Why Karst Areas Need Education and Protection

A karst landscape is characterized by interior drainage. Rainfall runs off into sinkholes and sinking creeks, rather than forming streams and rivers. Underground, water collects in vertical shafts and underground rivers flowing through caves. Cave waters find an outlet in a spring feeding a base level stream. Most karst is developed by solution and collapse in limestone bedrock. Underground streams carry away the dissolved rocks and fill, such as sand, soil, and organic matter that comes into the cave from the surface.

Four requirements come together to make caves. 1. A source of water, such as rainfall. 2. Rocks with cracks such as joints, bedding planes, faults, or fractures. Water can flow through the cracks transporting materials to make the cave larger. 3. Moveable rocks, most often carbonate rocks that can be dissolved or loosened by water and humic acid and carried away. The solution and transport of materials through time enlarge passages. 4. A drain to carry away the ground water. All four requirements must be present to make a cave.

Caves are vulnerable and can also cause damage in many ways. They can flood and back water onto the surface of the karst through ponds in sinkholes. This is because a cave is usually a flow-restricted system. In normal weather cave passages may carry free surface streams. In heavy rains the quantity of water overwhelms the flow capacity of the cave conduits and the water can pond behind the restrictions to a depth two or more times the rise of the master surface river.

Caves, which are natural conduits for ground water, provide little or none of the filtration and exposure to sunshine that tends to purify surface streams naturally. Materials, such as sewage or chemicals, discharged on the surface can be carried through the cave and can injure or kill cave biota as well as contaminate the water supply.

Sinkholes are partially formed by collapse and solution, and enlarged as water carries away the loose materials. Caves themselves collapse as a result of structural weakness of passages. Cave breakdowns can reduce the cross-section of passages. Occasionally, where cave roofs are thin, catastrophic collapses can extend to the surface and create new entrances as well as wreck manmade structures built above the cave.

Education is needed to tell people about how caves and their living organisms, endangered species, and water supply can be destroyed by ignorance or stupidity. Millions of dollars are spent needlessly by developers that fail to understand the special dangers and vulnerability of karst terrain. Karst geologists and engineers exist who know some ways to safeguard against expensive failures, but developers and contractors often ignore their advice. The Kentucky Transpark is an expensive case in point: Some self-styled leading experts on karst problems made recommendations for avoiding collapse, flooding, and contamination. Some of their recommendations were heeded, most ignored. Millions of dollars of avoidable loss resulted due to collapses, flooding, and contamination. KEEP has documented more than $22 million of avoidable karst failures in south central Kentucky, where the practice is to Ignore karst; Build now: Fix later.

Karst needs to be protected because to many it looks like a handy way to dispose of trash, sewage, or spilled chemicals. Some shortsighted developers tell owners that it costs little more to build on karst than to build anywhere else. When collapse, flooding, or contamination take place they blame it on an Act of God, charge the owner dearly to fix it, and point the finger of blame in all directions. Millions of dollars of taxpayer funds are literally squandered "down the drain" in this world class karst area.

KEEP has published several brochures about the dangers surrounding the Kentucky Transpark. This 4000 to 6000 industrial park/airport/rail distribution center is advertised as "environmentally friendly", which is marketing hyperbole for a project that is being built on the most collapse prone, flood prone, and contamination prone karst in all of Kentucky.

Frequently asked questions about karst

Q: How much karst topography is there?

A: One estimate is 10% of the world land surface. An estimate for the United States is also about 10%. Some have used an estimate of 45%, but this guess classifies all carbonate rocks as karst, which is silly. Many states with carbonate basement rocks are mostly covered by a thick mantle and show little evidence of karst topography. Nobody really knows.

Q: Who says sinkholes are dangerous to construction?

A: Property casualty insurance companies routinely refuse to pay claims in karst areas and also areas where underground mine subsidence occurs.

Q: How many kinds of sinkholes are there?

A: One kind covers all cases. Geomorphology books used to classify sinkholes as "solution" or "collapse". Actually both processes are present, plus a third process of material transport. Each sinkhole has a unique history, but all start with water enlarging cracks in rocks. When the cracks fail to support surrounding rocks, loose pieces collapse into the voids and are carried away by water into caves below. All sinkholes lead to caves.

Q: What does the cross-section of a sinkhole look like?

A: A typical sinkhole resembles a small funnel connected by several vertical pipes to a large upside down funnel. There is seldom just one vertical pipe and often there are many adjacent pipes. Furthermore, the bedrock in which the sinkhole is developed may exhibit wide partings that have been enlarged by solution.

Q: Isn't it easy to plug a sinkhole just by filling it with rocks?

A: A sinkhole is a dynamic erosional structure, rather than a simple funnel as shown in some engineering handbooks. Often the so-called throat does not exist because there are multiple throats and multiple pathways for water to drain. Partings may conduct the water sideways for scores of feet. Attempts to scoop out a smooth basin and line the sinkhole with a membrane often fail because the subgrade is inherently unstable. Also, liner life is limited to not more than 20 years. A ponded sinkhole is likely to overflow during heavy rains and scour alternative drainage routes into the cave below.

Q: Do sinkholes collapse when pumping lowers the water table below?

A: Much expensive damage in Florida is attributed to subsidence from lowering the water table. Florida has extensive areas of highly developed underwater karst due to the peninsula's repeated emergence and submergence through geologic time. Scuba divers report extremely large underwater chambers in may Florida caves and springs.

Q: Do karst areas dilute contaminants?

A: A karst area will actually concentrate airborne contaminants, such as heavy metals, that fall onto the ground. These materials are transported to swallow points where some become coatings on rocks underground. Surface contaminants are carried into rock conduits rather than diffused or dispersed through gravel or particles. Contaminants can reduce biodiversity or kill cave animals.