The eighth layer, hydrogeologic setting, reflects general geomorphology and varies nationally by region. Florida lies within region 11, the Southeast Coastal Plain, of the Ground water region of the United States as described by Heath in USGS Water Supply Paper 2242. The methodology utilizes existing hydrogeological information to produce color-coded maps which display areas that are more or less likely to be affected by pollution introduced on the ground's surface. These maps depict areas which are more or less sensitive to land use changes which may affect ground water quality.
Drastic maps are composites made up of eight individually mapped hydrogeological parameters.
The eighth, hydrogeologic setting, is useful for general map interpretation but, it is not included in the summary index. Drastic maps are most useful as a generalized tool to assess regional potential aquifer vulnerability. Except for soils and topography layers, the source maps used were regional, water management district or statewide in scale and scope of coverage. The county coverages were then edgematched and mapjoined into a statewide coverage.