During the past three decades, the Dead Sea (DS) water level has dropped at an average rate of ~1 m/year, resulting in the formation of thousands of sinkholes along its coastline that severely affect the economy and infrastructure of the region. The sinkholes are associated with gradual land subsidence, preceding their collapse by periods ranging from a few days to about five years. We present the results of over six years of systematic high temporal and spatial resolution interferometric synthetic aperture radar (InSAR) observations, incorporated with and refined by detailed Light Detection and Ranging (LiDAR) measurements. The combined data enable the utilization of interferometric pairs with a wide range of spatial baselines to detect minute precursory subsidence before the catastrophic collapse of the sinkholes and to map zones susceptible to future sinkhole formation. We present here four case studies that illustrate the timelines and effectiveness of our methodology as well as its limitations and complementary methodologies used for sinkhole monitoring and hazard assessment. Today, InSAR-derived subsidence maps have become fundamental for sinkhole early warning and mitigation along the DS coast in Israel and are incorporated in all sinkhole potential maps which are mandatory for the planning and licensing of new infrastructure.

The sinkholes along the Dead Sea (DS) shores form by dissolution of an 11–10 kyr old subsurface salt layer (hereafter named the ‘Sinkholes Salt’) that precipitated on the lake’s floor during periods of negative water balance, water level decline and salinity increase. We analyze the variations in absolute elevation and thickness of this layer in 40 boreholes along the western shores of the DS, reconstruct water-body stratification, past lake levels, and paleo-bathymetry during salt deposition, and comment on the role of the salt-layer elevation in future sinkhole formation. In the northern basin of the DS, maximum thickness of salt (~ 23 m) is found where salt top and bottom elevations are below ~ 440 meters below sea level (mbsl) and ~ 465 mbsl, respectively. Above these elevations the salt layer gradually thins out until 416 mbsl, above which it is no longer found. These relationships suggest that thermohaline stratification, with a thermocline at 25–30 m depth, similar to the present day dynamics of the DS, developed annually during the salt-precipitation period, giving rise to uniform salt accumulation below the thermocline and partial to full dissolution above it. Salt accumulation was controlled by the bathymetry of the lake and its configuration relative to the thermocline, and locally hampered by discharge of subaqueous under-saturated groundwater. The truncation of the salt layer at elevation of 416 mbsl is attributed to salt dissolution down to this elevation by a relatively diluted upper water layer that developed following inflow of fresh surface water at the end of the salt period. This event also marks the change to a positive water balance and lake level rise from its lowest stand of ~ 405 mbsl, as determined from limnological considerations.