Estimation of Areas 



TWo sources of information were available for estimating areas of land, water, and wetlands 

 within the New Jersey study area: (1) USGS 7.5-minute quadrangles and (2) New Jersey 

 Department of Environmental Protection (1:2,400 scale) wetland photo maps with marsh types 

 delineated. 



Using the topographic and wetland zonation maps, we estimated the number of acres of 

 each subenvironment for each tide-range zone. For budgetary reasons, it was not possible to 

 analyze the 100 wetland maps that make up the study area. Instead, several of these 

 representative 1:2,400 photo maps were chosen for detailed area checks on the ratio of high 

 marsh to low marsh and tidal flats. These ratios were checked against our surveys to ensure 

 consistency with the composite transects. As in the Charleston case study, the level of precision is 

 limited, but reasonable for scenario modeling. In contrast to Charleston, the New Jersey study 

 area had a more even mix of highland, marsh, and water. In the Tuckerton subdivision, highland, 

 high marsh, and water areas each made up about 30 percent of the area. The next highest area, 

 with 7 percent coverage, was the transition zone. Interestingly, low marsh comprises barely 

 2 percent of the low tidal-range zone. 



With the Great Bay Boulevard subdivision, water, high marsh, and tidal flats dominate in a 

 4:2:1 ratio, comprising 96 percent of the area. Little highland, transition zone, or low marsh 

 occurs. The total area of the study subdivisions was 16,400 acres (Tuckerton marsh) and 18,300 

 acres (Great Bay Boulevard marsh), compared with 45,500 acres for the Charleston study area. 



SCENARIO MODELING AND RESULTS 



After establishing the basic relationships among elevation, wetland habitats, and species 

 occurrence for Tuckerton/Little Egg Harbor, we developed a conceptual model for changes in 

 marsh under accelerated sea level rise and applied the model to the case study area. 



Assumptions Used for Scenario Modeling 



The major assumptions we used for scenario modeling concerned the annual rise in sea 

 level, the average sedimentation rate, and the cutoff elevations for the various subenvironments. 



Rise in Sea Level. Based on an earlier study (Barth and Titus 1984), we chose three 

 scenarios of future sea level rise: baseline, low, and high (described in Chapter l). 3 To be 

 consistent with the previous study, we projected the scenarios to the year 2075—95 years after 

 the baseline date of 1980 used to determine "present" conditions. 



Sedimentation Rate. The model for future wetlands zonation also accounted for 

 sedimentation and peat formation which raise the substrate (absolute elevation) in concert with 

 sea level rise. Sedimentation and peat formation have kept pace with rising relative sea level of 

 3 mm (.1 in) per year during the past century over much of the East Coast [e.g., Ward and 

 Domeracki (1978), Due (1981), Boesch et al. (1983)]. If sea level rises much more rapidly than 

 vertical accretion rates, however, wetland zones will migrate landward. 



Weathering rates in the middle Atiantic states are generally lower than the southeastern 

 United States. Nevertheless, after review of the literature on marsh sedimentation, we found no 

 substantial difference between the Charleston and New Jersey study areas. For the Charleston 

 case study, we assumed for modeling purposes an average annual rate of 5 mm (.2 in) per year 

 based on limited reports by Ward and Domeracki (1978) and summaries by Hatton et al. (1983). 

 Similarly, limited results are available for the New Jersey region. Meyerson (1972) reported a rate 

 of 5.8 mm (.23 in) per year for a marsh in Cape May, New Jersey. In nearby Delaware, rates of 

 5.0-6.0 mm (.20-.24 in) per year were reported by Stearns and MacCreary (1957) in S. altemiflora 

 marsh and by Lord (1980) in short 5. altemiflora marsh. Richard (1978) reported rates of 2.0- 

 4.2 mm (.08-.17 in) per year in a Long Island (New York) 5. altemiflora marsh. Although the rate 



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