A Critical Research Gap Study of Sinkhole Hazard Assessments

Karst landscapes are perceived as sensible environments due to soluble rocks (limestone, marble, dolomite, etc.) being the predominant features. The dissolution process in karstic structures poses serious multiple hazards to the communities on which they are built. Sinkholes and ground subsidence are the main geological hazards from these areas causing damage to lives and livelihoods. Meteorological events such as heavy rainfall leading to flooding play an important aggravating factor for these areas which often can collide with the special geological situation resulting in a cascade of hazards (flooding and sinkhole collapse). Consequently, such multi-hazard-forming environments like karst regions present a need to better understand the complex interrelationship of water in the form of flooding and underground cavity collapses. Yet, till the present, our approaches to these hazardous events have been often fragmented and inadequate. Moreover, with climate change having a significant impact on Earth, a change in hydrological processes followed by increasing dissolution of limestone, which may lead to more flooding and sinkhole occurrences, can be predicted in the immediate future. Therefore, research on interrelated hazards will be imperative in order to set priorities for complex natural events. While numerous research works have made attempts to study sinkholes and their contributing factors, to date if not any, few studies have perceived and assessed flooding and sinkhole as a multi-hazard event. Since globally, a shift from single to multi-hazard assessment is being encouraged by international risk communities, the present study is to provide new insight towards flooding and sinkholes assessment emphasising multi-hazard approaches. This critical review aims at understanding the current state of sinkhole-related researches, reviewing grey- and peer-review literature. Afterwards, the studies are classified into seven research themes (Morphology, Flood impacts on karst, Monitoring and prediction, Hazard & risk assessment, Multi-hazard-mapping modelling, Mitigation measure, and Others), demonstrating the more favourite research directions and research gap in the field of sinkhole hazard assessment. The results highlight the importance of the integrated multi-hazard assessment in the areas affected by both flooding and karst hazards and show that so far sinkhole risk assessment (70 articles – 35%) followed by sinkhole morphology (63 articles – 31,5%) have been the most popular research subject within the discipline. This research aids future research to bridge the existing gap towards improving mitigation planning and helping policy and decision-makers in their inclusion of multi-hazard interactions in municipal policies and approaches.