simulation of braided river elevation model time series with multiple point statistics abstract a new method is proposed to generate successive topographies in a braided river system indeed braided river morphology models are a key factor influencing river aquifer interactions and have repercussions in ecosystems flood risk or water management it is essentially based on multivariate multiple point statistics simulations and digital elevation models as training data sets on the one hand airborne photography and lidar acquired at successive time steps have contributed to a better understanding of the geomorphological processes although the available data are sparse over time and river scales on the other hand geostatistics provide simulation tools for multiple and continuous variables which allow the exploration of the uncertainty of many assumption scenarios illustration of the approach demonstrates the ability of multiple point statistics to produce realistic topographies from the information provided by digital elevation models at two time steps

characterization of karst hazards from the perspective of the doline triangle using gpr examples from central ebro basin spain ground penetrating radar gpr is a widespread technique to locate and characterise karst hazards cavities and paleocollapses in this paper we show that the internal structure of sediments obtained from gpr surveys can also be used as an indicator of active karst processes a classification of karst hazard problems by means of gpr in the gpr doline triangle is proposed with three end members cavities evidences of subsidence and paleocollapses these end members show particular signatures in the gpr profiles the field examples shown in this paper indicate that gpr survey is a geophysical technique that offers a very high resolution and provides structural and sedimentological information of the subsoil the use of grid maps elaborated from gpr data is an efficient way to determine anomalous sectors lateral changes of electromagnetic properties different reflectivity and qualitative penetration depth variations or velocity wave propagation changes their relationships with the structural features obtained from gpr profiles on lap geometries zones with depressed reflectors folded reflectors or laterally abrupt structural limits can be used as indicators of karstic processes

collapse hazard assessment in evaporitic materials from ground penetrating radar a case study evaporitic materials have been studied by means of ground penetrating radar gpr in order to evaluate the collapse hazard the obtained 200 mhz gpr profiles show a low signal noise ratio over the first 3 m depth where well defined and continuous reflectors can be observed between 3 and 4 5 m depth the signal to noise ratio decreases due to attenuation of the electromagnetic em waves as a result reflectors located deeper than 3 m become more discontinuous and poorly defined gpr profiles show trails of continuous and subhorizontal reflectors with a slightly undulated and irregular geometry although some of these reflectors laterally vanish or seem to disappear sudden interruptions or hyperbolic reflections that could be originated by the occurrence of cavities have not been detected these reflectors have been interpreted as corresponding to several evaporitic layers gypsum that constitute the main lithology in the area clear interruptions of reflectors have only been observed in some gpr profiles and they could be attributed to small 1 2 m long subvertical faults with only a few centimetres offset these faults may be generated by the accommodation of the evaporitic layers to local collapses affecting deeper materials

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

polygonal impact craters in the argyre region mars evidence for influence of target structure on the final crater morphology impact craters that in plan view are distinctly polygonal rather than circular or elliptical are common on mars and other planets ohman et al 2005 their actual formation mechanism however is somewhat debatable we studied the polygonal craters of different degradational stages in the region of the argyre impact basin mars the results show that in the same areas heavily degraded moderately degraded and fresh polygonal craters display statistically similar strike distributions of the straight rim segments the fact that the strike distributions are not dependent on lighting conditions was verified by using two data sets viking and moc wa having different illumination geometries but similar resolutions in addition there are no significant differences in the amount of polygonality of craters in different degradational stages these results clearly imply that large scale polygonality is not caused by degradation but originates from the cratering process itself concurring with the findings regarding lunar craters by eppler et al 1983 the straight rims of polygonal craters apparently reflect areal fracture patterns that prevail for a geologically long time

morphological perspective on the sedimentary characteristics of a coarse braided reach tagliamento river ne italy abstract in order to understand heterogeneity distribution of hydraulic properties many studies have proposed models of coarse braided river deposits however they often focus either on the surface near surface or on ancient deposit analysis furthermore the link between morphological surface and sedimentological outcrops information has not been fully explored yet this publication aims to characterize the morphodynamics of a braided gravel bed reach of the tagliamento river ne italy and to assess its relationship with the subsurface heterogeneity the morphological analysis is based on a lidar derived dem aerial and satellite photographs from 1998 to 2011 as well as field observations a water stage time series allows the morphological changes to be related to the discharge dynamics the sedimentological knowledge on coarse braided deposits was mainly gained from the observation of analog pleistocene coarse deposits in switzerland the main geomorphological elements are identified in terms of their topographic signature and genesis setting apart the trichotomy water vegetation bar the braidplain is characterized by higher lying zones with dentritic gully drainage networks and active zones where most of the morphology reworking occurs furthermore two morphologies mark the active zones a low discharge morphology low discharge incisions and channels slip face lobes etc superimposed on a high discharge morphology gravel sheets scours etc each morphological element is related to a depositional i e sedimentological element whose preservation potential in the subsurface is assessed as a function of the river bed aggradation dynamic the settings that impact the subsurface flow in terms of fast pathway and connectivity are addressed

is there evidence for polar wander on europa abstract the orientations of the albedo lineaments bands and lineations on europa s surface have been compared in previous studies with the global stress fields set up by orbital eccentricity orbital recession and nonsynchronous rotation of these orbital and rotational effects nonsynchronous rotation combined with an offsetting of the tidal bulge comes closest to providing agreement between the stress field generated and the lineation orientations if the lineations trace tension or extension fractures mcewen 1986 nature321 49 51 however inferred minimum principal stress directions for a broad region of wedge shaped bands near the anti jove point cannot satisfactorily be accounted for by any of the stress fields above but are consistent with the stresses resulting from a rotation of europa s ice shell about an axis through the sub and anti jove points clockwise as seen from the anti jove hemisphere p m schenk and w b mckinnon 1989 icarus79 75 100 calculations by ojakangas and stevenson 1989 icarus81 220 241 of the thermal state of europa s ice shell indicate that spatial variations in the thickness of the shell may cause it to undergo such a reorientation we have investigated whether any reorientation of the shell about an axis through the sub and anti jove points produces a stress field consistent with the full global set of prominent lineations on europa s surface we find that no such reorientation provides a good fit between the lineations and plausible fracture orientations derived from the principal stress trajectories topographic ridges identified in a limited zone south of the anti jove point are roughly consistent with compression due to clockwise polar wander but the orientations of these ridges may be strongly biased by illumination direction within the limitations of the presently available imagery nonsynchronous rotation is still the most likely cause of the prominant fractures on europa s surface and the best specific albeit regionally limited tectonic evidence consistent with recent polar wander remains the wedge shaped bands

variability of bedload transport and channel morphology in a braided river hydraulic model this paper investigates variability in bedload transport and channel morphology for 11 replicate experimental runs in an approximately 1 50 braided river model the experiments each of 90 h duration were carried out in a 20 3m tilting flume all the experiments started with the same initial conditions bedload transport was measured at 5 min intervals in a collection drum at the exit from the flume the model showed reasonable hydraulic similarity when compared to prototype rivers results show that mean bedload transport rates for the 11 runs vary in the range 0 98 to 1 49gs 1 mean 1 21 coefficient of variation 11 per cent within run transport rates commonly vary from close to zero to two and occasionally three or four times the mean rate within the bedload series several irregular phases of transport intensity can be observed but time series analysis of the data show little underlying serial structure an ar 2 autoregressive model is appropriate channel patterns are narrow braided are established quickly and remain relatively stable throughout the runs although channel widths increase between 20 and 103 per cent over the 11 runs channel behaviour varies from aggradational to transitional between aggradation and degradation time averaged bedload transport rate is weakly correlated with braiding intensity in general these results demonstrate that for a given set of controlling variables bedload transport and channel morphology can be approximately replicated

integrated high resolution geophysical investigations as potential tools for water resource investigations in karst terrain karstic aquifers can be particularly vulnerable to both pollution from surface activities and large scale dewatering from mineral winning operations this is because of the enhanced vertical and lateral flow paths resulting from the dissolution of carbonate species by rainfall often this process results in the development of voids that can range in size from several centimetres to several tens of metres to date groundwater vulnerability maps for england and wales including karst areas have been produced using a methodology that does not consider the presence of karst features the uncertainties that are presented by the potential for pollution by the presence of water carrying conduits in karst areas where there are proposed or existing limestone quarries require new techniques for detecting and delineating underground cave systems in order for any mapping technique to provide an acceptable assessment of vulnerability the location and spatial distribution of high permeability flow paths need to be established of the available geophysics techniques that may allow for the identification of such features microgravity and resistivity imaging are likely to be the most successful microgravity surveying has the potential to identify the presence and location of such voids and with the integration of electrical tomographic work can provide targets for the location of monitoring boreholes whilst these techniques are intensive and may not be cost effective on a regional scale they do have the potential to provide high resolution data over smaller areas which would be invaluable to any site or area specific assessment of vulnerability

gravel transport and morphological change in braided sunwapta river alberta canada the relation between morphological change and patterns of variation in bedload transport rate in braided streams was observed by repeated daily topographic surveys over a 25 day study period in a 60 m reach of the proglacial sunwapta river alberta canada there are two major periods of morphological change each lasting several days and each involving the complete destruction and reconstruction of bar complexes bar complex destruction was caused by redirection of the flow and by downstream extension of the confluence scour zone upstream reconstruction involved accretion of unit bars on bar head flank and tail and in one case was initiated by disection of a large lobate unit bar high rates of sediment movement measured from net scour and fill of the cross sections coincided with these morphological changes sediment was supplied from both bed and bank erosion and patterns and distances of transfer were highly variable rates of transport estimated by matching upstream erosional volumes with downstream deposition were much greater than those estimated from either a step length approach or a sediment budget measurements of scour and fill and observations of morphological change indicate that step lengths virtual transport distances were typically 40 100m during a diurnal discharge cycle shorter step lengths occurred when transfer was confined to a single anabranch and longer steps involved channel changes at the scale of the entire reach sediment budgeting was used to describe the spatial patterns of sediment transport associated with the morphological changes and to estimate minimum daily reach averaged transport rates mean bedload transport rates correlate with discharge but with considerable scatter the largest deviations from the mean relation can be tied to phases of channel incision bank erosion scour hole migration bar deposition and channel filling apparently controlled by changes and fluctuations in sediment supply from upstream independent of discharge these are interpreted as field evidence of autopulses or macropulses in bedload transport previously observed only in laboratory models of braided streams

a pseudo genetic model of coarse braided river deposits a new method is proposed to produce three dimensional facies models of braided river aquifers based on analog data the algorithm consists of two steps the first step involves building the main geological units the production of the principal inner structures of the aquifer is achieved by stacking multiple point statistics simulations of successive topographies thus mimicking the major successive flooding events responsible for the erosion and deposition of sediments the second step of the algorithm consists of generating fine scale heterogeneity within the main geological units these smaller scale structures are generated by mimicking the trough filling process occurring in braided rivers the imitation of the physical processes relies on the local topography and on a local approximation of the flow this produces realistic cross stratified sediments comparable to what can be observed in outcrops the three main input parameters of the algorithm offer control over the proportions the continuity and the dimensions of the deposits calibration of these parameters does not require invasive field measurements and can rely partly on analog data

investigation of a large collapse sinkhole affecting a multi storey building by means of geophysics and the trenching technique zaragoza city ne spain an active sinkhole around 100 m long has been investigated in the city of zaragoza ne spain subsidence activity on this depression including the sudden occurrence of a collapse sinkhole 5 m across led to the abandonment of a factory in the 1990s at the present time a building with 100 flats and shallow pad foundations partially built on the sinkhole is affected by rapid differential settlement the development of the sinkhole results from the karstification of the halite and glauberite bearing bedrock and the sagging and collapse of the overlying bedrock and alluvium more than 30 m thick gpr and electrical resistivity profiles have provided information on the distribution and geometry of the subsidence structure the application of the trenching technique and geochronological methods ams and osl dating has allowed us to infer objective and practical data on the sinkhole including 1 limits of the subsidence structure 2 subsidence mechanisms 3 cumulative subsidence 408 cm 4 subsidence rates on specific failure planes 1 8 cm year 5 episodic displacement regime of some fault planes the available information indicates that the progressive deformation recorded in the building will continue and might be punctuated by events of more rapid displacement this work illustrates the practicality of the trenching technique for the study of sinkholes in mantled karst areas

gypsum karst and its evolution east of hafik sivas turkey abstract sivas and its surroundings is the most important gypsum karst terrain in turkey with a massive lower miocene gypsum formation 750 m thick the region east of hafik has a wide variety of well developed karstic features such as karrens dissolution dolines collapse dolines blind valleys karstic springs swallow holes caves unroofed caves natural bridges gorges and poljes the karstification started in the early pliocene the piezometric level to the east of hafik has lowered at least 200 m since the early pliocene and 90 100 m since the early pleistocene there is a youthful karst doline karst on the higher plateau 1520 1600 m and a mature karst on lower plateau 1315 1420 m the mature karst evolved in two stages first stage where excessively karstic paleovalleys uvalas and collapse dolines appear and the second stage where poljes collapse dolines and degraded collapse dolines dominated

karstification in miocene gypsum an example from sivas turkey in this study karstification developed in the miocene gypsum which covers a large area around sivas turkey the relation between regional tectonics and karstification and hydrogeological features have been investigated

use of ground penetrating radar to map subsurface archaeological features in an urban area the ground penetrating radar gpr technique was used to investigate the subsurface in an urban area located in mesagne italy to obtain a map of the archaeological features in the ground the gpr survey was undertaken at selected locations placed near about 50 m to a necropolis dating from the messapian to the roman imperial age using a gssi sir system 2 incorporating 200 and 500 mhz centre frequency antennae the selected areas a and b were surveyed along parallel 1 m spaced profiles using a 200 mhz antenna in area a and along parallel 0 5 m spaced profiles using a 500 mhz antenna in area b for the selected areas the processed data were visualised in 3d space not only by means of the standard time slice technique but also by means of a recently proposed approach namely by iso amplitude surfaces of the complex trace amplitude the immediacy in revealing the spatial positioning of highly reflecting bodies such as the anomaly interpreted as an old hypogeum room in area a makes 3d visualisation techniques very attractive in archaeological applications of gpr their sensitivity to the signal noise ratio is on the other hand highlighted by the quite poor performance in area b where the only reliable result provided by all the techniques was the ancient living surface reflection whereas none of them could effectively enhance the visibility of weak hyperbola reflections noted on 2d sections and probably related to the walls located on the ancient living surface the performance of the various techniques in these two different situations allowed insights into their main advantages and drawbacks to be gained

changes in braided river morphology resulting from aggradation and degradation forty three experiments were completed in a large flume 1 8 x 18 3 m to examine the effects of sediment load sediment size and channel gradient on braided river morphology the laboratory results were supported by field research and analogs from the published literature subaerially exposed braid bars were formed by the dissection and further accretion of stalled linguoid dunes which are actively migrating bedforms bar forming processes and channel dynamics were the same in both sand and gravel bed channels however linguoid dunes stalled and were transformed into braid bars more frequently in gravel bed channels and therefore gravel bed channels were more intensely braided aggradation resulted in the development of more bars rather than in an increase in the size of preexisting braid bars the number of actively migrating linguoid dunes also increased with sediment load in the highly mobile sand bed channels conversely in degrading channels the number of braid bars decreased and average bar

geophysical investigation of a sinkhole in the northern harz foreland north germany the creek jerstedter bach is part of the ringelheimer mulde along the northern rim of the harz mountains in northern germany a trough structure comprising steeply dipping limestones the limestones are well karstified and drain parts of the region efficiently via sub surface flow as the entire region is intensively used by agriculture contamination of the fast flowing karst aquifer is a potential problem during 2006 a small sinkhole windmuhlenweg developed alongside the jerstedter bach close to the city of goslar the sinkhole enlarged rapidly with a small cave within the gravel cover diverting part of the creek to the subsurface karst catchment geophysical methods gravimetry geoelectrics were used around the sinkhole to determine its extent and possible evolution a negative bouguer anomaly was found over the sinkhole indicating more voids further downstream the geoelectric survey helped to identify the old meandering course of the small river which was straightened during the cultural land reform in the twentieth century

length scale of braided river morphology 1 pool bar topography in single channel rivers has a length scale proportional to channel width in braided rivers confluence bifurcation units are analogous to pool bar morphology and in some cases develop from initial alternate bars consequently confluence bifurcation units are expected to have length that scales with the central anabranch width and that constitutes a basic length scale braided channel morphology this idea was tested using measurements from a physical model of a gravel bed braided river and from aerial photographs of braided rivers length distance from confluence to bifurcation anabranch width and confluence angle of confluence bifurcation units were measured a simple length scaling is evident across the range of scales confluence bifurcation length is 4 5 times the channel width this scaling is a fundamental element of braided river morphology and suggests that braided patterns are created by processes and have morphological regularity similar to pool bar units of low sinuosity single thread rivers

topographic constraints on impact crater morphology on venus from high resolution stereo synthetic aperture radar digital elevation models 1 high resolution digital elevation models dems derived from magellan left left stereo synthetic aperture radar data of venus for a set of impact craters ranging in rim diameter from 5 to 300 km exhibit depths broadly as expected from theory but with significant departures for both large and small craters in craters larger than 38 km diameter rim floor depth becomes independent of diameter with a mean of about 900 m most craters smaller than 18 km diameter are also found to be unexpectedly shallow we discuss the accuracy and principal sources of error in our dems and conclude that this shallowness is real this shallowness of small craters shows that midsize bolides 200 1000 m diameter fragment in venus atmosphere and disperse over an area 10 to 20 times the original bolide diameter we identify these craters as a new class of impact feature the compound crater which may correspond to the knobby base morphological class defined by others

environmental hazard analysis of a gypsum karst depression area with geophysical methods a case study in sivas turkey in the study area the geophysical properties of gypsum and filling materials karst structures that developed in gypsum and groundwater level were investigated according to the results of geophysical studies it was thought that the depression and dissolution weathering areas in the karst could be completely or partially filled with water air gypsum particles and one several or all of the alluvial units it was determined that resistivity and s wave velocity average 10 263 14 412 m average 655 m s and resistivity and s wave velocity of lsvz in the gypsum surfaced far from the source were lower 91 3 m 585 m s compared to the gypsum bedrock therefore it was observed that the resistivities and seismic velocities of the gypsum in the surfaced area were higher compared to the depression area the results were associated with karst as the main reason for dissolutions and depressions because the water draining leaking spreading from the water source progressed by creating low resistivity areas in the permeable filling material and the groundwater was near the surface therefore karst structures will probably continue to develop in this area and natural hazards may occur in the future

reduction of conceptual model uncertainty using ground penetrating radar profiles field demonstration for a braided river aquifer abstract hydrogeological flow and transport strongly depend on the connectivity of subsurface properties uncertainty concerning the underlying geological setting due to a lack of field data and prior knowledge calls for an evaluation of alternative geological conceptual models to reduce the computational costs associated with inversions parameter estimation for a given conceptual model it is beneficial to rank and discard unlikely conceptual models prior to inversion here we demonstrate an approach based on a quantitative comparison of ground penetrating radar gpr sections obtained from field data with corresponding simulation results arising from various geological scenarios the comparison is based on three global distance measures related to wavelet decomposition multiple point histograms and connectivity that capture geometrical characteristics of geophysical reflection images using field data from the tagliamento braided river system italy we demonstrate that seven out of nine considered geological scenarios can be discarded as they produce gpr sections that are incompatible with those observed in the field the retained scenarios reproduce important features such as cross stratified deposits and irregular property interfaces the most convenient distance measure of those considered is the one based on wavelet decomposition direct analysis of the distances is the most intuitive and fastest way to compare scenarios

identification prediction and mitigation of sinkhole hazards in evaporite karst areas sinkholes usually have a higher probability of occurrence and a greater genetic diversity in evaporite terrains than in carbonate karst areas this is because evaporites have a higher solubility and commonly a lower mechanical strength subsidence damage resulting from evaporite dissolution generates substantial losses throughout the world but the causes are only well understood in a few areas to deal with these hazards a phased approach is needed for sinkhole identification investigation prediction and mitigation identification techniques include field surveys and geomorphological mapping combined with accounts from local people and historical sources detailed sinkhole maps can be constructed from sequential historical maps recent topographical maps and digital elevation models dems complemented with building damage surveying remote sensing and high resolution geodetic surveys on a more detailed level information from exposed paleosubsidence features paleokarst speleological explorations geophysical investigations trenching dating techniques and boreholes may help in investigating dissolution and subsidence features information on the hydrogeological pathways including caves springs and swallow holes are particularly important especially when corroborated by tracer tests these diverse data sources make a valuable database the karst inventory from this dataset sinkhole susceptibility zonations relative probability may be produced based on the spatial distribution of the features and good knowledge of the local geology sinkhole distribution can be investigated by spatial distribution analysis techniques including studies of preferential elongation alignment and nearest neighbor analysis more objective susceptibility models may be obtained by analyzing the statistical relationships between the known sinkholes and the conditioning factors chronological information on sinkhole formation is required to estimate the probability of occurrence of sinkholes number of sinkholes km2 year such spatial and temporal predictions frequently derived from limited records and based on the assumption that past sinkhole activity may be extrapolated to the future are non corroborated hypotheses validation methods allow us to assess the predictive capability of the susceptibility maps and to transform them into probability maps avoiding the most hazardous areas by preventive planning is the safest strategy for development in sinkhole prone areas corrective measures could be applied to reduce the dissolution activity and subsidence processes a more practical solution for safe development is to reduce the vulnerability of the structures by using subsidence proof designs

changes in morphometric meander parameters identified on the karoon river iran using remote sensing data abstract river meander dynamics and mobility are important indicators of environmental change related to climate changes and anthropogenic activities at local and river basin scales the aim of the present study is to identify morphological changes of the karoon river in iran using high accuracy maps and landsat satellite images by analyses during the time period 1989 2008 in this study 20 meandering reaches were analyzed over a 128 km long river reach located in the middle part of the karoon river iran morphometric indicators such as river width w meander neck length l axis length a radius of curvature r water flow length s and sinuosity of meander c were extracted for the identified meanders the results of a paired t test showed that river width w and meander neck length l have significantly changed during the study period 1989 2008 with an increase of 3 5 m for w and a decrease of 274 m for l spearman correlation analysis has shown that meander parameter changes are highly correlated to each other the parameters that do not have significant correlation together are c with w and l w and l and l with s and a during the period of the study the flow length and river sinuosity decreased for the whole river reach by 4 77 km and 0 11 respectively analysis of land use land cover categories 1989 and 2008 using the support vector machine svm and kernel function method served as one of the tools for interpretation of the meander parameter changes these changes can be attributed not only to lu lc riparian vegetation to agriculture area ratio but also to dam construction in the upstream part of the river that leads to major hydrological regime and sediment transfer alteration sediment extraction may also be an important factor

environmental geological assessment of a solid waste disposal site a case study in sivas turkey the selection of the disposal site is probably the most important step in the development of solid waste management in site selection geology plays a determining role this study evaluates the characteristics of the environment on the basis of the geological hydrogeological and geo engineering properties of the solid waste site of the sivas city turkey the area is underlain by the oligocene miocene rocks which have limited aquifer properties thin quaternary alluvium and soil cover overlie the oligo miocene rocks which are represented as well graded sand and inorganic silt of low plasticity the quaternary alluvium and soil cover are classified as inorganic clays having a low plasticity and the permeability varies from 1 2 10 6 to 3 11 10 6 m s these values are much higher than 1 10 8 m s which is accepted for waste disposal standards seepage waters have a potential to pollute the ground water and the kizilirmak river which is 500 m to the southwest of the waste disposal area and because the disposal site is close to the river the potential for flash flooding poses a high pollution risk the waste disposal area must be covered by clay layers or an impervious artificial membrane in addition seepage must be controlled and removed from the site

simulation of braided river flow using a new cellular routing scheme abstract results are presented from a numerical simulation of two dimensional flow patterns in a braided river using a simple cellular routing scheme the results of the routing scheme are compared with field measurements of discharge per unit width obtained within the study reach at low flow and for higher flows with the predictions of a more sophisticated hydraulic model that solves the two dimensional shallow water form of the navier stokes equations an assessment is made of the sensitivity of the routing scheme to variations in the values of its main parameters and appropriate values are determined based on the physical characteristics of the study site and available flow measurements it is shown that despite the simple approach adopted by the cellular routing scheme to simulate processes of water redistribution it is able to replicate accurately both the field data and the results of the more sophisticated hydraulic model these results indicate that the routing scheme outlined here is able to overcome some of the limitations of previous simple cellular automata models and may be suitable for use in modelling bedload transport and channel change in complex fluvial environments as such this research represents a small and ongoing contribution to the field of numerical simulation of braided river processes

resurfacing saturn s satellites models of partial differentiation and expansion abstract the faulting seen on the surfaces of saturn s icy moons may have been caused either by external events such as large impacts or internal stresses caused by the expansion of the moons as long lived radionuclides produced internal heating and phase changes we estimate the stress as a function of radius expansion is 44 r r kbar the extensional stress needed for fracture is probably something less than 40 bar so extensional fracture is likely to occur when r r is greater than one part in a thousand the radius change for these moons can be calculated analytically given suitable assumptions in addition detailed time dependent computer models of the thermal and physical evolution of tethys dione rhea and iapetus were carried out from these calculations we conclude that the most reasonable cause for rifting on dione and rhea is the refreezing of an ammonia water eutectic melt inside these moons roughly two billion years after their formation while the rift on tethys was caused by a large impact and little rifting should be expected on iapetus

polygonal impact craters on dione evidence for tectonic structures outside the wispy terrain abstract plan view impact crater geometries can be indicative of pre impact structures within the target material impact events that occur on a pre fractured surface generate craters exhibiting one or more straight rim segments termed polygonal impact craters pics impact craters that appear to be pics are abundant on the surface of saturn s icy satellite dione both within the wispy terrain a region with large visible fractures and also outside the wispy terrain the non wispy terrain where less evidence for fracturing has been observed in the non wispy terrain subtle lineaments are hypothesized to be ne sw nw se and e w trending fractures suggesting that tectonism may have been an important process in this terrain results of previous studies have shown that pic straight rim segment azimuths pic azimuths commonly parallel pre impact fracture azimuths although disagreements about this relationship exist in the literature we investigated the hypothesis that fractures either subtle or nonvisible with available spacecraft images are present within dione s non wispy terrain our first step was to assess the relationship between pics and pre existing fracture azimuths in the wispy terrain our results from this initial assessment show a parallel relationship between pic azimuths and fracture azimuths based on this correlation in the wispy terrain we find it likely that this relationship would hold true in the non wispy terrain if pics are present we tested for pics using crater rim azimuth data collected from randomly distributed study locations throughout the non wispy terrain from these data we identified widespread pics in this terrain which supports the hypothesis that subtle fractures are also present analysis of the pic azimuth data yield a pattern for these inferred fractures across dione s surface that is consistent with the hypothesized global deformation that would result from a combination of satellite despinning and volume expansion our results provide evidence for these previously hypothesized events in dione s history and demonstrate that mapping pics and their azimuths is a useful tool for investigating subtle fractures on solar system bodies

use of ground penetrating radar for assessment of potential sinkhole conditions an example from ghor al haditha area jordan sinkholes are near surface indicators of active karst features at depth such as cavities conduits and solutionally enlarged fractures this study tests the usefulness of ground penetrating radar gpr to identify and locate buried sinkholes as a means of interpreting the existence of these subsurface hydraulically active karst features gpr survey was made at the ghor al haditha area west of the jordan dstf in the jordan valley escarpment at the eastern dead sea shoreline gpr profiles 100 mhz made along the eastern dead sea shoreline showed a trough like pattern of radar reflections outlining a series of possible filled sinkholes this feature is about 38 m wide and about 12 m deep its width is consistent with the width of the feature obtained from the topographic map of the area the gpr survey suggests that this feature has been filled with relatively dense and resistive materials this structure lies almost directly above a major water bearing zone

cover collapse sinkholes in the tournaisis area southern belgium abstract in the tournaisis area southern belgium cover collapse sinkholes have been reported since the beginning of this century in this area the relatively flat lying carboniferous limestone is overlain by an unconformable mesocenozoic cover recent research has shown that these sinkholes developed from reactivated paleokarsts the intensive pumping for domestic and industrial water supply combined with the dewatering due to deep limestone quarries operations resulted in the lowering of groundwater levels this triggered the reactivation of paleokarstic systems and thus the occurrence of cover collapse sinkholes these sudden and unexpected collapses have already had major impacts in the region in 1977 about thirty sinkholes opened up along the escaut river downstream from the city of tournai as a consequence the groundwater was polluted by an extensive loss of river water into the carboniferous aquifer more recently a house and industrial facilities were severely damaged by such cover collapse sinkholes in this context a geoharzard map would be a valuable tool as far as regional development is concerned this points at the importance to develop methods to locate and characterize hidden paleokarsts a study site has been chosen in an area where sinkholes have been opening up for about ten years a geophysical survey of the site which included electrical resistance mapping of the area has shown weakness lineaments these lineaments are parallel to a main fault affecting the region

a cellular model of braided rivers a broad sheet of water flowing over non cohesive sediment typically breaks up into a network of interconnected channels called a braided stream fig 1 the dynamics of such networks are complex channels migrate laterally split rejoin and develop bars with the flow shifting unpredictably from one part of the network to another many processes are known to operate in a braided river1 3 but it is unclear which of these are essential to explain the observed dynamics we describe here a simple deterministic numerical model of water flow over a cohesionless bed that captures the main spatial and temporal features of real braided rivers the patterns arise from local scour and deposition caused by a nonlinear dependence of bedload sediment flux on water discharge although the morphology of the resulting network depends in detail on the sediment transport rule used in the model our results suggest that the only factors essential for braiding are bedload sediment transport and laterally unconstrained free surface flow

planning for gypsum geohazards in lithuania and england the rapid underground dissolution of gypsum and the evolution of the gypsum karst in lithuania and england results in subsidence problems which can make construction difficult the natural dissolution yields sulphate rich groundwater of poor quality and the karst is susceptible to the rapid transmission of pollutants in the north of lithuania gypsum karst is developed in devonian gypsum here the towns of birai pasvalys and the surrounding countryside suffer subsidence and some buildings have been damaged the majority of the potable water in these areas is derived from groundwater extracted from sandstone sequences that underlie the gypsum in lithuania conservation measures have been introduced to control agriculture and prevent pollution of the gypsum karst these measures include environmentally friendly farming restrictions on land use and exclusion zones around subsidence hollows in england subsidence caused by the dissolution of permian gypsum has caused severe problems in the vicinity of the town of ripon numerous buildings have been damaged and new sites are difficult to develop here formal planning regulations have recently been introduced to help to protect against the worst effects of subsidence resulting from gypsum dissolution

characteristic features and structural evolution of a post collisional basin the sivas basin central anatolia turkey abstract the ene ssw trending sivas basin is located at the easternmost wedge like tip of the central anatolian block and exhibits characteristics of two other basins one in west central anatolia and the other in eastern anatolia the sivas basin started to form within a collisional mosaic during maastrichtian time with the pre maastrichtian basement the latter composed of continental metamorphic rocks jurassic lower cretaceous platform carbonates of the tauride belt and ophiolites and ophiolitic melange derived from closure of the northern branch of neo tethys similar tertiary basins were developed on comparable collisional mosaics in other parts of anatolia the sivas basin is asymmetrical in both the longitudinal and transversal directions its infill is dominated by a thick maastrichtian tertiary shallow marine continental succession resting unconformably on pre maastrichtian basement rocks and dissected into several subbasins this infill consists of post collisional deposits which overlie paleotectonic units unconformably and each subbasin is bounded by northeast southwest trending oblique slip faults exhibiting dominant strike slip the subbasins are characterized by contrasting stratigraphic successions although all are composed of interstratified continental and shallow marine facies both the northern and southern margins of the subbasins include upper eocene olistostromes containing mega blocks of varied origin the latter are sourced in paleotectonic units and were reworked in a shallow marine depositional setting the fill of the middle subbasins exhibits strong vertical and lateral facies changes characterized by local and regional unconformities and includes continental to shallow marine volcanic rocks this basin was deformed under north south directed compression during late pliocene quaternary times during the neotectonic phase of deformation this deformation divided the basin into new small scale mainly pull apart subbasins including those at imranli ishani altinyayla and arkisla from stratigraphic and structural correlations a post collisional intra continental basin model for the sivas basin is preferred

gypsum karst problems in constructing dams in the usa gypsum is a highly soluble rock and is dissolved readily to form caves sinkholes disappearing streams and other karst features that typically are also present in limestones and dolomites gypsum karst is widespread in the usa and has caused problems at several sites where dams were built or where dam construction was considered gypsum karst is present at least locally in most areas where gypsum crops out or is less than 30 60 m below the land surface these karst features can compromise on the ability of a dam to hold water in a reservoir and can even cause collapse of a dam gypsum karst in the abutments or foundation of a dam can allow water to pass through around or under a dam and solution channels can enlarge quickly once water starts flowing through such a karst system the common procedure for controlling gypsum karst beneath the dam is a deep cut off trench backfilled with impermeable material or a close spaced grout curtain that hopefully will fill all cavities in oklahoma the proposed upper mangum dam was abandoned before construction because of extensive gypsum karst in the abutments and impoundment area catastrophic failure of the quail creek dike in southwest utah in 1989 was due to flow of water through an undetected karstified gypsum unit beneath the earth fill embankment the dike was rebuilt at a cost of us 12 million with construction of a cut off trench 600 m long and 25 m deep other dams in the usa with severe gypsum karst leakage problems in recent years are horsetooth and carter lake dams in colorado and anchor dam in wyoming