CREATION OF A SINKHOLE DENSITY MAP OF CARROLL COUNTY, MARYLAND

Using Google Earth imaging and GIS applications, a sinkhole density map was created for Carroll County, Maryland. Regions of Carroll County are susceptible to sinkhole formation due the chemical dissolution of underlying limestone bedrock. The main sinkhole forming units in Carroll County are the Wakefield Marble and the Silver Run Limestone, which both occur in the central part of the county. The Wakefield Marble is characterized as a predominantly white fine-grained marble; the Silver Run Limestone is a finely grained and schistose limestone which occurs with a calcareous shale. Both units are quarried in Carroll County for aggregate and cement production. Sinkholes across the country can cause millions of dollars in damage to infrastructure each year. Building in areas with a high risk of collapse can endanger lives and pose a serious hazard to public safety. Therefore, the development of a sinkhole density map can be beneficial to both planners and residents in a sinkhole prone region.

The map was compiled by developing a database of the latitude and longitude of existing karst features (e.g. closed sinkholes, depressions, sinkholes) identified through Google Earth images. The identified features were then ground checked to confirm the presence of a karst feature. The study resulted in the identification of 87 karst features, most of which were closed depressions. Additionally, 692 sinkholes from a historical database kept by the Carroll County Government were added to the database. A map was generated using both sets data. The resulting map highlighted three areas of karst surface features in Carroll County, Maryland. The majority of the features were found in the northern and western parts of the county, consistent with the location of the Wakefield Marble and Silver Run Limestone. Sinkhole density maps can be used by development companies to mitigate risk when planning future developments by highlighting areas with the highest risk of karst features.