37 research outputs found

    Sinkhole monitoring and early warning: An experimental and successful GB-InSAR application

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    AbstractSinkholes represent a natural risk that may hit catastrophically without clearly detectible precursors. However, they are often overlooked by people and administrators. Therefore sinkhole monitoring and associated early warnings constitute important research topics but, currently, only a few papers about sinkhole prediction can be found. In this paper an experience of sinkhole monitoring and early warning with GB-InSAR is described. The latter is a highly precise instrument that is able to produce displacement maps with metric spatial resolution. The described activities were carried out on Elba Island (central Italy), where karstified limestone set off the occurrence of nine sinkholes since 2008, all within less than 3000m2, causing major damage to an important road and many indirect losses. In 1year of monitoring two deforming areas were detected, and the point where a sinkhole was about to propagate to the street level was predicted, thus permitting the preventive closure of the road. The deformation area was larger than the hole generated by the sinkhole, thus showing a subsidence that continued for a prolonged time even after the cavity was filled up. The occurrence of a 1.5-m-wide sinkhole, undetected by the GB-InSAR, also showed the lower detection limit of the instrument

    Railway deformation detected by DInSAR over active sinkholes in the Ebro Valley evaporite karst, Spain

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    Subsidence was measured for the first time on railway tracks in the central sector of Ebro Valley (NE Spain) using Differential Synthetic Aperture Radar Interferometry (DInSAR) techniques. This area is affected by evaporite karst and the analysed railway corridors traverse active sinkholes that produce deformations in these infrastructures. One of the railway tracks affected by slight settlements is the Madrid-Barcelona high-speed line, a form of transport infrastructure highly vulnerable to ground deformation processes. Our analysis based on DInSAR measurements and geomorphological surveys indicates that this line shows dissolution-induced subsidence and compaction of anthropogenic deposits (infills and embankments). Significant sinkhole-related subsidence was also measured by DInSAR techniques on the Castejón-Zaragoza conventional railway line. This study demonstrates that DInSAR velocity maps, coupled with detailed geomorphological surveys, may help in the identification of the railway track sections that are affected by active subsidence

    Land subsidence and its relations with sinkhole activity in karapınar region, turkey: A multi-sensor insar time series study

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    The Karapinar basin, located in the Central Anatolian part of Turkey, is subjected to land subsidence and sinkhole activity due to extensive groundwater withdrawal that began in the early 2000s. In this study, we use Interferometric Synthetic Aperture Radar (InSAR), Global Navigation Satellite System (GNSS), and groundwater level data to monitor and better understand the relations between groundwater extraction, land subsidence, and sinkhole formation in the Karapinar basin. The main observations used in the study are InSAR-derived subsidence velocity maps calculated from both Sentinel-1 (2014–2018) and COSMO-SkyMed (2016–2017) SAR data. Our analysis reveals broad areas of subsidence with rates exceeding 70 mm/yr. The InSAR-derived subsidence was compared with GNSS data acquired by a continuously operating GNSS station located in the study area, which show a similar rate of subsidence. The temporal characteristic of both InSAR and GNSS time series indicate a long-term subsidence signal superimposed by seasonal variability, which follows the overall groundwater level changes, with over 80% cross-correlation consistency. Our results also indicate that sinkhole activity is limited to slow subsidence areas, reflecting strong cohesion of near-surface rock layers that resist subsidence but yield to collapse in response to aquifer system deformation induced by groundwater extraction

    Land subsidence and its relations with sinkhole activity in karapınar region, turkey: A multi-sensor insar time series study

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    The Karapinar basin, located in the Central Anatolian part of Turkey, is subjected to land subsidence and sinkhole activity due to extensive groundwater withdrawal that began in the early 2000s. In this study, we use Interferometric Synthetic Aperture Radar (InSAR), Global Navigation Satellite System (GNSS), and groundwater level data to monitor and better understand the relations between groundwater extraction, land subsidence, and sinkhole formation in the Karapinar basin. The main observations used in the study are InSAR-derived subsidence velocity maps calculated from both Sentinel-1 (2014–2018) and COSMO-SkyMed (2016–2017) SAR data. Our analysis reveals broad areas of subsidence with rates exceeding 70 mm/yr. The InSAR-derived subsidence was compared with GNSS data acquired by a continuously operating GNSS station located in the study area, which show a similar rate of subsidence. The temporal characteristic of both InSAR and GNSS time series indicate a long-term subsidence signal superimposed by seasonal variability, which follows the overall groundwater level changes, with over 80% cross-correlation consistency. Our results also indicate that sinkhole activity is limited to slow subsidence areas, reflecting strong cohesion of near-surface rock layers that resist subsidence but yield to collapse in response to aquifer system deformation induced by groundwater extraction

    Delayed subsidence of the Dead Sea shore due to hydro-meteorological changes

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    Many studies show the sensitivity of our environment to manmade changes, especially the anthropogenic impact on atmospheric and hydrological processes. The effect on Solid Earth processes such as subsidence is less straightforward. Subsidence is usually slow and relates to the interplay of complex hydro-mechanical processes, thus making relations to atmospheric changes difficult to observe. In the Dead Sea (DS) region, however, climatic forcing is strong and over-use of fresh water is massive. An observation period of 3 years was thus sufficient to link the high evaporation (97 cm/year) and the subsequent drop of the Dead Sea lake level (− 110 cm/year), with high subsidence rates of the Earth’s surface (− 15 cm/year). Applying innovative Global Navigation Satellite System (GNSS) techniques, we are able to resolve this subsidence of the “Solid Earth” even on a monthly basis and show that it behaves synchronous to atmospheric and hydrological changes with a time lag of two months. We show that the amplitude and fluctuation period of ground deformation is related to poro-elastic hydro-mechanical soil response to lake level changes. This provides, to our knowledge, a first direct link between shore subsidence, lake-level drop and evaporation

    Detection of sinkhole occurrence, experiences from South Africa

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    Abstract: Sinkholes are alarming and dangerous events, they have a worldwide occurrence, and are imposing a potential risk to urban communities and the widely developed built environment. Losses due to catastrophic sinkhole collapse, foundation, pavement and structural repairs, occur more often, due to the increased pressure to develop even on sinkhole prone land, and the aging of existing water supply infrastructure in the majority of cities. Remote sensing earth observation methods have proved to be valuable tools during the last two decades in long-term sinkhole hazard assessment. Satellite air borne and ground earth observation methods have primarily facilitated the wide detection of continuous displacement on the earth’s crust. National sinkholes catalogues are necessary for town planers decision makers, and government authorities. In many instances the ground collapse is the result of water ingress from old poorly maintained leaking pipelines, or extensive dewatering activities. In the current study a comprehensive review of the current literature is presented in order to show experiences from South Africa and present recent mapping using PSInSAR methodology in Centurion South Africa

    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

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    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

    Differential Radar Interferometry Applied to the Detection and Monitoring of Geological Hazards

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    We live in a constantly changing environment, characterized by climate changes, extreme weather events and the occurrence of more frequent geological hazards that have a strong negative impact on the territory and society, interrupting services, damaging buildings and infrastructure and jeopardizing the life of millions of people worldwide. For this reason, there is the need to build a society resilient to natural-hazards, which can understand how the natural system behaves and responds to natural and human-induced modifications and can adapt to these changes. The monitoring of the territory is necessary to comprehend the triggering factors and the mechanisms of geological hazards and to plan the most suitable actions to prevent and mitigate the risk. The monitoring of geological hazards with conventional ground-based techniques such as Global Positioning System (GPS) and levelling is usually expensive and time consuming, which limits the number of measured points and the overall duration of the surveys. One of the best way to overcome to these problems is to use remote-sensing techniques to monitor large portion of territory reducing operating costs and time. Advanced Differential Synthetic Aperture Radar Interferometry (A-DInSAR) is one of the best tool to monitor and study ground displacements over very large portions of territory in a cost-effective way. In this Doctoral Thesis, we applied A-DInSAR to the monitoring of the geological instabilities occurring in different areas characterized by unique geological and environmental features. The selected areas include different environments such as vegetate territories, low and steep topography, coastal areas, salty deserts, urbanized land, each of them affected by hazards of natural and anthropic origin such as landslides, subsidence and karstic activity. In each case study, the monitoring activity presented its own challenges that were overcome adopting specific technical solutions in the data processing and management. The aim of this work is to give an overview of the potential of A-DInSAR techniques when applied to the study of geological hazards in different environments. This can be useful to show to local Authorities that A-DInSAR can be fully integrated as part of the activities carried out to manage the territory and to prevent and mitigate the risk related to geological hazards

    Morphometry and evolution of sinkholes on the western shore of the Dead Sea. Implications for susceptibility assessment

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    Sinkhole development is a hazardous geomorphic process responsible for increasing economic losses worldwide. The highly dynamic eogenetic salt karst of the Dead Sea is one of the most striking examples of a human-enhanced sinkhole hazard. Since the 1980s, the shores of the Dead Sea have been affected by thousands of sinkholes while the lake level has been declining. Sinkholes pose a major threat, but their rapid development also offers an exceptional opportunity to study their evolution. Although the evolution of the morphometry and distribution of sinkholes provides essential data for hazard assessment, this kind of studies are almost lacking because of the typical slowness of the processes. Here we present multi-temporal cartographic sinkhole inventories of a sector in the western shore of the Dead Sea. The database was constructed using aerial and satellite imagery, high-resolution three-dimensional photogrammetric models, and fieldwork. Most of the depressions mapped were single, small, relatively shallow, subcircular, collapse sinkholes nested within large sagging basins. From 2005 to 2021, the 702 new sinkholes have been concentrated along a narrow N-S-oriented strip comprising tightly packed alignments and clusters. Sinkhole expansion by mass wasting and coalescence play an essential role in the evolution of the sinkhole landscape. An average subsidence rate of 45 cm/year has been calculated for the total area affected by sinkholes, providing an indirect estimate for the rate of subsurface salt dissolution. This research illustrates how multi-temporal geomorphic mapping and morphometric analyses provide an objective basis for the development of reliable spatial predictions for sinkhole evolution
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