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Sinkholes: Sinkhole Flooding and Collapse in the Barren River Area
The threats associated with sinkholes vary across the Barren River Area. While
sinkholes are nonexistent in some areas, much of the region is a well-developed
sinkhole plain. Sinkhole flooding occurs when stormwater runoff exceeds the
drainage capacity of a sinkhole, where drainage capacity depends on the size of
the open passage into the aquifer and the level of the water table (Figure 10-2).
Sinkhole collapse occurs when soil and debris beneath the surface are eroded to
the point that the surface soil can not be supported. The resulting collapse can
leave anything from a small hole to a large pit (Figure 10-3).
Figure 10-2. Runoff after a heavy rainfall collects and floods sinkholes. (Photo Credit: Center for Cave and Karst Studies/Western Kentucky University)
Figure 10-3. A sinkhole collapse in an undeveloped area. (Photo Credit: Center for Cave and Karst Studies/Western Kentucky University)
An analysis of the Barren River Area landscape by Crawford (1986) led to a map
of the relative risk levels associated with sinkhole development in the region
(Figure 10-4). A rectangular grid of cells measuring 1.25 minutes of latitude and
longitude was defined. Each cell was examined to determine where sinkhole
development was evident. If sinkhole development covered at least ten percent
of the total area, the cell was classified as a high-risk area. If sinkholes
covered from one to ten percent of the area, then the cell was designated as
moderate risk. Cells with carbonate rock but less than one percent sinkhole
development were identified as low risk areas. The areas that had no carbonate
rock have no risk.
Figure 10-4. Risk associated with development of sinkholes in the Barren River Area. (Source: N. Crawford, Center for Cave and Karst Studies, Western Kentucky University).
A high-risk area that traverses the region from roughly the southwest to the
northeast bisects the Barren River Area. This area forms a band approximately
20-miles wide. On its fringes are narrower bands or sections considered to
be at moderate risk for sinkhole development. Beyond these the risk factor is
reduced to low. The northern part of Butler County and northwestern Edmonson
County has non-carbonic rock and is at no risk of sinkhole formation.
Some variation in risk can be expected within each zone. Natural variations in
relief affect the size and shape of sinkholes, making some more vulnerable than
others to flooding or collapse. Of much greater importance, urban land
development can drastically alter the environment of a sinkhole, frequently
enhancing the risk of flooding or collapse. Hence, the risk-level designations
are a useful guide, but individual sites must be assessed in evaluating the
risks associated with sinkholes.
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