Induced and natural sinkholes in Alabama — A continuing problem along highway corridors : Newton, J G Transp Res Rec, N612, 1976, P9–16

Abstract

Sinkholes are divided into two categories, induced (man-related) and natural. Since 1900, an estimated 4000 induced sinkholes or related features have formed in Alabma,; fewer than 50 natural sinkholes have been reported. Most induced sinkholes are caused by water-level declines due to pumpage; others result from factors associated with construction. Almost all occur where cavities develop in unconsolidated deposits overlying openings in bedrock. The downward migration of the deposits and the development of the cavities are caused or accelerated by a water-level decline that results in the loss of buoyant support and increases the velocity of water movement, the magnitude of water-level fluctuations, and the induced recharge. Most sinkholes caused by construction are due to the diversion of drainage over openings in bedrock. Many natural sinkholes are caused by the collapse or downward migration of unconsolidated deposits into openings in bedrock. The downward migration that sometimes creates cavities in the deposits results from natural declines in the water table, progressive enlargement by solution of openings in the top of bedrock, or a combinstion of both. The failure of bedrock roofs over solutionally enlarged openings is a rare occurrence. The time required for the development of natural sinkholes is far greater than that associated with induced sinkholes. /Author/