Sinkhole Risk Research Articles

Evaporite sinkhole risk for a building portfolio

Karst-related hazard can be a problem for buildings, especially in the case of evaporite karst. This study aims at evaluating the risk posed by evaporite karst for a building portfolio in western Switzerland, using a susceptibility map and an event inventory. Since the inventory is not complete, different corrections aim at obtaining a frequency of sinkhole events damaging a building as close as possible to the actual frequency. These corrections account for the variation of the building stock during the inventory period, the varying inventory quality among the municipalities and the partial knowledge, even in the best case. This approach is preferred here to estimating spatially the hazard, since the amount of information on the frequency and magnitude is insufficient to draw a proper hazard map. The distribution of loss ratios is also retrieved from the inventory, thanks to the estimated or actual price of the remedial works. Annual losses are then estimated using a Monte Carlo approach, which consists in sampling for a number of damaged buildings from a Poisson distribution, for a distribution of loss ratios and for a building value. Different exceedance curves relying on different hypotheses are presented, and the mean annual loss that the public insurance company might have to compensate is estimated at CHF 0.8–1.5 million.

The application of GPR and ERI in combination with exposure logging and retrodeformation analysis to characterize sinkholes and reconstruct their impact on fluvial sedimentation

AbstractThis work illustrates the practicality of investigating sinkholes integrating data gathered by ground penetrating radar (GPR), electrical resistivity imaging (ERI) and trenching or direct logging of the subsidence‐affected sediments in combination with retrodeformation analysis. This mutidisciplinary approach has been tested in a large paleosinkhole developed during the deposition of a Quaternary terrace on salt‐bearing evaporites. The subsidence structure, exposed in an artificial excavation, is located next to Puilatos, a village that was abandoned in the 1970s due to severe subsidence damage. Detailed logging of the exposure revealed that the subsidence structure corresponds to an asymmetric sagging and collapse paleosinkhole with no clear evidence of recent activity. The sedimentological and structural relationships together with the retrodeformation analysis indicate that synsedimentary subsidence controlled channel location, the development of a palustrine environment and local changes in the channel pattern. GPR profiles were acquired using an array of systems with different antenna frequencies, including some recently developed shielded antennas with improved vertical resolution and penetration depth. Although radargrams imaged the faulted sagging structure and provided valuable data on fault throw, they did not satisfactorily image the complex architecture of the fluvial deposit. ERI showed lower resolution but higher penetration depth when compared to GPR, roughly capturing the subsidence structure and yielding information on the thickness of the high‐resistivity alluvium and the nature of the underlying low‐resistivity karstic residue developed on top of the halite‐bearing evaporitic bedrock. Data comparison allows the assessment of the advantages and limitations of these complementary techniques, highly useful for site‐specific sinkhole risk management. Copyright © 2016 John Wiley & Sons, Ltd.

Inadequate stakeholder management and its effect on a coherent sinkhole risk management strategy: The case of the Merafong Local Municipality, South Africa.

The Merafong Local Municipality (MLM) has historically suffered financial and human losses because of the presence of dolomite and the consequent formation of sinkholes. There is a great need for the MLM to address the risk posed by sinkholes to ensure the continued safety of communities. However, as the risk is so pervasive, the MLM needs to coordinate their risk reduction strategies with a wide array of stakeholders in the municipality. Efficient stakeholder management is thus crucial if the sinkhole risk is to be addressed appropriately. This article reviews the current status of stakeholder management in the MLM as it pertains to the formulation of a holistic sinkhole risk reduction strategy. Findings indicate that there are serious deficiencies in the MLM’s stakeholder management relating to key risk management processes such as community involvement in risk management structures, disaster risk assessment, training and awareness, and early warning and response. Improved stakeholder management could be characterised by the following factors: improved two-way communication between the municipality and community stakeholders, fostering a relationship based upon trust and equality amongst stakeholders, participation by a wide array of stakeholder groups affected by the sinkhole risk and a mutual commitment by all stakeholders to address the risk. These factors could contribute to enhancing current and future sinkhole risk reduction strategies.

The Tlokwe City Council Dolomite Management Desk: a communication and relationship management perspective

ABSTRACTTwo-way communication and strong relationships between government and affected communities are necessary to enhance the latter's resilience to disaster risks. The Tlokwe City Council (TCC) in the North-West province, South Africa, is facing a dolomite and sinkhole disaster risk that threatens the safety of several residential areas, including informal settlements. A dolomite disaster risk reduction (DRR) management system such as the TCC Dolomite Management Desk (DMD) can be used to facilitate two-way communication and strong relationships between government and the affected communities. Semi-structured interviews with two different groups of people were conducted and the responses evaluated to determine in what way DRR communication via the Tlokwe DMD served to establish strong relationships between the TCC and the affected community. It was found that the two groups of interviewees had contradictory views on the risk communication and quality of relationships as facilitated by the Tlokwe DMD. These views illuminated the predicament of communicating about the dolomite and sinkhole risk. The Tlokwe DMD is unique in South Africa and its ability to enable communication and strong government–community relationships needs to be developed further. Recommendations are made in this regard.

Sinkhole Risk Assessment in the Metropolitan Area of Napoli, Italy

The city of Naples and its neighboring is an example of urban area affected by frequent anthropogenic sinkholes. They occur where the mining of tuff at shallow depth left a wide and complex network of cavities. The collapse is usually triggered by the soaking of the overlying pyroclastic soils forwarded by the presence of leakage from aged aqueducts and sewerages. This note reports the first results of a multidisciplinary research activity aimed at enhance the knowledge of the triggering factors of these phenomena in urban contexts. The study focused on an area characterized by the presence of cavities dug in tuff, starting from the research and collection of their location and that of past collapse events. In particular, the paper presents the results of sinkhole occurrence assessment at both local and metropolitan scale. In the first case, in order to define the most likely triggering mechanisms a case study among the recent sinkholes was investigated. A detailed field survey of the phenomena permitted to define the stratigraphical and geometrical setting of the pre-existing cavity and collect soil and rock samples for the geotechnical characterization. The attained results permitted to identify the most relevant parameters that influence the susceptibility assessment in a study area at metropolitan scale. This study represents contribute to the definition of a procedure to study anthropogenic sinkhole in intensely urbanized areas and it represents a valuable support for future planning strategies of risk mitigation.

Sinkhole risk assessment by ERT: The case study of Sirino Lake (Basilicata, Italy)

The presence of natural or artificial lakes and reservoirs that can drain because of natural phenomena can generate catastrophic events affecting urban and agricultural areas next to the source area.Therefore, geophysical prospecting techniques have been applied in the study of Sirino Lake, which, during the last century, was affected by the sudden opening of small sinkholes, resulting in the almost total draining of the lake and in the sudden increase of water flow rates of distal springs. Two electrical resistivity tomographies (ERTs) were carried out across the lake, using electrode arrays located on land and across the water body. Self-potential (SP) data were acquired around the lake shore and the surrounding area. The geophysical prospecting contributed significant data toward explaining the unique hydrogeological characteristics of the lake. Integration of geophysical, geological, hydrogeological, and geomorphological data allowed us to estimate the thickness of the lacustrine deposits beneath the lake, to describe the main patterns of the subsurface fluid flows in the area, and to identify possible water escape routes causing the piping phenomena.

Assessing sinkhole activity in the Ebro Valley mantled evaporite karst using advanced DInSAR

Sinkholes in karst areas may cause subsidence damage in transportation infrastructures, demolition of buildings and even the loss of human lives when they occur in a catastrophic way. Differential Interferometry (DInSAR) is a promising technology for detecting and characterizing sinkholes, as well as for reducing the associated risk when combined with other sources of data such as a sinkhole inventory. In this work, the usefulness of InSAR techniques and data for sinkhole risk management has been analyzed through the comparison of three DInSAR-derived velocity maps with a comprehensive sinkhole inventory in the Ebro Valley, NE Spain. The DInSAR maps have contributed to improve the sinkhole inventory in different ways: (1) detection of non-inventoried sinkholes; (2) revision of sinkhole areas previously classified as inactive as active; and (3) refinement of underestimated sinkhole boundaries. The obtained results suggest that DInSAR products are suitable for analyzing active dissolution-induced subsidence. The application of these techniques may help in recognizing and better characterizing previously unknown karst subsidence problems and in preventing personal and property losses. However, the analysis reveals that the available DInSAR maps combined overlook about 70% of the previously mapped active sinkholes mainly due to decorrelation.

Modelling of cave-in occurrence using AHP and GIS

Abstract. The analysis of mining-induced sinkholes occurrence is a very important issue as far as the spatial development optimization is concerned. Research conducted for this paper was focussed on examining the applicability of GIS and the associated AHP method (analytic hierarchy process) for estimating the risk of discontinuous deformation occurrence on the surface. Qualitative factors were accounted for in the sinkhole risk assessment, thus creating bases for the research. These elements play an important role in the process of sinkholes formation; however, they were not used in prediction models. Another assumption lay in minimizing the number of variables in the model. Accordingly, the most important qualitative and quantitative risk factors were finally selected on the basis of whether the risk of cave-ins occurrence on the surface could be calculated. The results of the estimation of potential sinkhole zones were verified. The locations of actual and high-risk potential discontinuous deformation were compared. The congruence between predicted values and the actual observations of sinkholes was very high. The results of research presented prove the necessity to evaluate sinkhole hazards in view of qualitative factors.

Characterizing Sagging and Collapse Sinkholes in a Mantled Karst by Means of Ground Penetrating Radar (GPR)

Research Article| May 01, 2014 Characterizing Sagging and Collapse Sinkholes in a Mantled Karst by Means of Ground Penetrating Radar (GPR) V. RODRIGUEZ; V. RODRIGUEZ 1 Departamento de Ciencias de la Tierra, Universidad de Zaragoza, C/. Pedro Cerbuna 12, 50009 Zaragoza, Spain 1Corresponding author email: veronicarodtrib@gmail.com Search for other works by this author on: GSW Google Scholar F. GUTIÉRREZ; F. GUTIÉRREZ Departamento de Ciencias de la Tierra, Universidad de Zaragoza, C/. Pedro Cerbuna 12, 50009 Zaragoza, Spain Search for other works by this author on: GSW Google Scholar A. G. GREEN; A. G. GREEN ETH Zürich, Institute of Geophysics, Zürich, Switzerland Search for other works by this author on: GSW Google Scholar D. CARBONEL; D. CARBONEL Departamento de Ciencias de la Tierra, Universidad de Zaragoza, C/. Pedro Cerbuna 12, 50009 Zaragoza, Spain Search for other works by this author on: GSW Google Scholar H. HORSTMEYER; H. HORSTMEYER ETH Zürich, Institute of Geophysics, Zürich, Switzerland Search for other works by this author on: GSW Google Scholar C. SCHMELZBACH C. SCHMELZBACH ETH Zürich, Institute of Geophysics, Zürich, Switzerland Search for other works by this author on: GSW Google Scholar Environmental & Engineering Geoscience (2014) 20 (2): 109–132. https://doi.org/10.2113/gseegeosci.20.2.109 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation V. RODRIGUEZ, F. GUTIÉRREZ, A. G. GREEN, D. CARBONEL, H. HORSTMEYER, C. SCHMELZBACH; Characterizing Sagging and Collapse Sinkholes in a Mantled Karst by Means of Ground Penetrating Radar (GPR). Environmental & Engineering Geoscience 2014;; 20 (2): 109–132. doi: https://doi.org/10.2113/gseegeosci.20.2.109 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Sinkhole development created by diverse subsidence mechanisms (suffosion, collapse, sagging) constitutes the main hazard in most karst terrains. Precisely mapping the limits of sinkholes and inferring the subsidence mechanisms are critically important for the effective mitigation of sinkhole risk. Gathering this information commonly requires the application of subsurface investigation methods, such as geophysics or trenching. Here, we analyze the potential of ground-penetrating radar (GPR) for sinkhole characterization in covered karsts. Extensive GPR surveys have been conducted across two buried active sinkholes of contrasting genetic types (collapse vs. sagging) in the mantled evaporite karst of Zaragoza city, NE Spain. Data were acquired with 100 MHz and 50 MHz unshielded antennas and ∼180 MHz shielded antennas. Interpretation of the processed GPR profiles allowed us to map reliably the boundaries of the sinkholes, characterize their internal geometries (deformation style), infer the subsidence mechanisms, and estimate subsidence magnitudes. The suitability and limitations of the GPR technique in covered karsts are illustrated considering different sinkhole types and sizes, as well as data acquired with different antennas (shielded versus unshielded and various frequencies). You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Detection of cavity migration and sinkhole risk using radar interferometric time series

Upward migration of underground cavities can pose a major hazard for people and infrastructure. Either via sudden collapse sinkholes, or by eroding the support of building foundations, a migrating cavity can cause the collapse of buildings, water defense systems, or transport infrastructure. The main problem for risk assessment is the lack of a priori knowledge on the location of a potentially hazardous cavity. Here we demonstrate the feasibility of satellite radar interferometry to detect a migrating cavity under the city of Heerlen, the Netherlands, leading to foundation instability and the near-collapse of a part of a shopping mall in December 2011. We exploit the data archives of four imaging radar satellites, between 1992 and 2011, to investigate the dynamics of the area and detect shear strain within the structure of the building. Time series analysis shows localized differential vertical deformation rates of ~3mm/yr during 18years, followed by a dramatic increase of up to ~15mm/yr in the last few years. These results imply that the driving mechanism of the 2011 near-collapse event had a very long lead time and was likely due to a long-lasting gradual process, such as the upward migration of a cavity.

Hydrogeochemical characterization of an evaporite karst area affected by sinkholes (Ebro Valley, NE

The main processes controlling the hydrochemistry of an alluvium-covered evaporite karst area with high sinkhole risk (Ebro Valley, NE Spain) are examined by means of multivariate analyses (Principal Component Analysis and Hierarchical Cluster Analysis), ion correlations and geochemical speciation-solubility calculations. The hydrogeochemistry of the studied system seems to be governed by the interaction between the groundwater from the salt-bearing evaporitic karst aquifer and from the overlying Ebro River alluvial aquifer. The observed hydrochemical features in the alluvial-karst aquifer system are mainly determined by the relative contribution of gypsum/anhydrite and halite dissolution, showing a wide spectrum from relatively fresh recharge waters (mainly irrigation waters) to highly evolved groundwater from the evaporitic aquifer. The variability of these contributions is especially evident at sinkhole ponds which, in some cases, seem to be associated with discharge areas of the karst aquifer in the valley bottom alluvium. Calculated saturation indexes suggest that, in contrast to gypsum, the amounts of halite in the sampled portions of evaporitic aquifer are not large enough to attain equilibrium, which is consistent with the predominance of gypsum/anhydrite reported for these materials. Furthermore, the observed Na:Cl and Ca:SO4 correlations and stoichiometries suggest that other possible processes, such as glauberite dissolution or Na/Ca-exchange, generally play a minor role (compared to halite and gypsum dissolution) in this system. Another important process in the system is the dissolution of carbonate minerals (dolomite and, possibly, calcite) fostered by the input of CO2(g), which is probably produced by pedogenic processes. Dolomite dissolution seems to be particularly relevant in the evaporitic materials probably due to dedolomitisation triggered by gypsum/anhydrite dissolution.

Geotechnical analysis and 4D GPR measurements for the assessment of the risk of sinkholes occurring in a Polish mining area

ABSTRACTThe study presented in this paper concerns georadar investigations at a selected former coal mining site in Upper Silesia (Poland) where the risk of sinkhole appearance is high. The results of 3D GPR surveys obtained in three measurement sessions in December 1997, October 2006 and March 2007 were interpreted. The 4D interpretation, i.e., a time‐space analysis, allowed for the identification of loose zones in the ground and fractured zones of the rock mass, which might be a source of sinkhole creation. After the first measurement session, on the basis of the GPR survey results, a dangerous, fractured zone in the ground was localized. This zone was confirmed by a borehole. Between the second and third sessions, a large sinkhole appeared on site, as predicted on the basis of georadar investigations. The geomechanical analyses presented in this paper explain the development of the fractured zones over the earlier mining excavations. Such zones accumulate water and high contrasts of dielectrical permittivity appear, allowing the use of the GPR method for the location of these zones.

Quantitative sinkhole hazard assessment. A case study from the Ebro Valley evaporite alluvial karst (NE Spain)

Quantitative sinkhole hazard assessments in karst areas allow calculation of the potential sinkhole risk and the performance of cost-benefit analyses. These estimations are of practical interest for planning, engineering, and insurance purposes. The sinkhole hazard assessments should include two components: the probability of occurrence of sinkholes (sinkholes/km2 year) and the severity of the sinkholes, which mainly refers to the subsidence mechanisms (progressive passive bending or catastrophic collapse) and the size of the sinkholes at the time of formation; a critical engineering design parameter. This requires the compilation of an exhaustive database on recent sinkholes, including information on the: (1) location, (2) chronology (precise date or age range), (3) size, and (4) subsidence mechanisms and rate. This work presents a hazard assessment from an alluvial evaporite karst area (0.81 km2) located in the periphery of the city of Zaragoza (Ebro River valley, NE Spain). Five sinkholes and four locations with features attributable to karstic subsidence where identified in an initial investigation phase providing a preliminary probability of occurrence of 0.14 sinkholes/km2 year (11.34% in annual probability). A trenching program conducted in a subsequent investigation phase allowed us to rule out the four probable sinkholes, reducing the probability of occurrence to 0.079 sinkholes/km2 year (6.4% in annual probability). The information on the severity indicates that collapse sinkholes 10–15 m in diameter may occur in the area. A detailed study of the deposits and deformational structures exposed by trenching in one of the sinkholes allowed us to infer a modern collapse sinkhole approximately 12 m in diameter and with a vertical throw of 8 m. This collapse structure is superimposed on a subsidence sinkhole around 80 m across that records at least 1.7 m of synsedimentary subsidence. Trenching, in combination with dating techniques, is proposed as a useful methodology to elucidate the origin of depressions with uncertain diagnosis and to gather practical information with predictive utility about particular sinkholes in alluvial karst settings: precise location, subsidence mechanisms and magnitude, and timing and rate of the subsidence episodes.

Geological and environmental implications of the evaporite karst in Spain

In Spain, evaporite outcrops cover approximately 7% of the total area of the country. Most of the evaporitic formations are made up of Ca-sulfates (gypsum/anhydrite) or Ca-sulfates and halite. Certain Paleogene marine evaporites also contain K-Mg-chlorides, and some Tertiary continental formations bear substantial amounts of Na-sulfates in the subsurface (glauberite and thenardite). Mesozoic evaporitic formations commonly wedge out towards the ground surface, passing into condensed sequences and dissolution-collapse breccias. Some of these highly porous breccias constitute major regional aquifers. In several areas, interstratal karstification of the evaporites has given rise to gravitational deformations such as basin structures, monoclines, and collapse structures covering several square kilometers that record a cumulative subsidence in excess of 200 m (Teruel and Calatayud Grabens). A widespread consequence of evaporite dissolution processes in Spain is the hydrochemical degradation of surface waters. Some of the largest and most outstanding lake systems, from an environmental perspective, occur in karstic depressions developed in evaporitic formations (Fuente de Piedra, Gallocanta, Bujaraloz, and Banolas lakes). Sinkhole activity is a major geohazard in several evaporite karst areas. The sinkhole risk has a particularly high impact in sectors where Tertiary evaporites are overlain by Quaternary alluvial aquifers (Calatayud, Zaragoza, and Madrid areas). Some of the detrimental effects of subsidence include severe damage to historical monuments (Calatayud), the demolition of a whole village (Puilatos), or the derailment of a freight train (Zaragoza area). The deepest gypsum caves are found in Triassic diapiric structures (El Sumidor Cave, 210 m deep), and the longest ones are developed in horizontally lying Neogene sequences (Sorbas caves, and Estremera maze cave). The Cardona diapir hosts salt caves up to 4,300 m long whose genesis is related to flooding of mine galleries caused by the interception of a phreatic conduit. The main anthropogenic impacts on the endokarstic systems are related to the disposal of wastewaters and the destruction of caves by quarrying. The fluvial valleys that cross Tertiary evaporitic outcrops commonly show peculiar geological characteristics related to dissolution-induced synsedimentary subsidence phenomena: (1) Thickened alluvium filling dissolution basins up to several tens of kilometers long and more than 100 m deep. The largest thickenings are found in areas where the bedrock contains halite and glauberite. (2) Superimposed alluvial units locally bounded by angular unconformities. (3) Abundant deformational structures and paleosinkholes related to the rockhead and/or interstratal karstification of the substratum. These fluvial valleys typically are flanked by a prominent gypsum escarpment. Rock-falls favored by the dissolutional enlargement of joints derived from these scarps are the type of mass movement which has caused the highest number of casualties in Spain.

Environmental and economic risks from sinkholes in west-central Florida

Data from the last 20 yr for sinkhole occurrences in west-central Florida are used in conjunction with population and housing data, including house prices, to assess the risk of a house being affected by a sinkhole, together with the likely economic loss. The top five relocation cities in each of Hillsborough, Pasco, and Pinellas counties are investigated in detail to determine the relative risk as well as the absolute risk. Because of the massive urbanization occurring in these areas, which are characterized by karst topography, the sinkhole risk is increasing because of the excessive demand for water and the subsequent overpumping of groundwater. Pinellas County is better placed in this regard than Hillsborough or Pasco counties because of its lower karst component. The city with the highest likelihood of risk is Tampa, probably because of its massive urbanization over the last 20 yr. Coastal cities most at risk from sinkhole effects on housing are New Port Richey and Hudson, but they are a very distant second and third compared to Tampa. Economic damage risks to housing are estimated to be about $5 million/yr for Tampa and are probably going to increase in the near future if the current trends of population increase and demands on the aquifer system's water are to continue.

Roadway construction in karst areas: management of stormwater runoff and sinkhole risk assessment

In karst-rich regions, it is inevitable that roadways cross karst landscapes. Road building across such terranes faces environmental and engineering challenges because of impacts on water quality from stormwater runoff and concerns of sinkhole collapse under or near roadways. When highway runoff drains rapidly into subsurface conduit networks through open sinkholes and/or sinking streams, the impact of the runoff on the karst aquifer can be qualitatively evaluated by mixing cell models. Formulation of a comprehensive stormwater runoff management plan prior to roadway construction can minimize the associated adverse impacts. The commonly used “best management practices” help manage the stormwater runoff effectively in some sites. Site-specific management plans are preferable for other sites because of concerns of flooding and land stability. Proactive measures should be taken to identify areas of the greatest sinkhole collapse risk along the proposed route and the associated groundwater drainage patterns.

Classification of Karstic Terrains Based on Sinkhole Risk

Types of karstic risk are briefly defined as a function of the character of possible negative consequences of karsts. Basic trends in the classification of karstic terrains are indicated on the basis of sinkhole risk. A modified approach to classification of terrains is presented as a function of predictable risks associated with the formation karst sinkholes.

Application of matrix analysis in delineating sinkhole risk areas along highway (I-70 near Frederick, Maryland)

Sinkhole collapse in the area of Maryland Interstate 70 (I-70) and nearby roadways south of Frederick, Maryland, has been posing a threat to the safety of the highway operation as well as other structures. The occurrence of sinkholes is associated with intensive land development. However, the geological conditions that have been developing over the past 200 million years in the Frederick Valley control the locations of the sinkholes. Within an area of approximately 8 km 2 , 138 sinkholes are recorded and their spatial distribution is irregular, but clustered. The clustering indicates the existence of an interaction between the sinkholes. The point pattern of sinkholes is considered to be a sample of a Gibbsian point process from which the hard-core Strauss Model is developed. The radius of influence is calculated for the recorded sinkholes which are most likely to occur within 30 m of an existing sinkhole. The stochastic analysis of the existing sinkholes is biased toward the areas with intensive land use. This bias is adjusted by considering (1) topography, (2) proximity to topographic depressions, (3) interpreted rock formation, (4) soil type, (5) geophysical anomalies, (6) proximity to geologic structures, and (7) thickness of overburden. Based on the properties of each factor, a scoring system is developed and the average relative risk score for individual 30-m segments of the study area is calculated. The areas designated by higher risk levels would have greater risk of a sinkhole collapse than the areas designated by lower risk levels. This risk assessment approach can be updated as more information becomes available.