Identifying Sinkholes Using a Geographic Information System (GIS)

Sinkholes are closed depressions in soil or bedrock that form through chemical dissolution of carbonate rock in karst regions. Several studies have identified geologic and hydrologic features that promote sinkhole formation and influence their spatial distribution. This study used a GIS to analyze the relationships between sinkholes and proximity to faults, proximity to streams, and soil thickness in Genesee County, NY. It was hypothesized that a higher frequency of sinkholes (more than half of the number of sinkholes) would occur 1,000 meters or less from a fault, 150-450 meters from a stream, and in areas with one meter or less of soil thickness. Each factor was evaluated individually using previously mapped sinkholes within the study area. A Euclidean distance function with a ten-meter resolution was used to calculate the distance from each sinkhole to the nearest fault and stream. In the study area, 38% of the sinkholes were located within 1,000 meters of a fault, and 22% of the sinkholes were located within 150-450 meters of a stream. These results do not support the hypothesis. However, 50% of the sinkholes occurred less than 450 meters from a stream. Sixty-three percent of the sinkholes occurred in areas with thin (one meter or less) carbonate soils, which supports the hypothesis. The results of this study suggest that: 1) proximity to faults and streams as well as soil thickness may be useful parameters for predicting the likelihood of sinkhole formation in karst regions, and 2) mapping these factors may be a useful strategy for identifying sinkholes remotely in a GIS