* 



Channel Entrenchment 



Entrenched channels are deep 

 with high banks. Entrenched 

 channels are most frequently 

 found in highly erodible 

 terrain. Changes in a channel's 

 hydrology, sediment supply, or 

 erosive energy can cause 

 entrenchment, which is also 

 called downcutting. 



What Causes Entrenchment? 



• Straightening or shortening a channel 



• Decreasing sediment supply, such as by trapping 

 sediments in upstream reservoirs 



• Increasing channel's water supply 



Effects of Entrenchment 



• Lowers level of local water table to new stream 

 elevation, which: 



— Changes streamside plants and affects fish 



habitat and stream flow 

 — Impacts irrigation diversion and 



groundwater wells 



• Eliminates access to the floodplain, which 

 increases stream energy and bank erosion 



• Reduces aesthetic values and recreational uses 



• Reduces property value 



• May increase water supply to a channel 



Lessening the Impact 



• Prevent downcutting by protecting 

 channel and banks from erosion, 

 and by maintaining healthy 

 vegetation along stream banks 



• As soon as you notice downcutting, 

 consult a stream management 

 specialist for help 



• Conduct a stream inventory or tour 

 the upper watershed to identify 

 potential problems 





23 



