Peer-Reviewed Article
Bedrock Collapse Sinkhole Analysis of Bowling Green, Kentucky
Author Brittiny Paige Moore, SA-7788 Abstract
Warren County, Kentucky is located atop bedrock consisting of karstic Mississippian age limestones marked by sinking streams, caverns, sinkholes and springs. Though sinkholes are common throughout the state, southcentral Kentucky has the highest density. The most common type of sinkhole in Kentucky is the cover (or sediment) collapse which occurs in the soil or other loose material that overlies soluble bedrock. A second type of sinkhole is called a bedrock collapse, which occurs when the ceiling of a cave collapses, exposing the cave passage. This type of collapse is considered rare. The purpose of this study is to determine the increased risk of bedrock collapse sinkholes as a geohazard as a result of human activities in Bowling Green, Kentucky. Methods include the use of remote-sensing, GIS, cave data and maps to interpret areas in Bowling Green that pose the greatest risk of bedrock collapse and, thus, damage and loss of infrastructure. There are over 350 cave entrances in Warren County and more than 30 km of cave passages; among those, bedrock collapse sinkholes are relatively rare. However, preliminary results indicate that bedrock collapse sinkholes can be induced by human activities.
Introduction
The Kentucky landscape stretches 105,000 km2, of which 38,000 km2 is karst terrain. About 36% of the state has some type of karst development, because its bedrock – commonly limestone – is dissolved by water. Karst in Kentucky occurs in five principal regions (Figure 1). The largest of the karst regions is the Western Pennyroyal, which is home to the lon-
gest cave in the world, Mammoth Cave, followed by the Inner Bluegrass region, the Eastern Pennyroyal, and the Carter Caves region (Currens 2002).
Between 4,000 and 6,000 sinkholes collapse annually in the state of Kentucky. The most common type of sinkhole in the state is the cover (or sediment) collapse which occurs in the soil or other loose material that overlies soluble bedrock (Currens 2002). A second type of sinkhole is called a bedrock collapse: this occurs when the ceiling of a cave collapses, exposing the cave passage to the surface. Bedrock collapse is naturally occurring and occurs in all karstic environments. Its development, in relation to its influ- ence on the stability of the bedrock surface, is dependent on the geology of the area, including geologic structures, and the maturity of the solution process in relation to geologic time (Figure 2 on page 10). Collapse of bedrock due to this process can be accelerated or even initi- ated by imposed loads from sources such as construction and the daily activity that ensues thereafter (Waltham, Bell, and Culshaw 2005).
The purpose of this study was twofold: 1) assess the distribution of natural and anthropogenic bedrock collapse sink- holes and their relationship to known cave passages and infrastructure devel- opment within the city of Bowling Green, Kentucky and 2) to locate areas that are at risk of bedrock collapse from infra- Figure 1 - Kentucky has been divided in several physiographic regions based largely on the structure development and to determine
geology of each area.
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