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Floodplains are a natural feature of rivers.  They are the mostly flat land adjacent to the river and form due to the actions of the river.  Rivers erode their own banks and redeposit the eroded material downstream.  Material is added to the floodplain during floods, a process called overbank deposition.  The material that underlies floodplains is a mixture of thick layers of sand and thin layers of mud.

Floodplains in their natural form are beneficial for a number of reasons:  a) reducing the number and severity of floods, b) minimizing non-point source water pollution, c) filtering storm water, d) providing habitat for plants and animals, and e) aesthetic beauty and outdoor recreation benefits.

During high water events, some of the water is absorbed by the floodplain, helping to keep the river from overflowing.  The absorbed water can then be returned to the stream during times of low water.  If a high water event is large enough, water will overflow the channel of the river and flow onto and spread over the floodplain, which slows the flow of the water.  Reduced water flow can help prevent severe erosion and flooding downstream.      

Floodplains are also home to many types of plants and animals and may also have forests and wetlands on or adjacent to them.  These river edges provide habitat for insects, birds, reptiles, amphibians, and mammals.  The vegetation also helps filter contaminants out of the water flowing into the river.  Additionally, vegetated floodplains provide shade for the adjacent rivers and streams, increasing dissolved oxygen levels and consequently improving habitat for aquatic plants and animals.



The Lilly ARBOR Project is a CEES floodplain restoration project directly west of the IUPUI campus in downtown Indianapolis.  It is an 8-acre (~1 mile) strip of land directly next to the White River located between 10th Street and New York Streets.  The photos below - taken from the 10th Street bridge, looking south - show the function of the Lilly ARBOR Project floodplain during times of high water.  To learn more about the Lilly ARBOR Project, visit the web site at:  ..\..\Research\Restoration\ARBOR\index.htm

Normal Flow



Center for Earth and Environmental Science
 School of Science
 Indiana University~Purdue University, Indianapolis
 723 West Michigan Street, SL118
 Indianapolis, IN 46202