Chapter YI 

 CONTINUITY OF FLOW IN LONG TIDAL CHANNELS 



Paragraphs- 

 Definitions 285 



Equation of contiauity 296-299 



Cubature, definition 300 



Basic data 301-302 



Representative tides 303-306 



Computations .. 307-310 



Graph of discharge and velocities 311-314 



Conclusion 315- 



DEFINITIONS 



295. A few definitions may simplify the ensuing discussion: 



The tidal prism of a channel is the prism between low water and 

 high water. 



A long tidal channel is one of such length that the filling and empty- 

 ing of the successive sections of its tidal prism affects, more or less 

 profoundly, the tidal currents and the tidal heights through the 

 channel. 



A connecting tidal channel connects two tidal seas. In a long con- 

 necting channel the tides and tidal currents through the channel are 

 caused both by the surface head between the tides at the entrances 

 and by the storage and release of water in its tidal prism. As a special 

 case, a connecting channel may join a tidal with a tideless body of 

 water.. A natural connecting channel is usually termed a strait, 

 and a short connecting channel leading from the ocean to a tidal or 

 tideless bay or sound is termed an inlet. 



A closed tidal channel leads inland from a tidal sea and terminates 

 in a dead end. Its tides and currents are due solely to the filhng 

 and emptying of its tidal prism, together with the chscharge of any 

 flow which may enter the channel from the uplands. 



A tidal canal is an artificially excavated tidal channel of regular 

 dimensions. 



EQUATION OF CONTINUITY 



296. Equation of continuity for steady flow. — Let: 

 A" be the area of a cross section of a channel, 



Q the quantity of waiter passing through the cross section in 

 a unit of time; designated as the discharge at the section. 



V the mean velocity of the current at the section. Then 

 obviously: 



v^QIX (181) 



(145) 



