27S 



Coastal iS Marine Ecosyatein.', — Our Living Rt'soiirces 



Figure. Classification of annual 

 shoreline change around the 

 United States (modified from U.S. 

 Geological Survey 1985). 



Table 1. Primary factors (geologic 

 and human ) affecting coastal areas 

 ranked by decreasing relative 

 importance (modified from 

 Williams et al. IMQlb). 



Long-term survey data by the U.S. 

 Geological Survey and others, based on analy- 

 ses of archive maps, reports, and aerial pho- 

 tographs, demonstrate that coastal erosion is 

 affecting each of the 30 coastal states (Figure; 

 William's et al. 1991a). About 80% of U.S. 

 coastal barriers are undergoing net long-term 

 erosion at rates of less than I m (3.3 ft) to as 



Undeveloped Coastal Barriers 



Since 1982 the U.S. Fish and Wildlife 

 Service (and now the National Biological 

 Service) has been conducting inventories of the 

 CBRS along the Atlantic and Gulf of Mexico 

 coasts and the Great Lakes, as defined by the 

 Coastal Banner Resources Act of 1982 (Public 



much as 20 m (65.6 ft) per year. Natural 

 processes such as storms, rise in relative sea 

 level, and sediment starvation (a reduction in 

 volume of sediment transported by rivers reach- 

 ing the coast), which may also be a result of 

 human interference, are responsible for most of 

 this erosion; but human factors such as mineral 

 extraction, emplacement of hard coastal-engi- 

 neering structures, and dredging of sand from 

 navigation channels are now recognized as hav- 

 ing major effects on shoreline stability (Table 

 1). 



Primary factors affecting coastal areas 



Land subsidence (sediment compaction) 

 Storm impacts 



Coastal processes (waves, winds, tides) 

 Eustatic sea-level change 

 Sand supply al the coast 



Human activities: dredging, dams, mining, engineering structures, with- 

 drawal of fluids (e.g., oil, gas, and water) 

 Regional tectonic movements 



Law 97-384) and the Coastal Barrier 

 Improvement Act of 1990 (Public Law 101- 

 591 ). (The Pacific undeveloped coastal barriers 

 are under review by DOI as required by Section 

 6 of Public Law 101-591.) 



The photographic inventories from aerial 

 color infrared photographs (scales 1:12.000 to 

 1:65.000) provide a precise visual identification 

 for each unit within the CBRS. Undeveloped 

 coastal barriers are defined as areas that have 

 less than one structure per 2 ha (4.9 acres) of 

 fastland (areas suitable for building structures). 

 Additionally, there are no areas in CBRS that 

 are less than 0.4 km (0.25 mi) long. The entire 

 barrier coastline was reviewed for inclusion into 

 the CBRS system; inclusion into the CBRS 

 means that the areas were ineligible for direct or 

 indirect federal financial assistance that might 

 support or encourage development. 



The total shoreline length of the CBRS sys- 

 tem for the United States is 2,055 km (1,276 

 mi), encompassing an area of about 537,000 ha 

 (1.3 million acres; Table 2). 



