CHANNEL SIDE 



OCEANSIDE 



\ - 





yS* 



hi 







■ 



T~ 



1 





1X2 i# 



Scour Protection 



c 



*-jt— Weir 







-y^i^s/-^:/-:^:- 



Submerged Weir During Floodflow 

 q =cV(2g (h,-h 2 ) (}h, + Y h 2) 



Figure 14. Definition sketch of flow across 

 weir with submerged nappe. 



*************** EXAMPLE PROBLEM 1*************** 



GIVEN: 



The tides on the channel and ocean sides of a weir jetty are as 



shown in Figure 11. 



FIND: Determine the time variation of the discharge per unit width of weir 

 crest if (a) the weir crest is at MTL, and (b) the weir crest is 1.5 feet 

 below MTL. Find the average discharge for each case and the total volume 

 of water per foot of weir length carried across the weir. 



SOLUTION ; The solution of (a) above (weir crest at MTL) is given in Table 

 2 and shown graphically in Figure 15. Equation (8) is used to compute 

 the values of q in the table. For example, when t/T = 0.30, h = 0.70 

 foot and h = 0.40 foot; therefore, 



q- C /2g(h 1 - h 2 ) (1 hl +^h 2 ) 

 q = 0.6(4.40)(0.6) = 1.58 ft 3 /s-ft 



The other values of q are similarly computed. Note that for t/T 

 > 0.475, the water level on the channel side of the weir is above the 

 water level on the oceanside and the direction of flow reverses. The 



values of 1 

 respectively 



and 



are then taken from columns 3 and 2 in Table 2, 



29 



