important to select sites for sewage and dredge spoil dump sites, 

 sewage outfalls, offshore nuclear powerplants, and deepwater 

 terminals. 



The studies indicate that the sandy inner shelf floor undergoes 

 brief, intense periods of sand entrainment and transport. These flow 

 events last for hours or days and are associated with winter storms. 

 They are separated by days or weeks of quiescence. One or two 

 major storm flows a year appear to move more sand than all the rest 

 of the flow events combined. 



Continued study of such flow events will aid in the delineation of 

 long-term areas of erosion and deposition on the sea floor. Such 

 studies will require more detailed and systematic observations of 

 near-bottom flow and sea-floor response than are presently being 

 obtained with available instrumentation. Current meters that can 

 efficiently resolve shallow water motions dominated by oscillatory 

 wave surge are presently being developed. Sea-floor sensing 

 systems that use these meters to measure fluid motions and that also 

 measure turbidity, bottom roughness, and the passage of surface 

 waves are being developed under the sponsorship of NOAA, USGS, 

 ERDA, and NSF. 



Important supplementary evidence concerning the nature of 

 sediment transport on the continental shelf is being gained by 

 NOAA's studies of topography and bedforms on the Atlantic 

 Continental Shelf. Formerly, shelf sediments were thought to have 

 dated from lower stands of sea level, and the shelf floor was 

 considered to be an area where negligable sediment transport 

 occurred. Evidence is now accumulating to indicate that winter 

 storms may set the entire Middle Atlantic Shelf water column into 

 motion, with velocities sufficient to entrain bottom sand across 

 much of the shelf surface. This surface is characterized by a ridge 

 and swale topography, at sand ridges 10 meters high and 2 to 4 

 kilometers apart. Swales between ridges tend to be marked by a 

 "sand ribbon" pattern of bands of sand 10 to 100 meters wide, 

 separated by bands of coarser sand or gravel. The sand ribbons 

 appear to be the "signature" of storm flows, the result of zones of 

 bottom current divergence and convergence during individual 

 storms, or storm seasons. The larger sand ridges appear to be 

 analogous to the large-scale dune systems of the world's deserts. 

 They have been slowly growing to their present size for part or all of 

 the period since the Pleistocence ice age. The stability of the ridge 

 and swale topography bears directly on the use of the shelf surface 

 for ocean dumping and for sea-floor structures (sewage outfalls, 

 nuclear powerplants, and oil rigs). 



Other programs of research on the transport of continental shelf 

 sediments are funded by NSF, the Navy, ERDA, and BLM. With the 



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