IV-524 



Unrestricted river entrances and embayments dominate the estuarine 

 zone and are rather evenly distributed throughout all the regions, 

 with the common type of estuarine system being a coastal embayment 

 with drainage from only the local coastal area. Many of these 

 latter embayments have large marsh areas, but the Middle Atlantic, 

 South Atlantic, and Gulf are the regions in which marshes are the 

 predominant feature in some parts of the estuarine zone. 



THE WATER 



The unique nature of water movement and circulation patterns in 

 the estuarine zone are the result of the meeting and mixing of 

 fresh river water and salty ocean water of slightly greater density 

 under the oscillating influence of the tide. There may be additional 

 complicating factors such as temperature and wind action, but the 

 resulting circulation nearly always reflects the interaction of 

 river flow and estuary shape with the tidal flow of the ocean 

 water. General water movement patterns are predictable for each 

 category of estuarine shape. 



It is where moderately large rivers and streams meet the sea that 

 the unique estuarine circulation patterns occur most frequently. 

 Large fresh water flows in well-defined channels tend to slide 

 over the top of the denser sea water without rapid mixing. Water 

 movement in such cases exhibits various degrees of stritification. 



