Sinkhole expert: Urban development common culprit of sudden collapse

WEST LAFAYETTE, Ind. - Although water main breaks can cause sudden holes to open up as they wash away dirt and material, much like the one that swallowed three cars in Chicago, a different issue of urban development is more often responsible for such collapses, according to a Purdue University sinkhole expert.

Housing developments and irrigation for farms cause changes in the water table that often lead to the sudden opening of a sinkhole, says Terry West, a professor of earth, atmospheric and planetary sciences and civil engineering.

"There can be a cavity developing underground for years as water slowly dissolves the bedrock, but it is actually a drop in the water table that often triggers the sudden collapse and opening of the sinkhole," he says. "The groundwater actually strengthens the layer of dirt bridging over the hole and helps it support the structures on top of it. When that water goes away, the dirt can no longer carry the same load and it collapses into the void beneath it."

The groundwater supports the dirt through an upward buoyancy force that pushes up against it, he says.

Sinkholes can happen anywhere with bedrock that can dissolve, such as limestone, dolomite, gypsum and salt, and areas in the United States at risk include southern Indiana, the Appalachian Plateau, southern Missouri, Kansas, Alabama, Georgia and Florida, he said.

Although West classifies them differently from sinkholes, he says other human development-driven causes of sudden holes opening in the ground include collapsing mines or sewer systems. 

Writer: Elizabeth K. Gardner, 765-494-2081, ekgardner@purdue.edu