of 2,0 or more could be used. This would result in a buffer width of 52 

 m X 2.0, or 64 m. 



It is possible to find a braided configuration where the length of bank 

 defining the buffer is not adjacent to an active channel, e.g., area B in 

 Figure A-6. In this situation, the migration rate at area A can be applied to 

 area B and modified for various considerations. Assuming an 8-year life is 

 desired, the starting width is 32 m. This width can probably be reduced, the 

 amount of reduction depending on the annual lateral activity level of the 

 active channels. Assume that the activity level is low. One might reduce the 

 number to 24 m in that situation. However, if the active channel does shift, 

 it will likely impinge on the bank at a relatively large angle, increasing 

 erosion potential. As a result, the width should be increased to 36 m instead 

 of decreased to 24 m. With relatively stable channels, the safety factor can 

 be about 1.5 to obtain a 54-m wide buffer. 



Split Configuration . Rivers with split channel configurations are typ- 

 ically much more laterally stable than braided rivers. Thus, a historical 

 record of erosion rates for a split river is fairly reliable for projecting 

 future erosion rates. Channel alignment with respect to the buffer bank is an 

 important consideration, with larger erosion rates expected from channels with 

 larger angles to the bank. The factor of safety to apply to buffers on rivers 

 with split configurations may be as low as 1.2; the factor of safety would 

 increase with increasing channel activity and with decreasing confidence in 

 the buffer width estimate. See discussions of meandering and braided config- 

 urations for hypothetical examples of extending historical erosion rates. 



Meandering Configuration . Rivers with meandering configurations typically 

 experience varying degrees of lateral migration, but the location and direc- 

 tion of migration is fairly predictable. A historical record of erosion rates 

 for a meandering system can be used to predict future erosion rates with a 

 high degree of reliability relative to previous configurations. Channel align- 

 ment with respect to an eroding bank tends to remain constant. The factor of 

 safety to apply to the width of buffers on rivers with meandering configura- 



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