Subdivision of thick sedimentary units into layers for simulation of groundwater flow

Subdividing thick sedimentary units into model layers based solely on stratigraphy can lead to serious violation of groundwater flow modeling restraints and produce erroneous results. Borehole geophysical data can be used to suggest relative permeabilities and delineate model layers that are more likely to have uniform hydraulic properties than layers delineated by stratigraphic definitions alone. The uniformity within layers emphasizes the permeability contrast between layers, thereby allowing a quasi three-dimensional approach. These methods are applied to the thick sedimentary units of the Gulf Coastal Plain, USA.