Table 35. Hurricane surges in Alabama 1772-1979 (modified from U.S. Army Corps 

 of Engineers 1967). 



U.S. GEOLOGICAL SURVEY HYDROLOGIC UNITS 



A hydrologic unit is a geographic area representing part or all of a 

 surface drainage basin or distinct hydrologic feature as delineated by the 

 United States Geological Survey (USGS), Office of Water Data Coordination on 

 the State Hydrologic Unit Maps. The USGS divides hydrologic areas into 

 regions, subregions, accounting units, and cataloging units. Each hydrologic 

 unit has an eight digit code, such as 03160205, the first two digits specify- 

 ing region, the next two subregion, then accounting unit and cataloging unit. 



140 



