Sinkhole Development Research Articles

Velocity–resistivity versus porosity–permeability inter-relations in Dead Sea salt samples

This study is intended to investigate Dead Sea (DS) salt porosity–permeability (hydraulic conductivity) inter-relations, as well as their relationship to geophysical parameters such as compression and shear wave velocities (Vp, Vs, respectively), and specific resistivity (ρx) in laboratory and field conditions, to estimate representative properties affected by porosity changes during sinkhole development. Some 41 salt samples were subjected to porosity measurements, and 25 samples were tested to reveal hydraulic conductivity. The salt of the coastal Dead Sea area, composed of halite, is revealed in 10,200–10,800year-old layers. The halite commonly appears as rock salt. The 7–30m thick salt unit is located below the groundwater table at depths of 20–50m from the surface. Salt layers are very conductive hydraulically and water-saturated with the DS brine is of very high salinity with total dissolved solids [TDS] of 340–380g/l. Two types of salt have been studied: Crystalline transparent salt (CTS) distributed along the entire DS's western shore and white massive salt (WMS) found locally along the southern DS and along the dike. Salt porosity measured in samples varies in the range of 5–21%, whereas hydraulic conductivity varies between 10−5 to 10–9m/s. Density is changed in the range of 1681–2116kg/m3 in wet samples and between 1638 and 2106kg/m3 in dry samples. During the laboratory testing of DS salt samples, we have measured the following geophysical parameters: Vp=3700–4460m/s, Vs=1900–2620m/s and ρx=2–100Ωm. On the other hand, our previous field studies based on S-wave seismic refraction, surface wave prospecting (SWP) and Transient Electromagnetic (TEM) methods have shown that in in-situ salt velocities Vp range between 2900 and 4240m/s, Vs varies between limits of 750m/s to more than 1650m/s, and ρx is of 0.8 to 2.5Ωm. These values are considerably less than the analogous parameters measured in the salt samples. The same conclusion has been made from the comparison of salt sample properties and borehole logging; both studied by ultrasonic method. Geophysical data testify that in-situ porosity calculated using relationships obtained during this study exceeds those in the laboratory samples, especially in zones of heightened voidness (where it is >25%). Hydraulic conductivities in the same zones exceed a value of 10−6m/s and even 10−5m/s. We expect that in larger salt volumes these parameters can yet increase.

Florida sinkholes: science and policy

Brinkmann skillfully takes a technically and legally complex topic and weaves it into a shape that experts and the general public will understand and enjoy. Richly referenced to support further study, this book is very readable and includes pleasant but unexpected information on how Florida s history was shaped by George Veni, Executive Director, National Cave and Karst Research Institute The most comprehensive and thorough resource to date on Florida s Robert Brinkmann draws on decades of personal experience with Florida s complex karst landscape to focus on the pressing issues of sinkhole development, public perception of the danger, and possible solutions for the future. Jason Polk, Western Kentucky University, Associate Director, Hoffman Environmental Research Institute An excellent and fascinating review of the science and policy issues behind the remarkable phenomenon of karst sinkholes in Florida. Recommended not only for environmental geology and karst specialists but also for members of the general public in Florida whose lives are actually or potentially affected by sinkholes or who want to learn more about the environment they live in. Alexander Klimchouk, director, Ukrainian Institute of Speleology and KarstologyFlorida Sinkholes the first comprehensive book on the subject is an easy-to-follow guide to understanding how sinkholes form and what to do about them. City planners, construction managers, developers, and homeowners alike will find this book invaluable because of the heavy impact and increasing frequency of sinkhole formation in the state. Packing an abundance of sound scientific fact into frank, readable language, this book examines case studies of notable sinkholes, explains karst the Swiss cheese like formations of soluble rock that underlie Florida s peninsula and reviews practical concerns like structural damage, repairs, and insurance problems related to sinkholes.

Quantitative Assessment of In-situ Salt Karstification Using Shear Wave Velocity, Dead Sea

The Dead Sea (DS) coastal areas have been dramatically affected by sinkhole formation since around 1990. Such sinkholes along both Israeli and Jordanian shores are linked to karst cavities that form through slow salt dissolution. A quantitative estimate of such in-situ salt karstification would be an important indicator of sinkhole hazard. One of the indications of salt karstification is its increased hydraulic conductivity, caused by the development of dissolution cavities forming conducting channels within the salt layer. We measured the hydraulic conductivity (K) versus shear-wave velocity (Vs) of DS salt in situ for estimating the actual salt karstification in areas of sinkhole development. These parameters were measured with the Magnetic Resonance Sounding (MRS) and Multichannel Analysis of Surface Waves (MASW) methods, respectively. Understanding of the field relationships was augmented by similar inter-relations obtained in the laboratory on samples of DS salt. In-situ salt velocities Vs vary from 750m/s to over 1650m/s, while hydraulic conductivity (K) in the same zones varies between about 10−4m/s to slightly over 10−8m/s. Both field and laboratory K and Vs values fit the exponential function ln(K)=−0.0045∗Vs−5.416 with a determination coefficient (R2) of 0.88. A classification based on Vs and K was generated for salt conditions and the corresponding degrees of sinkhole hazard, which was verified in the Mineral Beach sinkhole development area. The mapping of sinkhole sites shows that they form within highly conductive zones with K≥5.5∗10−5. It is suggested that this methodology, with some modification, can be used for evaluating the conductive properties of karstified rock and associated sinkhole hazards.

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.

Bayou Corne, Louisiana, sinkhole: Precursory deformation measured by radar interferometry

Catastrophic sinkholes are formed through the collapse of natural or human-made subterranean caverns, and are common in areas with evaporite and carbonate rock. Despite their danger, advance warning of these events is rare. We report a measurement of precursory surface deformation of as much as 260 mm, derived with interferometric synthetic aperture radar (InSAR) and evident over a month before surface collapse, at the site of the Bayou Corne, Louisiana (USA) sinkhole that formed in August 2012. Data collected by the airborne Uninhabited Aerial Vehicle SAR (UAVSAR) instrument were used for the study. Analysis of data acquired from two flight tracks with near-opposing imaging geometries reveal a deformation pattern consistent with compressive loading at the surface due to loss of support from a subterranean cavity collapse related to Texas Brine Oxy Geismar Well #3. The precursor deformation was nearly entirely horizontal, i.e., oriented along the surface, and manifested as movement of surface material toward the location where the sinkhole later formed. The sinkhole formed in the area with the largest gradient in surface strain, but did not cover the full extent of the precursory deformation detected with radar. This work suggests that InSAR data collected operationally for hazard monitoring could, in some cases, identify sinkhole development before surface collapse, and decrease subsequent danger to people and property.

Characterization of land degradation along the receding Dead Sea coastal zone using airborne laser scanning

The Dead Sea, the lowest place on the Earth's continents, was at its highest level in 1896, reaching an elevation of ~388.4m below mean sea level (m.b.m.s.l) and ~390m in the early 1920s. Since then it has almost constantly been dropping, reaching the level of 426m.b.m.s.l in 2013. Since the late 1990s its level has been decreasing by approximately 1 my−1. The rapid lake retreat accelerates large-scale environmental deterioration, including soil erosion, land degradation, rapid headcut migration and widespread development of collapse sinkhole fields. These geomorphic elements threaten the natural environment and anthropogenic infrastructure.We provide an overview of the geomorphic processes in the form of soil erosion, channel incision, land degradation, and the development of collapse sinkholes. We take advantage of the high-resolution airborne laser scanning technology for three-dimensional detection of surficial changes, quantification of their volumes, and documentation of the present state of the terrain with utmost accuracy and precision. This type of information and the identification of future trends are vital for proper planning of any rapidly-changing environment.

Detection of geophysical features in InSAR point cloud data sets using spatiotemporal models

In this article, we introduce an approach for detecting evolving geophysical features within interferometric synthetic aperture radar (InSAR)-derived point cloud data sets. This approach is based on the availability of models describing both spatial and temporal behaviours of the geophysical features of interest. The model parameters are used to generate a multidimensional space that is then scanned with a user-defined resolution. For each point in the parameter space, a spatiotemporal template is reconstructed from the original model. This template is then used to scan the point cloud data set for regions matching the spatiotemporal behaviour.We also introduce a proportional measure where the residual for each point in the data set is compared to both the data and the template to provide a scale invariant measure of the behavioural matching. The matching is evaluated for every point in the parameter over a region of influence determined by the parameters. The resulting multidimensional space is then collapsed onto geographical coordinates to produce an overlay map identifying regions whose spatiotemporal behaviour matches the feature of interest.We tailored our approach to the detection of subsidence behaviour, indicative of the development of sinkholes, modelled as Gaussian with amplitude linearly increasing with time. We verified the validity of our model using both synthetic and actual InSAR data sets. The latter was obtained by processing imagery of a region near Wink, Texas, containing ground truth sinkhole data.We applied this framework to a 40 km × 40 km area of interest located in western Virginia and performed ground validation on a subset of the identified regions. The results show good agreement between the locations detected by our algorithm and the evidence of subsidence observed during the ground validation campaign.

Sinkhole precursors along the Dead Sea, Israel, revealed by SAR interferometry

The water level in the Dead Sea (Israel and Jordan) has been dropping at an increasing rate since the 1960s, exceeding one meter per year during the last decade. This drop has triggered the formation of sinkholes and widespread land subsidence along the Dead Sea shoreline, resulting in severe economic loss and infrastructural damage. In this study, the spatiotemporal evolution of sinkhole-related subsidence and the effect of human activities and land perturbation on sinkhole development are examined through interferometric synthetic aperture radar measurements and field surveys conducted in Israel during 2012. Interferograms are generated using COSMO-SkyMed satellite images and a high-resolution (0.5 m/pixel) elevation model obtained from LiDAR measurements. As a result of this unique combination of high-resolution data sets, millimeter-scale subsidence has been resolved in both natural and human-disturbed environments. Precursory subsidence over a period of a few months occurred before the collapse of all three sinkhole sites reported in this study. The centers of the subsiding areas migrated, possibly due to progressive dissolution and widening of the underlying cavities. Filling of newly formed sinkholes with gravel, and mud injections into drill holes, seem to enhance land subsidence, enlarge existing sinkholes, and form new sinkholes. Apart from shedding light on the mechanical process, the results of this study may pave the way for the implementation of an operational sinkhole early-warning system.

Fault — Dissolution front relations and the Dead Sea sinkhole problem

There are two conflicting models of sinkhole development along the Dead Sea (DS). The first one considers structural control on sinkholes, constraining them to tectonic lineaments. This hypothesis is based on seismic reflection studies suggesting that sinkholes are the surface manifestations of active neotectonic faults that may serve as conduits for under-saturated groundwater, enabling its access across aquiclude layers. Another hypothesis, based on results of multidisciplinary geophysical studies, considers the salt edge dissolution front as the major site of sinkhole formation. This hypothesis associates sinkholes with karstification of the salt edge by deep and shallow undersaturated groundwater. Our recent seismic reflection and surface wave studies suggest that salt formed along the active neotectonic faults. Sinkholes form in a narrow strip (60–100m wide) along a paleo-shoreline constrained by faults and alluvial fans which determined the edge of the salt layer. This scenario reconciles the two major competing frameworks for sinkhole formation.

Sinkhole hazards prediction at Ghor Al Haditha, Dead Sea, Jordan: “Salt Edge” and “Tectonic” models contribution—a rebuttal to “Geophysical prediction and following development sinkholes in two Dead Sea areas, Israel and Jordan, by: Ezersky, M.G., Eppelbaum, L.V., Al-Zoubi,A.3, Keydar S., Abueladas, A-R., Akkawi E., and Medvedev, B.”

Mikhail Ezersky et al. have published the article “Geophysical prediction and following development sinkholes in two Dead Sea areas, Israel and Jordan” (February 2013) in which the paper “Salt karst and tectonics: sinkholes development along tension cracks between parallel strike-slip faults, Dead Sea, Jordan” published by Closson D, Abou Karaki N, Hallot F in 2009 (Earth Surface Processes and Landforms, 34(10), 1408–1421) is questioned. In this short paper, we propose some clarifications and discuss the criticisms of these authors.

Urban development in karst and collapse-prone geologic environments

The development of marginal land necessitated by urban sprawl is producing undesirable consequences derived from inadequate design or construction, or both, of storm water systems in karst and collapse-prone geologic environments. The St. Peters, Missouri karst area is presented as an example. Sufficient knowledge of the geohydrologic setting, combined with proper planning of water discharge, is essential for engineers, developers, and property owners when developing storm water drainage systems. The design of community and individual storm water drainage systems, lot sizes, roads, and selection of vegetative cover are controlled more often by economics and aesthetics than by existing natural conditions. Frequently, the geohydrologic character of the bedrock, composition and stability of the surficial material, existing topography, and adjoining land use may not fully be considered. Improper design and location of storm drainage discharge leads to sinkhole development as well as increased erosion. In developed karst settings with thick loess deposits, residential lot sizes are frequently too small to control erosion; the structures and infrastructure tend to be located adjacent to valley walls and on steeply sloping topography. The vegetative cover is typically stripped, promoting slope instability, resulting in increased erosion and mass wasting. Road placement, structure location, and drainage design can direct surface water to infiltrate localized areas of surficial materials. This promotes adhesive dissolution in weakly cemented loess, resulting in slope instability and eventual collapse. It is clear that three factors influencing collapses are frequently overlooked in the development of marginal land areas. First, it is essential to recognize the presence of soluble bedrock that exhibits a high degree of secondary permeability. Second, loess is weakly cemented and it loses cohesiveness with water infiltration, making it more erodible and collapse-prone. Third, the hydrology of the site is closely associated with the bedrock and surficial material and significantly influences the occurrence of subsidence and collapse events.

Geophysical records of anthropogenic sinkhole formation in the Delaware Basin region, Southeast New Mexico and West Texas, USA

A significant minority of sinkholes that formed in gypsum bedrock in the Delaware Basin region are of human origin. These anthropogenic sinkholes are often associated with improperly cased abandoned oil wells or with solution mining of salt beds in the shallow subsurface. In July 2008, a sinkhole formed abruptly at the site of a brine well in northern Eddy Co., New Mexico. The well operator had been injecting fresh water into underlying salt beds and pumping out the resulting brine for use as oil field drilling fluid. Borehole problems had prevented the operator from conducting required downhole sonar surveys to assess the dimensions of subsurface void space. The resulting sinkhole formed in just a few hours by catastrophic collapse of overlying mudstone and gypsum and in less than 1 month had reached a diameter of 111 m and a depth of 64 m. Fortuitously, a seismometer had been deployed 13 km southeast of the brine well a few months earlier and precursor events were captured on the seismograph record a few hours before the subsurface cavity breached the surface. Four months later, another sinkhole collapse occurred in northern Eddy Co., again associated with a brine well operation. These events prompted the New Mexico Oil Conservation Division to review its regulations regarding brine well operations in the southeastern New Mexico oil fields. A third brine well within the city limits of Carlsbad, N. Mex., has been shut down to forestall possible sinkhole development in this more densely populated area. Electrical resistivity surveys have been conducted adjacent to the Eddy Co. sinkholes to assess the potential for additional subsidence or collapse events in the future.

Morphometric analysis of sinkholes in a karst coastal area of southern Apulia (Italy)

Salento, the southern portion of Apulia region (SE Italy), is a narrow and elongated peninsula in carbonate rocks, with prevailing low coastlines, locally interrupted by high rock cliffs. The long stretches of low coasts are marked by typical karst landforms consisting of collapse sinkholes. As observed in many other karst coastal settings worldwide, development of sinkholes may be particularly severe along the coasts, where both natural and anthropogenic processes contribute to accelerate the dissolution of carbonate rocks and subsidence processes, even influencing the coastline evolution. Following a previous study, where the main features of sinkholes at Torre Castiglione (Taranto province) were investigated and described, and a preliminary susceptibility map produced, at the light of updated data and elaborations in the present paper we perform a detailed morphometric analysis on the sample of identified sinkholes. The main morphometric parameters generally used for sinkhole characterization have been considered in this study: shape of the sinkhole, azimuth and length of maximum and minimum axes, depth, elongation ratio, and distance from the shorelines. Each of them is described, both as individual parameter and in conjunction with the others, in the attempt to identify the main factors controlling development of sinkholes in the area, and their evolution as well. With regard to this latter aspect, beside simple morphometry of the sample of sinkholes at Torre Castiglione, we also focused our attention on the likely relationships existing between distribution and shape of the sinkholes and the tectonic discontinuities. To investigate the matter, a three-stage analysis has been carried out in this study by means of: field measurements of the fractures bounding the sinkholes, field measurement of the long axes azimuth of the elongated sinkholes, comparison of the previously described sets with the strikes of the main regional geological structures. The obtained results show, in addition to the coincidence of the main regional discontinuity systems with the major axis of elongated sinkholes, a clear control exerted by development and evolution of the sinkholes on the formation of coastal inlets and bays. Eventually, the approach here presented may be applied in other karst coastal sinkhole-prone areas, to gain new knowledge on the genesis and evolution of coastal sinkholes, and to properly evaluate the hazard they pose to the anthropogenic environment.

Geophysical prediction and following development sinkholes in two Dead Sea areas, Israel and Jordan

Geophysical methods—seismic refraction (SRFR), electrical resistivity tomography (ERT), and microgravity—were applied to the Dead Sea (DS) sinkhole problem in the Ein Gedi area at the earlier stage of the sinkhole development (1998–2002). They allowed determining the sinkhole formation mechanism and localizing the sinkhole hazardous zones. The SRFR method permitted to delineate the underground edge of a salt layer at the depth of 50 m. The salt edge was shaped like the sinkhole line on the surface. It was concluded that the sinkhole development is linked to the salt edge. Geoelectrical quasi-3D mapping based on the ERT technique detected large resistivity anomalies with 250–300 m2 diameter and 25–35 m deep. The Ein Gedi area has been also mapped by the use of Microgravity method. The residual Bouguer gravity anomaly map shows negative anomalies arranged along the edge of the salt layer. Those gravity anomalies overall are very similar in plan to the resistivity distribution in this area. The results of forward modeling indicate that both high resistivity and residual gravity anomalies are associated with a subsurface decompaction of the soil mass and deep cavity at the sinkhole site. Following monitoring of the sinkhole development carried out by the Geological Survey of Israel confirmed our suggestions. The drilling of numerous boreholes verified the location of the salt edge. Geographical Information System (GIS) database testifies that during 2003–2009 new sinkholes are continuing to develop along the salt edge within a narrow 50–100 m wide strip oriented approximately in north–south direction (slightly parallel to the shoreline). No promotion in west–east direction (perpendicularly to the DS shoreline) was observed in Israel. Collapse of sinkholes and their clustering have been occurred within the area of high resistivity anomaly and negative residual gravity anomaly. Similar studies carried out at the Ghor Al-Haditha area (Jordan) have shown that sinkholes there are also arranged along the winding line conforming to the salt edge. In this area sinkholes are slowly moved to the Dead Sea direction. Results of geophysical studies in numerous DS sites indicate similar sinkhole development. It allowed generating of the sinkhole formation model based on ancient (10,000–11,000-year old) salt belt girding the Dead Sea along its shores

Hazards and landscape changes (degradations) on Hungarian karst mountains due to natural and human effects

In order to study the karstological processes within the karst ecological system, the geohazards and degradation of karst landscapes on the karst areas of the Bakony mountains (Hungary), we investigated the abiotic elements of the environment, soil and cover deposits, erosion soil decay; the changes in the quantity and quality of karst waters: contamination at swallow holes, contamination of karst springs; and the biogenic factors: surface vegetation coverage by the corine land cover method, plant-ecological examinations, qualification of surface waters with the help of biological water labeling. We recognized that t he increasing human activities during the past few centuries have had significant impact on the investigated landscapes of karst areas because of their spatial sensitivity. In the scope of our research we concluded that the landscape changes due to natural and human effects can vary strongly on the different karst areas. These differences can arise from the climatic and geomorphologic situation, the cover-layer’s qualities, etc., but primarily from the different utilization of the investigated karst areas (e.g. the intensity, characteristics and territorial extension of utilization). On the spot investigation we detected traces of new and fast geomorphological processes (gully formation, landslides, collapses, new sinkhole development) and landforms (sinkholes, gullies, swallow holes), which are clear evidences of the effect of climatic changes.

A GIS Analysis of the Relationship between Sinkholes, Dry-Well Complaints and Groundwater Pumping for Frost-Freeze Protection of Winter Strawberry Production in Florida

Florida is riddled with sinkholes due to its karst topography. Sometimes these sinkholes can cause extensive damage to infrastructure and homes. It has been suggested that agricultural practices, such as sprinkler irrigation methods used to protect crops, can increase the development of sinkholes, particularly when temperatures drop below freezing, causing groundwater levels to drop quickly during groundwater pumping. In the strawberry growing region, Dover/Plant City, Florida, the effects have caused water shortages resulting in dry- wells and ground subsidence through the development of sinkholes that can be costly to maintain and repair. In this study, we look at how frost-freeze events have affected West Central Florida over the past 25 years with detailed comparisons made between two cold-years (with severe frost-freeze events) and a warm year (no frost-freeze events). We analyzed the spatial and temporal correlation between strawberry farming freeze protection practices and the development of sinkholes/dry well complaints, and assessed the economic impact of such events from a water management perspective by evaluating the cost of repairing and drilling new wells and how these compared with using alternative crop-protection methods. We found that the spatial distribution of sinkholes was non-random during both frost-freeze events. A strong correlation between sinkhole occurrence and water extraction and minimum temperatures was found. Furthermore as temperatures fall below 41°F and water levels decrease by more than 20 ft, the number of sinkholes increase greatly (N >10). At this time alternative protection methods such as freeze-cloth are cost prohibitive in comparison to repairing dry wells. In conclusion, the findings from this study are applicable in other agricultural areas and can be used to develop comprehensive water management plans in areas where the abstraction of large quantities of water occur.

Geospatial Modeling for Sinkholes Hazard Map Based on GIS & RS Data

The Kinta Valley is an area of karst in the north-western part of Peninsular Malaysia. Over 30 years of uncontrolled land use and development has led to significant changes in topography and geomorphology, such as the appearance of sinkholes. In this paper, geospatial techniques were utilized to the task of evaluating sinkholes susceptibility map using a spatial multi criteria evaluation approach (SMCE). Sinkhole location and a spatial database were applied to calculate eight inherent causative factors for limestone instability namely: lithology, structure (lineament), soil cover, slope, land use mining, urban area features, ponds and rivers. The preparation of the sinkhole geohazard map involved summing the weighted values for each hazard element, which permits the construction of geohazard model; the results of the analysis were validated using the previous actual sinkholes locations in the study area. The spatial distribution of sinkholes occurrence, urban development, faults distribution and ex-mining ponds are factors that are directly responsible for all sinkholes subsidence hazards. Further, the resulting geo-hazard map shows that 93% of recent sinkholes occur in areas where the model flags as “high” and “very high” potential hazard, located in the urbanized part of the valley, while less-developed areas to the west and southwest suffered less sinkhole development. The results can be used for hazard prevention and land-use planning.

Karst risk assessment for engineering in Nizhny Novgorod region, Russia

Federal Standards of the Russian include the requirement of mandatory assessment of the risks induced by natural processes in order to make sure their values do not exceed acceptable limits. To meet the requirement a number of karst risk assessment methods have been developed for the regions of the country where the most significant hazard is presented by karst sinkholes. For this particular application karst risk is understood as specific probability of sinkhole development on a unit area per a unit time span with account of probable economic, social and environmental components of damage. The probability of sinkhole development is evaluated by specialists in engineering karstology and designers. They make use of the acceptable data on the environmental conditions and apply stochastic laws of sinkhole development in time and space, alongside with focusing on all other relevant specificity of the building or facility to be built. Acceptable limits of karst risks should be specified by a multidisciplinary team including designers, lawyers, economists, insurers, environmentalists, engineering karstologists and other specialists on the basis of their expert knowledge. It has been demonstrated that a ratio between predicted and acceptable karst risk values can serve a practically meaningful karst risk level indicator for the purposes of building on karst. This ratio can be used with a rather high degree of objectiveness to develop a programme of antikarst activities during both facilities construction and operation.

Devonian salt dissolution-collapse breccias flooring the Cretaceous Athabasca oil sands deposit and development of lower McMurray Formation sinkholes, northern Alberta Basin, Western Canada

The sub-Cretaceous paleotopography underlying giant Lower Cretaceous Athabasca oil sands, northern Alberta, has an orthogonal lattice pattern of troughs up to 50km long and 100m deep between pairs of cross-cutting lineaments. These structures are interpreted to have been inherited from a similar pattern of dissolution collapse-subsidence troughs in the underlying Middle Devonian salt beds. Removal of more than 100m of halite salt fragmented the overlying Upper Devonian strata into fault blocks and collapse breccias that subsided into the underlying dissolution troughs. The unusually low 1:2 to 1:3 thickness ratios of halite salts to the overlying strata resulted in the Upper Devonian strata collapse-subsidence into underlying salt dissolution troughs being more cataclysmic during the first phase of salt removal. The second phase of slower but complete salt removal between the earlier troughs resulted in a more gradual subsidence of the overlying strata. This obliterated the earlier pattern of giant cross-cutting dissolution troughs bounded by major lineaments. The collapse breccia fabrics underlying the earlier troughs differ from those from areas between the troughs. Collapse breccias underlying the large troughs often have crushed fabrics distributed in zones that rapidly pinched out between fault blocks. Breccias between troughs developed as giant mosaics of detached carbonate blocks that formed breccia pipe complexes.Multiple sinkholes up to 100m deep aligned along multi-km linear valley trends that dissected the sub-Cretaceous paleotopography. These sinkhole trends formed orthogonal patterns inherited from underlying lattice of NW–SE and NE–SW salt structured lineaments. These cross-cutting sinkhole trends have a smaller 5km scale reticulate pattern similar to the giant 50km scale pattern of collapse-subsidence troughs. Other sinkholes developed as lower McMurray strata sagged when underlying Devonian fault blocks and breccia pipes differentially subsided.

Quaternary alluvial sinkholes: Record of environmental conditions of karst development, examples from the Ebro Basin, Spain

The central Ebro Basin is an exceptional region for studying karstification through time and under different environmental conditions, as sinkholes have been developing since the Early Pleistocene. Knowledge of active sinkholes is complemented with research on paleosinkholes and contemporary deposits. Sedimentological, min- eralogical, geomorphological and structural approaches permit interpretation of the natural environmental conditions that favored karst in the past and the main genetic mechanisms involved. The sedimentary features of Pleistocene terraces indicate that they were deposited by a gravel braided fluvial system characterized by higher water and sediment availability than today, probably related to meltwater flows coming from glaciated source areas, mainly in the Pyrenees. Genesis of paleosinkholes was mainly linked to this high water supply. Some of them acted as small lakes where fine sediments are exceptionally well conserved to give clues about environmental conditions. The neo- formation of palygorskite and sepiolite suggests arid to semiarid climatic conditions, in agreement with the idea of cold glacial episodes. During Pleistocene times, development of sinkholes was influenced by tectonics. Currently, the genesis and evolution of numerous sinkholes are also influenced by water supplies from human activities such as irrigation or urbanization, sharply changing the nearly steady state exhibited in the past.