Methodological Considerations in Cover-Collapse Sinkhole Analyses: A Case Study of Southeastern China’s Guangzhou City

Abstract. Cover-collapse sinkholes can present significant hazards to human habitation and communal facilities in soil-covered karst regions. Therefore, for human security and land-use planning in sinkhole-prone areas, appropriate approaches are required prior to construction in order to understand the cover-collapse sinkhole genesis and its likely evolution. The study seeks to contribute to performing an integrated analysis of karst hazards in mantle karst regions where karst evidence can be masked, with the ultimate goal of developing a methodological framework utilizing different techniques and approaches. A small area located in Guangzhou City of southeastern China’s Guangdong Province was analyzed. The detailed typology, morphometry, and chronology inventory of 49 cover-collapse sinkholes in the study area were analyzed using various surface investigation methods, such as field surveys, aerial photography, and photogrammetry. The Quaternary deposits and indicators of the active underground karst features in the aforementioned mantle karst region were geotechnically characterized using drilling and geophysical techniques. These techniques included ground penetrating radar (GPR), electrical resistivity imaging (ERI), natural source audio frequency magnetotellurics (NSAMT), and micro-tremors. During this study’s investigations, three karst fissure zones covered by Quaternary soil were observed using multiple techniques. In addition, it was found that the groundwater dynamic monitoring data confirmed that the sinkholes in the study area were closely related to changes in groundwater levels. Therefore, the efforts which have been made to investigate and monitor the sinkhole development will be required to continue into the immediate future.