Many karst areas have poor soil, and do not retain water easily, allowing it to go directly underground. These reversible sinks, called estavelles , are among the curiosities of karst. Many theories, but no one knows why, for sure. Another oddity of Missouri karst is the karst window , where one may look into a cave or water filled sink below, but getting down there is another matter entirely. Karst makes for beautiful scenery, but it is very vulnerable to groundwater pollution, due to ease of water flow.
Natural filtration is nearly non-existent in karst.
To make matters worse, the use of cave conduits as natural sewer lines, and sinkholes as garbage dumps in small towns and rural areas puts the local drinking water supplies at risk. It is only recently that these problems are being addressed. Urban expansion in karst areas often means the building of houses on land which cannot support them and problems with septic tanks, underground pipeline breaks and landfills. Some of the most beautiful sites in Missouri are a result of karst processes, as are some of our most pressing land use problems. Since the undeveloped land seemed to have managed very well, it is up to people to use some sense when they go to develop it, and take its unusual character into account.