Mapping and predicting sinkholes by integration of active remote sensing and spectroscopy methods

Abstract:

The Dead Sea coastal area in Israel is exposed to the destructive process of sinkhole collapse. The increase in sinkhole activity in the last two decades has been substantial, resulting from the continuous decrease in the Dead Sea's level, with more than 2,000 sinkholes developing as a result of upper layer collapse. Sinkholes, which can reach 50 m in diameter, are concentrated mainly in clusters in several dozens of sites with different characteristics. This study aimed to investigate different techniques for mapping, monitoring and identifying areas with potential for new sinkhole development using active and passive remote-sensing means. We used a field spectrometer, geophysical ground-penetration radar (GPR) and a frequency domain electromagnetic (FDEM) instrument. The research was conducted in three stages: (i) literature review and data collection; (ii) mapping regions with an abundance of sinkholes in various stages, and areas that are vulnerable to them; (iii) data analysis and transformation to cognitive and accessible scientific information. Field spectrometry enabled a comparison of the spectral signatures of soil samples collected near active or progressing sinkholes, and those collected in regions with no visual sign of sinkhole occurrence. FDEM and GPR investigations showed that electrical conductivity and soil moisture are higher in regions affected by sinkholes. Measurements taken at different time points over several seasons allowed monitoring the progress of an 'embryonic' sinkhole.