APPENDIX C 



RIVER-TRAINING STRUCTURES AND 



BANK PROTECTION DEVICES ; 



INTRODUCTION 



River-training structures and bank protection devices may be required 

 during gravel removal operations or site closure, or both. Their purposes can 

 include protection of the site from flow during operation or after closure 

 and reduction of the potential for downstream siltation. River-training 

 structures also may be used to protect the bank of a buffer from excessive 

 erosion. River-training structures and bank protection devices generally 

 should not be used unless absolutely necessary because they usually disrupt 

 natural river processes, often resulting in scour and erosion elsewhere in 

 the system . In addition, bank protection devices can alter banks and their 

 adjacent riparian zones. 



Revetments constitute the major group bank protection devices. River- 

 training structures in gravel removal operations primarly consist of dikes; 

 other types of these structures include retards, guide banks, spurs, and 

 jetties. Several publications are available that discuss the design of such 

 structures; these include California Division of Highways {I960); Karaki et 

 al. (1974); Neil I (1973); U.S. Army Corps of Engineers (1970) and Winkley 

 (1971). The following paragraphs discuss briefly dikes and revetments. 



DIKES 



Dikes are long embankments used to control the overflow of water into 

 the material site. Dikes may be constructed along an active channel or across 

 a high-water channel, or both. Dikes may also be used to block active side 

 channels in those cases where the bed is to be scraped. For these purposes, 

 the dikes should be impermeable, high enough to prevent overtopping, and 

 protected from erosion. Impermeable dikes are often constructed of stone or 

 earth, or both. 



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