DEVELOPMENT OF A SINKHOLE RISK ASSESSMENT IN THE VIRGINIA VALLEY AND RIDGE USING ARCGIS SURVEY123

This project developed a sinkhole risk assessment in ArcGIS Survey123 for use by geologists at the Virginia Department of Energy who are completing sinkhole derivative maps in the Virginia Valley and Ridge geologic province. Assessing sinkhole risk is crucial for proper decision making concerning public safety, construction, and mitigation measures. The risk assessment was generated using a similar assessment by Robert Denton and Dr. Joshua Valentino of Terracon Consultants, Inc. Their assessment used the presence, absence, and intensity of various sinkhole features including open throat, parapet, soil raveling, drainage channels, and vegetation to determine risk level. These characteristics help assess erosion, growth, and ease of surface runoff/drainage into the feature, which estimate the risk of potential collapse or growth. For this assessment, refuse was also used as a factor to determine possibility of underground water pollution facilitated by runoff/drainage into sinkholes. Additional features include photo upload and automatic GPS coordinate calculation.

The assessment was developed for ease of use in the field. Each risk factor is given a series of numeric values, with a higher value indicating greater vulnerability. The values of all the factors are then added to determine a final risk score. Risk is broken down into equal intervals: very low (0 – 2), low (3 – 5), moderate (6 – 8), high (9 – 11), and severe (12 – 14). The corresponding risk score provides an initial assessment of the necessity and urgency with which to address the site. Initial testing of the survey was done in the Virginia Bridgewater, Broadway, and Harrisonburg 7.5-minute topographic quadrangles.

Future work will include additional testing and implementation of this tool within the active Virginia Energy mapping areas along the Interstate-81 corridor. It is the intention that this standardized assessment will be used to efficiently evaluate risk in the field and allow for improved management decisions by landowners, consultants, and government agencies.