Self‐accelerated development of salt karst during flash floods along the Dead Sea Coast, Israel

• Published in: Journal of geophysical research. Earth surface 2016-01, Vol.121 (1), p.17-38
• Main Authors: Avni, Yoav, Lensky, Nadav, Dente, Elad, Shviro, Maayan, Arav, Reuma, Gavrieli, Ittai, Yechieli, Yoseph, Abelson, Meir, Lutzky, Hallel, Filin, Sagi, Haviv, Itai, Baer, Gidon
• Format: Article
• Language: English
• Subjects: Aquifers; Brackish; Chemical analysis; Coastal aquifers; Dissolution; Flash floods; Floods; Floodwater; Flow velocity; Formations; Geochemistry; Groundwater; Groundwater flow; Groundwater levels; Groundwater recharge; Groundwater runoff; InSAR; Karst; Land; Land subsidence; lidar; Marine; Multidisciplinary research; Overburden; Ponding; Salt; Salts; Seawater; Sinkholes; Subsidence; Surface runoff; Water analysis
• ISSN: 2169-9003; 2169-9011
• DOI: 10.1002/2015JF003738

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. Key Points A self‐accelerated active salt karst system is formed along the Dead Sea coast Land subsidence and sinkhole formation documented at high temporal resolution (minute to annual) Groundwater levels and chemistry respond abruptly to recharge by floodwater through sinkholes