River and Canal Engineering, the characteristics of open flowing streams, and the principles and methods to be followed in dealing with them.

by E. S. Bellasis

APPENDIX B

Pitching and Bed Protection ([Chap. VI., Art. 3], and [Chap. X., Art. 2]).—Any scour upstream of a weir is merely due to the eddies formed upstream of the crest (Hydraulics, Chap. II., Art. 7), and is not serious. And, similarly, as to scour upstream of a pier. A hole formed alongside a pier or obstruction, if there is no floor, may work upstream. The chief use of a floor extending far upstream is to flatten the hydraulic gradient ([Chap. X., Art. 3]).

For pitching of the sides, monolithic concrete is not very suitable, because it may settle unequally and crack. For heavy pitching, concrete blocks can be used. They can rest on a layer of 3 to 6 inches of rammed ballast or gravel. The toe wall, as shown in [fig. 13], page 65, is sometimes dispensed with, the pitching being merely continued to a suitable depth below the bed, and the bottom edge being at right angles to the slope instead of horizontal. The portion below the bed may be of concrete.