Des Moines. Cedar Rapids. Burlington. Dubuque. Interstate 80. Out of nowhere and without warning, sinkholes are appearing all over Iowa and often swallowing everything in their path. And you thought teenagers had a bottomless appetite.
This is no horror movie plot. This is reality for thousands of unsuspecting Midwest homeowners. As hundreds of evacuated homeowners in Fraser, Mich., discovered in December, sinkholes can strike anywhere.
The threats sinkholes pose to American homes are coast to coast. The United States Geological Survey estimates 20 percent of U.S. land is susceptible to sinkholes. The truly scary news is most American homeowners are completely unaware of the existence of potential sinkholes on their land and in their community.
And often lying in wait for centuries to emerge, sinkholes rarely announce their presence quietly when they finally emerge.
“When sinkholes do occur, the effect can be quite spectacular,” Tony Coleman of the British Geological Survey said, “so they tend to get noticed, especially when they cause the collapse of a building.”
And there very well could be a sinkhole on your land. Some sinkholes have been traced to land-use practices, especially from groundwater pumping, construction and development. Sinkholes can also form when natural water drainage patterns are changed and new water diversion systems are installed and implemented.
In Iowa, Karst terrain (defined as the presence of easily dissolved bedrock like limestone and dolomite near the ground surface) is prime real estate for potential hazards. Iowa’s recent rash of flooding – such as the floods of 2008 and 2016 — has covered even more of the state with Karst terrain.
Sinkholes in Iowa are especially common in residential neighborhoods built atop old coal mines. The Iowa Department of Natural Resources estimates 2,700 Iowa homes sit atop aging, forgotten coal mines. The Iowa Geological Survey notes there may be as many as 6,000 underground coal mines scattered across 38 of Iowa’s 99 counties, putting nearly 80,000 state acres at risk for sinkholes.
“If you’re in the Des Moines area, there’s a good chance there’s a coal mine beneath you,” Calvin Wolter, a Geographic Information Systems analyst with the Iowa Department of Natural Resources, told the Des Moines Register.
The IGS also reports most of Iowa’s sinkholes occur in rural areas where their main impact is rendering some land unsuitable for row-crop agriculture and causing the failure of farms, ponds and roads. Sinkholes sometimes allow surface runoff to directly enter bedrock aquifers, presenting implications for groundwater quality.
So how can Iowa homeowners get a sound reading on the potential for sinkholes on their property? The first rule of sinkhole awareness is if something looks suspicious on your land, call your local U.S. Natural Resources Conservation Services office. Here are some of the most common signs of potential sinkholes from sinkhole.org:
- Cracks in Home Interior Joint Areas, Windows or Doors
- Cracks in Home Exterior Block or Stucco
- Windows and Doors Becoming Harder to Close Properly
- Depressions in Your Yard or Other Yards Near You
- Deep Cracks and Separation of Paved Concrete Walks and Drives
- Circular Patches of Wilting Plants
- Sediment in Your Water
- Neighbors Have Had or Confirmed Possible Sinkhole Activity
- Observation of an Actual Cavity Beginning to Open
All potential homeowners should always quiz their realtor on the potential of sinkholes impacting their property and research the probability of sinkholes on the land and communities they are considering purchasing. The good news: the Iowa Administrative Code prohibits new, expanding and modified confinement operations from constructing within 1,000 feet of a sinkhole unless secondary containment is provided.
Like earthquakes and tornados, sinkholes offer their victims little or no warning, but being fully aware and educated on the probability of a sinkhole striking your home can have you and your family prepared for if and when the ground opens up under or near your home.