CP wrote an explainer about sinkholes, because they are difficult to understand, but questions remained. Now, more questions about sinkholes answered, with some background information from Daniel Bain, a professor in Geology and Environmental Science Department at the University of Pittsburgh.
Are sinkholes in general caused by the natural landscape or human activity?
"The reason you can't figure out if it's one or the other is because it's both," says Bain. Sinkholes can be caused by a karst landscape (heavy with limestone, which can be dissolved by water). Poor infrastructure can also be a factor; if roads aren't filled correctly, they can deteriorate over time, which is more likely the cause of the sinkhole Downtown. Bain says filling under the road with wood or other decomposable materials could lead to collapse.
Climate change is bringing heavier rain to Pittsburgh. Will that affect sinkholes?
It rained a total of 57.83 inches in 2018 (the current rainfall for 2019 is 45.31 inches, around three inches below the 2018 rainfall this time last year). Water can deteriorate material underneath the road, but Bain notes that it's not just the large quantity of rain, but the speed at which it comes down.
"What's more important is we seem to be getting storms that dump a lot of rain in a shorter period than they did before. So that would make the stormflow much bigger. The bigger it is, the more sentiment it'll move," he says. "If you have a lot of stormflow in a stream, you get bank erosion. If you have a lot of storm flow in a pipe underground, it can get the equivalent of stream bank erosion underground and again can evacuate a space and cause a sinkhole."
So while sinkholes are not a direct result of climate change, they might be caused by weather events that are a direct result of climate change, like increased rainfall.
"We know that there's going to be more stressors, but we don't know how resilient the system is to those stressors," says Bain.
So what happens if you find a sinkhole? Or if it finds you?
You should hope that there aren't any major damages to your person or property because, according to Bain, it's difficult to prove anything when taking someone to court over a sinkhole.
"If you were to try to go to court to try and recover things, you would require an engineering geologist to probably testify, because there's so many variables that are distinct from site to site," says Bain. "It's easy to concoct multiple stories. Coming up with the most likely story requires some time and energy."
If you do encounter a sinkhole, you can report it to 311. They might fill it, or at least put some cones around it.