a 



Figure C-5. Schematic showing plan view of end protection configurations: 

 a) extension out of the zone of erosion with a potential reduction in thick- 

 ness, and b) increasing the thickness at the ends of the revetment. 



The base of the riprap revetment can be undercut by scour of the bed 

 if the toe is not protected. Extending the riprap layer below the level 

 of the bed and backfilling is recommended (Figure C-6a). If this cannot 

 be done, the riprap layer should be continued on the channel bed with an 

 increased thickness to provide material to fill any scour holes that de- 

 velop, thus preventing the scour from undercutting the riprap (Figure C-6bl 



125 



