1 4 ^0j< jcjMjlJ \n TjiJSrji la M5_ 



Channel Straightening 



Why Streams are Straightened 



To reduce the number of highway and 

 railroad crossings 



To develop land more easily along 

 streams 



To control overbank flows 



To protect property by eliminating 

 channel migration 



P^M^ 





Streams that flow through steep, 

 narrow valleys run relatively fast and 

 straight. But once a stream moves into 

 less steep and less confining land 

 forms, it slows and begins to curve and 

 meander. When the natural sinuosity 

 of a stream is altered, the stream 

 becomes steeper and its flow increases 

 in energy. The stream reacts to these 

 changes by making adjustments. 



Effects of Our Impact 



• Eliminates meanders and shortens 

 stream length, which increases 

 slope and reduces natural energy 

 dissipation 



• Increases velocity of water, which 

 increases erosion downstream 



• Increases flood intensity 



— Speeds movement of peak flows 

 — Eliminates storage capacity of 

 stream 



• Decreases channel stability and 

 increases channel migration as the 

 channel attempts to come to a new 

 equilibrium; this also increases 

 problems upstream and 

 downstream 



Lessening Our Impact 



Stream managers rarely recommend straight- 

 ening channels. Instead, they suggest these 

 alternatives: 



• Plan roads and other developments 

 away from streamside areas 



Control upstream sediment sources 

 to reduce downstream instability 



Stabilize channel banks 



•is 



■ni'^S "anient 



1= 



age' 

 tlvcit 



ar^^^ 



trecii^^'^'^eVc'^'^'lMrniriS' 





Hcin^' 



c\s' 



traig' 



Hten 



If your stream is already 

 straightened, consult a stream 

 management specialist about 

 restoring straightened sections 

 to their original channel shape 

 and pattern. 



24 



