Sinkhole Hazards

Sinkholes or dolines are closed depressions characteristic of terrains underlain by soluble rocks (carbonates and/or evaporites). They may be related to the differential dissolutional lowering of the ground surface (solution sinkholes) or to subsidence induced by subsurface karstification (subsidence sinkholes). Three main subsidence mechanisms may operate individually or in combination: collapse, sagging, and suffosion. Subsidence sinkholes may cause severe damage to human built structures, and the occurrence of catastrophic collapse sinkholes may lead to the loss of human life. Dissolution and subsidence processes involved in the development of subsidence sinkholes are controlled by a wide range of natural and anthropogenic factors. Recent literature reviews reveal that the vast majority of the damaging sinkholes are induced by human activities (e.g., water table decline, water input to the ground). The main steps in sinkhole hazard and risk assessment include: (a) construction of comprehensive sinkhole inventories and detailed sinkhole characterization; (b) development of independently tested sinkhole susceptibility and hazard models, preferably incorporating magnitude and frequency relationships; (c) assessing risk combining hazard and vulnerability data. Sinkhole risk models may be used as the basis to perform cost-benefit analyses that allow the cost-effectiveness of different mitigation strategies to be estimated. Three main concepts may be applied to reduce sinkhole risk: (a) avoiding sinkholes and sinkhole-prone areas (preventive planning); (b) diminishing the activity of dissolution and/or subsidence processes (hazard reduction); (c) incorporating special designs in the structures (vulnerability reduction). Although our capabilities to investigate sinkhole hazards and reduce the associated risks will continue to increase in the near future, the damage related to sinkholes will also increase, largely due to the adverse changes caused by human activities on the karst environments and the ineffective knowledge transfer between scientists, technicians, and decision-makers. This article presents the processes and factors involved in sinkhole development and reviews the main approaches used to assess and manage sinkhole hazards and risks.