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August 16, 2011—Since late summer of 2009, the Ohio Geological Survey has been locating and mapping karst formations (sinkholes and caverns) in western Delaware County and vicinity, including parts of Franklin, Marion, Morrow, and Union counties. In collaboration with the Delaware Soil & Water Conservation District and the Upper Scioto River Watershed Project, the Survey will release the finalized maps in September. The maps will include photographs and descriptions of a large portion of sinkholes in the region.
Through extensive data research and field work, funded by the Great Lakes Geologic Mapping Coalition, staff geologists have confirmed over 350 sinkholes in the area and another 51 that are suspected. The majority of the sinkholes occur in the Scioto River corridor, where glacial drift is thin or nonexistent. A cluster of sinkholes also has been found in the Olentangy River corridor. Most of the sinkholes are formed in the Columbus Limestone or Delaware Limestone, both of which are particularly prone to karst formation.
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This large sinkhole, along Township Road 143 in Delaware County, serves as a drain for runoff from the local neighborhoods (culvert on left). It is very close to the road, though it has been partly terraced to help slow erosion. No sinkholes are apparent across the road, and limestone is present at the bottom of this sinkhole.
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Karst is a geologic hazard that poses specific environmental concerns for land owners and planners, developers, and officials. Such formations can cause water quality and pollution problems by permitting contaminants, such as fertilizers and sewage, to flow directly into the water table and rivers. Karst also poses challenges for building and construction projects and the developers and engineers seeking to build in or above karst-prone areas. Where karst is found, remediation efforts are often necessary to mitigate its effects.
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Map of karst features in Delaware County and vicinity. Click to enlarge.
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As Ohio’s fastest-growing county, Delaware County has seen its share of development in recent years. The new karst maps will give residents and planners information they can use to account for these hazards when planning new homes, buildings, and infrastructure.
Additionally, the Survey has expanded its knowledge and experience in using a technology known as LiDAR (Light Detection and Ranging) to map karst formations.
“We’ve learned a lot about differentiating types of enclosed low areas,” says Doug Aden, lead geologist for the project, “most importantly how to determine which low spots are culverts or broken field tiles versus naturally formed sinkholes by looking at air photography and other information, such as rock type and depth to bedrock.”
These skills will be useful as the Survey moves on to other areas of the state. Potential areas for future karst mapping include Clark County, the Adams-Highland County region, and the Bellevue region near Sandusky, which experienced extensive flooding in 2008 due in large part to karst.
To access Open-File Report 2011-4, Karst of the Western Delaware County, Ohio, Region, which features the maps produced from the recent project, click here. For more information about karst and LiDAR technology or to report a suspected sinkhole, explore the links below.
Further Information
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