Karst/Sinkhole

Table of Contents

 Kentucky is one of the most famous karst areas in the world, and karst is present in all 6 of KIPDA’s Hazard Mitigation counties. Essentially, karst is formed by dissolving limestone or dolemite, which creates sinkholes, sinking streams, subterranean drainage, and caves. Kentucky’s karst terrain significantly increases the likelihood of KIPDA’s communities experiencing sinkholes, which are essentially holes in the surface landscape due to the removal of soil or bedrock. Sinkholes can vary in size from less than a meter to several hundred meters in diameter and depth and can be formed suddenly or gradually. Often sinkholes are formed when underground limestone is dissolved by rain or when the surface materials collapse into underlying cavities in the rock.

Background + Extent

Why do sinkholes form?

Often sinkholes are formed when underground limestone is dissolved by rain or when the surface materials collapse into underlying cavities in the rock. Sinkholes often occur naturally from gradual erosion; however, human activities such as groundwater drainage and construction can cause sinkholes to form. For example, groundwater pumping lowers groundwater levels, which can lead to sinkhole formation. 

Types of sinkholes

  • Solution Sinkholes: formed by the weathering by dissolution of exposed soluble bedrock (limestone, dolomite, marble, and rock salt) at the land surface. Surface water collects in the natural depressions and slowly dissolves a sinkhole.
  • Collapse Sinkholes: form when the surface materials suddenly sink into a subsurface cavity or cave. Cavities form slowly over time as groundwater moves along fractures in soluble bedrock which enlarges them through dissolution. Collapses may occur when the cavity gets sufficiently large and the “roof” becomes too thin to support the weight of any overlying rock or sediment causing the cavity to collapse; or if groundwater levels are lowered causing the overlying sediment to first erode and then collapse into the dewatered cavity.
  • Subsidence Sinkholes – Similar to solution sinkholes, except the soluble bedrock is covered by a thin layer of soil and/or sediment. Surface water infiltration dissolves cavities where the bedrock is most intensely fractured resulting in the overlying sediment to gradually move downward into the expanding cavity.

How are sinkholes measured?

Sinkholes are typically measured by their diameter in feet. USGS or KGS typically provides these measurements. 

Location + Past Events

Sinkhole Count by Jurisdiction

Bullitt County:

  • Topo: 402
  • LiDAR: 1550

Fox Chase:

  • Topo: 0
  • LiDAR: 15

Hebron Estates:

  • Topo: 0
  • LiDAR: 0

Hunters Hollow:

  • Topo: 0
  • LiDAR: 0

Mount Washington:

  • Topo: 0
  • LiDAR: 108

Pioneer Village:

  • Topo: 6
  • LiDAR: 11

Shepherdsville:

  • Topo: 2
  • LiDAR: 2

Henry County:

  • Topo: 113
  • LiDAR: Unavailable (automated process for identification not completed yet by Kentucky Geological Survey for all HMP counties as of 2021)

Campbellsburg:

  • Topo: 5 
  • LiDAR: Unavailable

Eminence:

  • Topo: 0
  • LiDAR: Unavailable

New Castle:

  • Topo: 0
  • LiDAR: Unavailable 

Smithfield:

  • Topo: 0
  • LiDAR: Unavailable

 

Oldham County: 

  • Topo: 495
  • LiDAR: 3,169

Crestwood:

  • Topo: 17
  • LiDAR: 32

Goshen:

  • Topo: 0
  • LiDAR: 0

La Grange:

  • Topo: 5
  • LiDAR: 77

Orchard Grass Hills:

  • Topo: 0
  • LiDAR: 1

Pewee Valley:

  • Topo: 1
  • LiDAR: 3

Shelby County:

  • Topo: 138
  • LiDAR: 506

Shelbyville:

  • Topo:2
  • LiDAR: 2

Simpsonville:

  • Topo: 2
  • LiDAR: 2

Spencer County:

  • Topo: 21
  • LiDAR: Unavailable (automated process for identification not completed yet by Kentucky Geological Survey for all HMP counties as of 2021)

Taylorsville:

  • Topo: 0
  • LiDAR: Unavailable

Trimble:

  • Topo: 484
  • LiDAR: Unavailable (automated process for identification not completed yet by Kentucky Geological Survey for all HMP counties as of 2021)

Bedford:

  • Topo: 0
  • LiDAR: unavailable

Milton:

  • Topo: 1
  • LiDAR: unavailable

Extent

KIPDA staff inquired to each county about sinkhole extent. Oldham County is the only county that could provide this information and therefore, KIPDA GIS staff used estimates for the other counties. 

From a County-level zoom, the most visually most prominent sinkhole was selected for inspection.  The elevation around the edge of each sinkhole was examined by using the identify tool at multiple locations and comparing those returned values from the LiDAR-derived Digital Elevation Model to determine an approximate average elevation depicted by the boundary of the sinkhole.  Multiple locations were identified within the boundary of each sinkhole to determine an approximate maximum depth within each.  The two elevations (boundary average and maximum depth) were compared to determine the depth of each sinkhole.  The measure tool was then used at the widest point of each sinkhole boundary to determine the maximum width of each. 

Bullitt: 713 – 710 = 3ft deep / 380 ft across

 

From a County-level zoom, the most visually most prominent sinkhole was selected for inspection.  The elevation around the edge of each sinkhole was examined by using the identify tool at multiple locations and comparing those returned values from the LiDAR-derived Digital Elevation Model to determine an approximate average elevation depicted by the boundary of the sinkhole.  Multiple locations were identified within the boundary of each sinkhole to determine an approximate maximum depth within each.  The two elevations (boundary average and maximum depth) were compared to determine the depth of each sinkhole.  The measure tool was then used at the widest point of each sinkhole boundary to determine the maximum width of each. 

Henry: 544 – 502 = 42ft deep / 3650ft across at widest

 

  • A sinkhole on Fairway Lane in Goshen caused the roadway to partially collapse. The sinkhole was roughly 30 feet deep and 40-50 feet across. This hazard has been mitigated by Oldham County.

From a County-level zoom, the most visually most prominent sinkhole was selected for inspection.  The elevation around the edge of each sinkhole was examined by using the identify tool at multiple locations and comparing those returned values from the LiDAR-derived Digital Elevation Model to determine an approximate average elevation depicted by the boundary of the sinkhole.  Multiple locations were identified within the boundary of each sinkhole to determine an approximate maximum depth within each.  The two elevations (boundary average and maximum depth) were compared to determine the depth of each sinkhole.  The measure tool was then used at the widest point of each sinkhole boundary to determine the maximum width of each. 

Shelby: 895 – 887 = 8ft deep / 1315 ft across

From a County-level zoom, the most visually most prominent sinkhole was selected for inspection.  The elevation around the edge of each sinkhole was examined by using the identify tool at multiple locations and comparing those returned values from the LiDAR-derived Digital Elevation Model to determine an approximate average elevation depicted by the boundary of the sinkhole.  Multiple locations were identified within the boundary of each sinkhole to determine an approximate maximum depth within each.  The two elevations (boundary average and maximum depth) were compared to determine the depth of each sinkhole.  The measure tool was then used at the widest point of each sinkhole boundary to determine the maximum width of each. 

Spencer: 515 – 509 = 6ft deep / 1335 ft across

 

From a County-level zoom, the most visually most prominent sinkhole was selected for inspection.  The elevation around the edge of each sinkhole was examined by using the identify tool at multiple locations and comparing those returned values from the LiDAR-derived Digital Elevation Model to determine an approximate average elevation depicted by the boundary of the sinkhole.  Multiple locations were identified within the boundary of each sinkhole to determine an approximate maximum depth within each.  The two elevations (boundary average and maximum depth) were compared to determine the depth of each sinkhole.  The measure tool was then used at the widest point of each sinkhole boundary to determine the maximum width of each. 

Trimble: 895 – 889 = 6ft deep / 615ft across at widest point

 

Probability

Karst Potential

This map was compiled from a digital version of the 1:500,000-scale geologic map of Kentucky (Noger, M.C. comp., 1988, Geologic map of Kentucky: U.S. Geological Survey). The areas of potential karst development were delineated using stratigraphic units mapped on the geologic map. The classification of the potential for karst development was based on the field experience of the authors and other data. Moderate karst potential is defined as a karst area without sinkholes present and an area with major karst potential is defined as an area with 1-9 sinkholes per square kilometer. A number of isolated carbonate units that would not have otherwise been differentiated on the geologic map were newly digitized for the map.

The karst map should not be used for evaluating karst geologic hazards or hydrogeology at scales larger than 1:500,000. The base geologic map was digitized at 1:500,000 scale and is limited in precision to that scale.

The map above shows karst potential in the KIPDA region. Sinkholes are a quintessential feature of karst terrain, and the presence of karst terrain significantly increases a community’s risk to sinkholes. Moderate karst potential is defined as a karst area without sinkholes present and an area with major karst potential is defined as an area with 1-9 sinkholes per square kilometer. As shown above, moderate karst potential is present in all KIPDA HMP counties, and Bullitt, Oldham, Henry, and Trimble counties contain terrain that has major karst potential. 

Climate Change

The research conducted on the relationship between climate change and karsts/sinkholes is still relatively small. The current available research indicates that climate change is increasing the occurrences of sinkholes. A 2017 study that collected evidence from the Fluvia Valley in Spain posited that sinkhole activity is enhanced during droughts. When the water table drops, there is less buoyant support and the weight on cavity roofs is increased, causing them to collapse. [1] The increase of drought as a result of climate change would thus increase the occurrence of sinkholes. A different case study, in Florida, conducted in 2018 yielded similar results. [2] Another aspect is the variability of the weather. As climate change increases the variability of rainfall and alters the hydrological process, the earth is bound to become more volatile. [3]

Kentucky has experienced more drought and drought like conditions in the past few years. Scientists expect the Midwest to experience more flash droughts. [4] This increase in the occurrence of drought may then lead to an increase in the occurrence of sinkholes. 55% of Kentucky sits upon karst-prone substrate. The Office of Advanced Planning and Sustainability in Louisville, KY declared that the risk of sinkholes in the city was increased although uncertain. [5]

Overall Probability

Overall, the KIPDA HMP ranks the probability of sinkhole occurrence as high because of the high number of sinkholes identified in the region and moderate to high karst potential in each county. 

Vulnerability & Impact

Impact Statements

Throughout history there have been many sinkhole events in the KIPDA region. As detailed below, these events can affect our social, built, and natural environments, and more importantly critical infrastructure and vulnerable populations. 

In 2019, the Kentucky Transportation Cabinet had issues with a sinkhole in Oldham County. One sewer service line had been backing up every few days. The KYTC crews would make repairs and then a few days later it would fail again. They found a sinkhole near one of the manholes to the lines that was exacerbating the issue. If the issue had not been fixed, there could have been a serious disturbance in the sewer services within this area of the county. For more information on this incident, click here. 

In 2021, Shelby County Veteran residents experienced the consequences of a sinkhole affecting the foundation of their home. They realized the hole that had been dug for the basement of their home had been expanding to the point of almost swallowing their home whole. The damage caused by the expanding sinkhole could cost them around $75,000 in damages. For more information on this incident, click here. 

Vulnerability

There is not one age, social, or income group that is more vulnerable to sinkholes. If an individual is present when a sinkhole dissolves, they could suffer injury or die; however, this is incredible rare. 

Those living in urban areas underlain by karst geology may have issues with sewer, natural gas lines, and underground utilities. This can impact individuals’ ability to access key services.

Sinkholes can also negatively impact the quality of drinking water. Groundwater contamination is also more prevalent in acres of karst geology, as percolation occurs more quickly. Contaminants such as oil from automobiles in parking lots, pesticides and herbicides from lawns, and urine and feces from cattle feed lots end up in water supplies used by surrounding communities. This type of contamination is particularly dangerous in areas where private wells are used instead of water that comes from public works. However, according to the Commonwealth of Kentucky’s 2018 Hazard Mitigation Plan, none of KIPDA’s public water suppliers are located within a karst area.

The effects of sinkholes and other features typically present in karst terrain vary from the mild to the extreme and can, no doubt wreak havoc on infrastructure in urban areas. Storm-water drainage is of major concern in urban areas underlain by karst geology, as the ground surface area necessary for the even infiltration of rainwater into the groundwater supply system is covered with impervious substances such as blacktop and cement. This imbalance can often have serious consequences, leading to movement of the ground which may rupture sewer lines, natural gas lines, or effect underground utility lines. 

Sinkholes also threaten transportation infrastructure such as highways. Such sinkholes can lead to substantial damage and require significant repairs.

Sinkholes can also damage dams and cause water leakage through bedrock.

Sinkholes can cause damage to foundations and can even swallow buildings in entirety if they dissolve.

Sinkholes can lead to groundwater contamination as mentioned within the social environment section.

Data Limitations

Sinkholes are not systematically recorded at the jurisdictional level, and therefore, risk is assessed at the county level. 

Hazard Vulnerability Summary Analysis

Overall, the KIPDA region and its counties experience low to moderate vulnerability to sinkholes because no past events have caused serious property damage, injuries, or deaths. Moreover, public water utilities in the KIPDA region are not located within a karst area.

While this analysis applies to all KIPDA HMP counties, it should be recognized that some counties, especially Bullitt and Oldham, are more likely to experience sinkholes due to karst terrain. 

  • Based on KGS’s data there are 1,952 Topo and LiDAR-identified sinkholes within Bullitt County. In the unincorporated areas of the county (only county land), there are 1,108 topo and LiDAR-identified sinkholes.
  • Moderate and major karst potential is present in Bullitt County. 
  • None of Bullitt County’s public water suppliers are located within a karst area. 

Due to these factors, Bullitt County experiences low to moderate vulnerability to sinkholes. The risk for Bullitt County’s cities is analyzed below.

  • Fox Chase has 15 LiDAR-identified sinkholes and 0 topo-identified sinkholes. Its vulnerability is low.
  • Hebron Estates has no identified sinkholes. Its vulnerability is low.
  • Hunters Hollow has no identified sinkholes. Its vulnerability is low.
  • Mount Washington has 0 topo-identified sinkholes, but it has 108 lidar-identified sinkholes. Its vulnerability is low to moderate.
  • Pioneer Village has 11 LiDAR-identified sinkholes and 6 topo-identified sinkholes. Its vulnerability is low.
  • Shepherdsville has 2 LiDAR-identified sinkholes and 2 topo-identified sinkholes. Its vulnerability is low.
  • Based on KGS’s data there are 113  topo-identified sinkholes. LiDAR analysis has not been conducted in Henry County to date In the unincorporated areas of the county (only county land), there are 108 topo-identified sinkholes.
  • Moderate and major karst potential is present in Henry County.
  • None of Henry County’s public water suppliers are located within a karst area. 

Due to these factors, Henry County experiences low to moderate vulnerability to sinkholes. The risk for Henry County’s cities is analyzed below.

  • Campbellsburg has 5 topo-identified sinkholes. Its vulnerability is low.
  • Eminence has 0 topo-identified sinkholes. Its vulnerability is low.
  • New Castle has 0 topo-identified sinkholes. Its vulnerability is low.
  • Smithfield has 0 topo-identified sinkholes. Its vulnerability is low.
  • Based on KGS’s data there are 3,664 topo and LiDAR-identified sinkholes within Oldham County. In the unincorporated areas of the county (only county land), there are 3,529 topo and LiDAR-identified sinkholes.
  • Moderate and major karst potential is present in Oldham County. 
  • A sinkhole on Fairway Lane caused the roadway to partially collapse.
  • None of Oldham County’s public water suppliers are located within a karst area. 

Due to these factors, Oldham County experiences low to moderate vulnerability to sinkholes. The risk for Oldham County’s cities is analyzed below.

  • Crestwood has 17 topo-identified sinkholes and 32 LiDAR-identified sinkholes sinkholes. Its vulnerability is low to moderate.
  • Goshen has no identified sinkholes. Its vulnerability is low.
  • La Grange has 5 topo-identified sinkholes, but it has 77 lidar-identified sinkholes. Its vulnerability is low to moderate.
  • Orchard Grass Hills has 0 topo-identified sinkholes and 1 LiDAR-identified sinkholes. Its vulnerability is low.
  • Pewee Valley has 1 LiDAR-identified sinkholes and 3 topo-identified sinkholes. Its vulnerability is low.
  • Based on KGS’s data there are 644 topo and LiDAR-identified sinkholes within Shelby  County. In the unincorporated areas of the county (only county land), there are 636 topo and LiDAR-identified sinkholes.
  • Shelby County has moderate karst potential. It does contain a small section of major karst potential near its border with Franklin County. 
  • A sinkhole on Fairway Lane caused the roadway to partially collapse.
  • None of Shelby County’s public water suppliers are located within a karst area. 

Due to these factors, Shelby County experiences low to moderate vulnerability to sinkholes. The risk for Shelby County’s cities is analyzed below.

  • Shelbyville has 2 topo-identified sinkholes and 2 LiDAR-identified sinkholes sinkholes. Its vulnerability is low.
  • Simpsonville has 2 topo-identified sinkholes 2 LiDAR-identified sinkholes. Its vulnerability is low.
  • Based on KGS’s data there are 21 topo-identified sinkholes. LiDAR analysis has not been conducted in Spencer County to date In the unincorporated areas of the county (only county land), there are 21 topo-identified sinkholes.
  • Moderate karst potential is present in Spencer County.
  • None of Spencer County’s public water suppliers are located within a karst area. 

Due to these factors, Spencer County experiences low vulnerability to sinkholes. The risk for Spencer County’s city is analyzed below.

  • Taylorsville has 0 topo-identified sinkholes. Its vulnerability is low.
  • Based on KGS’s data there are 484 topo-identified sinkholes. LiDAR analysis has not been conducted in Trimble County to date In the unincorporated areas of the county (only county land), there are 483 topo-identified sinkholes.
  • Moderate and major karst potential is present in Trimble County.
  • None of Trimble County’s public water suppliers are located within a karst area. 

Due to these factors, Trimble County experiences low to moderate vulnerability to sinkholes. The risk for Trimble County’s cities is analyzed below.

  • Bedford has 0 topo-identified sinkholes. Its vulnerability is low.
  • Milton has 0 top-identified sinkholes. Its vulnerability is low. 

References

[1] Linares, R., Roqué , C., Gutié rrez, F., Zarroca, M., Carbonel, D., Bach, J., & Fabregat, I. (2017). The impact of droughts and climate change on sinkhole occurrence. A case study from the evaporite karst of the Fluvia Valley, NE Spain. Science of The Total Environment, 579, 345-358. doi:10.1016/j.scitotenv. 2016.11.091

[2] Meng, Y., & Jia, L. (2018). Global warming causes sinkhole collapse – Case study in Florida, USA. doi:10.5194/nhess-2018-18

[3] Mathiesen, K. (2014, February 20). Are humans causing more sinkholes? Retrieved July 24, 2020, from https://www.theguardian.com/environment/ 2014/feb/20/are-humans-causing-more-sinkholes

[4] Kratzenberg, J., & *, N. (2019, October 03). Drought declarations issued throughout Kentucky. Retrieved July 24, 2020, from https:// www.lanereport.com/117661/2019/10/drought-declarations-issued- throughout-kentucky/

[5] Develop Louisville, Advanced Planning and Sustainability. (2020, March). Climate Change Vulnerability in Louisville, Kentucky. Retrieved from https://climatewise.org/images/projects/louisville/louisville- vulnerability-assessment-\inal.pdf