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Floodplains 



During a flood is not the time to figure out that you built your 

 house in the floodplain, too close to a stream. 



Floodplains are critical 

 components of a healthy stream 

 or river system. They provide 

 room for flood waters to spread 

 out and soak in to recharge 

 groundwater and to reduce the 

 flood's erosive energy. The fertile 

 soil of floodplains enables 

 abundant vegetation to grow and 

 provides impwrtant wildlife 

 habitat. If you armor your stream 

 bank and raise its height to 

 prevent flooding on your land, 

 you are sending more erosive 

 energy doivnstream to your 

 neighbors. 



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How We Impact Floodplains 



• Poor agricultural and grazing practices 



• Residential and commercial 

 construction 



• Protecting property by building dikes, 

 levees, and retaining walls; by installing 

 riprap; and by eliminating overflows 

 into side channels 



Effects of Our Impact 



• Decreases ability of floodplain to 

 disperse stream energy during flood 

 flows, which: 



— Increases energy of flood downstream 

 — Increases peak flood levels 

 — Increases bank and bed erosion on 

 neighboring property 



• Decreases vegetation cover, which may 

 cause spring runoff to occur earlier and 

 over a shorter period of time, and to 

 produce higher peak flows 



• Decreases ability of floodplain to 

 recharge local aquifers, which: 



Effects of Our Impact (continued) 



— Decreases riparian vegetation 



— Reduces channel flows in drier months 



• Reduces aquifer volume 



• Increases size and frequency of floods, 

 causing more damage to property and 

 stream channels 



• Increases pumping costs 



Lessening Our Impact 



• Avoid construction in the floodplain 



• Do not restrict floods from flowing into 

 side channels without consulting stream 

 management experts and obtaining a 

 permit 



• If construction activities must occur on 

 floodplains, minimize disruption of the 

 soils and vegetation 



• Use agricultural methods that minimize 

 impact on floodplain 



• Establish greenbelts or stream protection 

 corridors in floodplains 



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