We document and analyze the rapid development of a real-time karst system within the subsurface salt layers of the Ze'elim Fan, Dead Sea, Israel by a multidisciplinary study that combines interferometric synthetic aperture radar and light detection and ranging measurements, sinkhole mapping, time-lapse camera monitoring, groundwater level measurements and chemical and isotopic analyses of surface runoff and groundwater. The >1 m/yr drop of Dead Sea water level and the subsequent change in the adjacent groundwater system since the 1960s resulted in flushing of the coastal aquifer by fresh groundwater, subsurface salt dissolution, gradual land subsidence and formation of sinkholes. Since 2010 this process accelerated dramatically as flash floods at the Ze'elim Fan were drained by newly formed sinkholes. During and immediately after these flood events the dissolution rates of the subsurface salt layer increased dramatically, the overlying ground surface subsided, a large number of sinkholes developed over short time periods (hours to days), and salt-saturated water resurged downstream. Groundwater flow velocities increased by more than 2 orders of magnitudes compared to previously measured velocities along the Dead Sea. The process is self-accelerating as salt dissolution enhances subsidence and sinkhole formation, which in turn increase the ponding areas of flood water and generate additional draining conduits to the subsurface. The rapid terrain response is predominantly due to the highly soluble salt. It is enhanced by the shallow depth of the salt layer, the low competence of the newly exposed unconsolidated overburden and the moderate topographic gradients of the Ze'elim Fan.
Bibliographical noteFunding Information:
InSAR measurements were carried out using COSMO-SkyMed (CSK®) products, ©ASI (the Italian Space Agency), delivered under an ASI license and could be available for purchase through e-GEOS (http://www.e-geos.it/products/cosmo. html). Lidar 2011 data were obtained by SEE Advanced Mapping Systems and Solutions Ltd. (Israel), and the 2005 and 2013 lidar campaigns were carried out by Ofek Aerial Photography. Lidar data can be made available by request for scientific collaborative research from G.B. (firstname.lastname@example.org). Borehole logs were generously made available to us by Svetlana Yelsky of the Dead Sea Works Ltd. We are highly grateful to JGR-ES Associate Editor Jason Kean and to Francis Rengers and two anonymous reviewers for their thorough and knowledgeable reviews that significantly improved this paper. The research was funded by Israel Science Foundation (ISF) grant 958/13 to G.B. and Y.Y. and by the Israeli Government under GSI DS project 40391.
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- flash floods
ASJC Scopus subject areas
- Earth-Surface Processes