This article is concerned with the properties of peatland that function in the karst depression in the northern part of the Opoczno Hills. The geological and geomorphological properties that ...display the preview of the genesis of said landforms are discussed. The depressions that developed as a result of the collapse of Jurassic limestone and are covered with a thin layer of Pleistocene moraine till serve as an environment that is very conducive to the development of water bodies and peatbogs with deposition of biogenic sediments. A core sample of the biogenic sediments has been extracted from one of the peat bogs north of Paradyz and analysed to determine the ash content, pH value, electrolytic conductivity, as well as calcium carbonate content. It allowed to formulate conclusion on the environmental conditions of the depression and the phases of development of the peatbog.
Collapse sinkholes are problematic for the hazards they bring to property, infrastructure, and human life but the prediction of their formation in time and space remains elusive. We make use of ...long-term data gathered in a small, highly monitored, hydrologically constrained basin; Primrose Creek, Bucks County, Pennsylvania, USA, to examine the relation between groundwater extraction, precipitation, terrain position, and cover collapse sinkhole development. The selected site is unique as a natural laboratory to explore induced sinkhole processes in that it is a clearly demarcated topographic basin with geological structural and lithologic boundaries; the stressor is extreme, has been plainly identified, and effectively captures all upstream runoff and groundwater; the groundwater withdrawals and water-level elevations have been closely monitored over a period of 20 years; and the general record of land conditions goes back more than a century. We evaluated the history of a carbonate-rock quarry, its development and expansion over many decades, as well as associated precipitation and ground-water level data, and cover collapse sinkhole occurrence within the basin. Interception of discrete high conductivity zones in the Paleozoic carbonate rocks by quarry expansion was an important factor in propagating collapse occurrence. Collapses occurred mainly, though not exclusively, along drainageways and at lithologic boundaries. They formed in time-based clusters with delay of up to several years. Surprisingly, distance of collapse formation from the pumping area was not directly correlated with time elapsed; i.e., collapses did not begin to form close to the quarry, and then later form farther away. Monitoring wells were unsuccessful in delineating the pumping zone of influence although some documented water table decline and response to weather and anthropogenic events. This comprehensive study shows that in order to successfully monitor and control impacts from quarry dewatering in Paleozoic carbonate rocks it is critical to 1) develop a detailed conceptual model of groundwater pathways, 2) try to avoid excavating into high permeability zones, 3) clearly document karst features when exposed, and 4) carefully site a suitable number of monitoring wells and collect data at short intervals.
•Greater distance of collapse sinkholes from disturbance may not be time-dependent.•Multi-decade monitoring record and constrained basin give unique insight to collapses.•Weather events may trigger cover collapse sinkholes without being the cause of such.
LiDAR-based digital terrain models (DTMs) represent an advance in the investigation of small-scale geomorphological features, including dolines of karst terrains. Important issues in doline ...morphometry are (i) which statistical distributions best model the size distribution of doline morphometric parameters and (ii) how to characterize the volume of dolines based on high-resolution DTMs. For backward compatibility, how previous datasets obtained predominantly from topographic maps relate to doline data derived from LiDAR is also examined. Our study area includes the karst plateaus of Aggtelek Karst and Slovak Karst national parks, whose caves are part of the UNESCO World Heritage. To characterize the study area, the relationships between doline parameters and topography were studied, as well as their geological characteristics. Our analysis revealed that the LiDAR-based doline density is 25% higher than the value calculated from topographic maps. Furthermore, LiDAR-based doline delineations are slightly larger and less rounded than in the case of topographic maps. The plateaus of the study area are characterized by low (5–10 kmsup.−2), moderate (10–30 kmsup.−2), and medium (30–35 kmsup.−2) doline densities. In terms of topography, the slope trend is decisive since the doline density is negligible in areas where the general slope is steeper than 12°. As for the lithology, 75% of the dolines can be linked to Wetterstein Limestone. The statistical distribution of the doline area can be well modeled by the lognormal distribution. To describe the DTM-based volume of dolines, a new parameter (k) is introduced to characterize their 3D shape: it is equal to the product of the area and the depth divided by the volume. This parameter indicates whether the idealized shape of the doline is closer to a cylinder, a bowl (calotte), a cone, or a funnel shape. The results show that most sinkholes in the study area have a transitional shape between a bowl (calotte) and a cone.
Sinkhole is one of major geohazards in karst area where soluble carbonate bedrock is underlain by cover soils (e.g., sandy or clayey soils) and active groundwater circulation is present. Groundwater ...recharge easily erode the overburden soils away into cavities in the bedrock, and ultimately structural collapse in ground. The induced ground collapse/subsidence may pose a great threat to human safety, environment, and buildings and infrastructure. The goal of this study is to develop a method/tool to spatially assess the possibility of sinkhole occurrence. The paper presents two main taks: (1) development of a probabilistic spatial prediction model of sinkhole susceptibility and (2) a geographical information system (GIS)-based regional-scale sinkhole susceptibility map. The study area is the east central Florida (ECF) region that has been experiencing more abrupt and larger cover collapse sinkholes. The research methodology employs two statistical methods for the spatial prediction model, frequency ratio (FR) and logistic regression (LR), accounting for six criteria that are soil erosion, mechanical stability, distance, geology, human activity, and climate condition. The final section of factors includes head difference, soil permeability, thicknesses of aquifer systems (overburden, surficial/intermediate aquifer), distance to karst features, surficial geology, lithology, land use/land cover, and rainfall. Once the models were constructed, both models were validated and compared by using receiver operating characteristics (ROC) analysis. The results indicate that the LR model better delineates high susceptibility areas of sinkhole and hydrological factors (recharge and head difference) are more accurately reflected on the model of the LR.
•Develop probabilistic spatial susceptibility model of carbonate karst sinkhole.•A regional-scale sinkhole susceptibility map for the east central Florida region.•Evaluate the performance of Frequency Ratio (FR) and Logistic Regression (LR) methods in the sinkhole susceptibility model.•Statistical analysis on the impact of sinkhole contributing factors.
Distributed optical fiber sensors (DOFS) have been postulated as a suitable technique for long-range monitoring of sinkhole-related subsidence, and possibly for the anticipation of catastrophic ...collapse (early-warning systems). The strain data published in previous works refer to artificial experiments considering real and virtual cover collapse sinkholes characterized by rapid subsidence and sharp lateral deformation gradients. The influence of the subsidence mechanism (sagging, collapse, suffosion) on the capability of DOFS to satisfactorily detect active subsidence is discussed. Sagging sinkholes with poorly-defined lateral edges, low lateral deformation gradients and slow subsidence are identified as the most challenging scenario. The performance of BOTDA optical fiber for monitoring such type of sagging sinkholes is evaluated in the active Alcalá sinkhole, which affects a flood-control dike creating a high-risk and -uncertainty scenario. This sinkhole shows active subsidence in sections tens of meters long with maximum subsidence rates ranging between 5 and 35 mm/yr. The comparison of vertical displacement data measured by high-precision leveling and the strain recorded by two types of fiber optic cables shows good spatial and temporal correlation. The subsidence sections are captured in the strain profiles by: (1) troughs of negative strain (contraction) in the area affected by subsidence, with the maximum strain associated with the point of most rapid settlement; and (2) lateral ridges of positive values (extension) in the marginal zones. A subsidence acceleration phase associated with a flood is also captured by substantial increments in the strain values. In this challenging scenario, despite the reasonably good spatial and temporal correlation between the displacement and strain data, the unambiguous identification of the active subsidence area with the fiber optic data alone might be difficult. Better results could be obtained improving the monitoring system (e.g., tighter cable-ground coupling) and testing other types of sinkholes with more localized deformation zones and higher subsidence rates.
•Slow moving sagging sinkhole monitored by BOTDA optical fiber.•Spatial and temporal correlation with subsidence measured by high-precision leveling.•Impact of the subsidence mechanism of the performance of optical fiber sensors.•Potential applicability of optical fiber sensors to early warning.
In recent years, the study of anthropogenic sinkholes in densely urbanized areas has attracted the attention of both researchers and land management entities. The city of Naples (Italy) has been ...frequently affected by processes generating such landforms in the last decades: for this reason, an update of the sinkhole inventory and a preliminary susceptibility estimation are proposed in this work. Starting from previous data, not modified since 2010, a total of 270 new events occurred in the period February 2010–June 2021 were collected through the examination of online newspapers, local daily reports, council chronicle news and field surveys. The final consistence of the updated inventory is of 458 events occurred between 1880 and 2021, distributed through time with an increasing trend in frequency. Spatial analysis of sinkholes indicates a concentration in the central sector of the city, corresponding to its ancient and historic centre, crossed by a dense network of underground tunnels and cavities. Cavity-roof collapse is confirmed as one of the potential genetic types, along with processes related to rainfall events and service lines damage. A clear correlation between monthly rainfall and the number of triggered sinkholes was identified. Finally, a preliminary sinkhole susceptibility assessment, carried out by Frequency Ratio method, confirms the central sector of city as that most susceptible to sinkholes and emphasizes the predisposing role of service lines, mostly in the outermost areas of the city.
As the world's largest city cluster, the Guangdong–Hong Kong–Macao Greater Bay Area (GBA) is vulnerable to significant subsidence. The widely distributed sediments and rapid urbanization in the GBA ...result in the concurrence of large- and small-scale subsidence. Mono-sensor synthetic aperture radar (SAR) images usually suffer from the limitation of either low resolution or small coverage, and thus, are not applicable to completely monitoring the GBA. In this study, we used Sentinel-1 (S1), COSMO-SkyMed (CSK) and TerraSAR-X (TSX) images jointly to reveal multi-scale subsidence of the GBA. The overall subsidence ranged from 0 to 112.3 mm/yr derived from the 2015–2017 S1 images. Three regional subsidence bowls (Zhuhai–Zhongshan, Jiangmen, and Guangzhou–Zhongshan) formed in the western alluvial plain. The high correlation between regional subsidence and Quaternary sediments confirms that sediment consolidation is the main cause of subsidence. The land use and numerical modeling results suggest that groundwater extraction and artificial loading are the triggering factors. Two representative local subsidence cases were analyzed using high-resolution images: reclamation settlement at the Hong Kong International Airport (HKIA) and sinkhole subsidence due to the excavation of the Shenzhen Wenbo skyscraper foundation pit. The validation at the HKIA showed that the measurements from the CSK and S1 data both agreed well with the leveling data. However, CSK outperformed S1 in the sense that it increased the point density by a factor of 5, improved the height precision by a factor of 4, and showed fewer false alarms. CSK is therefore more applicable to monitoring the local subsidence of key infrastructures. The cross-heading tracks of TSX and CSK images detected precursory subsidence before the sinkhole collapse from two sides, indicating that the cross-heading tracks benefit the comprehensive monitoring of local subsidence in high-rise and high-density built environments. In summary, the synergistic use of multi-sensor SAR images demonstrates the practicability of the operational surveillance of multi-scale subsidence from regional surveying to the fine monitoring of local areas in the GBA.
•Multi-scale SAR data were used to remotely sense ground subsidence.•The first overall subsidence map in the GBA was derived and interpreted.•Sediment consolidation and rapid urbanization are main causes.•The benefits and constraints of medium- and high-resolution data were evaluated.
Os ambientes cársticos são caracterizados por serem áreas de intensa dissolução rochosa, o que permite gerar diversas feições típicas dessas regiões. A identificação e análise da distribuição dessas ...feições são de grande importância para a avaliação da vulnerabilidade de aquíferos. O objetivo deste trabalho foi identificar feições cársticas doliniformes, utilizando o método semiautomático de identificação de dolinas a partir de Modelos Digitais de Elevação, na parte Oeste do Grupo Bambuí. Com base nos resultados, foram identificadas pelo método semiautomático 777 feições deprimidas, as quais coincidiram, dentro dos quadrantes, em 20,63% com outras feições já validadas e em 63,49% com as cavidades subterrâneas. O Subgrupo Paraopeba, em destaque a Formação Lagoa do Jacaré, indicou ser a área de maior carstificação, devido à maior incidência de feições identificadas. Conclui-se que a utilização do método semiautomático em conjunto com os parâmetros morfométricos mostrou-se uma abordagem promissora na identificação de feições deprimidas cársticas.
Active evaporite karst processes in the Baltic states are associated with a few relatively small regions where gypsum rocks can be found close to the Earth's surface. One of these areas lies in the ...vicinity of the Pandu bog. However, such a possibly active karst region, which is covered by peat and in which the mapping of karst formations is complex, has not been previously investigated. In this study, we present a buried and peat‐filled karst cover‐collapse sinkhole mapping approach that involves a combination of ground‐penetrating radar (GPR), electrical resistivity tomography (ERT) and conventional boreholes. A detailed map of the bog's substratum topography was constructed from a geophysical surveying dataset. It reveals 15 distinctly expressed sinkholes with diameters of several tens of metres. Overall, 140 potential sinkholes were also mapped using remote sensing data in the vicinity of the bog. Higher electrical resistivity anomalies were identified inside the peat; they coincide with scatter‐free zones in GPR data and water layers in boreholes. Highly disturbed internal peat layering was also detected in these sinkholes. It is suggested that these water layers and disturbed peat layering may have formed due to the subsidence of the lower peat layers, and thus they represent relatively younger sinkholes. This is also supported by evidence from orthophoto maps, which showed the formation and disappearance of surficial lakes and depressions on the bog surface. Our results revealed the presence of active and widespread karst processes under the bog that have not been previously noticed despite the fact that they have implications for the assessment of geohazards in this area.
A geophysical study from a bog located over karst susceptible bedrock show karst activity, which has not been appropriately evaluated before. Both GPR and ERT results show water layers within peat‐filled sinkholes.
