LOW-HEAD DEVELOPMENTS 



71 



charges. The pondage may also be materially increased by 

 placing flashboards on top of the dam, and by this means an addi- 

 tional head is also gained. 



Precautions must always be taken to guard against floating 

 logs, debris, ice, etc., and for this a wing dam, having submerged 

 arches through which the water enters the forebay, has been built 

 at right angles to the main dam, between which and a rock-fill 



FIG. 26. Sectional Elevation of Power House, Cedars Rapids Mfg. and 



Power Company. 



above there are floating booms, which serves to deflect such ice, 

 etc., which is carried towards the forebay. Care should be taken 

 that the arches of the wing dam are submerged at least two feet 

 when the water level is at its lowest. 



Any ice which enters the forebay despite these safeguards, as 

 well as ice which may be formed there, can be diverted by provid- 

 ing ice chutes from the forebay toward the tailrace. The crests 



