When You Get That Sinking Feeling
Sinkholes around the world have been making the news lately. From car-swallowing potholes in Rome to sinkholes threatening entire communities in Florida, soils worldwide are shifting in unsettling ways.
But what’s causing this sudden epidemic of sinkholes? Signs point to climate change and the inability of infrastructure developers to keep up with the demands of changing topographies. Everything from acid rain to clear-cutting is playing a role in the stability of the soil beneath our feet.
Sinkholes: Environmental Extremes
Climate change is perhaps the biggest catalyst for sinkhole formation. Higher rainfall rates are causing extreme groundwater saturation, which doesn’t bode well for calcareous soils. These soils—which have bedrock bases of sandstone, chalk, gypsum or limestone—are highly porous and easily eroded. When exposed to extreme groundwater saturation for long periods of time, the bedrock begins to disintegrate, allowing sand and soil to fall through.
The result of disintegrating bedrock is an “upward-creeping void,” which comes to fruition as a sinkhole. By the time the bedrock has dissolved to an unstable level, the soil above it has already begun to sink and settle. When the surface finally breaks, many sinkholes can already be many meters deep!
To add to this, acidic rainwater is also a growing contributor to soil instability. Contaminated rainwater works even quicker to dissolve limestone and other calcareous soil foundations. Sinkholes develop faster and with more severity—often resulting in newsworthy coverage due to their catastrophic eruption.
Poor Infrastructure Planning
Climate change isn’t the only contributor to sinkhole development. Land management and infrastructure practices are also to blame: namely improper irrigation and clear-cutting practices.
Improper irrigation exacerbates the soil saturation problem. For example, while urban irrigation systems may keep groundwater levels away from the foundation of tall buildings—via de-watering wells and caissons—that water is displaced elsewhere. The result can be extreme saturation, eventually resulting in bedrock dissolution and, ultimately, sinkhole formation.
Clear-cutting works in the opposite way, with similar effects. Removing natural foliage and growth from the land lowers its erosion resistance properties. Soil is more freely shifted, resulting in erosion and unstable shifting of soils. Eventually, this extreme erosion and saturation creates karst land, paving the way for further disfigurement by sinkholes.
How to Spot a Sinkhole Before It’s Too Late
Predicting where and when sinkholes will form is far from an exact science. Thankfully, there are methods of prediction and prevention using new materials and technology.
Perc testing of soil is a simple way to determine its potential for saturation. Likewise, a simple soil test can reveal the nature of soil composition, to help identify at-risk areas where bedrock could be prone to erosion. Certain anti-erosion and land grading tactics are also effective in remediating soil saturation issues.
For every day, run-of-the-mill situations, simply observing the land is often enough to call out a developing sinkhole. Areas where the land bows inward or where clear foundation shifting and shearing have taken place often indicate unsettling in the bedrock. It’s important for developers to test soil and for homeowners to pay keen attention to suspect areas. Soil Advocates provides a wide range of testing services to help whether you are a homeowner, developer or landowner. Contact us at 289-221-0164 to find out more.