203 



It further may be expected that in an even longer canal the currents 

 would become so small at some point near the middle of the canal that 

 the tides could be said to meet. 



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Figure i 



Lunar liour^ 



-Discharges and storage, canal 360,000 feet long. 



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18 



392. Second example. — The computations of the tides and currents 

 in a connecting canal whose width and cross section is not uniform 

 throughout may be illustrated by applying them to the Chesapeake 

 and Delaware Canal, connecting the estuary of the Delaware River 

 with the head of Chesapeake Bay, after it had been converted into a 

 sea level canal for barge traffic but before it was enlarged to accom- 

 modate ocean shipping. The canal then had a horizontal bottom at a 

 project depth of 12 feet below Delaware River low water datum, a 

 designed bottom width of 150 feet from the 12 foot depth contour in 

 the Delaware (station 3+400) to station 10 + 300, a distance of 9,900 

 feet; and of 90 feet thence to Back Creek, a tributary of Chesapeake 

 Bay, at station 77+000; a distance of 66,700 feet. Between -Reedy 

 Point Bridge, station 9 + 780, and Biddies Point, station 19 + 600, 

 the canal was bordered by wide marshes having a large tidal storage. 

 A second outlet to the Delaware, with a depth of 6 feet below datum, 

 and a bottom width of 50 feet, entered the canal near Biddies Point. 

 Some tidal storage outside of the prism proper extended to the deep 

 cut beginning at about station 50, but thence almost to station 77 

 the only tidal storage was in the prism of the canal. The upper part 

 of Back Creek afforded a tidal basin inside of the bridge at station 77. 

 The canal was designed with side slopes of one on two, but as 

 excavated the cross section generally was somewhat in excess of that 

 projected. 



393. RejJresentative entrance tides selected. — To afford a comparison 

 between the computed and measured currents, the representative 

 entrance tides will be taken as the recorded tides at stations 5 + 000 



192750—40 14 



