Geographic: “Before-and-after satellite images of the St. Louis, Missouri, region show the orderly path of America’s Mississippi River and its tributaries in 1991 and the catastrophic flooding that occurred when unusually heavy rains caused them to overflow their banks in 1993.” Image courtesy of NASA.

Why are we talking specifically about floodplains? Isn’t the important part the actual river? We’re glad you asked. Natural floodplains are incredibly important natural features, with a number of ecological functions and ecosystem services to offer. Every natural floodplain formed through a unique blend of erosion, sedimentation and deposition over many years, providing a geological history of the river.

The main role of floodplains is to regulate and manage water cycling in the river. The sediment provides a natural reservoir for flooding, absorbing excess water and releasing it slowly when things start to dry up. Floodwaters that move downstream too quickly are a big source of erosion after storms, and floodplains help water to move downstream at a slower, more digestible pace.

Major floodplains, like that of the Amazon River in South America or the Zambezi River’s Barotse floodplain in southern Africa, can act as enormous wetlands for their landscapes. These floodplains can form entire lakes (known as oxbow lakes), support endangered species, or move such large amounts of sediment that small islands or river deltas form. 

Barotse Floodplain, Zambia. Photo by @ewitait via Flickr.

Other benefits of floodplains include:

  • Fish and wildlife habitat
  • Surface water quality maintenance
  • Groundwater recharge (surface water moves downwards, “recharging” groundwater sources)
  • Providing space for biological productivity
  • Recreational areas
  • Flood mitigation to protect engineered structures

So next time you’re near your local river, don’t just jump right in the water– take a second to appreciate the entire landscape!

Read more here from National Geographic.

Featured image (top): White River, Canada. Photo by Paul Nicklen, National Geographic

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