due to limitations of Landsat coverage, the Geological Survey of Alabama did 

 derive an estimate of the total shoreline based on the application of a ratio 

 obtained through conventional opisometer techniques. If the total length of 

 Alabama's shoreline were measured by a NASA land/water interface technique, 

 it would total approximately 1,314 km (816 mi). 



In February 1982, as part of the preparation of this atlas, an aerial 

 survey was made of Mobile Bay and its environs to note areas of active 



erosion. It is these areas that have been shown on the 1:100,000 soils and 



landforms maps. While there is a reasonable amount of historical data on 



coastal erosion, only current data is shown on the maps to direct users' 



attention to the most active areas. The historical trend maps that follow 

 are, however, detailed and informative. 



An interesting map published by the Geological Survey of Alabama is 

 entitled "Historical Trends of Shoreline Changes, Alabama Coastal Area, 

 1917-1974" (Figure 8). This map, although small in scale, contains 

 information compiled from records from 1917 and from 1956-74. When this map 

 was drawn (1974), the shoreline was measured (by opisometer) as 811.4 km 

 (503.9 mi) long. The shoreline showed a net erosional trend of 355.7 km 

 (220.9 mi) and net accretional trend of 455.7 km (283.0 mi), which equaled an 

 approximate net state of equilibrium (Hardin, et al . 1976). 



Because several areas around Mobile Bay are more actively eroding than 

 others, the "Historical Trends" map (Figure 8) divides the surrounding lands 

 into nine regions so that more detailed information can be presented. Con- 

 sult the Hardin et al . (1976) study for 34 pages of detailed maps, trend 

 tables, and graphs keyed specifically to the regions depicted on Figure 8. A 

 brief overview of each of these regions, based on Hardin et al . (1976), 

 follows . 



1. Mobile Delta Region (Mobile auadrangle): Over the past 3,000 years, 

 this prograding (accreting) delta has filled in excess of 64 km (40 mi) of 

 the original estuary. The harbor (lower) portion of the delta region has 

 been affected by dredging and landfill and consequently is treated as a 

 separate region. 



Between 1917 and 1967, the shoreline of the Mobile Delta has shown a 

 trend toward net erosion although a few areas exhibit a state of equilibrium. 

 Erosion has occurred principally along the channel margins of distributary 

 rivers such as the western bank of the Blakeley River, the eastern bank of 

 the Apalachee River, and along areas of both banks of the Tensaw and Spanish 

 Rivers. Most of the accretion has occurred within the interdi stributary bays 

 and along the remaining banks of the distributaries. The tips of the natural 

 levees marginal to the distributaries show both erosion and accretion. 

 Between 1953 and 1967, there was a distinct erosional trend in all the inter- 

 distributary bays, which reverses the accretional trend of the past 36 years. 



Between 1917 and 1967, a net loss of 8.92 ha (22.04 acres) of area 

 occurred in the Mobile Delta. In an environment where sediment deposition 

 and land-building might be expected, such a loss indicates that the delta's 

 progradation has decelerated. Such a situation might be partly caused by a 



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