TABLE 4-5 



PARAMETERS EMPLOYED 



Process 



Rate 



Comments 



Sea Level Rise 

 low 

 high 



Accretion of Wetlands 

 low 



moderate 

 high 



Sedimentat ion 

 nondeltaic 

 deltaic 



1.444 m by 2100 

 2.166 m by 2100 



2 mm/yr 



5 mm/yr 



10 mm/yr 



half of accretion 

 same as accretion 



See Chapter 1 

 See Chapter 1 



Low value reported 

 Common midrange 

 Approx. highest value 

 observed 



cf. Bartberger 1976 

 cf. DeLaune et al. 1983 



Erosion 



fetch < 1km 

 1 km < fetch < 

 3 km < fetch < 

 fetch > 9 km 



km 

 km 



none 



little 



low 



heavy 



calibrated and 



personal observation 



without water adjacent to it), the cell becomes open or sheltered water, depending on its 

 exposure. This algorithm permits the gradual erosion of the edge of an extensive marsh until 

 such time as the entire marsh is inundated. By testing for adjacent water only in the direction of 

 dominant waves for 7 out of 8 cycles (35 out of 40 years), the protection afforded wetlands in the 

 lee of obstructions is modeled reasonably well. As more water occurs in the map area, the 

 qualitative erosion rate increases, mimicking the lateral scour due to increased fetch that has 

 been observed in deteriorating wetlands (Baumann, Day, and Miller 1984). 



Mangrove swamp is treated in much the same way as salt marsh except that it can occur on 

 exposed coasts. If the average elevation is less than embayed MLW and there is adjacent water, 

 the cell becomes tidal flat. If the average elevation is less than MLW, the cell becomes open sea or 

 sheltered water, depending on its exposure. 



If a cell is tidal flat, its average elevation is a result of sea level rise and sedimentation. If the 

 cell is protected by a dike, it does not change. Otherwise, when the elevation is less than 

 embayed MLW, the cell becomes sheltered water (which can convert to open sea if there is 

 adjacent open sea). If the average elevation is above mean sea level, if erosion is not heavy, and if 

 the coast is not rocky, the cell becomes mangrove swamp or salt marsh. 



Undeveloped sheltered beaches become tidal flats if the average elevation is below mean sea 

 level but above embayed MLW; if the average elevation is below embayed MLW, these beaches 

 become sheltered water. If there is essentially no erosion (due to lack of fetch for waves), a 

 sheltered beach is converted to tidal flat. Exposed beaches become open sea when the average 

 elevation becomes less than mean sea level. Developed beaches are treated the same as 

 undeveloped beaches unless they are protected by dikes or the user has chosen the option of 

 protecting all developed areas. It is assumed that fast-rising sea level will not result in significant 

 new dune fields. High dunes become beach when the average elevation becomes less than 

 MHWS. 



103 



