mechanics of upward propagation of cover collapse sinkholes cover collapse sinkholes occur by failure of the walls of a soil void above cavernous bedrock i examine conditions for failure in compression by crack propagation and coalescence and for failure by sloughing in which pore water pressure produces a net tension perpendicular to the wall of the void compressive failure without relaxation of stress does not explain observed long term stability of thick soils nor failures in thin residual soils if stress relaxation occurs with compressive failure soil voids tend to stabilize and sinkholes are not predicted sloughing failure is not predicted for steady state pore pressure fields even for a perched water table at the surface over a drained void transient pore pressure conditions that could produce sloughing may result from 1 rapid drawdown causing soil consolidation and transient high pore pressure gradients 2 approach of a wetting front in unsaturated soil with high permeability behind the front 3 dissolution of air from bubbles in the soil and exsolution near the void producing a low permeability zone near the void

prediction of undrained sinkhole collapse sinkholes are surface depressions or shafts resulting from the collapse of a submerged cavity in soil the cavities that lead to sinkholes form as a result of underlying geology in limestone areas or as a result of human activity such as mining or leakage from a sewer the formation of sinkholes is often sudden and can lead to extensive damage and loss of life especially in urban areas much of the literature on the subject of sinkhole formation is empirical in nature often being associated with specific locations this paper presents the results of a study using numerical modeling of the undrained stability of the submerged cavities that lead to sinkhole formation finite element limit analysis techniques using programs developed at the university of newcastle are used to obtain upper and lower bound values of a suitable load parameter which bracket the exact solution the results are compared to analytical solutions both from literature and derived independently

a review on natural and human induced geohazards and impacts in karst karst environments are characterized by distinctive landforms related to dissolution and a dominant subsurface drainage the direct connection between the surface and the underlying high permeability aquifers makes karst aquifers extremely vulnerable to pollution a high percentage of the world population depends on these water resources moreover karst terrains frequently underlain by cavernous carbonate and or evaporite rocks may be affected by severe ground instability problems impacts and hazards associated with karst are rapidly increasing as development expands upon these areas without proper planning taking into account the peculiarities of these environments this has led to an escalation of karst related environmental and engineering problems such as sinkholes floods involving highly transmissive aquifers and landslides developed on rocks weakened by karstification the environmental fragility of karst settings together with their endemic hazardous processes have received an increasing attention from the scientific community in the last decades concurrently the interest of planners and decision makers on a safe and sustainable management of karst lands is also growing this work reviews the main natural and human induced hazards characteristic of karst environments with specific focus on sinkholes floods and slope movements and summarizes the main outcomes reached by karst scientists regarding the assessment of environmental impacts and their mitigation

a field based classification scheme for gravel beaches a tripartite classification of gravel beaches based upon morphodynamic properties is proposed and demonstrated for 42 new zealand beaches the main advantage of this scheme is that it is based on simple visual classification that can be applied globally in the field and is underpinned by morphodynamic differences between the beach types the three types identified from the results are 1 pure gravel beach 2 mixed sand and gravel beach 3 composite gravel beach pure gravel beaches have steep slopes tan 0 08 0 24 and gravels extending from the storm berm to below mean low water spring tide level mixed sand and gravel beaches have moderate slopes tan 0 04 0 13 with sand and gravel entirely mixed both cross shore and at depth composite gravel beaches have a steep gravel berm fronted by a low angle intertidal terrace with overall beach slopes of tan 0 05 0 14 on composite beaches there is distinct hydrodynamic cross shore sorting of the sand and gravel component these broad types are tested using discriminant analysis and the three classes are shown to be highly significant f 16 24 df 8 p 0 00005 the key discriminating variables are iribarren number beach width average grain size and storm berm height

viscoelastic damage modeling of sinkhole formation abstract the sinkholes along the dead sea coast are observed in two main sedimentary environments alluvial fan sinkholes which usually form abruptly as deep 20 m and narrow 3 m sinkholes and mud flat sinkholes which usually form as shallow a few centimeters and wide 5 m sinkholes and deepen later the mechanical collapse of all sinkholes is triggered by cavities created by the dissolution of an underlying salt layer by relatively fresh groundwater the processes attributed to the mechanical formation of the sinkholes are viscous flow and brittle fracture failure we use a two dimensional viscoelastic damage rheology numerical model to quantitatively explain the brittle and ductile aspects of collapsed sinkholes three cases of the rheology of the collapsed sediments are simulated 1 damage controlled failure 2 viscoelastic controlled failure and 3 an intermediate damage viscoelastic case results show that viscoelasticity cannot be the sole process acting on the deformed layer because all sinkholes are characterized by sharp boundaries the damage accumulation progresses until arched cavities are created in the soil layer because of the geometric heterogeneity of the layer represented by the heterogeneity of the mesh smaller blocks continue to fall after the first breakup into the cavity advancing the arched cavity upwards this propagation finally stops when the cavity is shallow enough to hold the irregular arch the combination of these two processes creates competition within the stress reduction mechanism that may lead to either magnified or reduced deformation the deformation is magnified in high shear stress locations where the dispersion of the viscous flow spreads damage failure and it is reduced in low shear stress locations where viscous flow disperses shear stress before the onset of damage

karst breakdown mechanisms from observations in the gypsum caves of the western ukraine implications for subsidence hazard assessment the term karst breakdown is employed in this paper to denote the totality of processes and phenomena of gravitational and or hydrodynamic destruction of the ceiling of a karst cavity and of the overlying sediments it refers not only to the existence of a surface subsidence collapse feature but first of all to the internal hidden in the subsurface structures that precede development of a surface form this study reports and discusses the results of direct mapping and examination of breakdown structures in the gypsum karst of the western ukraine at the level of their origin i e in caves the accessibility of numerous laterally extensive maze cave systems in the region provided an excellent opportunity for such an approach which made it possible to examine the relationship between breakdown structures and particular morphogenetic or geological features in caves and to reveal stages of breakdown development it is found that breakdown is initiated mainly at specific speleogenetically or geologically weakened localities which classify into a few distinct types the majority of breakdowns which are potent to propagate through the overburden relate with the outlet cupolas domepits that represent places where water had discharged out of a cave to the upper aquifer during the period of transverse artesian speleogenesis distribution of breakdown structures does not correlate particularly well with the size of the master passages several distinct mechanisms of breakdown development are revealed and most of them proceed in several stages they are guided by speleogenetic geological and hydrogeological factors the study confirms that a speleogenetic approach is indispensable to the understanding of breakdown pre requisites and mechanisms as well as for eventual subsidence hazard assessment direct observations in caves aimed both at speleogenetic investigation and breakdown characterization on regional or site specific levels should be employed wherever possible

sea ripple formation the heterogeneous sediment case abstract ripple formation beneath sea waves is analyzed both by experimental and analytical means when the bottom is made up of a mixture of sands an oscillatory flow is obtained in a closed duct by the oscillations of two rigidly connected pistons located at the ends of the duct the amplitude and period of the oscillations can be continuously varied a fixed tray located at the bottom of the duct and filled with different types of sediments allows ripple formation to be observed the presence of graded sediments is found to have a stabilizing effect and causes longer ripples to appear moreover a selective sediment transport is observed and quantified which tends to pile up the coarse grains at ripple crests leaving the fine ones in the troughs as in the companion paper the theory is based on a linear stability analysis of a flat sandy bottom subject to an oscillatory flow because of the presence of a mixture a modified version of exner equation is used and an hiding factor should be inserted in the sediment transport rate formula the flow regime in the bottom boundary layer is assumed to be turbulent the conditions for ripple appearance are determined along with their wavelengths as they form good agreement is found between experimental data and theoretical findings

morpho sedimentary dynamics of a micro tidal mixed sand and gravel beach playa granada southern spain abstract this paper addresses the changes in the morphology and sedimentology of a micro tidal mixed sand and gravel beach playa granada southern spain forced by wave and water level variations and human intervention through nourishment monthly and storm event driven beach surveys consisting of topographical measurements and sediment sampling in two selected areas were carried out over a one year period three prevailing sediment fractions sand fine gravel and coarse gravel and two end member morphological states of the upper beach profile convex with multiple berms and concave with a single storm berm were identified between them several transitional profiles were formed characterized by developing berms that progressively overlapped generating sediment variability both across the beach profile and with depth the results indicate that the total run up including water level reached during an event represents a more accurate threshold for differentiating between erosional and depositional conditions than wave height they also suggest that mixed sand and gravel beaches recover faster from storm erosion than sandy beaches the long term benefit of the artificial nourishment that took place at the end of the survey period was very limited and this is attributed to the too fine sediment used for the nourishment and its placement too high on the beach clearly nourishment interventions must take into account the natural sediment distribution and the profile shape to avoid rapid losses of the nourished sediment

mechanism and mechanical model of karst collapse in an over pumping area through geological investigation of karst collapses at zaozhuang city china it was found that the mechanism of karst collapse in areas of excess water extraction is characterized by a seepage effect and that the seepage pressure effect is the initial factor that induces karst collapse the causation mechanisms for karst collapse can be divided into two phases the inter collapse phase and the surface collapse phase therefore based on the limit equilibrium theory this paper has established mechanical models for the surface collapse phase and determined values for the stability of the arch formed by the soil hole in an inter collapse phase in addition an evaluation of a karst collapses at zaozhuang city china was completed using mechanical models the results show that the mechanical models agree with the theory of karst collapse at zaozhuang city thus it is proved that the karst collapse models can be used for the evaluation of karst collapse in areas that are over pumped

hydrodynamics and morphological adjustment of a mixed sand and gravel beach torere bay of plenty new zealand detailed measurements of cross shore wave energy transformation swash sediment transport and beach profile change under low energy conditions are reported from a mixed sand and gravel beach at torere bay bay of plenty new zealand measurements were undertaken during a 10 day period following a storm event and document post storm recovery of the beach nearshore wave spectra identify periods in which incident wave energy is dominated by swell and wind wave energy results show that wind wave energy observed in the nearshore is effectively removed from beachface spectra at the break point step under lower tidal stages swash is driven by longer period swell energy although dissipation of short period wave energy is critical in entraining sediments on the lower beach at higher tidal stages wind wave energy is able to propagate across the break point step shoal and break on the lower beachface tidal modulation of wave processes across the lower beachface under low incident wave conditions is found to stimulate active sediment reworking migration of the break point step and shoreward sediment flux to promote beach accretion

salt dissolution and sinkhole formation along the dead sea shore 1 the formation of sinkholes at the dead sea area reflects subsurface cavities formed by salt dissolution this dissolution is related to the recession of the dead sea the groundwater level and the fresh saline water interface along the shore decline at a similar rate to the rate of the dead sea recession and brines that used to occupy layers below this interface are flushed out by freshwater our finite element modeling shows that dissolution of this salt layer is a plausible mechanism to explain the rapid creation of subsurface holes that collapse and form sinkholes the positive feedback between the rate of flow the rate of chemical reaction and the change in permeability accelerates the dissolution processes and might result in reactive infiltration instability which is manifested in fingers of cavities into which fluid is channeled and salt is dissolved the spacing between the sinkholes and the rate of their creation is controlled by several factors including properties of lineaments faults incoming groundwater flux the salinity of the incoming groundwater the rate of dissolution the effective specific surface area the permeability of the salt and clay layers the permeability porosity relation the dispersivity and the thickness of the layers we show that the creation of sinkholes occurs only under specific conditions these conditions must cause an unstable dissolution front which then causes formation of cavities and eventually sinkholes the simulations which utilized the best estimated parameters of the studied area yield results that are similar to those exhibited in the field

atmospheric hydrodynamic coupling in the nearshore 1 natural beach shorelines commonly present morphological rhythmic or non rhythmic features of varying geometrical characteristics traditionally their formation is believed to be due to wave induced processes a line thoroughly investigated during the last few decades however these natural beach formations are frequently bounded by coastal cliffs or capes and are affected by intense winds a fact not previously considered this paper presents the results of a field survey demonstrating the existence of atmospheric hydrodynamic coupling in the nearshore region outside of the breaking zone at carchuna beach motril spain where the atmospheric conditions are influenced by a lateral geographic obstacle cape sacratif

measurements of morphodynamic and hydrodynamic overwash processes in a large scale wave flume overwash is an important process that controls short term barrier dynamics as well as long term barrier migration but this process is difficult to study in the field due to its rare occurrence and the challenging conditions under which it occurs this paper uses data collected during the bardex ii experiment in the delta flume the netherlands where a proto type barrier was subjected to a range of wave and water level conditions the objectives of this research are to 1 compare the morphologic response to overwash on a gravel barrier bardex 2008 experiment with that on a sandy barrier bardex ii 2 understand the influence of wave period on overwash characteristics and sediment transport and 3 improve current knowledge of overwash hydrodynamics the comparative analysis shows that barrier overwash can be affected by negative feedback that stabilises the barrier through barrier crest accretion on gravel barriers and by submerged bar development on sandy barriers an increase in the wave period induced a reduction in overwash frequency over the crest but no significant relation was found between wave peak period and overwash discharge nevertheless overall water discharge during an overwash episode significantly correlates with overall overwash sediment transport rate overwash flow depths during the experiment were relatively shallow and velocities were similar compared to those measured during previous studies and reported in the literature despite the controlled laboratory conditions collection of reliable and accurate measurements of overwash velocities remains challenging

the effects of topography on magma chamber deformation models application to mt etna and radar interferometry we have used a three dimensional elastic finite element model to examine the effects of topography on the surface deformation predicted by models of magma chamber deflation we used the topography of mt etna to control the geometry of our model and compared the finite element results to those predicted by an analytical solution for a pressurized sphere in an elastic half space topography has a significant effect on the predicted surface deformation for both displacement profiles and synthetic interferograms not only are the predicted displacement magnitudes significantly different but also the map view patterns of displacement it is possible to match the predicted displacement magnitudes fairly well by adjusting the elevation of a reference surface however the horizontal pattern of deformation is still significantly different thus inversions based on constant elevation reference surfaces may not properly estimate the horizontal position of a magma chamber we have investigated an approach where the elevation of the reference surface varies for each computation point corresponding to topography for vertical displacements and tilts this method provides a good fit to the finite element results and thus may form the basis for an inversion scheme for radial displacements a constant reference elevation provides a better fit to the numerical results

high resolution insar constraints on flood related subsidence and evaporite dissolution along the dead sea shores interplay between hydrology and rheology abstract sinkhole generation and land subsidence are commonly attributed to dissolution of subsurface layers by under saturated groundwater and formation of cavities along the dead sea ds shorelines this process also involves seasonal flash floods that are drained into the subsurface by existing and newly formed sinkholes we quantify the contribution of flash floods to salt dissolution and land subsidence using high resolution interferometric synthetic aperture radar insar subsidence rates during a 3 year period 2012 2015 were calculated from 57 cosmo skymed x band interferograms bracketing major flood events and intra flood periods in 21 sinkhole sites the sites are located within channels and alluvial fans along the western shores of the dead sea israel the observed subsidence reaches maximum rates of 2 5 mm day accumulating in specific sites to 500 mm year in most of the sinkhole sites a gradual increase in the annual subsidence rate is observed during the 3 year study period three different modes of response to floods were observed 1 sites where floodwater is not directly channeled into sinkholes do not respond to floods 2 sites adjacent to active channels with sinkholes are unaffected by specific floods but their subsidence rates increase gradually from early winter to mid summer and decay gradually until the following winter and 3 sites in active channels with sinkholes are characterized by an abrupt increase in subsidence rates immediately after each flood by a factor of up to 20 and by a subsequent quasi exponential subsidence decay over periods of several months in these latter sites subsidence rates after each flood are temporally correlated with alternating groundwater levels in adjacent boreholes the rapid rise in groundwater head following floods increases the hydraulic gradient of the under saturated groundwater and hence also the groundwater discharge and the dissolution rate of the subsurface salt layer a subsequent quasi exponential water level drop results in similar deceleration in dissolution and subsidence rates with a similar characteristic decay time of about 150 days the observed subsidence decay pattern may also be explained by viscoelastic relaxation of the overburden in response to instantaneously formed dissolution cavities utilizing a kelvin viscoelastic model we show that the contribution of this process is most probably

the influence of shelf indenting canyons and infralittoral prograding wedges on coastal morphology the carchuna system in southern spain abstract submarine canyons and progradational sedimentary bodies are common features of continental margins worldwide few studies have analyzed the relationship between the coastal morphology and the morphology and sedimentary characteristics of the adjacent shelf in wave dominated coasts or the potential role played by shelf indenting canyons as inducers of sediment deposition in shallow waters this work presents a study that correlates the coastal morphology with the characteristics of the adjacent offshore shallow shelf in an area with a complex inner bathymetry the carchuna system spain the study area is characterized by large scale non rhythmic cuspate features in the coastline whereas the inner bathymetry exhibits a shallow water infralittoral prograding wedge ipw and a shelf indenting canyon that has tributaries located a short distance from the coastline using detailed bathymetric measurements observational data and wave propagation modeling the influence of the different bathymetric elements was quantified and a mechanism proposed for the generation of the carchuna ipw the wave propagation results show that the canyon is the main source of the alongshore modulation of nearshore waves and that it plays a major role in the generation of the large scale cuspate features in the shoreline additionally these results suggest that the long term coastal erosion associated with extreme storms yielded sufficient sediment which when subsequently transported eastward the dominant littoral drift direction formed the ipw once formed the ipw modified the wave propagation patterns and contributed to the development and reinforcement of the shoreline features

sinkhole swarms along the dead sea coast reflection of disturbance of lake and adjacent groundwater systems more than a thousand sinkholes have developed along the western coast of the dead sea since the early 1980s more than 75 of them since 1997 all occurring within a narrow strip 60 km long and 1 km wide this highly dynamic sinkhole development has accelerated in recent years to a rate of 150 200 sinkholes per year the sinkholes cluster mostly over specific sites up to 1000 m long and 200 m wide which spread parallel to the general direction of the fault system associated with the dead sea transform research employing borehole and geophysical tools reveals that the sinkhole formation results from the dissolution of an 10 000 yr old salt layer buried at a depth of 20 70 m below the surface the salt dissolution by groundwater is evidenced by direct observations in test boreholes these observations include large cavities within the salt layer and groundwater within the confined subaquifer beneath the salt layer that is undersaturated with respect to halite moreover the groundwater brine within the salt layer exhibits geochemical evidence for actual salt dissolution na cl 0 5 0 6 compared to na cl 0 25 in the dead sea brine the groundwater heads below the salt layer have the potential for upward cross layer flow and the water is actually invading the salt layer apparently along cracks and active faults the abrupt appearance of the sinkholes and their accelerated expansion thereafter reflects a change in the groundwater regime around the shrinking lake and the extreme solubility of halite in water the eastward retreat of the shoreline and the declining sea level cause an eastward migration of the fresh saline water interface as a result the salt layer which originally was saturated with dead sea water over its entire spread is gradually being invaded by fresh groundwater at its western boundary which mixes and displaces the original dead sea brine accordingly the location of the western boundary of the salt layer which dates back to the shrinkage of the former lake lisan and its transition to the current dead sea constrains the sinkhole distribution to a narrow strip along the dead sea coast the entire phenomenon can be described as a hydrological chain reaction it starts by intensive extraction of fresh water upstream of the dead sea continues with the eastward retreat of the lake shoreline which in turn modifies the groundwater regime finally triggering the formation of sinkholes

beach face and berm morphodynamics fronting a coastal lagoon this study documents two different modes of berm development i vertical growth at spring tides or following significant beach cut due to substantial swash overtopping and 2 horizontal progradation at neap tides through the formation of a proto berm located lower and further seaward of the principal berm concurrent high frequency measurements of bed elevation and the associated wave runup distribution reveal the details of each of these berm growth modes in mode i sediment is eroded from the inner surf and lower swash zone where swash interactions are prevalent the net transport of this sediment is landward only resulting in accretion onto the upper beach face and over the berm crest the final outcome is a steepening of the beach face gradient a change in the profile shape towards concave and rapid vertical and horizontal growth of the berm in mode 2 sediment is eroded from the lower two thirds of the active swash zone during the rising tide and is transported both landward and seaward on the falling tide sediment is eroded from the inner surf and transported landward to backfill the zone eroded on the rising tide the net result is relatively slow steepening of the beach face a change of the profile shape towards convex and horizontal progradation through the formation of a neap berm the primary factor determining which mode of berm growth occurs is the presence or absence of swash overtopping at the time of sediment accumulation on the beach face this depends on the current phase of the spring neap tide cycle the wave runup height and indirectly offshore wave conditions and the height of the pre existing berm a conceptual model for berm morphodynamics is presented based on sediment transport shape functions measured during the two modes of berm growth c 2006 elsevier b v all rights reserved

scale free distribution of dead sea sinkholes observations and modeling there are currently more than 5500 sinkholes along the dead sea in israel these were formed due to the dissolution of subsurface salt layers as a result of the replacement of hypersaline groundwater by fresh brackish groundwater this process has been associated with a sharp decline in the dead sea water level currently more than one meter per year resulting in a lower water table that has allowed the intrusion of fresher brackish water we studied the distribution of the sinkhole sizes and found that it is scale free with a power law exponent close to 2 we constructed a stochastic cellular automata model to understand the observed scale free behavior and the growth of the sinkhole area in time the model consists of a lower salt layer and an upper soil layer in which cavities that develop in the lower layer lead to collapses in the upper layer the model reproduces the observed power law distribution without involving the threshold behavior commonly associated with criticality

storm flood impacts along the shores of micro tidal inland seas a morphological and sedimentological study of the vesterlyng beach the belt sea denmark abstract the morphological and sedimentological impacts of an extreme storm event bodil in december 2013 were investigated at a mixed sand and gravel beach vesterlyng in a micro tidal environment along the belt sea denmark the storm response was characteristic for mixed sand and gravel beaches gravelly storm berms with sandy to gravelly washover fans were formed at the upper beach where swash processes dominated during extreme water levels in combination with overtopping and overwash in addition storm scarps and gravel flats were formed the elevation of the storm berm crest was identical to a summation of the still water level 1 60 m in the belt sea during the storm flood and the wave run up 0 75 m at the shore the crest of 2 35 m is therefore a precise measure of the storm flood level this storm flood was classified as a large scale extreme event in a holocene perspective it is suggested that storm berm beach ridge heights above contemporaneous sea level can be used as a proxy of past flood events along micro tidal shores

six thousand years of coastline evolution in the guadalfeo deltaic system southern iberian peninsula abstract the 4000 bc to present day coastal and shallow marine changes of the guadalfeo river deltaic system southeast spain are studied using historic maps aerial photographs diverse submarine data and hydrodynamic models the deltaic system evolved with little anthropic influence until the 1940s when the river mouth was diverted to the west during the pre diversion stage the system evolved from an estuary to a delta due to the enormous sediment yield in the catchment induced both by anomalously wet climate conditions and by deforestation practices accordingly the coastline advanced significantly up to 3 3 m year 1 during this period particularly during the 1500 to 1873 interval the estimate for volumetric changes in the deltaic system shows very high specific sediment yield values around 60 65 t ha 1 year 1 in the catchment the deltaic system mainly evolved by cannibalization of the older lobate outlet depocentre after the river diversion and the generation of a more elongated depocentre coincident with the current outlet due to enhanced lateral redistribution of sediments from east to west the construction of two major dams in the trunk river in the last 30 years has severely blocked sediment supply to the system although expected coastline erosion has been partially mitigated by longshore sediment redistribution

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

bedload dynamics and associated snowmelt influence in mountainous and semiarid alluvial rivers abstract the influence of snowmelt in semiarid alluvial rivers is determined by the river bed configuration and erosion processes moreover the large amount of available sediment in the floodplains of these rivers limits traditional bedload sampling methodologies and suggests the use of large control volumes and long term studies to understand erosive dynamics in this study bedload monitoring in a large control volume 0 2 hm3 from 2004 to 2010 was used to study erosive processes of the guadalfeo river a semiarid alluvial river in southeastern spain with high mountain influences and a hydrological regime conditioned by snow dynamics the methodological approach to testing the performance of different transport models included characterization of the forcing agents precipitation and snowmelt events hydraulic configuration of the river determination of the river bed material surface and substrate and one off measurements for particular events the results indicate a sediment volume effective runoff relationship that is consistent with the existence of steep channels with a flashy runoff regime although the existence of an armored layer derived from snowmelt events greatly controls the transport dynamics with equivalent fractions of cobble gravel and sand in the measured bedload this apparent predominance of near equal mobility was confirmed by the calibrated hiding function exponent x 0 94 0 97 the thresholds for entrainment and transport efficiency are similar to those observed for mountain rivers that exhibit torrential flow although notable differences can be observed in the dynamics of the processes the strong performance of the original meyer peter and muller model with c 8 is shown to estimate the total transported volume associated with intense events when the variability of d50 is included in the analysis however this model does not sufficiently capture transport because of moderate events rain or snowmelt and thus underestimates bedload on medium and long timescales the calibrated model of parker klingeman adequately represents erosive dynamics with r50 values between 0 03 and 0 041 for moderate and intense events respectively and a flow threshold of 14 2 m3 s 1 that separates these two situations nevertheless these models based on hiding functions present greater dispersion if the variability of diameters related to cobbles and pebbles is considered for such cases the wilcock and crowe model performed better for both intense and moderate events the latter is important in the study area where snowmelt pulses occasionally exceed the critical flow and break the surface layer with significant sediment contributions these processes differentiate the transport dynamics from other studies and are distinctive characteristics that are more closely related to mountainous influences in semiarid environments where pulses of intense snowmelt are common despite its limitations the proposed methodology based on a large check dam has proven to be adequate and representative for assessment of erosion processes

sinkhole occurrence monitoring over shallow abandoned coal mines with satellite based persistent scatterer interferometry abstract unexpectedly occurring sinkholes caused by shallow submerged voids are one of the key problems of intensively built up post mining areas five percent of poland s territory is still under the influence of post mining deformation impending sinkholes which tend to develop randomly over very large areas cannot be detected by using traditional geophysical methods moreover geodetic measurement methods like global positioning system gps analyses tachymetry laser scanning or photogrammetry may be useful only for the registration of the dimensions and locations of sinkholes that have already occurred here we investigate an area in upper silesia poland where 345 sinkholes were recorded over a period of more than 20 years 1992 2013 most of the events occurred in intensively built up areas and thus these sinkholes posed a direct threat to the population in the test area 11 sinkholes were detected with a maximum depth of 16 m and maximum dimension of 25 m the root cause of sinkhole formation was the collapse of post mining shallow voids we used satellite radar technology to detect and monitor ground movements potentially associated with the impending sinkholes the findings showed that the application of persistent scatterer interferometry can support the identification of zones where sinkholes will occur given adequate spatio temporal sampling a stack of envisat synthetic aperture radar sar images acquired between march 2003 and august 2010 was used in the analysis and the results confirmed that precursory ground movements were detectable at an early stage of sinkhole development the land subsidence rate observed prior to sinkhole collapse was not constant in time accelerated ground movements within 100 m of an observed sinkhole were detected we conclude that satellite measurements may provide significant support in the early identification of areas prone to sinkhole occurrence

swash zone sediment transport step dynamics and morphological response on a gravel beach abstract state of the art morphodynamic field data were collected from slapton sands uk a fine gravel beach d50 2 10 mm over a 10 day period under a range of wave tide conditions comprising a mixture of southerly swell and easterly wind waves hs 0 5 1 m ts 4 8 s tide range 3 4 m over the field period the upper beach experienced accretion and berm formation during tides with low steepness swell dominated wave conditions h l 0 01 surprisingly the intertidal beach showed an opposite trend with sediment losses under swell conditions and an increase in sediment volume due to wind waves and suggests that upper beach morphological change can be decoupled from the overall sediment budget a submerged accretionary feature the beach step grew and migrated onshore on the rising tide typically reaching a maximum relief of around 0 5 m then gradually decreased in prominence while migrating offshore as the tide fell resulting in little net morphological change the step was better developed during the falling tide than the rising tide and through its control on the swash hydro and sediment dynamics the step had a significant effect on the development of the berm swash flow velocities under the conditions measured were often in excess of 2 m s 1 for both the uprush and the backwash onshore mean flows occurred in the upper swash region 40 inundation was characterised by offshore mean flows swash infiltration losses in the swash zone increased from 40 in the lower swash region to 100 in the upper swash region the most energetic swash flows and the strongest offshore mean flows occurred at the transition between swash zone and surf zone 90 100 inundation

salt dissolution and sinkhole formation results of laboratory experiments the accepted mechanism for the formation of thousands of sinkholes along the coast of the dead sea suggests that their primary cause is dissolution of a salt layer by groundwater undersaturated with respect to halite this is related to the drop in the dead sea level which caused a corresponding drop of the freshwater saltwater interface resulting in fresher groundwater replacing the brines that were in contact with the salt layer in this study we used physical laboratory experiments to examine the validity of this mechanism by reproducing the full dynamic natural process and to examine the impact of different hydrogeological characteristics on this process the experimental results show surface subsidence and sinkhole formation the stratigraphic configurations of the aquifer together with the mechanical properties of the salt layer determine the dynamic patterns of the sinkhole formation instantaneous versus gradual formation laboratory experiments were also used to study the potential impact of future stratification in the dead sea if and when the red sea dead sea canal project is carried out and the dead sea level remains stable the results show that the dissolution rates are slower by 1 order of magnitude in comparison with a nonstratified saltwater body and therefore the processes of salt dissolution and sinkhole formation will be relatively restrained under these conditions

multigrain sedimentation erosion model based on cross shore equilibrium sediment distribution application to nourishment design abstract in the light of global warming and sea level rise there are many coastal beaches that suffer from erosion beach nourishment has become a common practice to maintain the sediment balance on a shore face in this paper a three dimensional numerical model for evaluating long term impact of beach nourishment projects has been developed the model addresses the longstanding complex issue of coastal morphology and sediment grain size distribution from an unconventional angle which exploits the strong links between grain size distribution and the prevailing transport direction of each sediment constituent under average wave and storm action the present model predicts the redistribution of nourished sediment according to the subtle clues implied by equilibrium distribution curves and latest coastal wave transformation theories after verification against recent field observations in terschelling the netherlands the model was used to predict long term effects of different beach nourishment strategies it was found that a given the source sediment available in terschelling the tactics of large volume and less frequent implementation are better than otherwise and b from a pure engineering point of view waterline nourishment outperforms offshore trough nourishment the model offers an additional tool for coastal engineers to evaluate the feasibility effectiveness and the optimization of dumping locations for beach nourishment projects it is also a useful tool for stratigraphic modelling of shallow marine sedimentation in conjunction with sea level changes

the lowest place on earth is subsiding an insar interferometric synthetic aperture radar perspective since the early 1990s sinkholes and wide shallow subsidence features wssfs have become major problems along the dead sea shores in israel and jordan sinkholes are readily observed in the field but their locations and timing are unpredictable wssfs are often difficult to observe in the field however once identified they delineate zones of instability and increasing hazard in this study we identify characterize and measure rates of subsidence along the dead sea shores by the interferometric synthetic aperture radar insar technique we analyze 16 sar scenes acquired during the years 1992 to 1999 by the european remote sensing ers 1 and ers 2 satellites the interferograms span periods of between 2 and 71 months wssfs are observed in the lisan peninsula and along the dead sea shores in a variety of appearances including circular and elongate coastal depressions a few hundred meters to a few kilometers in length depressions in ancient alluvial fans and depressions along salt diapir margins phase differences measured in our interferograms correspond to subsidence rates generally in the range of 0 20 mm yr within the studied period with exceptional high rates that exceed 60 mm yr in two specific regions during the study period the level of the dead sea and of the associated ground water has dropped by 6 m this water level drop within an aquifer overlying fine grained marly layers would be expected to have caused aquifer system consolidation resulting in gradual subsidence comparison of our insar observations with calculations of the expected consolidation shows that in areas where marl layers are known to compose part of the upper 30 m of the profile estimated consolidation settlements are of the order of the measured subsidence our observations also show that in certain locations subsidence appears to be structurally controlled by faults seaward landslides and salt domes gradual subsidence is unlikely to be directly related to the sinkholes excluding the use of the wssfs features as predictable precursors to sinkhole formation

detailed investigation of overwash on a gravel barrier abstract this paper uses results obtained from a prototype scale experiment barrier dynamics experiment bardex undertaken in the delta flume the netherlands to investigate overwash hydraulics and morphodynamics of a prototype gravel barrier gravel barrier behaviour depends upon a number of factors including sediment properties porosity permeability grain size and wave climate since overwash processes are known to control short term gravel barrier dynamics and long term barrier migration a detailed quantification of overwash flow properties and induced bed changes is crucial overwash hydrodynamics of the prototype gravel barrier focused on the flow velocity depth and discharge over the barrier crest and the overwash flow progression across and the infiltration through the barrier during the bardex experiment overwash peak depth 0 77 m velocity 5 m s 1 and discharge max 6 m 3 m 1 were high especially considering the relatively modest wave energy significant wave height 0 8 m conversely to schemes found in the literature average flow depth did not linearly decrease across the barrier rather it was characterised by a sudden decrease at the crest a milder decrease at the barrier top and then propagation as a shallow water lens over the backbarrier the barrier morphological evolution was analysed over a series of 15 min experimental runs and at the timescale of individual overwash events overall the morphological variation did not result from an accumulation of many small consistently erosive or accretionary events but rather the mean bed elevation change per event was quite large 10 mm and the overall morphology change occurred due to a small imbalance in the number of erosive and accretionary events at each location two relationships between overwash hydrodynamic variables were deduced from results 1 between overwash flow depth and velocity a power type relation was obtained and 2 a linear relation was observed between overwash flow depth and maximum overwash intrusion distance across the barrier top i e overwash intrusion findings from this study are useful to enhance the knowledge of overwash processes and also have practical applications on the one hand results shown here can be use for the validation of overwash predictive models and additionally the simple empirical relations deduced from the dataset can be used by coastal managers to estimate overwash intrusion distance which in turn can assist in the location of areas under risk of overwash and breaching

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

concepts in gravel beach dynamics abstract the dominant processes in gravel beach dynamics are reviewed highlighting some common themes which unify the various components of the gravel beach system the repercussions of which impart on how gravel beach dynamics might be understood conceptually in particular gravel beach dynamics are thought to be highly dependent on the temporal and spatial variation in grain size and the continual adjustments made by an active beach step both of which act not only as the expression of changing morphodynamic conditions but also as a controlling influence morphodynamics the notion that the exchanges on beaches between the hydrodynamics sediment transport and morphological change takes the form of reciprocal relationships which are mediated through feedback mechanisms in such a way that they cannot be thought of or studied independently is not a new one yet it appears that for the gravel beach morphodynamics must be re defined to describe conditions where variations in sediment size are thought to deserve parity rather than as merely a sequent entity or boundary condition morpho sedimentary dynamics is a phrase coined to intuit such cause and effect detailing the co evolution of morphology hydro hydraulics and sediment properties whilst acknowledging causative pluralism feedbacks and multiplier effects this is the recommended conceptual framework within which to crystallise thought and organise further research for the gravel beach essentially it increases the minimum number of parameters needed to describe the state of the gravel beach as a physical system therefore it is advised that simplicity will be most expedient in our future modelling efforts if complexity is to be adequately encapsulated

a preliminary analysis of failure mechanisms in karst and man made underground caves in southern italy abstract natural and anthropogenic caves may represent a potential hazard for the built environment due to the occurrence of instability within caves that may propagate upward and eventually reach the ground surface inducing the occurrence of sinkholes in particular when caves are at shallow depth the effects at the ground surface may be extremely severe apulia region southern italy hosts many sites where hazard associated with sinkholes is very serious due to presence of both natural karst caves and anthropogenic cavities the latter being mostly represented by underground quarries the pliocene pleistocene calcarenite a typical soft rock was extensively quarried underground by digging long and complex networks of tunnels with time these underground activities have progressively been abandoned and their memory lost so that many apulian towns are nowadays located just above the caves due to urban expansion in the last decades therefore a remarkable risk exists for society which should not be left uninvestigated the present contribution deals with the analysis of the most representative failure mechanisms observed in the field for such underground instability processes and the factors that seem to influence the processes as for example those causing weathering of the rock and the consequent degradation of its physical and mechanical properties aimed at exploring the progression of instability of the cavities numerical analyses have been developed by using both the finite element method for geological settings represented by continuous soft rock mass and the distinct element method for jointed rock mass conditions both the effects of local instability processes occurring underground and the effects of the progressive enlargement of the caves on the overall stability of the rock mass have been investigated along with the consequent failure mechanisms in particular degradation processes of the rock mass as a consequence of wetting and weathering phenomena in the areas surrounding the caves have been simulated the results obtained from the numerical simulations have then been compared with what has been observed during field surveys and a satisfactory agreement between the numerical simulations and the instability processes as detected in situ has been noticed

a genetic classification of sinkholes illustrated from evaporite paleokarst exposures in spain this contribution analyses the processes involved in the generation of sinkholes from the study of paleokarst features exposed in four spanish tertiary basins bedrock strata are subhorizontal evaporites and in three of the basins they include halite and glauberite in the subsurface our studies suggest that formation of dolines in these areas results from a wider range of subsidence processes than those included in the most recently published sinkhole classifications a new genetic classification of sinkholes applicable to both carbonate and evaporite karst areas is thus proposed with the exception of solution dolines it defines the main sinkhole types by use of two terms that refer to the material affected by downward gravitational movements cover bedrock or caprock and the main type of process involved collapse suffosion or sagging sinkholes that result from the combination of several subsidence processes and affect more than one type of material are described by combinations of the different terms with the dominant material or process followed by the secondary one e g bedrock sagging and collapse sinkhole the mechanism of collapse includes any brittle gravitational deformation of cover and bedrock material such as upward stoping of cavities by roof failure development of well defined failure planes and rock brecciation suffosion is the downward migration of cover deposits through dissolutional conduits accompanied with ductile settling sagging is the ductile flexure of sediments caused by differential corrosional lowering of the rockhead or interstratal karstification of the soluble bedrock the paleokarsts we analysed suggest that the sagging mechanism not included in previous genetic classifications plays an important role in the generation of sinkholes in evaporites moreover collapse processes are more significant in extent and rate in areas underlain by evaporites than in carbonate karst primarily due to the greater solubility of the evaporites and the lower mechanical strength and ductile rheology of gypsum and salt rocks

collapse sinkholes and radar interferometry reveal neotectonics concealed within the dead sea basin 1 the dead sea ds pull apart basin is one of the more seismically active segments of the ds transform plate boundary in the last decade hundreds of collapse sinkholes have been formed along the ds coastlines in israel and jordan causing severe damage to the regional infrastructure the formation of these sinkholes is attributed to the dissolution of a buried salt layer by fresh groundwater due to the drop of the ds and the associated groundwater levels here we show that the sinkhole distribution combined with gradual land subsidence measured by radar interferometry insar track young fault systems suspected as active concealed within the fill of the ds rift this notion is supported by 1 sinkholes clustering along discrete lineaments with a striking trend similarity to that of the exposed rift margin faults 2 prominent discontinuities in seismic reflection profiles offsetting young sediments several kyrs old below sinkhole lines and 3 straight boundaries of gradual subsidence features that coincide with or parallel sinkhole lines combined the sinkhole lineaments and the insar measurements reveal a zigzag pattern of buried faults within the ds rift fill

insar based modeling and analysis of sinkholes along the dead sea coastline sinkholes commonly form by subsurface dissolution cavities that collapse after the overlying layers become mechanically unsupported sinkholes along the dead sea shorelines are preceded by associated with and followed by gradual surface subsidence that accompanies the cavities growth we exploit satellite radar interferometry interferometric synthetic aperture radar to resolve temporal and spatial relationships between gradual subsidence and sinkhole collapse the geometry of the deflating cavity roof is determined by elastic inverse modeling of the surface displacements a coulomb failure stress criterion is applied to calculate the stress field induced by the deflating cavity at the ground surface we find that the induced stress field favors generation of sinkholes at the perimeters of the subsiding areas rather than at their centers in agreement with field observations providing important information for sinkhole hazard assessment further our analysis suggests that short term deformation in consolidated gravel layers at shallow depths could be approximated by simple elastic modeling

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

large scale experiments on gravel and mixed beaches experimental procedure data documentation and initial results abstract this paper provides information on the experimental set up data collection methods and results to date for the project large scale modelling of coarse grained beaches undertaken at the large wave channel gwk of fzk in hannover by an international group of researchers in spring 2002 the main objective of the experiments was to provide full scale measurements of cross shore processes on gravel and mixed beaches for the verification and further development of cross shore numerical models of gravel and mixed sediment beaches identical random and regular wave tests were undertaken for a gravel beach and a mixed sand gravel beach set up in the flume measurements included profile development water surface elevation along the flume internal pressures in the swash zone piezometric head levels within the beach run up flow velocities in the surf zone and sediment size distributions the purpose of the paper is to present to the scientific community the experimental procedure a summary of the data collected some initial results as well as a brief outline of the on going research being carried out with the data by different research groups the experimental data is available to all the scientific community following submission of a statement of objectives specification of data requirements and an agreement to abide with the gwk and eu protocols

storm driven variability of the beach nearshore profile at duck north carolina usa 1981 1991 the us army corps of engineers field research facility frf at duck north carolina has collected approximately biweekly beach nearshore profile data to 8 m depth and associated wave data since 1981 sediment budget analysis was used to examine the medium scale years to a decade variability of the beach nearshore profile from 1981 to 1991 significant changes occurred during four groups of energetic storm events during february march of 1983 1987 1989 and december 1989 each group was comprised of at least two storms within a period of less than 39 days both with hmo 4 m during each storm group offshore sediment movement caused a distinct outer bar to migrate offshore and grow in size resulting in an abrupt increase in the volume of sediment on the upper shoreface the net profile changes were much larger than the changes due to single storms and the cumulative effect of the storms can be considered as one event during these events the first storm appears to have a destabilizing effect on the profile which has insufficient time to recover before the second and subsequent storm s as a result several storms in quick succession are able to have a large impact on the morphology the intervening periods between the groups of storm events termed fairweather conditions lasted up to 4 years they are characterized by slow but steady sediment redistribution averaging 33 m3 m 1 year 1 from the upper shoreface 5 m depth toward the shore while the total sediment volume was effectively constant the onshore feed of sediment was not significantly affected by individual storms during the fairweather conditions these two processes of 1 morphologic change during groups of storm events and 2 the steady onshore feed of sediments from the shoreface during fairweather conditions appear to play an important role on medium and long term profile evolution at least at duck

evolution of sinkholes over wink texas observed by high resolution optical and sar imagery abstract two caprock and cover collapse sinkholes wink sinks 1 and 2 in winkler county texas collapsed in 1980 and 2002 respectively they are located in a region underlain by the salado formation on the eastern edge of the delaware basin the sinkhole collapses were associated with intense hydrocarbon drilling and production activities in the hendrick oilfield production records and prior investigations imply the sinkholes developed after salt dissolution due to freshwater intrusion cavity formation roof failure and successive upward cavity migration high resolution 1 m aerial photography shows the ensuing expansion of wink sink 2 from 2002 through 2010 and relative stability of the ground surface after 2010 very high resolution 25 cm staring spotlight mode terrasar x reveals the spatiotemporal details of wink sinkhole deformations the vicinities around the two existing sinkholes wink sinks 1 2 deformed at a rate of 5 cm yr in line of sight los direction from october 2015 to march 2016 and the deformation was possibly caused by the gradual deposit of the debris from overlying unconsolidated alluvium and santa rosa sandstones infilling the cavity after the sinkhole collapse specifically the largest deformation of 53 cm yr in los direction was found 1 km east of wink sink 2 our study suggests that severe drought in 2011 widened and created fractures as well as ground fissures in the rocks overlying and underlying the salt formation due to the increased effective stress fractures ground fissures and the abandoned unplugged boreholes or improperly completed wells opened one or more vertical pathways of freshwater from groundwater flow and precipitation toward the salt bed finally causing the rapid salt dissolution and the opening of new cavities to explain the onset of a rapid subsidence near the wink sinkholes our study considers the combined effect of natural perturbation i e drought rock fractures ground fissures subsurface drainage precipitation and anthropogenic effects i e improper well control our method to explore high resolution imagery can be applied to characterize the sinkhole deformation and mitigate sinkhole related geohazards

high frequency in situ field measurements of morphological response on a fine gravel beach during energetic wave conditions this paper presents novel data collected over four weeks at loe bar a fine gravel barrier d50 3 5 mm exposed to energetic wave conditions hs10 2 4 m combined remote and in situ measurements were used to identify 3d morphological response profile change and runup behaviour during successive energetic periods hs 2 5 m small intertidal beach volume losses occurred under high steepness waves h0 l0 0 01 but in general the overall beach volume was remarkably stable in fact the greatest morphological response was evident not in cross shore sediment exchanges but due to the alongshore redistribution related to the three dimensional beach cusp system specifically during energetic wave conditions the cusp morphology underwent horn growth and embayment deepening leading to increased cusp definition an additional explanation for the stability of the cross shore beach profile is related to the development of the beach step during energetic conditions and long period waves significant deposition c 1 m occurred at the top of the beach step above the still water line the enhanced step provided a focal point for wave breaking considerably curtailing the swash motion and reducing the runup limit thereby providing protection to the upper beach this study provides much needed insight into complex morphological response and runup characteristics on gravel beaches fundamental for improved model development and leading towards better predictive tools

natural versus human control on subsurface salt dissolution and development of thousands of sinkholes along the dead sea coast one of the most hazardous results of the human induced dead sea ds shrinkage is the formation of more than 6000 sinkholes over the last 25 years the ds shrinkage caused eastward retreat of underground brine replaced by fresh groundwater which in turn dissolved a subsurface salt layer to generate cavities and collapse sinkholes the areal growth rate of sinkhole clusters is considered the most pertinent proxy for sinkholes development analysis of light detection and ranging lidar digital elevation models dems and interferometric synthetic aperture radar insar allows translation of the areal growth rate to a salt dissolution rate of the salt layer revealing two peaks in the history of the salt dissolution rate these peaks cannot be attributed to the decline of the ds level instead we show that they are related to long term variations of precipitation in the groundwater source region the judea mountains and the delayed response of the aquifer system between the mountains and the ds rift this response is documented by groundwater levels and salinity variations we thus conclude that while the ds level decline is the major trigger for sinkholes formation the rainfall variations more than 30 km to the west dominate their evolution rate the influence of increasing rainfall in the judea mountains reaches the ds at a typical time lag of four years and the resulting increase in the salt dissolution rate lags by a total time of 5 6 years

sinkholes in the salt bearing evaporite karst of the ebro river valley upstream of zaragoza city ne spain geomorphological mapping and analysis as a basis for risk management abstract a detailed sinkhole map has been produced in a stretch of the ebro valley 40 8 km2 including the western sector of zaragoza city ne spain during the last few decades around 70 of the original sinkhole area has been filled with anthropogenic sediments causing the disappearance of 137 ha of wetlands the interstratal karstification of salts halite and glauberite and a wnw ese trending joint set have played a major control in the development of sinkholes three morphometric types of sinkholes have been differentiated each attributed to a specific subsidence mechanism inferred from the paleosinkholes exposed in the surrounding of zaragoza city sagging of bedrock and cover collapse of bedrock and cover and collapse of cover material related to the downward migration of particles through dissolutional conduits each type of sinkhole is characterised by a distinctive behaviour in terms of controlling factors spatio temporal distribution and kinematics and consequently the proposed differentiation may have a practical utility the vast majority of the subsidence damage identified in the area occurs within the boundaries of pre existing sinkholes identifiable in old aerial photographs and topographical maps this fact demonstrates that the application of preventive planning strategies based on detailed geomorphological maps would have allowed avoidance of most of the large financial losses caused by subsidence in the area of the order of hundreds of thousands of euros per year

integrating geomorphological mapping trenching insar and gpr for the identification and characterization of sinkholes a review and application in the mantled evaporite karst of the ebro valley ne spain abstract this contribution illustrates the advantages of integrating conventional geomorphological methods with insar ground penetrating radar and trenching for sinkhole mapping and characterization in a mantled evaporite karst area where a significant proportion of the karstic depressions have been obliterated by artificial fills the main practical aim of the investigation was to elucidate whether buried sinkholes overlap the areas planned for the construction of buildings and services in order to apply a preventive planning strategy old aerial photographs and detailed topographic maps were the most useful sources of information for the identification of sinkholes and helped to obtain information on their chronology either a minimum age or bracketing dates the insar technique provided subsidence rate values ranging from 4 4 to 17 3 mm yr consistent with the spatial distribution of the mapped sinkholes this quantitative deformation data helped corroborating independently the existence of active buried sinkholes and improving the delineation of their limits the gpr profiles contributed to the precise location of sinkhole edges provided information on the geometry of buried sinkholes and deformation structures and helped to site trenches and to rule out the existence of sinkholes in particular areas the main input derived from the trenches includes 1 confirming or ruling out anomalies of the gpr profiles attributable to subsidence 2 precise location of the edge of some filled sinkholes 3 information on subsidence mechanisms recorded by various deformation structures and cumulative subsidence magnitude 4 calculating minimum long term subsidence rates using radiocarbon dates obtained from deformed sinkhole deposits 5 unequivocal evidence of active subsidence in areas assigned for the construction of buildings

dinsar measurements of ground deformation by sinkholes mining subsidence and landslides ebro river spain differential interferometric synthetic aperture radar dinsar has been applied to detect and measure ground deformation in a stretch of the ebro river valley spain excavated in salt bearing evaporites the capability of the small baseline subset sbas dinsar technique to detect ground displacement is analyzed comparing the dinsar results with the available geomorphological information the deformation map derived from 27 european remote sensing ers satellite images covering more than five years provides sub centimeter displacement measurements in zones coinciding with known active sinkholes and landslides moreover the map provides the first account of mining subsidence in the area the measured deformation rates reach 1 68 cm y for the sinkholes 0 80 cm y for the landslides and 1 45 cm y for the area affected by mining subsidence the sbas dinsar technique provided deformation measurements in a small proportion 5 10 of the known active sinkholes and landslides this limitation is mainly due to the lack of coherence in agricultural areas the spatial resolution of the deformation map pixel size of 90 m and the parallelism between the ers satellite line of sight and the linear escarpment on which most of the landslides occur despite this the interferometric technique provides valuable data that complement traditional geomorphological studies including the quantification of the deformation phenomena the identification of mining subsidence otherwise only recognizable by geodetic methods and the detection of creep deformation which might correspond to premonitory indicators of catastrophic sinkholes and landslides capable of causing the loss of lives detailed dinsar studies combined with field data would be required to improve the analysis of each deformation area copyright 2009 john wiley sons ltd

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

surface subsidence induced by the crandall canyon mine utah collapse insar observations and elasto plastic modelling summary the crandall canyon mine utah collapse in 2007 august resulted in a total of nine fatalities we processed data from the alos satellite acquired before and after the collapse to quantify surface subsidence associated with the collapse to better understand the collapse process the deformationshowsasteepv shapedpatternofsubsidencewithslightasymmetry wecompare the fit of four different models that simulate the subsidence pattern the first two models use elastic half space rheology we find that collapse alone cannot explain the observations and a component of normal faulting is required to fit the data the second set of models simulates collapseinelasto plasticmedia onlyasmallcomponentofnormalfaultingisrequiredinthese models we suggest that considering elasto plastic material behaviour is particularly important for shallow deformation modelling where microfractures and other non elastic rheology are common disregarding this material behaviour can lead to biased model parameter estimates

geochemical and geophysical responses during the infiltration of fresh water into the contaminated saprolite of the oak ridge integrated field research challenge site tennessee 1 at the oak ridge integrated field research challenge ifrc site tennessee the saprolitic aquifer was contaminated by leaks from the former s 3 disposal ponds between 1951 and 1983 the chemistry of the contaminant plume is also episodically impacted by fresh meteoritic water infiltrating vertically from a shallow variably saturated perched zone and the ditch surrounding the former s 3 ponds we performed a column experiment using saprolite from the contaminated aquifer to understand the geochemical and complex electrical conductivity signatures associated with such events the changes in the ph and pore water ionic strength are responsible for measurable changes in both the in phase and quadrature conductivities the pore water conductivity can be related to the nitrate concentration the main ionic species in the plume while the release of uranium is controlled by the ph we developed a simple model to determine the pore water conductivity and ph from the recorded complex conductivity this model is applied to time lapse resistivity data at the ifrc site time lapse inversion of resistivity data performed with an active time constrain approach shows the occurrence of an infiltration event during the winter of 2008 2009 with a dilution of the pore water chemistry and an increase of the ph a simple numerical simulation of the infiltration of fresh water into the unconfined contaminated aquifer is consistent with this scenario

ert gpr insar and tracer tests to characterize karst aquifer systems under urban areas the case of quebec city abstract urban infrastructures built over karst settings may be at risk of collapse due to hydro chemical erosion of underlying rock structures in such settings mapping cave networks and monitoring ground stability is important to assure civil safety and guide future infrastructure development decisions however no technique can directly and comprehensively map these hydrogeological features and monitor their stability the most reliable method to map a cave network is through speleological exploration which is not always possible due to restrictions narrow corridors passages or high water levels borehole drilling is expensive and is often only performed where the presence of karsts is suggested by other techniques numerous indirect and cost effective methods exist to map a karst flow system such as geophysics geodesy and tracer tests this paper presents the outcomes from a challenging application in quebec city canada where a multidisciplinary approach was designed to better understand the groundwater dynamics and cave paths two tracer tests in groundwater flowing through the cave system indicated that water flows along an approximately straight path from the sinking stream to the spring it also suggests the presence of a parallel flow path close to the one already partially mapped this observation was confirmed by combining ground penetrating radar gpr and electrical resistivity tomography ert techniques and ultimately by observing voids in several boreholes drilled close to the main cave path lowering the water levels at the suspected infiltration zone and inside the karst the infiltration cracks were identified and the hydraulic link between them was confirmed in fact almost no infiltration occurs into the karst system when the water level at the sinking stream drops below a threshold level finally sar interferometry insar using radarsat 2 images detected movements on few buildings located over a backfilled sinkhole intercepted by the karst system and confirmed the stability of the rest of the karst area the knowledge of the flow system described in this paper is used by policy makers to assure civil security of this densely populated area

sinkholes subsidence and subrosion on the eastern shore of the dead sea as revealed by a close range photogrammetric survey abstract ground subsidence and sinkhole collapse are phenomena affecting regions of karst geology worldwide the rapid development of such phenomena around the dead sea in the last four decades poses a major geological hazard to the local population agriculture and industry nonetheless many aspects of this hazard are still incompletely described and understood especially on the eastern dead sea shore in this work we present a first low altitude our analysis reveals a kilometer scale sinuous depression bound partly by flexure and partly by non tectonic faults the estimated minimum volume loss of this subsided zone is 1 83 106 m3 with an average subsidence rate of 0 21 m yr 1 over the last 25 years sinkholes in the surveyed area are localized mainly within this depression the sinkholes are commonly elliptically shaped mean eccentricity 1 31 and clustered nearest neighbor ratio 0 69 their morphologies and orientations depend on the type of sediment they form in in mud sinkholes have a low depth to diameter ratio 0 14 and a long axis azimuth of nne ne in alluvium sinkholes have a higher ratio 0 4 and are orientated nnw n from field work we identify actively evolving artesian springs and channelized sediment laden groundwater flows that appear locally in the main depression consequently subrosion i e subsurface mechanical erosion is identified as a key physical process in addition to dissolution behind the subsidence and sinkhole hazard furthermore satellite image analysis links the development of the sinuous depression and sinkhole formation at ghor al haditha to preferential groundwater flow paths along ancient and current wadi riverbeds