using lidar data to map gullies and headwater streams under forest canopy south carolina usa abstract the southeastern piedmont of the usa was severely gullied during the early 20th century a thick canopy established by reforestation in many areas now inhibits the identification or mapping of gullies by aerial photography or other conventional remote sensing methods an airborne laser scanning als or lidar mapping mission flown for the u s forest service in april 2004 acquired bare earth topographic data this paper tests the ability of the als topographic data to identify headwater channels and gullies for two branching gully systems in forested areas and to extract gully morphologic information comparisons are made with field traverses using differential gps and reference cross sections measured by leveling surveys at the gully network scale lidar data provide accurate maps the best available with robust detection of small gullies except where they are narrow or parallel and closely spaced errors in mapping channel location and network topological connectivity under forest canopy increase with attempts to identify smaller features such as large rills the ability of lidar data to map gullies and channels in a forested landscape should improve channel network maps and topological models at the gully reach scale attempts to use lidar data to extract gully cross section morphologic information under forest canopy were less successful due to systematic underestimation of gully depths and overestimation of gully top widths limited morphologic accuracy of the data set at this scale may be due to low bare earth point densities shadowing of gully bottoms and filtering of topographic discontinuities during post processing the als data used in this study are not suitable for detailed morphometric analysis or subtle change detection to monitor gullies or develop sediment budgets data collection may be improved by orienting flights over gullies and with increased point densities through improved scanner technology or better filtering and software capabilities to differentiate between vegetation and ground surfaces

analysis of dolines using multiple methods applied to airborne laser scanning data abstract delineating dolines is not a straightforward process especially in densely vegetated areas this paper deals quantitatively with the surface karst morphology of a miocene limestone occurrence in the styrian basin austria the study area is an isolated karst mountain with a smooth morphology former planation surface of pliocene age densely vegetated mixed forest and with a surface area of 1 3 km 2 the study area is located near the city of wildon and is named wildoner buchkogel the aim of this study was to test three different approaches in order to automatically delineate dolines the data basis for this was a high resolution digital terrain model dtm derived from airborne laser scanning als and with a raster resolution of 1 1 m the three different methods for doline boundary delineation are a the traditional method based on the outermost closed contour line b boundary extraction based on a drainage correction algorithm filling up pits and c boundary extraction based on hydrologic modelling watershed extracted features are integrated in a gis environment and analysed statistically regarding spatial distribution shape geometry elongation direction and volume the three methods lead to different doline boundaries and therefore investigated parameters show significant variations the applied methods have been compared with respect to their application purpose depending on delineation process between 118 and 189 dolines could be defined the high density of surface karst features demonstrates that solutional processes are major factors in the landscape development of the wildoner buchkogel furthermore the correlation to the landscape evolution of the grazer bergland is discussed

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

the mass balance of circum arctic glaciers and recent climate change the sum of winter accumulation and summer losses of mass from glaciers and ice sheets net surface mass balance varies with changing climate in the arctic glaciers and ice caps excluding the greenland ice sheet cover about 275 000 km2of both the widely glacierized archipelagos of the canadian norwegian and russian high arctic and the area north of about 60 n in alaska iceland and scandinavia since the 1940s surface mass balance time series of varying length have been acquired from more than 40 arctic ice caps and glaciers most arctic glaciers have experienced predominantly negative net surface mass balance over the past few decades there is no uniform recent trend in mass balance for the entire arctic although some regional trends occur examples are the increasingly negative mass balances for northern alaska due to higher summer temperatures and increasingly positive mass balances for maritime scandinavia and iceland due to increased winter precipitation the negative mass balance of most arctic glaciers may be a response to a step like warming in the early twentieth century at the termination of the cold little ice age arctic ice masses outside greenland are at present contributing about 0 13 mm yr 1to global sea level rise

on the size distribution of solution dolines in carbonate karst lognormal or power model abstract dolines or closed karst depressions are the most characteristic feature of karst landscapes the two main types of doline are those formed by the removal of material by solution and those formed by the geological processes of collapse or suffosion solution dolines are most frequently found in carbonate karst in high relief karst massifs various algorithms can be used to identify and delineate dolines in high resolution digital elevation models dem where the lower size limit is determined by the resolution of the dem i e the size of the cell or the dem pixel in terrain units the work presented here addresses the size distribution of dolines which is a significant component of the geomorphometric analysis of dolines on the basis of experimental results various authors have advocated the lognormal or the power distribution as the best fit to experimental data a power distribution is consistent with a fractal structure implying the fractal nature of the sizes of dolines which in turn may reflect a relationship between size and the structural controls of fracture networks and the fractal fragmentation of the terrain this paper presents case studies of four karst landscapes that are representative of karst massifs in spain two of these are located in the pyrenees in the north of spain and two are located in the betic mountains in the south of spain in all four cases a lognormal distribution provides a bad fit while a power law distribution provides a good fit in three cases and in the fourth case provides a good fit for dolines that have a diameter greater than 50 m

characterization of cover collapse sinkhole morphology on a groundwater basin wide scale using lidar elevation data a new conceptual model for sinkhole evolution abstract in karst regions of the world identifying areas that are inherently unsafe for certain types of land use is crucial high resolution lidar elevation data for the illinois sinkhole plain have exposed previously unnoticed geomorphologic details analysis of these data has revealed a pattern of long term evolution of cover collapse sinkholes within the groundwater basins the leading edge of a groundwater basin is known to be the site of progressively enlarging bedrock crevices and conduits that encroach into groundwater divides in karst areas of the u s midwest runoff creates surface streams at groundwater divides that flow into groundwater basins and form disappearing streams using this pattern as a starting point we developed a new conceptual model of cover collapse sinkhole development and evolution within groundwater basins as the boundaries of a groundwater basin migrate outward for tens of thousands of years stream valley shaped sinkholes at the leading edge seemingly migrate deeper into the basin the stream valley sinkholes then form numerous drains join other sinkholes through erosion and collapse along sinkhole boundaries and eventually become areally extensive and irregularly shaped compound sinkholes continued erosion of fine grained sediment overlying bedrock near the distal end of the groundwater basin reduces the elevation of land surface until nested sinkholes within the compound sinkholes become simple sinkholes with a single drain point near the discharge points of the groundwater basin the individual drains associated with the simple sinkholes partition the remaining upland surface forming a pattern of thiessen or voronoi polygons resulting from surface runoff among adjacent sinkholes

automated delineation of karst sinkholes from lidar derived digital elevation models abstract sinkhole mapping is critical for understanding hydrological processes and mitigating geological hazards in karst landscapes current methods for identifying sinkholes are primarily based on visual interpretation of low resolution topographic maps and aerial photographs with subsequent field verification which is labor intensive and time consuming the increasing availability of high resolution lidar derived digital elevation data allows for an entirely new level of detailed delineation and analyses of small scale geomorphologic features and landscape structures at fine scales in this paper we present a localized contour tree method for automated extraction of sinkholes in karst landscapes one significant advantage of our automated approach for sinkhole extraction is that it may reduce inconsistencies and alleviate repeatability concerns associated with visual interpretation methods in addition the proposed method has contributed to improving the sinkhole inventory in several ways 1 detection of non inventoried sinkholes 2 identification of previously inventoried sinkholes that have been filled 3 delineation of sinkhole boundaries and 4 characterization of sinkhole morphometric properties we applied the method to fillmore county in southeastern minnesota usa and identified three times as many sinkholes as the existing database for the same area the results suggest that previous visual interpretation method might significantly underestimate the number of potential sinkholes in the region our method holds great potential for creating and updating sinkhole inventory databases at a regional scale in a timely manner

lidar dem error analyses and topographic depression identification in a hummocky landscape in the prairie region of canada abstract topographic depressions are abundant in topographically complex landscapes a common practice with earlier low resolution digital elevation models dems was to remove all depressions to ensure that water flowed continuously to the edge of the dem domain the assumption was that most depressions were created due to errors in the dems this practice is no longer justified with the increasing availability of high accuracy dems however very few studies have addressed how dem processing options such as smoothing and coarsening and setting area and depth thresholds can affect depression identification in this study a site located in the prairie region of canada was examined the site is a hummocky glaciated landscape with many in field wetlands lidar topographic data were collected and were used to generate a 1 m by 1 m square grid dem detailed error analyses of the lidar dem were conducted a set of dems were generated after different degrees of smoothing and coarsening flowmapr an established terrain analysis tool was used to identify depressions in each dem with various user defined area and depth thresholds the results were validated against a field wetland survey we determined that the problems associated with depression identification using a lidar dem are two fold on one hand artefactual depressions created due to dem errors need to be eliminated for which the raw lidar dem need to be smoothed on the other hand it is also desirable to remove those topographic depressions that do not function as closed basins at the spatial or temporal scale of the processes of interest setting area and depth thresholds appeared to be the preferred choice for this we suggested using the un autocorrelated lidar dem error as the criterion for dem smoothing and considering depression connections in the selection of area and depth thresholds using lidar data on a hummocky landscape with loamy soils in the prairie region of canada 10 to 20 times smoothing operations with an area threshold of 200 m2 and a depth threshold of 0 1 m were recommended as guidelines for depression identification

the effect of continentality on glacier response and mass balance the continentality index is a good measure of the nature of the climate in a region as it reflects not only the temperature but also the large scale circulation it correlates well with glacier mass balance parameters the climate along the west east transect slightly north of the arctic circle across the scandinavian caledonides is gov erned by the prevailing westerlies however during winter the eastern part of the caledo nides is ini1uenced by weather systems from the southeast the differences in continentality meant by temperature and precipitation have a major impact on the res ponse times of glaciers the climatic change in this area has been dominated by increased summer mean temperatures 1910 20 and increased maritime influence since the 1980s the slower reacting glaciers on the swedish side of the mountains are still adapting to the temperature increase at the beginning of the 20th century and the increase in maritime influence gradually becomes less important towards the west thus differences in the be haviour of glacier fronts along the west east transect mirror differences in continentality

glacier change in northern sweden from ad 500 a simple geometric model of storglaciaren a simple geometric model of glacier volume is derived the model is based on the assumption that the net mass balance averaged over the glacier surface is related to the summer temperature and winter accumulation at a representative height on the glacier this height varies with time as climate changes in ways that are determined by the geometry of the glacier surface expressions are derived for the equilibrium glacier volume v eq as a function of summer temperature and winter accumulation and for the glacier response time as a function of volume the model is used to reconstruct the volume of storglaciaren over the period ad 500 1992 measured net mass balance data for storglaciren 1946 92 are used to estimate the model parameters for the summer temperature forcing the long treering based temperature reconstruction for northern fennoscandia is used to extend a temperature record near the glacier back to ad 500 for the past accumulation forcing a range of assumptions is tested the results show that the prime cause of the decrease in volume of storglaciaren between 1946 and 1992 was relatively low accumulation over 1946 89 as opposed to warm temperatures as previously supposed reconstructed volume changes agree well with geomorphological evidence where differences occur deductions can be made about past accumulation for example the maximum reconstructed glacier volume is associated with the cold period from 1580 to 1740 but relatively low accumulation probably limited the volume to values not much larger than that achieved around 1916

an integrated framework to identify and analyze karst sinkholes abstract sinkholes are the most typical surface feature of karst landscapes their correct mapping is of great importance for a proper assessment of the possible occurrence of new events and the likely effects they could have on the anthropogenic environment in this work we compare and discuss different ways to map sinkholes including heuristic approach automatic mapping through different resolution dtms and digital aerial photo interpretation aimed at highlighting advantages and drawbacks of the multiple approaches for our purpose we use a study area in the murge of apulia se italy where many sinkholes of several typologies are present to characterize the landscape to evaluate the reliability of the sinkhole mapping we set up a conceptual methodology that integrates a semi automatic method with the heuristic approach with a special focus on the importance of incorporating digital stereoscopic interpretation in detail we used as input two dtms at different resolution aimed to test the robustness of the automatic method in different circumstances comparison of the data produced by the different approaches illustrated how the number density and boundaries of the sinkholes may vary as a function of the input data the automated mapping provides reliable results in terms of number dimensions and morphometric attributes of sinkholes and appears to be particularly useful when large areas must be analyzed within the whole process we stress the role of the expert geomorphologist who must determine the accuracy of the product obtained with the automated mapping by correcting eliminating features not attributable to karst processes the presented approach highlights the potential of digital stereoscopy in substantially decreasing the errors encountered with traditional analog mapping simultaneously reducing the working time significantly

using alsm to map sinkholes in the urbanized covered karst of pinellas county florida 1 methodological considerations comparison of a database of interpreted sinkholes made using airborne laser swath mapping alsm with databases of sinkholes made from interpretation of aerial photographs reveals substantial disagreement the discrepancies involve the location number areas and circularity of interpreted sinkholes methodological factors that contribute to the discrepancies include blockage of alsm laser returns in thick vegetation multi path reflections and misrepresentation of the true extent of sinkholes comparison of two alsm derived databases made 1 independently from versus 2 in combination with earlier air photo analysis in undeveloped regions had the following result one fourth of the sinkholes interpreted by using the composite method were missed by the independent analysis and one third of the sinkholes that were interpreted from the independent analysis were not interpreted as sinkholes using the composite method subjective interpretation leads to a high level of uncertainty such that the results of the remote sensing studies are suspect if not invalid

object oriented identification of forested landslides with derivatives of single pulse lidar data in contrast to the many studies that use expert based analysis of lidar derivatives for landslide mapping in forested terrain only few studies have attempted to develop semi automatic methods for extracting landslides from lidar derivatives while all these studies are pixel based it has not yet been tested whether object oriented analysis ooa could be an alternative this study investigates the potential of ooa using only single pulse lidar derivatives such as slope gradient roughness and curvature to map landslides more specifically the focus is on both lidar data segmentation and classification of slow moving landslides in densely vegetated areas where spectral data do not allow accurate landslide identification a multistage procedure has been developed and tested in the flemish ardennes belgium the procedure consists of 1 image binarization and multiresolution segmentation 2 classification of landslide parts main scarps and landslide body segments and non landslide features i e earth banks and cropland fields with supervised support vector machines at the appropriate scale 3 delineation of landslide flanks 4 growing of a landslide body starting from its main scarp and 5 final cleaning of the inventory map the results obtained show that ooa using lidar derivatives allows recognition and characterization of profound morphologic properties of forested deep seated landslides on soil covered hillslopes because more than 90 of the main scarps and 70 of the landslide bodies of an expert based inventory were accurately identified with ooa for mountainous areas with bedrock on the other hand creation of a transferable model is expected to be more difficult

the influence of drought and anthropogenic effects on groundwater levels in orissa india summary investigating the response of groundwater levels to the extreme weather events provides essential information for sustainable planning and management of water resources the aim of this study was to identify and quantify the groundwater level trend of the state orissa india to understand the forcing mechanism of droughts in conjunction with the anthropogenic pressure using the non parametric mann kendall statistical procedure the pre and post monsoon groundwater level records of 1002 monitoring stations during the period 1994 2003 were analyzed the results show that the drawdowns due to deficient rainfall during dry years high temperatures and anthropogenic pressure have not been recovered through the recharge in wet years however this study does not determine whether drought high temperatures or anthropogenic effects have had largest influence on the groundwater levels decline the cases of significant water table declines are higher in number than those expected to occur by chance in the pre monsoon season 59 of the monitoring stations experienced groundwater declines as against 51 in the post monsoon season for the study area as a whole this could be interpreted that the fluctuation is not a part of noise but that a signal is being identified further the trend result showed wide spatial and seasonal differences irrespective of seasons the consolidated rock formation that covers 80 of the geographical area experienced significant water table decline however the semi consolidated and unconsolidated formations experienced water table decline in the pre monsoon summer season only the vulnerable sites where the groundwater level declined significantly were identified so that recharge measures could be taken up

extrusion flow demonstrated by bore hole deformation measurements over a riegel storglaciaren sweden inclinometry measurements in a 126 m bore hole slightly down glacier from the crest of a riegel on storglaciaren showed what appears to be indisputable extrusion flow during the last 3 weeks of july 1984 the velocity at the bed was about five times that at the surface and lay in a direction deviating 50 60 from that at the surface the increase in velocity with depth began more than 50 m above the bed in august and the first half of september the flow returned nearly to normal with only a slight tendency toward extrusion the flow in july appeared to be related to a period of large diurnal water pressure variation and cavity opening at the bed up glacier from the riegel decoupling of the ice from the bed on the lowest parts of the riegel may have permitted the extrusion the return to more normal conditions in august appears to have been related to a decrease in ice flux over the riegel and a widening of the zone of decoupling

geospatial technologies and digital geomorphological mapping concepts issues and research geomorphological mapping plays an essential role in understanding earth surface processes geochronology natural resources natural hazards and landscape evolution it involves the partitioning of the terrain into conceptual spatial entities based upon criteria that include morphology form genetics process composition and structure chronology environmental system associations land cover soils ecology as well as spatial topological relationships of surface features landforms historically the power of human visualization was primarily relied upon for analysis introducing subjectivity and biases with respect to selection of criteria for terrain segmentation and placement of boundaries this paper reviews new spatio temporal data and geocomputational approaches that now permit earth scientists to go far beyond traditional mapping permitting quantitative characterization of landscape morphology and the integration of varied landscape thematic information numerous conceptual theoretical and information technology issues are at the heart of digital geomorphological mapping dgm and scientific progress has not kept pace with new and rapidly evolving geospatial technologies consequently new capabilities exist but numerous issues have not been adequately addressed therefore this paper discusses conceptual foundations and illustrates how geomorphometry and mapping approaches can be used to produce geomorphological information related to the land surface and landforms process rates process form relationships and geomorphic systems

evaluation of tandem x elevation data for geomorphological mapping and interpretation in high mountain environments a case study from se tibet china abstract digital elevation models dems are a prerequisite for many different applications in the field of geomorphology in this context the two near global medium resolution dems originating from the srtm and aster missions are widely used for detailed geomorphological studies particularly in high mountain environments these datasets are however known to have substantial disadvantages beyond their posting i e data gaps and miscellaneous artifacts the upcoming tandem x dem is a promising candidate to improve this situation by application of state of the art radar technology exhibiting a posting of 12 m and less proneness to errors in this study we present a dem processed from a single tandem x cossc scene covering a study area in the extreme relief of the eastern nyainqentanglha range southeastern tibet the potential of the resulting experimental tandem x dem for geomorphological applications was evaluated by geomorphometric analyses and an assessment of landform cognoscibility and artifacts in comparison to the aster gdem and the recently released srtm 1 dem detailed geomorphological mapping was conducted for four selected core study areas in a manual approach based exclusively on the tandem x dem and its basic derivates the results show that the self processed tandem x dem yields a detailed and widely consistent landscape representation it thus fosters geomorphological analysis by visual and quantitative means allowing delineation of landforms down to footprints of 30 m even in this premature state the tandem x elevation data are widely superior to the aster and srtm datasets primarily owing to its significantly higher resolution and its lower susceptibility to artifacts that hamper landform interpretation conversely challenges toward interferometric dem generation were identified including i triangulation facets and missing topographic information resulting from radar layover on steep slopes facing toward the radar sensor ii low coherence values on leeward slopes iii decorrelation effects over water bodies and iv challenges for phase unwrapping in settings of strong topographic contrasts there is however a high probability that these drawbacks can be overcome by applying multiple interferograms exhibiting different perpendicular baselines as planned for the generation of the final tandem x dem product

identification of karst sinkholes in a forested karst landscape using airborne laser scanning data and water flow analysis abstract karst sinkholes dolines play an important role in a karst landscape by controlling infiltration of surficial water air flow or spatial distribution of solar energy these landforms also present a limiting factor for human activities in agriculture or construction therefore mapping such geomorphological forms is vital for appropriate landscape management and planning there are several mapping techniques available however their applicability can be reduced in densely forested areas with poor accessibility and visibility of the landforms in such conditions airborne laser scanning als provides means for efficient and accurate mapping of both land and landscape canopy surfaces taking the benefits of als into account we present an innovative method for identification and evaluation of karst sinkholes based on numerical water flow modelling the suggested method was compared to traditional techniques for sinkhole mapping which use topographic maps and digital terrain modelling the approach based on simulation of a rainfall event very closely matched the reference datasets derived by manual inspection of the als digital elevation model and field surveys however our process based approach provides advantage of assessing the magnitude how sinkholes influence concentration of overland water flow during extreme rainfall events this was performed by calculating the volume of water accumulated in sinkholes during the simulated rainfall in this way the influence of particular sinkholes on underground geomorphological systems can be assessed the method was demonstrated in a case study of slovak karst in the west carpathians where extreme rainfalls or snow thaw events occur annually we identified three spatially contiguous groups of sinkholes with a different effect on overland flow concentration these results are discussed in relation to the known underground hydrological systems

is the longitudinal profile of storglaciaren northern sweden in balance with the present climate the main perturbation in the mass balance of storglaciaren during the twentieth century was caused by a sudden 1 c increase in the summer mean temperature around 1910 later perturbations of the climate have been of minor importance in relation to the mass balance annual field surveys suggest that the mass budget on storglaciaren has been in near balance for the last 15 years because of this major step like change we can establish the validity of theoretical models giving response times for storglaciaren of the order of 50 years according to these models storglaciaren could by now have reached a profile in balance with the present climate to study this problem the emergence velocity was calculated and compared with the net balance the result shows that the emergence velocity either balances or exceeds the net balance for the entire tongue except for the lowermost part where it decreases to about half of the net balance a slight further recession of the front position would thus be expected with today s climate calculated balance velocities also suggest that most of the present profile is close to a steady state profile if the mean annual sliding velocity is about 50 of the surface velocity lower sliding velocities would imply a thickening

the non synchronous response of rabots glaciar and storglaciaren northern sweden to recent climate change a comparative study rabots glaciar and storglaciaren two small valley glaciers in the swedish arctic have not behaved synchronously in response to recent climate change both glaciers advanced late in the 19th century and then began to retreat in response to a 18c warming that occurred around 1910 by the mid 1980s the terminus and volume of storglaciaren had essentially stabilized so it may have completed its response to the earlier warming in contrast ongoing thinning and retreat of rabots glaciar are substantial and suggest its response time is considerably longer a time dependent numerical model was used to investigate each glacier s response to perturbations in mass balance this modeling suggests that for small perturbations volume timescales for storglaciaren and rabots glaciar are 125 and 215 years respectively another measure of response time i e length response time yields somewhat lower values for each glacier however what is significant is that by either measure and accounting for uncertainties the response time for rabots glaciar is consistently about 1 5 times longer than that for storglaciaren this implies that their non synchronous behavior is likely due to differences in response times the latter ultimately result from markedly different longitudinal geometries particularly near the termini velocity profiles and specific net balance gradients

new morphostructural subdivision of the western carpathians an approach integrating geodynamics into targeted morphometric analysis abstract a new quantitative method of morphostructure delimitation based on targeted morphometric analyses and multivariate statistical methods was applied to the western carpathians nine specific morphostructural regions and sixteen subregions were defined as an improvement on the preceding qualitative subdivision of the area the integration of geodynamics into the targeted morphometric analysis represents a prerequisite for better interpretability of the delimited regions the new subdivision of the western carpathians therefore reflects first of all the pliocene quaternary geodynamics that controls the development of the present day relief the results also help to understand the timing of the basic dome like morphostructural formation of the western carpathians which began 4 6 million years ago with the main stage continuing until the late pliocene and accelerated uplift taking place since the middle pleistocene as well as the mechanism of its formation the importance of the middle miocene extension for the development of the basin and mountain mosaic unique to the western carpathians is documented the projection of the older structural boundaries into the new morphostructural regions and the increasing prevalence of the young morpholineament systems n s and w e on the southern and northern periphery of the western carpathians could be an indication of the gradual spreading of the western carpathians into the surrounding lowlands during the last stage of the morphotectonic development

tv video observations of bed and basal sliding on storglaciaren sweden four boreholes in storglaciaren a small valley glacier in northernsweden were inspected with a video camera in two of the boreholes the apparentglacier bed was filmed in one borehole the bed was found to be composed of softsediment but in the other it consisted of bedrock in the latter the camera moved5 6 mm relative to the bed during an 80 min period the recorded camera movementshowed a background motion which is in the expected range of basal sliding superimposed on the background motion a jerky motion of a high speed spike wasfound the jerky motion is interpreted as a stress release induced by local topographyat the ice bed interface

assessing the impact of groundwater abstractions on river flows abstract groundwater abstractions affect the water balance in catchments of rivers in hydraulic continuity with groundwater and may lead to reductions in river baseflow the environment agency issues licences for groundwater abstractions and takes into account the risk of such adverse impacts when deciding whether to grant licences and what conditions to associate with each licence assessing the impact of a particular licence is a difficult task but analytical solutions to idealizations of the complex river aquifer interaction can help guide such judgements this paper presents a brief review of available analytical solutions and discusses their applicability to real groundwater systems the most useful analytical solutions developed by theis hantush and stang have been incorporated into a spreadsheet and a new methodology has been made available to support environment agency hydrogeologists working in abstraction licensing this offers a consistent approach to making an initial evaluation of the impact of groundwater abstraction on river flow that may be applied across the diverse hydrogeological systems found throughout the environment agency regions of england and wales the use of analytical solutions in this methodology inevitably represents a significant simplification of what is generally a very complex issue and the limitations of the new methodology are emphasized

karstic conduits and watershed identification based on the morphological characteristics of depressions in the yunnan guizhou plateau of china in the investigation of karstic form and underground karst water determination of the location and geometric properties of karstic conduits and underground watersheds is one of the greatest problems not yet adequately resolved in the karst terrain of the yunnan guizhou plateau of china karst depressions are a product of the formation and evolution of the groundwater system and the distribution of these depressions is a direct result of crustal uplift and the development of karstic conduits this terrain is characterized by differences in morphological characteristics of depressions between the region of recharge and the region of outflow discharge the region of recharge is marked extensively by circular and random depressions and is characterized by depressions with higher bottom elevations referred to here as higher depressions conversely the region of outflow and discharge is marked extensively by depressions that form long strips or irregular alignments that are distributed along with the karstic conduits and is characterized by depressions with lower bottom elevations referred to here as lower depressions here a methodology has been put forward to determine the possible location and principal directions of karstic conduits and underground hydrogeological watersheds based on surface morphological features of depressions in the region of the yunnan guizhou plateau china the methodology assumes that the contour map that results from determining the bottom elevations of karstic depressions is sufficient to determine the positions of underground hydrogeological divisions and karstic channels taking the two main conduits systems in guizhou province as an example a digital elevation model dem was derived from 1 10 000 scale topographic maps with arcgis 10 2 and the bottom elevations of depressions were marked then a contour map of the bottom elevations of the depressions was produced the directions of conduits and underground watersheds in the research area were identified from the valleys and ridges of the contour lines the methodology introduced in this paper offers a new means of determining the location and geometric properties of karstic conduits and extracting the spatial distribution of water systems in the region of the yunnan guizhou plateau china this methodology will be appropriate for investigating karstic areas with continuous crustal uplift and significant variation in the bottom elevation of depressions between the region of recharge and region of discharge

short term velocity and water pressure variations down glacier from a riegel storglaciaren sweden during the 1991 94 summer field seasons time correlated measurements of water pressure and surface speed were made over and down glacier from a major riegel on storglaciaren sweden measurements were made at sub hourly time scales in order to discern details in the diurnal cycle large water input events typically associated with rain storms produced coherent lagged surface velocity responses that could be understood in terms of till deformation or decoupling and these have been discussed elsewhere the consequences of smaller diurnal water pressure events were more enigmatic in that acceleration of ice flow generally preceded the onset of the local water pressure rise from consideration of these data and other work done on the hydrology of storglaciaren we infer that the ice in this area is generally pushed from behind via a relaxation in extensional strain across the riegel hence accelerations occur in response to increases in water pressure that occur up glacier and that precede local water pressure rises in addition following a period of large storm events surface speeds became more spatially coherent and were in phase with the diurnal ater pressure cycle this suggests that the large water pressure events lead to a spatially more homogeneous subglacial drainage system sliding laws need to take into accoun such temporal changes in spatial coherence of the subglacial drainage system

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

combining digital elevation data srtm aster high resolution satellite imagery quickbird and gis for geomorphological mapping a multi component case study on mediterranean karst in central crete abstract remote sensing data have become more and more popular for geomorphological investigations because their steadily increasing level of detail and accessibility opens up new potentials in this context this paper examines the application and quality of digital elevation models srtm and aster dems high resolution satellite imagery quickbird and gis techniques for the detection and mapping of karst landforms mainly enclosed depressions at different scales in the ida mountains of central crete besides discussing methodological issues and evaluating suitability potentials we conducted an exemplary case study based on spatial analysis of the regional karst morphology different input datasets and processing methods are applied gis based analysis land cover classification raster calculations etc in order to carry out an area wide surveying and mapping of karst depressions the findings are supported and validated by auxiliary field studies due to the level of detail and occasional data errors an exclusive use of satellite imagery or digital elevation models for automatic karst landform detection performs insufficiently our results demonstrate that mapping karst features through remote sensing is significantly dependent on scale of interest existing environmental conditions and data quality a semi automatic data integration approach on the basis of digital datasets generated by combined satellite image processing and dem analysis yields the best results especially when indirect karst indicating variables like iron oxide rich sediments are included as detection criteria the multi component application presented in this paper provides a time saving and effective tool for meso to macro scale object detection and extensive study areas however the potential of fully automated karst feature mapping still needs to be explored in future work concerning the spatial dimension of karstification in central crete the gis based results allow differentiating further geomorphological characteristics e g by indicating a significant altitudinal change of karst forms within the study area size and shape of depressions dolines uvalas and poljes vary considerably due to the geological setting climatic impacts neotectonics and elevation

intra seasonal changes in deformation profiles revealed by borehole studies storglaciaren sweden in 1985 1987 and 1988 we measured deformation of bore holes in the ablation zone of storglaciaren a different hole was used each year deformation profiles were determined for four consecutive time periods between mid july and early september all three holes were in an area where the glacier lies in an overdeepened part of the bed up glacier from a riegel the first hole was approximately on the glacier center line while the others were midway between the center line and one or the other margin despite large standard errors variations in the deformation profiles during the melt season are broadly consistent with other data we thus believe that they are real and that they reflect changes in the stress field resulting from changes in drag at the bed a decrease in drag early in the melt season coupled with convergence of the bed contours towards the riegel is believed to be responsible for a previously documented increase in vertical velocity just up glacier from the riegal at this time of year also noteworthy but perhaps problematical was an abrupt transverse shear of m at a depth of 25 m near the center of the glacier injuly 1985 the shear took place in the zone in which cold ice near the surface gives way to temperate ice deeper in the glacier

spatial pattern and stability of the cold surface layer of storglaciaren sweden the mechanisms controlling the spatial distribution and temporal fluctuations of the thermal structure in polythermal glaciers have to date been poorly investigated and are not fully understood