IV-67 



The Mississippi and Savannah Rivers are classic examples of this 

 "salt-wedge" circulation pattern. With this type of water movement, 

 salt and water from the bottom layer mix constantly into the top 

 layer, and more salt water flows in from the sea to replace it so 

 that the total amount of water in motion may be many times the 

 river flow plus the tidal flow. Such estuarine systems purge 

 themselves ^/ery rapidly of waste discharges. 



With wider channels, smaller river flows, and greater tidal ranges 

 more mixing occurs and other forces come into play. Embayment 

 shape, bottom configuration and material, and the effects of the 

 Earth's rotation all may play a role. In some estuarine systems 

 of this type, the degree of stratification may change with changes 

 1n Hver flow, temperature, wind, or other transient conditions. 



The James River 1s a drowned river valley in the Chesapeake Bay 

 Estuarine Region (Figure IV. 1.27). Its length of tidal influence 

 1s great 1n proportion to its width, and 1t exhibits some vertical 

 stratification. Delaware Bay 1s much wider than the James and 1s 

 stratified laterally (Figure IV. 1.28); that is, salt content along 

 the eastern shore tends to be higher than that along the western 

 shore. This phenomenon probably results from forces, associated 

 with the Earth's rotation, which in large bodies of water tend to 

 cause lateral stratification as a result of the different rates of 

 slipping of salt and fresh water on the spinning earth's surface. 



