The role of flow velocity in the vertical distribution of particulate organic matter on moss-covered travertine barriers of the Plitvice Lakes (Croatia), 2006, Milisa M. , Habdija I. , Primchabdija B. , Radanovic I. , Kepcija R. ,

We investigated the distribution patterns of particulate organic matter (POM) on travertine barriers in respect to flow velocity. Research was conducted on the barrage-lake system of the Plitvice Lakes, Croatia. Four layers were distinguished within the substrate (moss mat three travertine layers) in three hydraulic habitats at three sites. Substrate samples were collected monthly with a core sampler. The aim of the study was to explore the ability of moss mats and travertine substrate to accumulate POM; to ascertain the role of flow velocity and to produce a model of POM distribution pattern. The average of POM deposited in the 10 cm deep zone decreased significantly in the three sites along longitudinal profile of the system. Most POM was deposited in the moss mats, and the amounts decreased exponentially with depth. This was observed for coarse particulate organic matter (CPOM), ultra-fine particulate organic matter (UPOM) and total organic matter (TPOM) while fine organic matter (FPOM) deposition appeared unaffected by depth. More POM was accumulated in hydraulic habitats of low flow velocity. Correlation between flow velocity and POM accumulation was generally negative. Positive correlations between flow velocity and deposition rates were noted for CPOM in moss mats and top travertine layers; the deposition of other POM fractions was negatively influenced by the flow velocity. The influence of flow velocity decreased with increasing depth. In the deepest layers (7-10 cm) flow velocity influenced only the deposition of the smallest particles (UPOM)

Sinkhole distribution based on pre-development mapping in urbanized Pinellas County, Florida, USA, 2007, Brinkmann R, Wilson K, Elko N, Seale Ld, Florea L, Vacher Hl,

Locating sinkholes in Pinellas County, Florida, is confounded by the presence of a cover of Quaternary sediments that mute the surface appearance of these sinkholes. As a first step in addressing the sinkhole hazard in the county, we analysed aerial photographs from 1926 and 1995 that covered the entire county. We digitized all identifiable sinkholes in each set of photographs in a GIS (Geographical Information System) using a set of criteria established to differentiate between karst depressions and depressions resulting from other geological processes. The 1926 photographs, although of low quality, helped to establish a baseline prior to urbanization. The 1995 photographs provided a post-urbanization distribution of natural sinkholes and man-made depression features (e.g. retention ponds). From these two data sets, we are able to assess natural and anthropogenic changes in the karst landscape of the study area. In particular, we discovered that 87% of the sinkhole features identified in the 1926 photographs are no longer present in the photographs from 1995. Many of the lost depressions have been incorporated into retention ponds

Natural and anthropogenic hazards in the karst of Jamaica, 2007, Day Mj,

About two thirds of Jamaica is karst landscape, and karstic hazards affect much of the country and about half of the population, mostly in rural areas. The karst includes extensive areas of dolines and dry valleys, together with poljes and classical tropical tower and cockpit karst. With population and urbanization increases, and as infrastructure is developed, karstic hazards are becoming more prevalent and risks are increasing. One major natural hazard is seasonal drought, which disrupts water supplies, particularly in rural areas where groundwater resources are poorly developed and residents depend on rainwater and springs. Conversely, seasonal flooding, particularly that associated with tropical storms, causes property damage and human death, injury and displacement. Ground surface subsidence and collapse threatens developing infrastructure, dwellings and livestock, but the potential for catastrophic karstic failure of industrial facilities such as dams and retention ponds, including the storage facilities associated with bauxite mining and processing, appears to be relatively limited. Slope failure also occurs, but is not often recognized as a hazard and has not been studied in detail. Human impacts include quarrying, bauxite mining, groundwater abstraction, urbanization, agricultural development and tourism. Groundwater contamination is a serious anthropogenic hazard, particularly associated with the bauxite industry. Less than 10% of the karst area is within protected areas

Uranium-series dating of gypsum speleothems: methodology and examples, 2010, Sanna L. , Saez F. , Simonsen S. , Constantin S. , Calaforra J. M. , Forti P. , Lauritzen S. E.

The analytical problems of dating gypsum speleothems with the U-series technique are reviewed. Gypsum speleothems are, in general, very low in U content, challenging the limits of detection methods. Various approaches to dissolving gypsum and isolation of actinides from the matrix include ion-pairing dissolution with magnesium salts and using nitric acid. The most precise dating technique is Thermal Ionization Mass Spectrometry (TIMS), combined with Fe(OH)3 scavenging and anionic exchange chromatography. Less satisfactory, but much quicker, is direct retention of actinides from HNO3 by means of TRU resin and MC-ICP-MS detection. We have tested these methods on gypsum speleothems from the Sorbas karst in Spain and from the Naica caves in Mexico.

Uranium-series dating of gypsum speleothems: methodology and examples, 2010, Sanna L. , Saez F. , Simonsen S. , Constantin S. , Calaforra J. M. , Forti P. , Lauritzen S. E.

The analytical problems of dating gypsum speleothems with the U-series technique are reviewed. Gypsum speleothems are, in general, very low in U content, challenging the limits of detection methods. Various approaches to dissolving gypsum and isolation of actinides from the matrix include ion-pairing dissolution with magnesium salts and using nitric acid. The most precise dating technique is Thermal Ionization Mass Spectrometry (TIMS), combined with Fe(OH)3 scavenging and anionic exchange chromatography. Less satisfactory, but much quicker, is direct retention of actinides from HNO3 by means of TRU resin and MC-ICP-MS detection. We have tested these methods on gypsum speleothems from the Sorbas karst in Spain and from the Naica caves in Mexico.

Pit cave morphologies in eolianites: variability in primary structure control, 2011, Moore Paul J. , Seale L. Don, Mylroie John E.

The landforms of San Salvador, Bahamas, demonstrate extensive karst development, in particular epikarst features called pit caves. Studies on Hog Cay, an interior dune ridge located north of the San Salvador International Airport runway, indicate that some pit caves have morphologies controlled by bedding. These pit caves, initiating within the vadose zone, have a tendency to follow the foreset beds of the dune for some distance and are analogous to solution chimneys found in continental settings. These solution chimneys are distinguished from vertical shafts, which propagate vertically into the vadose zone of the
subsurface with little, if any, horizontal offset.

Previous field observations have described how eolian deposits can be sorted by grain size into alternating coarse-grained and fine-grained strata. The alternating strata undergo selective cementation, where the coarse-grained strata become poorlycemented and the fine-grained strata become well-cemented because of retention of pore waters. This is observed in weathered outcrops as poorly-cemented micro-recesses and well-cemented micro-ledges. In the subsurface, the coarse-grained, poorlycemented strata are the preferred flow path for vadose water. This water is perched upon and flows laterally along the foreset beds on the well-cemented, fine-grained strata. Pit caves forming under these conditions are described as solution chimneys. Also found on Hog Cay are pit caves that extend from the surface down to near sea level. These vertical shafts are generally found on the crests of dunes, with the deepest shaft being over 15 meters. They commonly display a near-perfect cylindrical shape and extend vertically with no horizontal offset. The walls of vertical shafts exhibit micro-ledge and micro-recess morphology; however, the vertical shafts have no indication of bedding control, which may be due to cementation in the fine-grained layers
being less complete in certain areas, facilitating vertical shaft development.

Preliminary XRD analysis of the pit caves shows that the top and bottom wall rocks of one pit is almost entirely calcite, but the wall rocks in the middle of the pit have a high aragonite content. These observations are consistent with long residence time of meteoric water in the epikarst at the top of the pits, and in the fill material at the base of the pits, such that aragonite was inverted to calcite. However, the rapid transit time of the vadose water along the pit walls allowed dissolution to enlarge the pit, but without inversion of the primary aragonite.

The visitors influence on air temperature of Yaltinskaya and Geofizicheskaya show caves (Ay-Petri massif, Mount Crimea), 2011, Amelichev, G. N. , Tokarev, S. V. , Klimchouk, A. B.

Monitoring of air temperature in the Yaltinskaya and Geofizicheskaya caves, situated in the Ay-Petri massif in the Mountainous Crimea, was conducted during 7 months. The purpose of this study is to determine the visitors’ influence on natural environment of the caves. Average temperature during the period of monitoring in Yaltinskaya cave was 7,55 °Ñ  (Ñv=0,01) and in Geophisicheskaya cave was 6,99 °Ñ(Ñv=0,06).

The visitation by tourists causes rising of air temperature up to 0,39 ˚Ñper day. In periods of low visitation the anthropogenic thermal anomalies broke down naturally during the night time, with the participation of processes of evaporation and condensation of cave moisture. In periods of high attendance a partial retention and accumulation of anthropogenic heat occurs. Daily thermal anomalies in starting and finishing periods of holiday season were at the average 0,04 ˚Ñ(Yaltinskaya) and 0,13 ˚Ñ(Geofizicheskaya). In the peak season they were 0,07 and 0,20 °Ñ, respectively.

The anthropogenic influence on the temperature of the studied caves has a seasonal character. It is unstable and is 1-2 orders of magnitude less than the seasonal variability of the natural temperature background.

Simulation of flow processes in a large scale karst system with an integrated catchment model (Mike She) – Identification of relevant parameters influencing spring discharge, 2012, Doummar J. , Sauter M. , Geyer T.

In a complex environment such as karst systems, it is difficult to assess the relative contribution of the different components of the system to the hydrological system response, i.e. spring discharge. Not only is the saturated zone highly heterogeneous due to the presence of highly permeable conduits, but also the recharge processes. The latter are composed of rapid recharge components through shafts and solution channels and diffuse matrix infiltration, generating a highly complex, spatially and temporally variable input signal. The presented study reveals the importance of the compartments vegetation, soils, saturated zone and unsaturated zone. Therefore, the entire water cycle in the catchment area Gallusquelle spring (Southwest Germany) is modelled over a period of 10 years using the integrated hydrological modelling system Mike She by DHI (2007). Sensitivity analyses show that a few individual parameters, varied within physically plausible ranges, play an important role in reshaping the recessions and peaks of the recharge functions and consequently the spring discharge. Vegetation parameters especially the Leaf Area Index (LAI) and the root depth as well as empirical parameters in the relationship of Kristensen and Jensen highly influence evapotranspiration, transpiration to evaporation ratios and recharge respectively. In the unsaturated zone, the type of the soil (mainly the hydraulic conductivity at saturation in the water retention and hydraulic retention curves) has an effect on the infiltration/evapotranspiration and recharge functions. Additionally in the unsaturated karst, the saturated moisture content is considered as a highly indicative parameter as it significantly affects the peaks and recessions of the recharge curve. At the level of the saturated zone the hydraulic conductivity of the matrix and highly conductive zone representing the conduit are dominant parameters influencing the spring response. Other intermediate significant parameters appear to influence the characteristics of the spring response yet to a smaller extent, as for instance bypass and the parameters a in the Van Genuchten relation for soil moisture content curves.

COVER-COLLAPSE SINKHOLE DEVELOPMENT IN THE CRETACEOUS EDWARDS LIMESTONE, CENTRAL TEXAS, 2013, Hunt B. B. , Smith B. A. , Adams M. T. , Hiers S. E. , Brown N.

Sudden cover-collapse sinkhole (doline) development is uncommon in the karstic Cretaceous-age Edwards limestone of central Texas. This paper presents a case-study of a sinkhole that formed within a stormwater retention pond (SWRP) in southwest Austin. Results presented include hydrogeologic characterizations, fate of stormwater, and mitigation of the sinkhole. On January 24, 2012, a 11 cm (4.5 in) rainfall filled the SWRP with about 3 m (10 ft) of stormwater. Subsequently, a sinkhole formed within the floor of a SWRP measuring about 9 m (30 ft) in diameter and 4 m (12 ft) deep. About 26.5 million liters (7 million gallons) of stormwater drained into the aquifer through this opening. To determine the path, velocity, and destination of stormwater entering the sinkhole a dye trace was conducted. Phloxine B was injected into the sinkhole on February 3, 2012. The dye was detected at one well and arrived at Barton Springs in less than 4 days for a minimum velocity of 2 km/day (1.3 mi/day).Review of pre-development 2-foot topographic contour and geologic maps reveals that the SWRP was built within a broad (5,200 m2; 6 acre), shallow depression bounded by two inferred NE-trending fault zones. Photographs taken during SWRP construction showed steep west-dipping bedrock in the northern SWRP wall. Following collapse of the sinkhole, additional hydrogeologic characterization included excavation to a depth of 6.4 m (21 ft), surface geophysics (resistivity), and rock coring. Geologic materials consisted mostly 89of friable, highly altered, clayey limestone consistent with epikarst in-filled with terra rosa providing a cover of the feature. Dipping beds, and fractured bedrock support proximity to the mapped fault zone. Geophysics and surface observations suggested a lateral pathway for stormwater flow at the junction between the wet pond’s impermeable geomembrane and compacted clay liner for the retention pond. The collapse appears to have been caused by stormwater down-washing poorly consolidated sediments from beneath the SWRP and into a pre-existing karst conduit system.

Mitigation of the sinkhole included backfill ranging from boulders to gravel, a geomembrane cover, and reinforced concrete cap. Additional improvements to the SWRP included a new compacted clay liner overlain by a geomembrane liner on the side slopes of the retention pond.

Variability of groundwater flow and transport processes in karst under different hydrologic conditions, 2013, Ravbar, Nataša

Significance of hydrological variability in karst is presented, which also discusses factors inducing such variability and consequences it may cause. Groundwater flow in karst aquifers is often characterized by strong variability of flow dynamics in response to different hydrologic conditions within a short time period. Consequently, water table fluctuations are often in the order of tens of meters, differences in flow velocities between low- and high-flow conditions can reach ten or even more times. In dependence to respective hydrologic conditions groundwater flow also results in variations of flow directions, and thus in contribution of different parts of the aquifer to a particular spring. The described hydrological variability has many implications for contaminant transport, groundwater availability and vulnerability. Groundwater level rising reduces thickness of the unsaturated zone and decreases protectiveness of the overlying layers. Higher water flow velocities reduce underground retention. Due to more turbulent flow, transport and remobilization of solute and insoluble matter is more effective. During high-flow conditions there is usually more surface flow and hence more concentrated infiltration underground. Particularly in karst systems that show very high hydrologic variability, this should be considered to correctly characterize, understand or predict the aquifers’ hydrological behaviour and to prepare proper protection strategies.