Irrigation Could Make Golf Courses Spawn Sinkholes

In the wake of the "golfer in the sinkhole" story from last week — in which Illinois golfer Mark Mihal spent about 20 minutes at the bottom of a 20-foot-deep sinkhole on a golf course — we started wondering if the landscaping techniques on these courses could have caused the sinkhole.

Sinkholes are formed when water washes out soft rocks — like limestone, gypsum, or salt beds — making underground holes covered in a thin layer of ground. These sinkhole-susceptible areas are areas called "karst terrain," which covers about 20 percent of the U.S.

We asked USGS geologist David Weary for his thoughts. He told Business Insider in an email on Friday:

In my opinion it is possible for irrigation and landscaping to affect the risk of sinkhole development on golf courses over karst areas. Normal irrigation of the grass would probably not put enough water on the surface to cause sinkholes directly. It is possible that over-irrigation over time could cause some movement of sediment in the subsurface (through caves) and result in eventual localized sinkhole development. Also, if landscaping resulted in a spot where the surface drainage ponds its possible that the combination of heavy standing water and enhanced drainage of that water to the subsurface could move sediment and initiate a collapse. Golf courses are usually graded to avoid standing water, so the chances of this should be pretty low.

The most likely causes of collapse sinkholes in areas like golf courses, are leaking irrigation pipes or leaking stormwater handling structures like drain pipes and retention ponds. Chronic water leaks can, over time, erode the subsurface soils and cave fills leading to creation of void spaces and subsequent collapse of the surface into them.

We don't have enough site-specific information about the Illinois golf course sinkhole to comment as to whether it is purely natural, or man-induced.