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Karst (Sinkhole) Hazard Analysis
The development of sinkholes because of subsurface dissolution of soluble rocks and subsidence of overlying rocks and sediments constitutes a significant hazard. In addition to dissolution, subsidence is commonly aggravated by activities that cause structural overloading or lowering of the water table through irrigation or dewatering of a confined aquifer. Dissolution-induced subsidence may damage human structures and catastrophic collapse sinkholes have cost human lives. Other hazardous processes associated with sinkholes include: flooding of surface depressions by runoff concentration and increases in water table levels, water leakage at dams or other hydraulic structures, and groundwater pollution.
We identify and characterize sinkholes and related karst features using integrated GPR and ERI surveys supplemented by some combination of coring, trenching, and geomorphic analysis. ERI readily allows distinction between limestone, clayey fill, and air to significant depths and so approximately locates sinkhole edges. GPR depicts fractures and voids with great accuracy and so closely locates the boundaries of concealed structures. Either data set can be acquired in 3D to reveal the internal geometry of sinkholes and subsidence mechanisms.
Using this strategy, our karst feature inventory includes accurate sinkhole boundaries, sinkholes that are covered by human activity or natural processes, information about subsidence mechanisms (collapse, suffusion, etc.), and information about sinkhole deformation history. The inventory provides quantitative baseline information for development of prediction models for future sinkhole change and assessment of the probabilities for such change.
Our inventory and prediction model deliverables include maps, cross-sections, 3D models of study area karst features, the geophysical data, core descriptions, pertinent analyses of core samples, and summary reports.