An evaluation of digital elevation models and geotechnical properties of the glacial deposits in Franklin County, Ohio, using a geographic information system

The importance of unconsolidated deposits is reflected in the extensive use of these materials in Franklin County, Ohio. This study organizes geologic and geotechnical data in a geographic information system (GIS) to better understand the nature of the unconsolidated materials in this area. These data are then utilized to update the bedrock topography maps, evaluate the relationship between the geotechnical data and the diamictons, and to refine the interpretation of the surficial geology of the study area.; It was found that discrepancies are common between the surface elevation of geologic borings and the current surface elevation, represented by a digital elevation model (DEM) constructed in this study. It was also shown that there are considerable differences in the surface representation between the DEMs constructed here and DEMs obtained from the USGS. Elevation differences between the DEMs and the surface elevations of geologic borings were confirmed by performing global positioning system surveys at several boring locations. This study concludes that the USGS DEMs do not always accurately represent the current surface in this area, primarily because of land surface modifications by humans. Accurate DEMs are important to surficial mapping, as these efforts often rely on this surface representation for the correct vertical placement of subsurface data. The utilization of DEMs for other purposes is also explored here, showing that the outcome of a particular application can be affected by the DEM utilized.; The updated bedrock topography maps are used to compare the bedrock drainage patterns, slopes, and aspect to some of the unconsolidated sediments. An evaluation of the geotechnical data is made to assess whether geotechnical properties of the diamictons show consistent variations with depth, and to determine if differences exist between diamictons found on carbonate and clastic bedrock. Standard penetration test values, Atterberg limits, and texture are found to differ somewhat for the diamictons above the different bedrock types, possibly attributed to different source materials for the tills. The diamicton properties in this area suggest they should be re-interpreted as deformation till. Geotechnical data from certain borings also imply that lacustrine deposits are present in several locations in northern Franklin County.