Dynamics of hydrological and geomorphological processes in evaporite karst at the eastern Dead Sea – a multidisciplinary study

Karst groundwater systems are characterized by the presence of multiple porosity types. Of these, subsurface conduits that facilitate concentrated, heterogeneous flow are challenging to resolve geologically and geophysically. This is especially the case in evaporite karst systems, such as those present on the shores of the Dead Sea, where rapid geomorphological changes are linked to a fall in base level by over 35 m since 1967. Here we combine field observations, remote-sensing analysis, and multiple geophysical surveying methods (shear wave reflection seismics, electrical resistivity tomography, ERT, self-potential, SP, and ground-penetrating radar, GPR) to investigate the nature of subsurface groundwater flow and its interaction with hypersaline Dead Sea water on the rapidly retreating eastern shoreline, near Ghor Al-Haditha in Jordan. Remote-sensing data highlight links between the evolution of surface stream channels fed by groundwater springs and the development of surface subsidence patterns over a 25-year period. ERT and SP data from the head of one groundwater-fed channel adjacent to the former lakeshore show anomalies that point to concentrated, multidirectional water flow in conduits located in the shallow subsurface (< 25 m depth). ERT surveys further inland show anomalies that are coincident with the axis of a major depression and that we interpret as representing subsurface water flow. Low-frequency GPR surveys reveal the limit between unsaturated and saturated zones (< 30 m depth) surrounding the main depression area. Shear wave seismic reflection data nearly 1 km further inland reveal buried paleochannels within alluvial fan deposits, which we interpret as pathways for groundwater flow from the main wadi in the area towards the springs feeding the surface streams. Finally, simulations of density-driven flow of hypersaline and undersaturated groundwaters in response to base-level fall perform realistically if they include the generation of karst conduits near the shoreline. The combined approaches lead to a refined conceptual model of the hydrological and geomorphological processes developed at this part of the Dead Sea, whereby matrix flow through the superficial aquifer inland transitions to conduit flow nearer the shore where evaporite deposits are encountered. These conduits play a key role in the development of springs, stream channels and subsidence across the study area.

Integrated reflection seismics, 3D-GPR, leveling, DInSAR to detect and characterize high-risk sinkholes in urban cover evaporite karst. A NE Italian case study.

&lt;p&gt;Sinkholes linked to cover evaporite karst in urban environments still represent a challenge in terms of clear identification and mapping considering the anthropic rehash and the presence of man-made structures.&lt;/p&gt;&lt;p&gt;We propose and tested a methodology to identify the subsiding features in an urban area within a cover evaporite karst environment, through an integrated and non-invasive multi-scale approach combining seismic reflection, DInSAR, leveling and full 3D GPR.&lt;/p&gt;&lt;p&gt;The analysis was conducted in a small village in the Tagliamento valley (Friuli Venezia Giulia region, NE Italy) named Quinis, where sinkholes are reported since a long time as well as the hazard linked to their presence: within the years, several houses have been demolished and at present many of them are damaged.&lt;/p&gt;&lt;p&gt;First we applied each methodology independently and after we compared, combined and integrated them to obtain more coherent and cross-validates results. Seismic reflection imagined the covered karst bedrock identifying three depocenters; DInSAR investigation allowed to identify an area with higher vertical velocities; leveling data presented a downward displacement comparable with DInSAR results; 3D GPR, applied here for the first time in the study and characterization of sinkholes, clearly defined shallow sinking features imaging also under a shallow dense pipe network. Combining all the obtained results with accurate field observations we identified and map the highest vulnerable zones.&lt;/p&gt;&lt;p&gt;The final result is the combining of the geophysical, DInSAR and leveling information, while also locating the damaged buildings, the local asphalt pavement breaks or renovation and the buildings which are nowadays demolished, by using vintage photographs and historical maps. The data are consistent, being the most relevant present damages and the demolished building within the zones with higher sinking velocity on the base of both leveling and DInSAR. Geophysically imaged depocenters lie within the most critical area and perfectly correlate with the local pavement damages.&lt;/p&gt;&lt;p&gt;In a complex geological and hydrological framework, as in the study area, a multidisciplinary and multi-scale approach is mandatory to identify and map the zone most affected by sinking phenomena. While punctual data such as borehole stratigraphy, local groundwater level variations with time, extensometers measurements and geotechnical parameters are useful to highlight local hazard due to occurring deformation, the proposed integrated methodology addresses a complete and quantitative assessment of the vulnerability of the area. It&amp;#8217;s fundamental, especially in anthropized environments, using different integrated techniques, without forgetting the role of the fieldwork of the geologists who can detect the precursors or already occurred, even elusive, signs of the ongoing or incipient sinking.&lt;/p&gt;

Dynamics of hydrological and geomorphological processes in evaporite karst at the eastern Dead Sea – a multidisciplinary study

Karst groundwater systems are characterised by the presence of multiple porosity types. Of these, subsurface conduits that facilitate concentrated, heterogeneous flow are challenging to resolve geologically and geophysically. This is especially the case in evaporite karst systems, such as those present on the shores of the Dead Sea, where rapid geomorphological changes are linked to a fall in base level by over 35 m since 1967. Here we combine field observations, remote sensing analysis, and multiple geophysical surveying methods (shear wave reflection seismics, electrical resistivity tomography [ERT], self-potential [SP] and ground penetrating radar [GPR]) to investigate the nature of subsurface groundwater flow and its interaction with hypersaline Dead Sea water on the rapidly retreating eastern shoreline, near Ghor Al-Haditha in Jordan. Remote-sensing data highlight links between the evolution of surface stream channels fed by groundwater springs and the development of surface subsidence patterns over a 25-year period. ERT and SP data from the head of one groundwater-fed channel adjacent the former lakeshore show anomalies that point to concentrated, multidirectional water flow in conduits located in the shallow subsurface (

Non-Invasive Methodological Approach to Detect and Characterize High-Risk Sinkholes in Urban Cover Evaporite Karst: Integrated Reflection Seismics, PS-InSAR, Leveling, 3D-GPR and Ancillary Data. A NE Italian Case Study

Sinkholes linked to cover evaporite karst in urban environments still represent a challenge in terms of their clear identification and mapping considering the rehash and man-made structures. In the present research, we have proposed and tested a methodology to identify the subsiding features through an integrated and non-invasive multi-scale approach combining seismic reflection, PS-InSAR (PSI), leveling and full 3D Ground Penetrating Radar (GPR), and thus overpassing the limits of each method. The analysis was conducted in a small village in the Alta Val Tagliamento Valley (Friuli Venezia Giulia region, NE Italy). Here, sinkholes have been reported for a long time as well as the hazards linked to their presence. Within past years, several houses have been demolished and at present many of them are damaged. The PSI investigation allowed the identification of an area with higher vertical velocities; seismic reflection imagined the covered karst bedrock, identifying three depocenters; leveling data presented a downward displacement comparable with PSI results; 3D GPR, applied here for the first time in the study and characterization of sinkholes, defined shallow sinking features. Combining all the obtained results with accurate field observations, we identified and mapped the highest vulnerable zone.

Uvalas and their relationship to sinkholes (dolines) in an evaporite karst setting

&lt;p&gt;Enclosed topographic depressions are characteristic of karst landscapes on Earth. The scale and morphological characteristics of such depressions are variable, but the most common depression type is a sinkhole (doline). Certain karst depressions that are much larger than sinkholes and that display gentler slopes and more complex three-dimensional shapes are known as uvalas. A single uvala typically contains numerous sinkholes within it. The developmental relationship between sinkholes and uvalas has been subject of debate, however, mainly because long developmental timescales impede direct observation in classical limestone karst, where such features are most commonly reported.&lt;/p&gt;&lt;p&gt;Here, we describe the development of five uvalas and numerous associated sinkholes in an evaporite karst setting on the eastern shore of the hypersaline Dead Sea. This karst landscape evolved rapidly over a 25-year period from 1992 to 2017 in response to the anthropogenically-driven decline in the Dead Sea level. Our remote sensing data and field observations show that both the sinkholes and the uvala-like depressions formed through subsidence in a very close spatio-temporal relationship. While many sinkholes developed initially in clusters, the uvalas developed around such clusters as larger-scale and gentler depressions that are structurally distinct both in space and time.&lt;/p&gt;&lt;p&gt;In agreement with inferences for examples in limestone karst settings, the uvalas in this evaporite karst setting do not form by a simple coalescence of sinkholes. Instead, these evaporite-karst uvalas form through subsidence (sagging), interpreted here as in response to distributed subsurface dissolution and physical erosion within a mechanically unstable subsurface volume (e.g. a groundwater conduit network). Sinkholes, on the other hand, are interpreted as discrete subsidence responses within that volume to smaller-scale zones of highly localised material removal (e.g. individual groundwater conduits). Our observations and interpretations are consistent with numerical modelling of subsidence produced by the development of multiple void spaces at progressively deepening levels. Morphometrically, our results also agree well in several respects with a recent re-evaluation of uvalas in some classical limestone karst areas. Consequently, this study helps to clarify the nature, occurrence and genesis of uvalas in karst systems generally.&lt;/p&gt;