CHAPTER 5. MANAGEMENT CONSIDERATIONS 



Rubble structures are constructed as 

 part of a management strategy to slow 

 coastal erosion and/or inlet migration. 

 They are designed to solve a local 

 problem, but they almost always have 

 broader impacts on the coastal 

 environment. These impacts are the major 

 focus of this chapter. In the Atlantic 

 Bight, rubble structures represent a 

 unique habitat in otherwise distinctly 

 different surroundings. They can attract 

 large numbers of fishes, but on a regional 

 scale, rubble structures have very little 

 impact on fish and wildlife population 

 sizes or distributions. There are, 

 however, some very localized benefits of 

 jetties to people who fish and to other 

 recreational enthusiasts. These are 

 discussed at the end of the chapter. 



5.1 SHORELINE EVOLUTION 



In the South Atlantic Bight most 

 rubble structures are installed on barrier 



islands. To understand the effects that 

 jetties and groins have on these islands 

 it is necessary to understand the 

 dynamics of the interaction between the 

 land and the sea. 



The fact of overriding importance is 

 that the level of the sea is rising. Some 

 15,000-18,000 years ago (at the end of the 

 last ice age) sea level was as much as 100 

 m lower than at present because of the 

 amount of water tied up in glacial icecaps 

 (Figure 28). As the glaciers melted, sea 

 level rose quite rapidly until about 5,000 

 years ago. Since then, although the rate 

 of rise has slowed, it continues at about 

 0.3 m a century (Pilkey et al . 1980). 

 Experts expect this rate of rise may 

 accelerate. The National Academy of 

 Science has warned that the burning of 

 fossil fuels and other activities have 

 resulted in the presence of extra carbon 

 dioxide and other "greenhouse gases" in 

 the atmosphere. The resulting "greenhouse 

 effect" causes the atmosphere to retain 



Prese.nl Sea Level 



5p00 years : 

 9000 years ago- 



13.000 years ago™ 

 17000 years ago — 



Figure 28. The sea-level rise during the past 17,000 years (from Pilkey et al. 1984). 



^* 



150 



47 



