flow of warm water above 400 m depth and northward flow of Antarctic 

 Intermediate Water below that. The upper layer transport was -6 x 10* m's" 

 towards the south offshore of the 200 m isobath, with an indication of com- 

 parable flow on the shelf. (Author). 



095 EVERTS, C. H., 1987. "Continental Shelf Evolution in Response to a Rise 

 in Sea-Level," Nummedal , D., Pilkey, 0. H., and Howard, J. D., eds . , Sea-Level 

 Fluctuations and Coastal Evolution . Special Publication No. 41, Society of 

 Economic Paleontologists and Mineralogists, Tulsa, OK, pp 49-58. 



As the shoreface part of the inner continental shelf retreats, its 

 trailing edge forms a new surface which becomes an extension of the ramp. 

 Waves are primarily responsible for shaping the concave shoreface at the 

 shallow, most landward part of the shelf. Shoreface retreat occurs because of 

 sand losses and/or sea- level rise. The ramp, located seaward of the 

 shoreface, is usually a planar feature with a seaward inclination. Its slope, 

 7, at the time it is formed is dependent upon the long-term average retreat 

 rate of the shoreface, s, and the long-term average rate of sea- level rise 

 relative to the shoreface, a. The shoreface and ramp usually join 

 asymptotically between 1 and 5 km from shore. Retreat of the shoreface may 

 occur without a significant change in shape. Shoreline retreat on the order 

 of kilometers is almost always the response of the shoreface to a long-term 

 rise in sea-level. 



Recent shoreline retreat rates measured over a short time period (10' to 

 10- years) can be compared to long-term average past rates (10' to 10'' years) 

 to forecast shoreline behavior in the future, unless sedimentation or 

 tectonism altered the ramp slope formed in the past. The recent shore retreat 

 rate, Sp, for a given recent sea-level rise rate, a^, is compared to the 

 present average slope of the ramp, y^, where y^ is assumed equal to a/s = y. 

 If Yp » ap/Sp, the present shore retreat rate is probably anomalously large 

 compared to the long-term average rate for the reach of coast being 

 considered. If 7p « ap/Sp, the present shore retreat rate is probably 

 anomalously small compared to the long-term average rate for that reach. The 

 future shore retreat rate, Sf, can consequently be expected to increase rather 

 than decrease in a trend more consistent with Sf = af/^p . When the reason for 

 present anomalous rates is established, a more definitive projection of the 

 future rate can be made . 



A test of the relationship of 7p to a^/s^ was made at five barrier island 

 sites along the mid-Atlantic coast of the United States. At Smith and 

 Assawoman Islands in Virginia, present shoreline retreat rates are similar to 

 the long-term shoreline retreat rates of the past when referenced to the same 

 relative sea-level rise rates. These islands are migrating landward (i.e., 

 both ocean and lagoon shorelines are moving away from the ocean at about the 

 same rate) as littoral sand is transported landward by overwash and tidal 

 inlet processes. At Ocean City, Maryland; Sandbridge, Virginia, and a portion 

 of the Outer Banks, North Carolina, the present shore retreat rate is 

 anomalously low when compared to the present relative rate of sea- level rise. 

 These islands are narrowing (i.e., ocean and lagoon shorelines are moving 

 toward each other) . When the islands reach a critical width (perhaps 350 m) , 



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