CONVOLUTION IN TIME-DEPENDENT SYSTEM FROM ARTIFICIAL TRACER TESTS RESPONSES IN POROUS OR KARST SYSTEMS - THEORY AND MODELING, 1995, Dzikowski M,

An instantaneous point injection of an artificial tracer makes it possible to identify the studied system directly. Whether or not convolutions can be carried out depends on the linearity and stationarity of the tracer-test system. Convolutions from the relations between the impulse responses and the hydrodynamic conditions in time-dependent systems are only allowed under special conditions. The framework in which such convolutions are possible is established and a convolution integral proposed which makes it possible to obtain the result of any input in time at one of the outlets of a vectorial system when an artificial tracer test has been carried out between the injection point and this outlet. A few theoretical examples of convolution results with variable flow rates are presented; these results were obtained with a computer code based on the proposed convolution integral

Convolution a debit variable a partir des reponses de tracages artificiels; application a un systeme karstique (Causse de Gramat, Lot, France): Convolution in time-dependent system from artificial tra, 1995, Dzikowski M, Delay F, Sauty Jp, Crampon N, De Marsily G,

ResumeLa realisation de tracages artificiels dans des conditions hydrodynamiques differentes sur le systeme karstique de I'Ouysse (Causse de Gamat, France) ainsi que de mesures physicochimiques portant entre autres sur les chlorures, nitrates et matieres en suspension ont permis d'exploiter les possibilites de l'analyse des systemes-tracages dependant du temps. Pour des tracages artificiels realises a des periodes hydrologiques differentes (basses-eaux et hauteseaux), les relations entre les reponses impulsionnelles a l'injection instantanee de traceur et les debits d'ecoulement variables associes sont mises en evidence sur un systeme a deux entrees (pertes de Themines et Theminettes) et une sortie (gouffre de Besaces). Ces relations etablissent une independance entre l'espace occupe par le traceur au cours de son transfert et les conditions hydrodynamiques dans la gamme de debits interessant chaque tracage. Des operations de convolutions d'entrees en chlorures, nitrates et matieres en suspension, basses sur l'hypothese d'un systeme a volume constant dependant du temps ont donc pu etre realisees. Les resultats sont compares au mesures experimentales au point de sortie (Besaces).AbstractArtificial tracer tests conducted under different hydrodynamic conditions on the karst system of Ouysse (Causse de Gramat, France) and chemical measurements have permitted the use of the time-dependent tracer test analysis. For artificial tracer experiments in different hydrologic periods (water rise and high flow), the relationships between the responses to an instantaneous injection are improved in a system defined by two inputs (losses of Themines and Theminettes). They show that the space occupied by the mass of tracer during its transfer can be considered as independent of the discharge according to the range of flow rate in which the tracer experiments have been conducted. Therefore, convolutions on chlorides, nitrates and suspended sediments are simulated under the hypothesis of a constant-volume and time-dependent system. The computed results are compared with the experimental data at the output (cave of Besaces)

Linear systems analysis in a karst aquifer, 1999, Long A. J. , Derickson R. G. ,

A linear systems analysis applied to ground-water flow is presented as an alternative modeling technique to traditional discretized ground-water models (i.e. finite-difference and finite-element), which require elaborate parameters and boundary conditions. Linear systems analysis has been used extensively for surface-water modeling and to 3 lesser extent for groundwater applications. We present a method for the analysis of an aquifer's response in hydraulic head to recharge that comprises two major components. The first component is to predict the drop in hydraulic head over time if recharge is eliminated. By fitting logarithmic curves to selected short-term hydraulic head recession periods, a long-term recession or 'base head' can be established. The estimation of base head is necessary for the second component of the method, which is the derivation of an impulse response function or transfer function. The transfer function H-as derived by deconvolution of two time series data sets - estimated recharge and the measured response in hydraulic head. An aquifer's response to recharge can be characterized and modeled by using the transfer function. which also establishes the time to peak response. the response time distribution, and the total memory length of the system. The method requires fitting smooth curves to the oscillatory transfer function derived by deconvolution in the Fourier transform domain. The smooth curve is considered to be the physically valid transfer function. In this analysis, curve fitting was more effective than other smoothing techniques commonly used. We applied the method to the karstic Madison aquifer and found that thr time to peak response is less than one month, the system's total memory is about six years, and a logarithmic curve best fits the system response. This method has potential to be useful as 3 predictive tool in aquifer management. (C) 1999 Elsevier Science B.V. All rights reserved

Linear and nonlinear input/output models for karstic springflow and flood prediction at different time scales, 1999, Labat D. , Ababou R. , Mangin A. ,

Karstic formations function as three-dimensional (3D) hydrological basins, with both surface and subsurface flows through fissures, natural conduits, underground streams and reservoirs. The main characteristic of karstic formations is their significant 3D physical heterogeneity at all scales, from fine fissuration to large holes and conduits. This leads to dynamic and temporal variability, e.g, highly variable flow rates, due to several concurrent flow regimes with several distinct response times. The temporal hydrologic response of karstic basins is studied here from an input/output, systems analysis viewpoint. The hydraulic behaviour of the basins is approached via the relationship between hydrometeorological inputs and outputs. These processes are represented and modeled as random, self-correlated and cross-correlated, stationary time processes. More precisely, for each site-specific case presented here, the input process is the total rainfall on the basin and the output process is the discharge rate at the outlet of the basin (karstic spring). In the absence of other data, these time processes embody all the available information concerning a given karstic basin. In this paper, we first present a brief discussion of the physical structure of karstic systems. Then, we formulate linear and nonlinear models, i.e. functional relations between rainfall and runoff, and methods for identifying the kernel and coefficients of the functionals (deterministic vs. statistical; error minimisation vs. polynomial projection). These are based mostly on Volterra first order (linear) or second order (nonlinear) convolution. In addition, a new nonlinear threshold model is developed, based on the frequency distribution of interannual mean daily runoff. Finally, the different models and identification methods are applied to two karstic watersheds in the french Pyrenees mountains, using long sequences of rainfall and spring outflow data at two different sampling rates (daily and semi-hourly). The accuracy of nonlinear and linear rainfall-runoff models is tested at three time scales: long interannual scale (20 years of daily data), medium or seasonal scale (3 months of semi-hourly data), and short scale or 'flood scale' (2 days of semi-hourly data). The model predictions are analysed in terms of global statistical accuracy and in terms of accuracy with respect to high flow events (floods)

Rainfall-runoff relations for karstic springs. Part I: convolution and spectral analyses., 2000, Labat D. , Ababou R. , Mangin A.

Rainfall-runoff relations for karstic springs. Part I: convolution and spectral analyses, 2000, Labat D. , Ababou R. , Mangin A. ,

Karstic basins contain large reserves of subsurface water. In this paper, three karstic systems located in the Pyrenees Mountains (Ariege, France) are studied. Long records of rainfall and discharge rates for these karstic springs are available, sampled at different rates: daily, hourly and half-hourly. This study aims at illustrating and assessing the capabilities and limitations of linear black-box methods for analysing rainfall-runoff type relationships and reconstructing runoffs from rainfall rate data using such systems. In this study, precipitation and discharge rates are considered as two autocorrelated and cross-correlated stochastic processes. A Linear and stationary rainfall-runoff model is adopted, which is used for identification and simulation purposes. Different versions are analysed, including a model based on a convolution integral between the precipitation rate P(tau) and a transfer function h(t - tau) which can be thought of as the unit impulse response of the system. It is shown that this linear stochastic model (i.e. the statistical version), although accurate in some respects, does not represent the hydraulic behaviour of the system very well during low flow episodes and floods. It is also shown that the use of Fourier analysis, alone, does not lead to a satisfactory reconstitution of observed runoff sequences. For these reasons, the use of non-linear random process input-output models based on Volterra integral series is proposed and discussed. (C) 2000 Elsevier Science B.V. All rights reserved

Composite transfer functions for karst aquifers, 2003, Icjukic V. , Jukic D. ,

Linear transfer functions have been extensively used in hydrological studies. Generally, we support this conclusion: rainfall-runoff models based on the convolution between rainfall rates and a nonparametric transfer function (NTF) are not successful at simulating karst spring discharges during long recession periods. The tails of identified transfer functions have irregular shapes and they are not accurate physical representation of the transport through a karst system. Irregularities are the result of unavoidable errors in input and output time series and simplifications made by considering the system as linear and time invariant. This paper deals with a new form of the transfer functions for karst aquifers, the so-called composite transfer function (CTF). The CTF simulates discharges by two transfer functions adapted for the quick flow and the slow flow hydrograph component modeling. NTF is responsible for the quick flow component. The slow flow component is modeled by a parametric transfer function that is an instantaneous unit hydrograph mathematically formulated and defined from a conceptual model. By using the CTF, the irregular shape of the tail of the identified transfer function can be avoided, and the simulation of long recession periods as well as the simulation of a complete hydrograph becomes more successful. The NTF, the Nash model, the Zoch model and other similar conceptual models can be considered separately as simplified forms of the CTF. The rainfall-runoff model based on the convolution between rainfall rates and the CTF was tested on the Jadro Spring in Croatia. The results of the application are compared with the results obtained by applying NTFs independently. (C) 2003 Elsevier Science B.V. All rights reserved

The application of Time-Lapse Microgravity for the Investigation and Monitoring of Subsidence at Northwich, Cheshire, 2003, Branston Mw, Styles P,

Peter Street is an area of terraced houses in Northwich suffering from subsidence, thought to be related to salt extraction in the 19th century. Microgravity and resistivity profiling have been used as non-invasive techniques to investigate the cause of this subsidence. Repeat (or time-lapse) microgravity has been used to assess the stability and evolution of the low-density areas. Time-lapse microgravity uses the characteristics of anomaly size and gradient to track the development of cavities as they propagate to the surface. It is possible to monitor the change in gravity with time and to model the increase in cavity volume and/or depth. A gravity low was found to be coincident with the area experiencing subsidence. Integratedmodelling techniques including Euler deconvolution, Cordell & Henderson inversion and GRAVMAG modelling have been used to investigate the depth and size of the body responsible for this anomaly. Resistivity imaging has been used to investigate the conductivity of the near surface and constrain the gravity models. Results from both techniques suggest that low density ground is now present at a depth of 3-4 m below the surface in the subsidence affected area. The use of time-lapse microgravity has shown that there has been an upwardmigration of a low-density zone at gravity anomaly C over the monitoring period

Runoff generation in karst catchments: multifractal analysis, 2004, Majone B. , Bellin A. , Borsato A. ,

Time series of hydrological and geochemical signals at two karst springs, located in the Dolomiti del Brenta region, near Trento, Italy, are used to infer how karst catchments work internally to generate runoff. The data analyzed include precipitation, spring flow and electric conductivity of the spring water. All the signals show the signature of multifractality but with different intermittency and non-stationarity. In particular, precipitation and spring flow are shown to have nearly the same degree of nonstationarity and intermittency, while electric conductivity, which mimics the travel time distribution of water in the karst system, is less intermittent and smoother than both spring flow and precipitations. We found that spring flow can be obtained from precipitation through fractional convolution with a power law transfer function. An important result of our study is that the probability distribution of travel times is inconsistent with the advection dispersion equation, while it supports the anomalous transport model. This result is in line with what was observed by Painter et al. [Geophys. Res. Lett. 29 (2002) 21.1] for transport in fractured rocks. (C) 2004 Elsevier B.V. All rights reserved

Sinkholes and the Engineering and Environmental Impacts of Karst, 2005, Beck B. F.

Conference Proceedings

Sinkholes and the Engineering and Environmental Impacts of Karst Contains over 70 papers addressing karst topography which impacts water resources, waste disposal, foundation stability, and a multitude of other geotechnical and environmental issues. These papers were presented at the 10th Multidisciplinary Conference held September 24-28, 2005 in San Antonio, Texas and Sponsored by the Geo-Institute of ASCE, P. E. LaMoreaux & Associates, Inc. and Edwards Aquifer Authority. The goal of this conference was to share knowledge and experience among disciplines by emphasizing practical applications and case studies. This proceedings will benefit environmental and geotechnical engineers, and others involved in water resources, water disposal, and foundation stability issues.

Contents:

 Application of Geophysical Logging Techniques for Multi-Channel Well Design and Installation in a Karst Aquifer (by Frank Bogle, ...)

 Case Studies of Massive Flow Conduits in Karst Limestone (by Jim L. Lolcama)
 
 A Case Study of the Samanalawewa Reservoir on the Walawe River in an Area of Karst in Sri Lanka (by K. Laksiri, ...)

 Characterization and Water Balance of Internal Drainage Sinkholes (by Nico M. Hauwert, ...) 

 Characterization of Desert Karst Terrain in Kuwait and the Eastern Coastline of the Arabian Penninsula (by Waleed Abdullah, ...)

 Characterization of a Sinkhole Prone Retention Pond Using Multiple Geophysical Surveys and Closely Spaced Borings (by Nick Hudyma, ...)
 
 Combining Surface and Downhole Geophysical Methods to Identify Karst Conditions in North-Central Iowa (by J. E. Wedekind, ...)

 Complexities of Flood Mapping in a Sinkhole Area (by C. Warren Campbell, P.E.)
 
 Conceptualization and Simulation of the Edwards Aquifer, San Antonio Region, Texas (by R. J. Lindgren, ...)

 Database Development and GIS Modeling to Develop a Karst Vulnerability Rating for I-66, Somerset to London, KY (by Michael A. Krokonko, ...)

 Design and Construction of the Foundations for the Watauga Raw Water Intake Facility in Karstic Limestone near the City of Johnson City, TN (by Tony D. Canale, P.E., ...)

 Detection of Three-Dimensional Voids in Karstic Ground (by Derek V. Morris, P.E., ...)

 Development and Evolution of Epikarst in Mid-Continent US Carbonates (by Tony L. Cooley, P.E.)

 Dye Tracing Sewage Lagoon Discharge in a Sandstone Karst, Askov, Minnesota (by Emmit Calvin Alexander, Jr., ...)

 The Effectiveness of GPR in Sinkhole Investigations (by E. D. Zisman, P.E., ...)

 Effects of Anthropogenic Modification of Karst Soil Texture on the Water Balance of ?Alta Murgia? (Apulia, Italy) (by F. Canora, ...)

 Environmental Isotope Study on Recharge and Groundwater Residence Time in a covered Ordovician Carbonate Rock (by Zhiyuan Ma, ...)

 Error and Technique in Fluorescent dye Tracing (by Chris Smart)
 
 Essential Elements of Estimating Engineering Properties of Karst for Foundation Design (by Ramanuja Chari Kannan, P.E., Fellow, ASCE)

 Estimating Grout Quantities for Residential Repairs in Central Florida Karst (by Larry D. Madrid, P.E., ...)

 Evaluation of Groundwater Residence Time in a Karstic Aquifer Using Environmental Tracers: Roswell Artesian Basin, New Mexico (by Lewis Land)

 Experience of Regional Karst Hazard and Risk Assessment in Russia (by A. L. Ragozin, ...)

 Experimental Study of Physical Models for Sinkhole Collapses in Wuhan, China (by Mingtang Lei, ...)

 Fractal Scaling of Secondary Porosity in Karstic Exposures of the Edwards Aquifer (by Robert E. Mace, ...)

 The Geological Characteristics of Buried Karst and Its Impact on Foundations in Hong Kong, China (by Steve H. M. Chan, ...)

 Geophysical Identification of Evaporite Dissolution Structures Beneath a Highway Alignment (by M. L. Rucker, ...)

 Geotechnical Analysis in Karst: The Interaction between Engineers and Hydrogeologists (by R. C. Bachus, P.E.)

 The Gray Fossil Site: A Spectacular Example in Tennessee of Ancient Regolith Occurrences in Carbonate Terranes, Valley and Ridge Subpovince, South Appalachians U.S.A. (by G. Michael Clark, ...)

 Ground-Water Basin Catchment Delineation by Bye Tracing, Water Table Mapping, Cave Mapping, and Geophysical Techniques: Bowling Green Kentucky (by Nicholas C. Crawford)

 Groundwater Flow in the Edwards Aquifer: Comparison of Groundwater Modeling and Dye Trace Results (by Brian A. Smith, ...)

 Grouting Program to Stop Water Flow through Karstic Limestone: A Major Case History (by D. M. Maciolek)

 Highway Widening in Karst (by M. Zia Islam, P.E., ...)

 How Karst Features Affect Recharge? Implication for Estimating Recharge to the Edwards Aquifer (by Yun Huang, ...)

 Hydrogeologic Investigation of Leakage through Sinkholes in the Bed of Lake Seminole to Springs Located Downstream from Jim Woodruff Dam (by Nicholas C. Crawford, ...)

 The Hydrologic Function of the soil and Bedrock System at Upland Sinkholes in the Edwards Aquifer Recharge Zone of South-Central Texas (by A. L. Lindley)

 An Integrated Geophysical Approach for a Karst Characterization of the Marshall Space Flight Center (by Lynn Yuhr, ...)

 Integrated Geophysical Surveys Applied to Karstic Studies Over Transmission Lines in San Antonio, Texas (by Mustafa Saribudak, ...)

 Judge Dillon and Karst: Limitations on Local Regulation of Karst Hazards (by Jesse J. Richardson, Jr.)

 Karst Groundwater Resource and Advantages of its Utilization in the Shaanbei Energy Base in Shaanxi Province, China (by Yaoguo Wu, ...)

 Karst Hydrogeology and the Nature of Reality Revisited: Philosophical Musings of a Less Frustrated Curmudgeon (by Emmit Calvin Alexander, Jr.)

 Karst in Appalachia ? A Tangled Zone: Projects with Cave-Sized Voids and Sinkholes (by Clay Griffin, ...)

 Karstic Features of Gachsaran Evaporites in the Region of Ramhormoz, Khuzestan Province, in Southwest Iran (by Arash Barjasteh)

 Large Perennial Springs of Kentucky: Their Identification, Base Flow, Catchment, and Classification (by Joseph A. Ray, ...)

 Large Plot Tracing of Subsurface Flow in the Edwards Aquifer Epikarst (by P. I. Taucer, ...)
 Lithology as a Predictive Tool of Conduit Morphology and Hydrology in Environmental Impact Assessments (by George Veni)

 Metadata Development for a Multi-State Karst Feature Database (by Yongli Gao, ...)

 Micropiling in Karstic Rock: New CMFF Foundation Solution Applied at the Sanita Factory (by Marc Ballouz)

 Modeling Barton Springs Segment of the Edwards Aquifer Using MODFLOW-DCM (by Alexander Y. Sun, ...)

 Multi-Level Monitoring Well Completion Technologies and Their Applicability in Karst Dolomite (by Todd Kafka, ...)

 National-Scale Risk Assessment of sinkhole Hazard in China (by Xiaozhen Jiang, ...)

 New Applications of Differential Electrical Resistivity Tomography and Time Domain Reflectometry to Modeling Infiltration and Soil Moisture in Agricultural Sinkholes (by B. F. Schwartz, ...)

 Non-Regulatory Approaches to Development on Karst (by Jesse J. Richardson, Jr., ...)

 PA State Route 33 Over Bushkill Creek: Structure Failure and Replacement in an Active Sinkhole Environment (by Kerry W. Petrasic, P.E.)

 Quantifying Recharge via Fractures in an Ashe Juniper Dominated Karst Landscape (by Lucas Gregory, ...)

 Quantitative Groundwater Tracing and Effective Numerical Modeling in Karst: An Example from the Woodville Karst Plain of North Florida (by Todd R. Kincaid, ...)

 Radial Groundwater Flow at Landfills in Karst (by J. E. Smith)
 
 Residual Potential Mapping of Contaminant Transport Pathways in Karst Formations of Southern Texas (by D. Glaser, ...)

 Resolving Sinkhole Issues: A State Government Perspective (by Sharon A. Hill)

 Shallow Groundwater and DNAPL Movement within Slightly Dipping Limestone, Southwestern Kentucky (by Ralph O. Ewers, ...)

 Sinkhole Case Study ? Is it or Isn?t it a Sinkhole? (by E. D. Zisman, P.E.)

 Sinkhole Occurrence and Changes in Stream Morphology: An Example from the Lehigh Valley Pennsylvania (by William E. Kochanov)

 Site Characterization and Geotechnical Roadway Design over Karst: Interstate 70, Frederick County, Maryland (by Walter G. Kutschke, P.E., ...)

 Soil Stabilization of the Valley Creek Trunk Sewer Relief Tunnel (by Jeffrey J. Bean, P.E., ...)

 Some New Approaches to Assessment of Collapse Risks in Covered Karsts (by Vladimir Tolmachev, ...)

 Spectral Deconvolution and Quantification of Natural Organic Material and Fluorescent Tracer Dyes (by Scott C. Alexander)

 Springshed Mapping in Support of Watershed Management (by Jeffrey A. Green, ...) 

 Sustainable Utilization of Karst Groundwater in Feicheng Basin, Shandong Province, China (by Yunfeng Li, ...)
 
 Transport of Colloidal and Solute Tracers in Three Different Types of Alpine Karst Aquifers ? Examples from Southern Germany and Slovenia (by N. Göppert, ...)

 Use of the Cone Penetration Test for Geotechnical Site Characterization in Clay-Mantled Karst (by T. C. Siegel, ...)

 The Utility of Synthetic Aperture Radar (SAR) Interferometry in Monitoring Sinkhole Subsidence: Subsidence of the Devil?s Throat Sinkhole Area (Nevada, USA) (by Rana A. Al-Fares)

 Void Evolution in Soluble Rocks Beneath Dams Under Limited Flow Condition (by Emmanuel S. Pepprah, ...)

2D and 3D GPR imaging of sinkholes and dissolution features in Jandaíra karst of Fazenda Belém oil field, Potiguar Basin-CE, northeast of Brazil, PhD Thesis, 2005, Xavier Neto, Pedro

In Fazenda Belém oil field (Potiguar Basin, Ceará State, northeast Brazil) occur frequently sinkholes and sudden terrain collapses associated to an unconsolidated sedimentary cap covering the Jandaíra karst. This research was carried out in order to understand the mechanisms of generation of these collapses. The main tool used was Ground Penetrating Radar (GPR). This work is developed twofold: one aspect concerns methodology improvements in GPR data processing whilst another aspect concerns the geological study of the Jandaíra karst. This second aspect was strongly supported both by the analysis of outcropping karst structures (in another regions of Potiguar Basin) and by the interpretation of radargrams from the subsurface karst in Fazenda Belém.


It was designed and tested an adequate flux to process GPR data which was adapted from an usual flux to process seismic data. The changes were introduced to take into account important differences between GPR and Reflection Seismic methods, in particular: poor coupling between source and ground, mixed phase of the wavelet, low signal-to-noise ratio, monochannel acquisition, and high influence of wave propagation effects, notably dispersion. High frequency components of the GPR pulse suffer more pronounced effects of attenuation than low frequency components resulting in resolution losses in radargrams. In Fazenda Belém, there is a stronger need of an suitable flux to process GPR data because both the presence of a very high level of aerial events and the complexity of the imaged subsurface karst structures. The key point of the processing flux was an improvement in the correction of the attenuation effects on the GPR pulse based on their influence on the amplitude and phase spectra of GPR signals. In low and moderate losses dielectric media the propagated signal suffers significant changes only in its amplitude spectrum; that is, the phase spectrum of the propagated signal remains practically unaltered for the usual travel time ranges. Based on this fact, it is shown using real data that the judicious application of the well known tools of time gain and spectral balancing can efficiently correct the attenuation effects. The proposed approach can be applied in heterogeneous media and it does not require the precise knowledge of the attenuation parameters of the media. As an additional benefit, the judicious application of spectral balancing promotes a partial deconvolution of the data without changing its phase. In other words, the spectral balancing acts in a similar way to a zero phase deconvolution. In GPR data the resolution increase obtained with spectral balancing is greater than those obtained with spike and predictive deconvolutions.


The evolution of the Jandaíra karst in Potiguar Basin is associated to at least three events of subaerial exposition of the carbonatic plataform during the Turonian, Santonian, and Campanian. In Fazenda Belém region, during the mid Miocene, the Jandaíra karst was covered by continental siliciclastic sediments. These sediments partially filled the void space associated to the dissolution structures and fractures. Therefore, the development of the karst in this region was attenuated in comparison to other places in Potiguar Basin where this karst is exposed. In Fazenda Belém, the generation of sinkholes and terrain collapses are controlled mainly by: (i) the presence of an unconsolidated sedimentary cap which is thick enough to cover completely the karst but with sediment volume lower than the available space associated to the dissolution structures in the karst; (ii) the existence of important structural of SW-NE and NW-SE alignments which promote a localized increase in the hydraulic connectivity allowing the channeling of underground water, thus facilitating the carbonatic dissolution; and (iii) the existence of a hydraulic barrier to the groundwater flow, associated to the Açu-4 Unity.


The terrain collapse mechanisms in Fazenda Belém occur according to the following temporal evolution. The meteoric water infiltrates through the unconsolidated sedimentary cap and promotes its remobilization to the void space associated with the dissolution structures in Jandaíra Formation. This remobilization is initiated at the base of the sedimentary cap where the flow increases its abrasion due to a change from laminar to turbulent flow regime when the underground water flow reaches the open karst structures. The remobilized sediments progressively fill from bottom to top the void karst space. So, the void space is continuously migrated upwards ultimately reaching the surface and causing the sudden observed terrain collapses. This phenomenon is particularly active during the raining season, when the water table – that normally is located in the karst – may be temporarily located in the unconsolidated sedimentary cap.