Similarly, when a stream is altered locally, the change often causes 

 modification of the channel characteristics for considerable distances both 

 upstream and downstream. The river response to changes is quite complex, but 

 all rivers are governed by the same basic forces. From a review of available 

 literature on river response to alterations, some general statements can be 

 made on the basis of past research results (Karaki et al. 1974). 



• Depth is directly proportional to water discharge and inversely 

 proportional to sediment discharge. 



• Channel width is directly proportional to water discharge and to 

 sediment discharge. 



• Channel shape (width:depth ratio) is directly related to sediment 

 d i scharge. 



• Meander wave length is directly proportional to water discharge 

 and to sediment discharge. 



• River slope is inversely proportional to water discharge and directly 

 proportional to sediment discharge and grain size. 



• Sinuosity is proportional to valley slope and inversely proportional 

 to sediment discharge. 



Although these relationships cannot be used to predict the exact re- 

 sponse of a river to alterations, they do reveal the i n terdependency of the 

 river parameters. 



Local modifications to a river can induce short-term and long-term 

 responses. During excavation, channel morphology and sedimentation charac- 

 teristics may be changed. After the operation has ceased, the river will 

 tend to readjust to the geometry and pattern that it had previously; if the 

 magnitude of the modification is large enough, the readjustment may take 

 many decades to complete. The short-term responses are usually observable 



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