177 



snagging are to remove major obstruc- 

 tions to the high flows, to prevent 

 bank erosion from flows deflecting off 

 debris, and to retain pools and riffles 

 for fish habitat. The retention of ade- 

 quate vegetation along the banks of 

 channels prevents erosion, and pro- 

 vides shade and abundant, diverse 

 habitats for wildlife. 



Wildcat Creek, San Pablo and North Rich- 

 mond, CA. The San Pablo Leo's Club 

 (Junior Chapter of the Lions Club) and 

 students of Verde School clean-up Wildcat 

 Creek. 

 m REVEGETATION 



Vegetation exhibits many qualities 

 which make it well suited for stream- 

 bank protection. A binding network 

 of roots increases the shear strength 

 of the soil. The flexibility and 

 resilience of vegetation acts to increase 

 roughness and to reduce local flow 

 velocity, counteracting the forces of 

 erosion and shear stress. Vegetation 

 creates a canopy, providing shade and 

 cover for animals and fish, and 

 enhances the aesthetic qualities of the 

 stream. 



Replanting of a stream is one of the 

 most simple methods of restoration. 

 Native riparian plants should be 

 chosen, and plantings can most effec- 

 tively be carried out in the fall. Con- 

 tainer stock may be used but the use 

 of live cuttings from nearby willows, 

 alders or other native riparian species 

 can be more successful at less cost. 



"Soil Bioengineering" techniques 

 are now enjoying a revival. These 

 methods include the use of structures 

 such as logs, cribwalls, rock gabions, 

 fences, etc. to help plants become 

 established on difficult sites and 

 ultimately provide long term stability 



8 



through revegetation. These techni- 

 ques stress the use of natural, locally 

 available materials such as ryck, 

 timber, and vegetation in contrast to 

 the more expensive and less flexible 

 concrete or steel. Some examples of 

 "bioengineering" techniques that can 

 be used in stream stabilization projects 

 are described in the following sec- 

 tions. These techniques save on 

 material costs and are more labor in- 

 tensive and so conservation corps, or 

 even volunteers are used to carry out 

 the work. 



■ CHECK DAMS 



Check dams can be constructed 

 with logs gathered near the site of the 

 restoration project, cut from planks of 

 long weathering wood such as red- 

 wood or Douglas fir, or made from 

 hay bales secured with re-bar. Check 

 dams are used as grade control struc- 

 tures and energy dissipators in which 

 sediment accumulates above the small 

 dams and produces gentler channel 

 gradients. A waterfall develops over 

 the dam which can then substantially 

 reduce the flow energy. Check dams 

 can help the revegetation of severe 

 gullies by checking headward erosion 

 or badly eroding stream channels by 

 storing sediment, retaining water on 

 site for longer periods of time, and 

 reducing flow velocities. 



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