A linear extrapolation of current trends is probably too conservative. 

 Climatic modeling strongly suggests accelerated global warming due to the 

 greenhouse effects of increasing atmospheric COj. As a consequence, the 

 global (eustatic) rate of sea-level rise is expected to increase due to steric 

 expansion of the seawater and continued melting of land-based polar ice caps. 

 For the next 40 years eustatic sea- level may rise at a rate of 9 mm/year. On 

 this basis one would predict that local sea- level on the Louisiana coast in 

 the year 2020 would stand about 72 cm higher than the present. Such a rise 

 would result in catastrophic inundation of coastal lowlands. 



Global warming also would increase tropical storm frequencies and the 

 extent of coastal storm tide inundation. 



The economic impact on south Louisiana due to local sea- level rise is 

 already severe and it is likely to increase in magnitude. It is imperative 

 that plans for coastal development and protection consider these long-term 

 trends. (Author) . 



248 NUMMEDAL. D., CUOMO, R. F., PENLAND, S. 1984. "Shoreline Evolution 

 Along the Northern Coast of the Gulf of Mexico," Shore and Beach , pp 11-17. 



The first paper in this series demonstrated that local relative sea- 

 level along the Louisiana coast currently is rising at an average rate in 

 excess of one centimeter per year. Only about 10 percent of this rise appears 

 to be eustatic, the remainder is due to sinking of the Louisiana coastal plain 

 in response to loading- induced dewatering of modern muds and subsidence of 

 older strata. 



Louisiana also has the most rapidly changing shoreline in the United 

 States. According to the coastal research group at the University of 

 Virginia, Louisiana is the only state where the average annual retreat rate 

 exceeds 3 m/year. As documented by Fenland et al . shoreline erosion rates 

 along many segments of the Louisiana coast exceed 15 m/year. Gerdes and 

 Penland et al . documented with studies of historical maps that the Louisiana 

 mainland coast at Caminada and the barrier island coast off Terrebonne Parish 

 (Isle Dernieres) both have retreated more than 2 km since the 1850 's. 



The correlation between rapid sea-level rise and dramatic coastal 



retreat in Louisiana is undeniable. It is the purpose of this paper to 

 examine the role that sea- level rise has played in this shoreline change. 

 (Introduction) . 



112 



