FIGURE 3-6 



CONCEPTUAL MODEL OF A LOW-SCENARIO SEA LEVEL RISE IN THE GREAT 



BAY BOULEVARD MARSH (Tidal Range = 3.18 ft) 



Transition 



2075 



1% 



High Marsh 

 — 2075 

 4% 



Low Marsh 

 2075 

 18% 



Tidal Flat 

 2075 - 

 5% 



'//////// ///,**»•««««*•« ™V ', 



1980 +1.8 



Transition 

 - 1980 

 1% 



High Marsh 

 1980 

 25% 



Water 

 2075 

 71% 



2075 (+ 4.5 ft.) 

 2075 < + 3.3 ft.) 

 2075 (+ 1.8 ft.) 

 2075 (+ 0.7 ft.) 



^-2075MSL 



Low Scenano 



¥-1980 MSL 



'Axis on left shows NGVD elevation; spot elevations are relative to 1980 or 2075 mean sea level. 



In a gradual scenario, this change would be facilitated by the present distribution of species 

 in the study area. Short S. altemiflora (present high marsh) would increase in area and adjust to 

 rising sea level easily as taller forms. S. patens, which is currently dominant in many high-marsh 

 areas, would recede inland since it is not adaptable to high water levels. It and many other high- 

 marsh species would most likely disappear as they lost suitable high-marsh habitat and were 

 compressed in narrowing zones between rising sea level and coastal development. A similar 

 situation is now occurring where S. patens is declining in coastal areas and is being replaced by 

 short S. altemiflora and Juncus gerardi is declining throughout (Niering and Warren, 1980). 

 Seagrasses would also be affected and might increase in abundance as present stagnant 

 depressions increased in depth and circulation. 



A summary of the predicted effects of gradual sea level rise (low scenario), without human 

 intervention and based on the adaptability of the plants, is presented in Table 3-6. Short S. 

 altemiflora is listed as a significant loss; however, the plants would simply adapt to become taller 

 forms. The critical losses in the high marsh would be Spartina patens, Distichlis spicata, and 

 Juncus gerardi. Losses in Phragmites communis would be attributable to increased salinity as 

 well as rising sea level. 



High Scenario. The high scenario predicts a net decrease in substrate elevation of over one 

 meter (3.3 ft) by the year 2075. Under this scenario, major land and marsh losses would occur 

 throughout the study area. In the Tuckerton marsh, 2,300 acres of present highland would 

 become inundated and almost 3,500 acres of marsh (57 percent) would be lost. Open water would 

 almost double by 2075. In the Great Bay Boulevard marsh, over 90 percent of the existing 

 wetlands would be lost. The percentage of open water would increase from 58 percent to 97 

 percent of the subdivision area. Overall for the New Jersey study area, about 50 percent of 

 existing highland would become inundated, water areas would increase by over 75 percent, and 

 marsh wetlands would decrease by over 70 percent. Figures 3-7 and 3-8 are conceptual models of 

 the marsh loss in these two areas. 



All of these estimates assume that wetlands form inland as sea level rises. For the Great Bay 

 Boulevard marsh, this is reasonable. However, for much of the case study area, the land 

 immediately inland of the marsh either is developed or could be developed in the next few 

 decades. These areas would have to be abandoned for new marsh to form inland. Otherwise, the 

 wetlands could be completely squeezed between an advancing sea and development, which does 

 not retreat. 



77 



