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CHAPTER 5 

 IMPACTS OF SEA LEVEL RISE 



The objective of this report is to project sea level 

 rise, not to evaluate its impacts. Nevertheless, because our 

 reason for estimating sea level rise is to help decision makers 

 and professionals anticipate its effects and evaluate its 

 importance, we provide a brief discussion of the impacts in 

 this section. 



THE MOST SIGNIFICANT DIRECT IMPACTS WILL BE SHORELINE RETREAT, 

 INCREASED FLOODING, AND SALT INTRUSION 



Sea level rise will have three major types of physical 

 effects: shoreline retreat, increased flooding, and landward 

 movement of saltwater. Shorelines will retreat because very 

 low land will be innundated and other land along the shore 

 will erode. For example, a thirty centimeter (one foot) rise 

 in sea level would erode most sandy beaches along the U.S. 

 Atlantic and Gulf Coasts at least thirty meters (one hundred 

 feet) . 



Even the historical sea level rise trend may be causing 

 significant erosion. _y Most shorelines are maintained by the 

 balance between sediment eroded by storms and sediment deposited 

 back on the beach by waves during calm periods. However, a 

 rise in sea level allows storm waves to strike and erode the 

 beach farther inland, and makes calm waves less effective at 

 "dredging" sand from the ocean floor and redepositing it onto 

 the beach. 



The Bruun Rule (illustrated by Figure 5-1) 2 /, a method 



