The swallow-holes of Lost River, Orange County, Indiana
Lost River of southern Indiana has an upper area of surface drainage on an upland limestone plain, a middle area of subterranean drainage through a perched sinkhole plain, and a lower area of intrenched drainage at or near baselevel. Intrenchment of the lower section of Lost River permitted the lowering of the watertable of the middle area and sinkhole topography and sinking drainage followed. The upper area of surface drainage on the limestone upland remote from the intrenched lower part of the stream basin remains unaffected and still has a watertable limited by the stream itself. The sinkholes, the sinking streams, the lengthened and little used dry-bed section of Lost River, and the capacious cavernous underground drainage routes of the middle section have been developed during the present cycle of drainage intrenchment, and they are the products of invading surface waters keeping pace with a progressively lowered or withdrawn watertable in the perched section of the limestone upland.