interdune areas of the back island dune field north padre island texas abstract the small young about 100 yrs back island dune field on north padre island south texas consists of fairly persistant oblique dunes up to 6 m high with well developed interdune areas that grade northwestward to small ephemeral transverse and barchan dunes with interconnected interdune areas thence sheet sand areas the subhumid climate is marked by rain associated with frontal systems and tropical storms winds are seasonally bimodal prevailing southeasterly are punctuated by northerly and northwesterly winds with the passage of frontal systems in winter the entire dune field and individual oblique dunes show a net migration of about 15 m yr 1 to the northwest the dunes however are on a seasonally reversing track changing their slipface direction and migration direction with frontal systems one year of monitoring shows sand transport in the dune interdune system to be complex and cyclic during the wind reversals of winter dunes are very ineffecfive sand traps owing to loss of flow separation and much sand is lost to the interdune areas interdune areas store sand during these wet winter months as a result of the wind reversals and higher moisture content during the summer the interdune areas deflate and the dunes build in size the overall dune field deposit appears to consist of three laterally contiguous zones from southeast to northwest 1 continuous climbing oblique dune and interdune deposits 2 discontinuous lenses of dune sand in overall interdune layers and 3 a chaotic mixture of dune and horizontal deposits of the sheet sand areas one year s mapping and trenching documents that interdune sedimentary structures are extremely variable laterally and vertically reflecting specific microenvironments within the interdune flat wet surface features consist of current and wave ripples channel fill miniature deltas wrinkle marks mini ripples rills algae and sand volcanoes abundant adhesion structures rain impacted ripples brecciated surfaces and microtopography reflect damp surface deposits dry surface features are predominately wind ripples others include small isolated barchan and shadow dunes organic debris lag surfaces deflation scours beetle bioturbation plant root structures associated with shadow dunes and grainfall from the adjacent dunes interdune deposits account for about 40 of the total dune field deposits which seems reasonable compared to some ancient examples by virtue of occupying a relative basin interdune deposits are selectively preserved compared to dune deposits in general interdune sedimentation is enhanced by non eolian depositional mechanisms a high water table early evaporatic cements and a variable wind regime the actual thicknesses of individual dune and interdune deposits are less on padre than ancient examples reflecting the relative scale of the bedforms in many respects sequences of sedimentary structure in padre island interdune deposits are typical of ancient coastal interdune strata but some marked departures occur adhesion structures relatively rare in some ancient examples but abundant within padre interdune deposits seem favored by the small size of dune and interdune area the climate and a variable wind regime penecontemporaneous deformation absent in padre interdune deposits but pronounced in some ancient examples probably reflects dune size and the nature of the deposits wavy laminae in ancient interdune deposits probably result from many causes but seem best represented by modern examples of evaporitic algal bacterial formed structures

paleohydrology of southwestern texas current statistical methods may be unable to accurately predict recurrence intervals of rare large magnitude floods especially in semiarid regions having positively skewed annual flood distributions great hydrologic variability and widely spaced gaging stations current approaches rely on historical data but catastrophic floods may have recurrence intervals far greater than the length of historical records in the lower pecos and devils rivers of southwestern texas paleoflood discharge and frequency estimates are extended over 10 000 years by the study of slack water flood sediments slack water deposits are typically fine grained sand and silt that accumulate during floods in areas where current velocity is reduced i e in back flooded tributary mouths channel expansions downstream from bedrock spurs and or slump blocks and in shallow caves along bedrock walls radiocarbon dating of organic detritus in slack water deposits establishes the flood chronology while paleoflood discharges can be estimated by slope area techniques paleoflood information extracted from slack water sediments can greatly extend flood records these floods may be weighted like historical data in log pearson type 3 calculations of flood frequency our morphostratigraphic approach combines recorded data with geomorphic evidence to derive estimates of flood frequency this technique offers an inexpensive and rapid way to assess catastrophic flood risk

a 2000 year natural record of magnitudes and frequencies for the largest upper colorado river floods near moab utah using well established procedures for paleoflood hydrology and employing optically stimulated luminescence osl geochronology we analyzed a very well preserved natural record of 44 upper colorado river extreme floods with discharges ranging from 1800 to 9200 m3s 1 these are the largest floods occurring during the last 2140 220 years and this natural record indicates that large floods are much more frequent than can be estimated by extrapolation from the stream gaging record that extends back to 1914 most of these large floods occurred during the last 500 years and the two largest floods in the record both exceeded the probable maximum flood pmf estimated at 8500 m3s 1 300 000 cfs for nearby moab utah another four floods with discharges greater than 7000 m3s 1 occurred during the last two millennia flood frequency analyses using the fldfrq3 model yields the following values depending on the manning n roughness coefficients 100 yr flood 4670 4990 m3s 1 500 yr flood 6675 7270 m3s 1 1000 yr flood 7680 8440 m3s 1 the presumed pmf discharge 8500 m3s 1 gets assigned a recurrence interval of about 1000 years and the largest historical 1884 flood 3540 m3s 1 a recurrence interval of 100 years flood frequency analysis for the moab valley based on the gaged record 1914 2012 yield 2730 m3s 1 for the 100 yr flood and 3185 m3s 1 for the 500 yr flood this underestimation of the frequency of large floods from the gage data results from effects on that record by modern regulation of upstream river flow and associated water extraction for agriculture

extraordinary hydro climatic events during 1800 1600 yr bp in the jin shaan gorges along the middle yellow river china abstract paleoflood slackwater deposits swds of the holocene were found at many sites along the jin shaan gorges in the middle yellow river basin a set of four paleoflood swd beds was identified at the pingduguan pdg sites and studied by field observations and laboratory analysis including particle size distribution and optically stimulated luminescence osl dating hydrological reconstruction using the hec ras model shows that the paleoflood peak discharges were between 39 000 and 50 220 m 3 s 1 they are about double the largest gauged flood 24 000 m 3 s 1 that has occurred since 1976 along the jin shaan gorges these extraordinary flood events were osl dated to between 1800 and 1600 yr bp during which climatic deterioration and disasters were documented over the yellow river basin various evidences show that severe flood and drought disasters during the episode resulted in frequent harvest failures famines social upheavals and population reduction invasions by nomads and even the fall and replacement of the dynasties climate decline documented by proxy records such as tree rings stalagmites ice cores and lake sediments from over the world is in agreement with the paleoflood events identified along the jin shaan gorges these mean that the extraordinary paleoflood events are closely related to increased climatic variability and instability this result provides solid evidence for understanding the response of hydroclimatic system to global climate change in the semi arid and sub humid regions of the world

impact of monsoonal climatic change on holocene overbank flooding along sushui river middle reach of the yellow river china abstract in the semiarid loess regions slackwater deposition of overbank flooding over the piedmont alluvial plains was episodic and alternated with dust accumulation and soil formation throughout the holocene the records of past hydrological events are therefore preserved within the architecture of loess and soils and are protected from subsequent erosion and destruction several holocene loess soil sequences with the deposits of overbank flooding over the semiarid piedmont alluvial plains in the southeast part of the middle reaches of the yellow river drainage basin were investigated by field observation osl and c14 dating measurement of magnetic susceptibility particle size distribution and chemical elements this enables the reconstruction of a complete catalog of holocene overbank flooding events at a watershed scale and an investigation of hydrological response to monsoonal climatic change as well during the holocene there are six episodes of overbank flooding recorded over the alluvial plain the first occurred at 11 500 11 000 a bp i e the onset of the holocene the second took place at 9500 8500 a bp immediately before the mid holocene climatic optimum after an extended geomorphic stability and soil formation the third overbank flooding episode came at about 3620 3520 a bp i e the late stage of the mid holocene climatic optimum and the floodwater inundated and devastated a bronze age town of the xia culture built on the alluvial plain and therefore the town was abandoned for a period of ca 100 years during the late holocene the alluvial plain experienced three episodes of overbank flooding at 2420 2170 1860 1700 and 680 100 a bp respectively the occurrence of these overbank flooding episodes corresponds to the anomalous change in monsoonal climate in the middle reaches of the yellow river drainage basin when rapid climate change or climatic decline occurs during at least the last four episodes both extreme floods and droughts occurred and climate departed from its normal condition which was defined as a balanced change between the northwestern continental monsoon and southeastern maritime monsoon over time great floods occurred as a result of extreme rainstorms in summers caused by rare intensive meridianal airflows involving northwestward moving tropical cyclone systems from the pacific these results could be applied to improve our understanding of high resolution climatic change and of hydrological response to climatic change in the semiarid zones

significance of interdune deposits and bounding surfaces in aeolian dune sands bounding surfaces and interdune deposits provide keys for detailed interpretations of the development shape type wavelength and angle of climb of aeolian bedforms as well as overall sand sea conditions current alternate interpretations of bounding surfaces require very different but testable models for sand sea deposition two perpendicular traverses of jurassic entrada sandstone utah reveal relations among cross strata first order bounding surfaces and horizontal strata these field relations seem explicable only as the deposits of downwind migrating climbing enclosed interdune basins horizontal strata and dune bodies consisting of superimposed smaller crescentic dunes cross stratified deposits a 1 7 km traverse parallel to the palaeowind direction provides a time transgressive view showing continuous cosets of cross strata first order bounding surfaces and interdune deposits climbing downwind at an angle of a few tenths of a degree changes occur in the angle of climb cross strata structure and interdune deposits these reflect changes in depositional conditions through time a 1 5 km traverse perpendicular to the palaeowind direction provides a view at an instant in geological time showing first order bounding surfaces and interdune deposits forming flat laterally discontinuous lenticular bodies the distribution of interdune sedimentary structures in this traverse is very similar to that of some modern interdune basins such as those on padre island texas hierarchies of bounding surfaces in an aeolian deposit reflect the bedform development on an erg the presence of three orders of bounding surfaces indicates dune bodies consisting of smaller super imposed dunes the geometry of first order bounding surfaces is a reflection of the shape of the inter dune basins second order bounding surfaces originate by the migration of the superimposed dunes over the larger dune body and reflect individual dune shape and type third order bounding surfaces are reactivation surfaces showing stages in the advance of individual dunes the presence of only two orders of bounding surfaces indicates simple dunes modern and entrada interdune deposits show a wide variety of sediment types and structures reflecting deposition under wet damp and dry conditions interdune deposits are probably the best indicators of overall erg conditions and commonly show complex vertical sequences reflecting changes in specific depositional conditions

paleoflood hydrology origin progress prospects from an origin in diverse studies of flood geomorphology and quaternary geology paleoflood hydrology emerged as a geophysical and an applied hydrological science during the 1970s and 1980s since acquiring its formal name in 1982 the most productive approach in paleoflood hydrology has become energy based inverse hydraulic modeling of discrete paleoflood events recorded in appropriate settings as slackwater deposits and other paleostage indicators swd psi or as various threshold indicators of non exceedence technological advances particularly in hydraulic modeling and geochronology were instrumental in moving the discipline to its present status the most recent advances include 1 new techniques for the accurate geochronology of flood sediments notably tams radiocarbon analyses and osl dating and 2 the phenomenal increase in computer power that allows complex hydraulic calculations to become feasible for routine studies from its initial demonstration in the southwestern united states swd psi paleoflood hydrology proved its widespread applicability to various landscape environments particularly important studies have been accomplished in australia china india israel south africa spain and thailand paleoflood hydrology has also generated its share of controversy in part because of the differing viewpoints and attitudes of the two scientific traditions from which it emerged quaternary geology geomorphology versus applied hydrologic hydraulic engineering nevertheless the future growth of the discipline is assured given the rapid pace of discoveries that it engenders indeed so many international studies exist that it is appropriate to pursue global syntheses to address interesting and timely questions of extreme flood phenomena in relation to global climatic change

spatial variability of active layer thickness detected by ground penetrating radar in the qilian mountains western china the active layer plays a key role in geomorphic hydrologic and biogeochemical processes in permafrost regions we conducted a systematic investigation of active layer thickness alt in northeastern qinghai tibetan plateau by using ground penetrating radar gpr with 100 and 200 mhz antennas we used mechanical probing pit and soil temperature profiles for evaluating alt derived from gpr the results showed that gpr is competent for detecting alt and the error was 0 08 m at common midpoint co located sites considerable spatial variability of alt owing to variation in elevation peat thickness and slope aspect was found the mean alt was 1 32 0 29 m with a range from 0 81 to 2 1 m in eboling mountain in yeniu gou mean alt was 2 72 0 88 m and varied from 1 07m on the north facing slope to 4 86 m around the area near the lower boundary of permafrost alt in peat decreased with increasing elevation at rates of 1 31 m km eboling mountain and 2 1 m km yeniu gou and in mineral soil in yeniu gou the rate changed to 4 18 m km at the same elevation alt on the south facing slope was about 0 8m thicker than that on the north facing slopes while the difference was only 0 18 m in peat covered area within a 100 m 2 area with a local elevation difference of 0 8 m alt varied from 0 68 m to 1 25 m both field monitoring and modeling studies on spatial alt variations require rethinking of the current strategy and comprehensive design

paleofloods and historical floods of the ardeche river france 1 better understanding of flood occurrences and long term floodplain planning and flood risk assessment is achieved by integration of gauged historical and paleoflood data the ardeche river is ideal for this historical flood paleoflood study because its historical flood levels record dates back as early as a d 587 and useful data date back to a d 1522 its systematic gauging record is over 100 years long and the geologic and geomorphic settings are optimal for paleoflood studies three sites provide three different thresholds for flood stages and swd accumulation according to our one dimensional 1 d step backwater calculations these three thresholds are 5200 5700 m3 s 1 4900 5400 m3 s 1 and 3600 4000 m3 s 1 recording 6 9 and 19 large holocene floods respectively dating the deposits enabled a correlation with the historical record these paleoflood studies indicate that there are long gaps in flood occurrences on the ardeche river the floods are not randomly distributed in time but are clustered they also indicate that the recent nineteenth century floods were the largest at the millennial timescale

a new approximation in determination of zonation boundaries of ignimbrite by ground penetrating radar kayseri central anatolia turkey ground penetrating radar gpr method is used as a tool to identify the zonation boundaries in ignimbrite series through their columnar section ignimbrites can be classified in terms of welding degree colour texture and mineralogical compositions the research area comprises a part of incesu kayseri ignimbrite at central anatolia turkey this ignimbrite is divided into three levels and each level has clear differences in terms of macroscopic and microscopic views this paper presents the results of an application of gpr for the determination of zonation boundary within the ignimbrite flow unit in the view of their textural and petrological features ramac cu ii equipment was used with 250 mhz shielded antenna on parallel ten profiles to observe the physical difference among the ignimbrite levels of the study area two levels out of three have been defined at the incesu ignimbrite and supported by field geology and petrographical studies the first level which is extremely fractured structure is about 1 5 m thick and matches with middle level of the incesu ignimbrite the second level has an average 50 75 cm thickness and matches with lower level of the ignimbrite in this manner vertical lithological variations should be taken into consideration during petrological investigation of the ignimbrites

palaeoflood record of the tagus river central spain during the late pleistocene and holocene abstract palaeoflood hydrology of the tagus river central spain was reconstructed from slackwater deposits and palaeostage indicators in two canyon reaches located at el puente del arzobispo in the central part of the catchment 35 000 km 2 in drainage area and in alcantara at the lower part of the catchment 52 000 km 2 in drainage area near the portuguese border the palaeoflood record with more than 80 flood events shows clusters of floods at specific periods from 9440 to 9210 14 c yr bp 8540 8110 bc 8500 to 8000 14 c yr bp 7500 7000 bc 6750 14 c yr bp 5000 bc 1200 to 950 14 c yr bp ad 785 1205 410 14 c yr bp ad 1450 1500 170 to 80 14 c yr bp ad 1670 1950 the largest flood s occurred during the periods 9440 to 9210 14 c yr bp 6750 14 c yr bp and 1200 to 950 14 c yr bp reaching minimum discharge estimates of between 4000 and 4100 m 3 s 1 in the el puente del arzobispo reach and 13 700 15 000 m 3 s 1 in the alcantara reach these periods with increased flood magnitude and or frequency in the tagus river are strongly related to increased moisture influx and winter precipitation in the iberian peninsula especially in the western zone proxy records sensitive to winter precipitation such as lake levels and vegetation changes indicated by pollen records are in good agreement with the clusters of floods found in the tagus river this flood variability seems to correspond to changes in the prevailing atmospheric circulation pattern affecting the iberian peninsula

responses of floods to holocene climatic change in the upper mississippi valley abstract dimensions of holocene relict channels and sedimentological characteristics of point bars associated with these relict channels were used to reconstruct a holocene history of long term changes in magnitudes of 1 58 yr floods in upper mississippi valley watersheds of southwestern wisconsin the reconstructed record of floods shows relatively large and persistent nonrandom departures from contemporary long term average flood magnitudes the flood history indicates climatic changes that are broadly similar to climatic changes indicated from fossil pollen in the same region the holocene floods ranged from about 10 15 larger to 20 30 smaller than contemporary floods of the same recurrence frequency large floods were characteristic between about 6000 4500 and 3000 2000 yr b p and during a brief interval after 1200 yr b p small floods were common between about 8000 6500 4500 3000 and 2000 1200 yr b p these fluvial responses were found to be closely associated with a long term episodic mobility and storage of sediments in the wisconsin watersheds during periods of relatively large floods relatively rapid lateral channel migration either reworked or removed extensive tracts of valley bottom alluvium in contrast during periods of relatively small floods relatively slow lateral channel migration is apparent and the channel and floodplain system appear to have been relatively stable

paleohydrologic bounds and extreme flood frequency of the upper arkansas river colorado usa article i nfo article history the upper arkansas river basin has experienced notable large floods including the event of 2 6 june 1921 that devastated the city of pueblo colorado we investigated flood and paleoflood hydrology at strategic sites to determine the frequency and geographic extent of extreme floods within the basin for a dam safety application streamgage historical and paleoflood data were utilized to develop frequency curves at sites near salida cotopaxi parkdale and pueblo soil stratigraphic descriptions radiocarbon dating and hydraulic modeling were used to estimate paleoflood nonexceedance bounds at the four sites which ranged from 400 to 2200 ybp for late holocene surfaces to late pleistocene surfaces near cotopaxi peak flow data are from lower magnitude snowmelt runoff in may and june in the upper basin and from high magnitude rainfall runoff from june to august in the lower basin flood frequency curves reflect this transition near parkdale from snowmelt to extreme rainfall runoff for similar return periods paleoflood peak discharges increase from about 480 m 3 s upstream at loma linda to about 4250 m 3 s downstream near pueblo this increase is attributed to the larger rainfall component derived from lower elevations between loma linda and pueblo return periods for design floods at pueblo dam exceeded 10 000 years based on paleoflood frequency curve extrapolations

palaeoflood hydrology of the salt river arizona geomorphic evidence along bedrock confined reaches of the salt river in east central arizona provides a record of the river s largest flood events fine grained flood slackwater deposits accumulated at channel margin irregularities several metres above the low flow channel discharges associated with flow events responsible for the deposits were estimated by computer flow modelling these estimates document flood magnitudes in excess of gauged historic streamflows relative and radiocarbon dating suggest that a flood record in excess of 600 y is preserved in the slackwater sequences a prominent flood scar cut into grussy hillslope soils allows the extension of the prehistoric flood record to several thousand years a maximum discharge estimate of 4600 m3s 1 affixed to the flood scar represents the largest flood event in the record and is given a minimum recurrence interval of 1000 2000 y the 1952 flood is the largest historic flow event experienced along the study reach and is estimated at 2900 m3s 1 two palaeoflood events preserved in the slackwater stratigraphy exceed the 1952 event and are given recurrence intervals of 300 and 600 y the latter flood event had an estimated discharge of 3200 m3s 1 it is apparent that discharge estimates affixed to these infrequent large magnitude flood events approach a maximum with decreased probabilities large recurrence intervals this suggests that a physical limit on discharge may exist within the salt river drainage basin and is perhaps directly related to drainage basin size

radiocarbon dating of flood events katherine gorge northern territory australia radiocarbon analyses of organic materials provide accurate dating of flood events in the katherine gorge northern territory australia selected flood events in the period 1955 1980 can be very precisely dated essentially to the calendar year through the use of curves showing the time variation of anomalously high 14 c activity in the troposphere that was generated by nuclear testing conventional radiocarbon analysis of alluvial charcoal and organic litter is used to establish dates for the largest katherine river floods of the past several centuries the improved geochronologic techniques demonstrated here will help improve paleoflood hydrologic interpretations

paleohydrologic techniques used to define the spatial occurrence of floods abstract defining the cause and spatial characteristics of floods may be difficult because of limited streamflow and precipitation data new paleohydrologic techniques that incorporate information from geomorphic sedimentologic and botanic studies provide important supplemental information to define homogeneous hydrologic regions these techniques also help to define the spatial structure of rainstorms and floods and improve regional flood frequency estimates the occurrence and the non occurrence of paleohydrologic evidence of floods such as flood bars alluvial fans and tree scars provide valuable hydrologic information the paleohydrologic research to define the spatial characteristics of floods improves the understanding of flood hydrometeorology this research was used to define the areal extent and contributing drainage area of flash floods in colorado also paleohydrologic evidence was used to define the spatial boundaries for the colorado foothills region in terms of the meteorologic cause of flooding and elevation in general above 2300 m peak flows are caused by snowmelt below 2300 m peak flows primarily are caused by rainfall the foothills region has an upper elevation limit of about 2300 m and a lower elevation limit of about 1500 m regional flood frequency estimates that incorporate the paleohydrologic information indicate that the big thompson river flash flood of 1976 had a recurrence interval of approximately 10 000 years this contrasts markedly with 100 to 300 years determined by using conventional hydrologic analyses flood discharge estimates based on rainfall runoff methods in the foothills of colorado result in larger values than those estimated with regional flood frequency relations which are based on long term streamflow data preliminary hydrologic and paleohydrologic research indicates that intense rainfall does not occur at higher elevations in other rocky mountain states and that the highest elevations for rainfall producing floods vary by latitude the study results have implications for floodplain management and design of hydraulic structures in the mountains of colorado and other rocky mountain states

distortion of isochronous layers in ice revealed by ground penetrating radar in addition to measuring ice sheet thickness ground penetrating radar can be used to delineate reflections in ice sheets1 2 3 these reflections are generally accepted to result from layers of isochronous deposition of snow and can reveal much about the dynamics of the ice flow here we present ground penetrating radar data from fletcher promontory antarctica which show arches and troughs in isochronous ice layers to a depth of 100 m we demonstrate that the origin of these features can be determined by their growth with depth and many features result from local anomalies in accumulation rate which can be correlated with the ice surface slope one arch appears to be the result of a local anomaly in vertical strain rate its proximity to the ice divide width and growth with depth indicate that this arch is one of a class of features postulated by raymond4 but not previously shown to exist in the field such a feature is an indication of the nonlinear rheology of ice and requires that palaeoclimate records from ice cores extracted from the vicinity of ice divides underlain by similar features should be specifically corrected for such effects on ice flow

river derived slackwater sediments in caves along cheat river west virginia abstract the november 1985 cheat river flood produced overbank slackwater deposits in caves of the cheat river canyon the deposits include loamy silt loamy sand to very fine sand and flotsam sediments deposited by the november 1985 flood lie within 1 m of the established high water mark and are good indicators of peak stage prehistoric overbank slackwater deposits are present in one cave these sediments are inferred to be 400 000 years old and are therefore unrelated to the modern cheat river overbank slackwater deposits are poorly preserved in the examined caves because cave streams actively remove sediments and the warm moist environment of the caves fosters decay of woody flotsam deposits of the 1985 flood are projected to survive at most a few centuries in contrast slackwater sediments inferred to be 400 000 years old are preserved within a cave shielded from significant runoff and biogenic activity

quaternary sediment architecture in the orkhon valley central mongolia inferred from capacitive coupled resistivity and georadar measurements abstract detailed information on shallow sediment distribution in basins is required to achieve solutions for problems in quaternary geology geomorphology neotectonics geo archaeology and climatology usually detailed information is obtained by studying outcrops and shallow drillings unfortunately such data are often sparsely distributed and thus cannot characterise entire basins in detail therefore they are frequently combined with remote sensing methods to overcome this limitation remote sensing can cover entire basins but provides information of the land surface only geophysical methods can close the gap between detailed sequences of the shallow sediment inventory from drillings at a few spots and continuous surface information from remote sensing however their interpretation in terms of sediment types is often challenging especially if permafrost conditions complicate their interpretation here we present an approach for the joint interpretation of the geophysical methods ground penetrating radar gpr and capacitive coupled resistivity ccr drill core and remote sensing data the methods gpr and ccr were chosen because they allow relatively fast surveying and provide complementary information we apply the approach to the middle orkhon valley in central mongolia where fluvial alluvial and aeolian processes led to complex sediment architecture the gpr and ccr data measured on profiles with a total length of about 60 km indicate the presence of two distinct layers over the complete surveying area i a thawed layer at the surface and ii a frozen layer below in a first interpretation step we establish a geophysical classification by considering the geophysical signatures of both layers we use sedimentological information from core logs to relate the geophysical classes to sediment types this analysis reveals internal structures of orkhon river sediments such as channels and floodplain sediments we also distinguish alluvial fan deposits and aeolian sediments by their distinct geophysical signature with this procedure we map aeolian sediments debris flow sediments floodplains and channel sediments along the measured profiles in the entire basin we show that the joint interpretation of drillings and geophysical profile measurements matches the information from remote sensing data i e the sediment architecture of vast areas can be characterised by combining these techniques the method presented here proves powerful for characterising large areas with minimal effort and can be applied to similar settings

reconstructing the ca 100 year flood in northern thailand the key utilities of palaeohydrological studies are the potential to extend the flood record of a catchment and improve estimates of flood frequency and magnitude in this study we use a hydraulic model to produce estimates of discharge based on psi palaeo stage indicator evidence from large floods for a study reach of the mae chaem river thailand careful calibration of this model especially manning s n was possible because of the availability of psis from several modern gauged flows organic psi evidence contained in a cave permitted dating of the largest flood for which evidence was available which is close to the 100 year flood the magnitude of this flood is twice that predicted from an extrapolation of the 49 year gauging record employing the gumbel ev1 flood frequency model officially endorsed by water management agencies in thailand this magnitude of flood is however very similar to that predicted from a power law model and suggests that extreme flood magnitude and frequency in this catchment conform to power law behaviour these results significantly increase the perception of flood risk for the area and this palaeohydrological case study represents the first for the region

controls on bedrock channel incision along nahal paran israel nahal paran drains 3600 km2 of egypt s sinai peninsula and israel s negev desert much of the channel is alluvial but a canyon 10 5 km long has been incised into late cretaceous chert and dolomite in the lower portion of the basin slackwater deposits and paleostage indicators preserved within the canyon record approximately 10 floods of 200 to 2500 m3 s 1 over a period of at least 350 years step backwater simulations of flood flow hydraulics indicate extreme variations in stream power per unit area along the length of the canyon and associated variability in energy expenditure and sediment transport these variations reflect channel cross sectional morphology the greatest values of stream power occur along the lower half of the study reach in association with three pronounced knickpoints and an inner channel the locations of these features reflect the exposure of thick resistant chert layers along the channel the presence of several similar but buried and inactive knickpoints along the upper study reach indicates that the locus of most active channel incision has shifted with time probably in response to baselevel changes associated with tectonic activity along the dead sea rift thus the rate and manner of channel incision along the canyon of nahal paran are controlled by lithologic variability and tectonic uplift as they influence channel morphology and gradient which in turn influence hydraulics and sediment transport

paleoflood evidence for a natural upper bound to flood magnitudes in the colorado river basin the existence of an upper limit to the magnitude of floods in a region is a long standing and controversial hypothesis in flood hydrology regional envelope curves encompassing maximum flood magnitudes stabilize with progressive increases in the areal coverage and period of observation wolman and costa 1984 however the short lengths of conventional gaging records limit substantial advances in testing whether this stabilization is evidence of an upper limit in the colorado river basin there are 32 120 station years of gage data but the average period at a gaging station is only 20 years with most stations having less than 70 years of observation paleoflood magnitudes derived from sediments of large prehistoric floods from 25 sites on rivers in arizona and utah provide additional data to extend the records of the largest floods the paleoflood data identify the maximum flood discharges that have occurred on individual rivers over the last several hundred to several thousand years even with this increase in the observational period the largest paleoflood discharges do not exceed the upper bound of maximum peak discharges delineated by the envelope curve derived from the available gaged and historical records this result accords with the hypothesis of an upper physical limit for flood magnitudes and suggests that for the colorado river basin the upper limit can be approximated by existing systematic and historical data for large floods similar relationships also hold when paleofloods and gaged records are presented for the subregion of southern arizona

extraordinary floods of 4100 4000 a bp recorded at the late neolithic ruins in the jinghe river gorges middle reach of the yellow river china abstract holocene palaeohydrological investigations were carried out in the middle reach of the jinghe river that drains the central part of the loess plateau a set of palaeoflood slackwater deposits was found interbedded in the holocene loess soil sequence within the cliff riverbanks both the sedimentary criteria and the analytical results show that this sediment was sourced from a suspended sediment load of floodwater the major cultural layer of a late neolithic settlement 4300 4000 a bp occurring at the same site is blanketed by this flood deposit directly slopewash with pottery shards charcoal and burnt earth occurs in between the palaeoflood slackwater deposit beds it indicates that each of the slackwater deposit beds has recorded one individual flood event and that these extraordinary floods occurred when the late neolithic people occupied the riverbank terrace land this pre historical settlement was abandoned after the floods eventually due presumably to repeated inundation by overbank floodwater the flood events were osl dated to between 4100 and 4000 a bp and checked by archaeological dating of the anthropogenic remains retrieved from the sequences peak discharges of the floods were estimated to between 19 500 and 22 000 m3 s 1 which is several times gauged maximum floods during the 4200 4000 a bp climatic event severe droughts were documented in china s monsoonal regions and great floods were known from an ancient legend this study provides a well dated sediment record of pre historical floods which occurred at the transition from the neolithic to the bronze age in the yellow river basin it shows that extraordinary floods were part of the abrupt climatic variability during the 4200 4000 a bp climatic event the highly variable unstable and catastrophic climate typified by both droughts and floods resulted in settlement abandonment and possibly the decline of the highly developed late neolithic civilizations in china s monsoonal regions

10 000 yr record of extreme hydrologic events well dated lacustrine sediments provide a hydrologic record indicating that the frequency and magnitude of runoff events and by inference storms have varied over the past 10 k y in northern new england we used five sediment cores and radiocarbon dating to develop a chronology of holocene hydrologic events for the ritterbush pond basin northern vermont chemical and physical analyses allow us to identify 52 distinct layers of predominately inorganic sediment that represent terrestrially derived material delivered to the pond by runoff events the thickness of some layers suggests hydrologic events at least equal in size to and probably much larger than any storm or flood recorded during nearly 300 yr of written regional history layer thickness and frequency and by analogy storm size and recurrence change through the holocene the largest events occurred 2620 6840 and 9440 calibrated 14c years before present cal 14c yr b p the most frequent hydrologic events occurred in three periods 1750 to 2620 6330 to 6840 and 8600 cal yr b p the recurrence interval of layer deposition during stormy periods averages 130 100 cal yr whereas the recurrence interval during less stormy periods is longer 270 170 cal yr the ritterbush pond event record illustrates the potential of inorganic lacustrine sediment to serve as a proxy record for estimating paleoflood frequency and deciphering climate change

the role of permafrost and seasonal frost in the hydrology of northern wetlands in north america abstract wetlands are a common landscape feature in the arctic subarctic and north temperate zones of north america in all three zones the occurrnce of seasonal frost results in similar surface water processes in the early spring for example surface ice and snow generally melt before the soil frost thaws causing melt water to flow into depressions over the land surface and at times across low topographic divides however evapotranspiration and ground water movement differ among the three climatic zones because they are more affected by permafrost than seasonal frost the water source for plants in the arctic is restricted to the small volume of subsurface water lying above the permafrost although this is also true in the subarctic where permafrost exists where it does not plants may receive and possibly reflect more regional ground water sources where permafrost exists the interaction of wetlands with subsurface water is largely restricted to shallow local flow systems but where permafrost is absent in parts of the subarctic and all of the temperature zone wetlands may have a complex interaction with ground water flow systems of all magnitudes

exploration of subsurface strata conditions for a limestone mining area in india with ground penetrating radar a study has been conducted for the exploration of underground voids and strata conditions at shallow depth in a limestone mine of manikgarh cement at maharashtra in india the manikgarh cement is surrounded with high quality limestone having platy formations with excessive fractures and fissures a perennial river the amal nala is flowing across the middle of limestone mining lease of the manikgarh cement captive mine the impact of this water body on the mining is the central theme of this study excavation of limestone is in progress in different blocks on both sides of the amal nala for the purpose of planning it was necessary to know the ground conditions of the area surrounding the amal nala so that seepage of the water can be checked if there is no adverse impact due to deepening of mining activity the minerals lying at depth can be safely exploited a ground penetrating radar gpr survey was carried out in the mining lease area to investigate the condition of the strata status of fractures cracks cavities etc through which seepage or water percolation takes place the results of this survey reveal that solid compact layers exist from the surface to depths varying from 2 to 5 m only along the three sections g1g1 g2g2 and g3g3 lying in the mining area of the manikgarh limestone along both sides of the amal nala fractured weathered rocks and solution cavities exist from the surface to depths varying from 4 to 16 5 m therefore extraction of limestone is possible only to depths of 2 to 5 m from the surface in this mining area if extraction continues below this depth the seepage of water from the amal nala will start due to the presence of enormous fractures and cavities solution holes in the underlying limestone strata in addition the water of the amal nala will be disturbed which is the main water reservoir of this area

mapping vertical profile of discontinuous permafrost with ground penetrating radar at nalaikh depression mongolia ground penetrating radar gpr has become an important geophysical tool which can provide a wealth of interpretive information about the vertical profile of discontinuous permafrost a gpr investigation was conducted in october 2006 at the nalaikh site at the southern boundary of the siberian discontinuous permafrost region in mongolia gpr data were collected along four 100 m long profiles to identify the location of the permafrost body which included an in situ drilling borehole and analysis of temperature observations and soil water content measurements from boreholes the gpr interpretation results indicated that the thickness of discontinuous permafrost at the study site was only 1 9 3 0 m and the permafrost is vulnerable to climate change the soil temperature and soil water content data demonstrate the precision of gpr image interpretation this case demonstrated that gpr is well suited for mapping the internal structure of discontinuous permafrost with relatively low soil water content

a 4500 year record of large floods on the colorado river in the grand canyon arizona a sequence of flood deposits left by the colorado river in the grand canyon arizona provides evidence of at least 15 floods with peak discharges greater than 5500 m 3 sec 1 over the last 4500 yr ten floods during the last 2000 2300 yr had discharges greater than 6800 m 3 sec 1 one flood 1600 1200 yr ago had a discharge exceeding 14 000 m 3 sec 1 a flow rate more than twice the largest gaged flood this record of flooding is one of the longest for a major u s river and combined with the gaged record of twentieth century floods allows determination of the frequency and history of large floods that have affected key aspects of colorado river geomorphology

paleoflood hydrology and extraordinary flood events paleoflood hydrology is the study of past or ancient flood events the most accurate technique involves the analysis of slackwater deposits and paleostage indicators swd psi slackwater deposits are sand and silt emplaced from suspension in exceptionally deep high velocity floods that characterize narrow deep canyons in resistant geologic materials these and other paleostage indicators are used to establish hydraulic grade lines for the generating flow events favorable sites for slackwater deposition include channel margin areas where stresses and velocities are reduced below critical values necessary to maintain fine grained bedload material sand and silt in suspension computerized procedures for hydraulic flow modeling are used to tie the elevations of the highest slackwater deposits to surveyed river cross sections the flood discharges calculated by this method can be calibrated through the study of modern floods on gaged rivers correlation of multiple swd psi sites along a river reach is used to identify the maximum paleostage achieved by a given flood advances in the dating of flood deposits permit estimates of flood frequency to be made extending over a data base of thousands of years the major geochronologic tool is radiocarbon dating of various kinds of organic matter intercalated with the slackwater deposits an important development is the use of the tandem accelerator mass spectrometer for direct measurement of 14c tiny blebs of charcoal seeds and other organics can be analyzed in order to date ancient flood deposits of hydrologic significance since swd psi studies yield very accurate determinations of paleoflood ages and magnitudes there is a pressing need for new statistical procedures that make optimum use of the information content in paleoflood records for flood frequency analysis nevertheless swd psi paleoflood hydrology has moved beyond the research phase its use should be encouraged in evaluating past experience of extraordinary floods at appropriate hazardous sites

late holocene slackwater deposits on the nakagawa river tochigi prefecture japan a continuous succession of slackwater deposits was investigated on the nakagawa river karasuyama town in tochigi prefecture japan forty one and 32 flood events were estimated from two sedimentary cores minimum sedimentation rate is estimated at 4 6 mm year and the calculated maximum flood recurrence interval is 14 years the sedimentation rates are high compared to other published data and are thought to be the key reason as to why these deposits were preserved in japan previously considered too humid high sediment accumulation rates are thought to compensate for any bioturbation activity that would disturb and homogenise the slackwater deposits this study is important because it presents a new arena for palaeoflood analysis suggesting that there is potential for slackwater preservation in similar humid settings

events episodes and phases signal from noise in flood sediment archives major floods have increased in frequency in many parts of the world and this is often attributed to anthropogenic climate change because of the short length of most gauged records 50 yr it is unclear whether these events represent a short term anomaly or a shift to a prolonged flood rich period in this paper we use event scale paleoflood records from upland and lowland floodplains to demonstrate the relationship between individual flood events clusters of events in multiyear episodes and multidecadal to centennial scale flood rich phases catchment and regional scale data show that individual events and episodes generally fall within extended flood rich phases controlled by climate furthermore contrary to recent suggestions that environmental signals may be rendered incomplete in fluvial systems by autogenic processes from a multidecadal and longer perspective it is clear that floodplain environments can register and preserve a useful multiscale hydromorphic signal of climate change

past hydrological events reflected in the holocene fluvial record of europe abstract a comprehensive database of radiocarbon dated fluvial units in great britain poland and spain has been compiled to investigate the relationship between environmental change flooding and holocene river dynamics following the methodology recently developed by macklin and lewin macklin m g lewin j 2003 river sediments great floods and centennial scale holocene climate change journal of quaternary science 18 101 105 radiocarbon dates in fluvial sequences that coincide with a modification in sedimentation rate or style have been highlighted allowing geomorphologically significant changes in holocene river activity to be identified data analysis has been undertaken at both national and sub national scales and on catchments of different size type and land use history multiple phases of higher flood frequency characterized by accelerated erosion and sediment deposition on floodplains are recognized and compared with a range of climate proxies the relative and varying roles of climate and land use on river dynamics are considered and the value of the database for reconstructing past hydrological events as well as for predicting river response to future environmental change is assessed

holocene flood histories in south western usa harden t macklin m g baker v r 2010 holocene flood histories in south western usa earth surface processes and landforms 35 6 707 716 sponsorship aberystwyth university university of arizona

permafrost dynamics in the 20th and 21st centuries along the east siberian transect 1 the east siberian transect which has been designated by the international geosphere biosphere program igbp as its far east transect has unique permafrost conditions not only does permafrost underlie the entire transect but also about one third of the region is underlain by an ice complex consisting of extremely ice rich late pleistocene sediments given the possibility of a predicted future increase in global temperatures an evaluation of the magnitude of changes in the ground thermal regime becomes desirable for assessments of possible ecosystem responses and impacts on infrastructure a soil model developed at the geophysical institute permafrost laboratory was used to simulate the dynamics of the active layer thickness and ground temperature in this transect both retrospectively and prognostically using climate forcing from six global climate models gcms analysis of future permafrost dynamics showed that within the southwestern part of the transect widespread permafrost thawing from the surface can begin as early as 2050 the spatial extent and temporal dynamics of the zone with thawing permafrost vary significantly among the different gcms according to all the gcms the mean annual ground temperatures could rise by 2 6 c and the active layer thickness could increase by 0 5 2 m everywhere within the transect by 2099 however the increases in mean annual ground temperature and active layer thickness are not uniform in time relatively cold and warm periods associated with natural fluctuations in air temperature and precipitation are superimposed on the background warming trend the most significant increases in mean annual ground temperatures and in the active layer thickness are projected to occur in the southwestern part of the transect and in areas with coarse grained sediments characterized by low water content and high thermal conductivity

the palaeoflood record of a hyperarid catchment nahal zin negev desert israel the palaeohydrology of nahal zin a 1400 km2 catchment in the hyperarid negev desert is inferred from slackwater deposits and palaeostage indicators in a canyon near its lower end the palaeoflood record augmented by the instrumental and historical records of the last decade includes 28 floods ranging from 200 to 1500 m3s 1 over the last 2000 years this helps to reanalyse the frequency of floods in this drainage system the clusters of floods around 1000 years bp and again during the last 60 years are characterized by high flow magnitudes periods with many floods correspond well to periods with high dead sea levels and are probably relatively wet periods while periods with few floods correspond well to low dead sea levels indicating a drier climate fluctuations in the frequency of floods are typical of periods of transition from one climate regime to another copyright 2000 john wiley sons ltd

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

response of extreme floods in the southwestern united states to climatic variations in the late holocene a regional synthesis of paleoflood chronologies on rivers in arizona and southern utah reveals that the largest floods over the last 5000 years cluster into distinct time periods that are related to regional and global climatic fluctuations the flood chronologies were constructed using fine grained slackwater deposits that accumulate in protected areas along the margins of bedrock canyons and selectively preserve evidence of the largest events high magnitude floods were frequent on rivers throughout the region from 5000 to 360014c yrs bp dendrocalibrated age 3800 2200 bc and increased again after 2200 bp 400 bc with particularly prominent peaks in magnitude and frequency around 1100 900 bp ad 900 1100 and after 500 yrs bp ad 1400 in contrast the periods 3600 2200 bp 2200 400 bc and 800 600 yrs bp 1200 1400 ad are marked by sharp decreases in the occurrence of large floods on these rivers in the modern record storms that generate large floods 10 year in the region fall into three categories 1 winter north pacific frontal storms 2 late summer and fall storms that draw in moisture from recurved pacific tropical cyclones and 3 summer storms mainly convective thunderstorms winter storms and tropical cyclones are associated with the most severe floods on the rivers in this study and are the most probable causes of the paleofloods over the last 5000 years floods from both winter storms and tropical cyclones occur when deep mid latitude troughs steer storm systems into the region composite anomaly maps of daily 700 mbar heights indicate that these floods are associated with a low pressure anomaly off the california coast and a high pressure anomaly over the aleutians or gulf of alaska a strong connection exists between the negative phase of the southern oscillation index often associated with el nin o conditions and the large floods associated with winter storms and tropical cyclones the paleoflood records confirm the existence of centennial scale variations in the conditions conducive to the occurrence of extreme floods and flood generating storms in this region the episodes with an increased frequency of high magnitude floods coincide with periods of cool wet climate in the western u s whereas warm intervals such as the medieval warm period are times of dramatic decreases in the number of large floods a positive relationship between the paleofloods and long term variations in the frequency of el nin o events is evident over the last 1000 years this relationship continues over at least the last 3000 years with warm coastal sea surface temperatures indicative of el nin o like conditions

paleofloods and a dam failure flood on the virgin river utah and arizona abstract flood deposits on the virgin river in southern utah and northern arizona preserve a record of the magnitude and frequency of the largest natural floods that have occurred on the river since ad 900 in the virgin river gorge several of the natural paleoflood discharges were comparable with or even greater than the flood from a catastrophic dam failure in 1989 that produced an estimated peak discharge of 1730 m3 s 1 in this reach of the virgin river to estimate the paleoflood discharges the heights of slackwater flood deposits in the lower bedrock gorge of the virgin river were compared with water surface elevations calculated with the hec 2 step backwater hydraulic model the timing of the paleofloods was determined by the ages of layers rich in human artifacts that are interbedded with the flood deposits the estimates of both the 1989 flood and the paleofloods were carried out in the virgin river gorge about 60 km downstream of the dam break site no natural floods of this magnitude have occurred within the relatively short period of the gaged record this study illustrates how incorporating rare extreme events from the long term paleoflood record improves the database for flood frequency analysis the 1989 flood serves as an analog to the effects of rare natural floods with similar magnitudes along the lower virgin river

investigating internal structure of permafrost using conventional methods and ground penetrating radar at honhor basin mongolia a ground penetrating radar gpr survey was conducted at the end of august 2009 in the suburb region of ulaanbaatar honhor basin mongolia in combination with conventional methods such as borehole drilling and measurement of ground temperatures the interface of frozen and unfrozen sediment was distinctly resolved in the interpreted gpr images verified by the borehole drilling records and 6 month measurement of ground temperatures the location of the permafrost table was assessed to be at the depth of 2 4 m in the study region a conspicuous ice saturated soil layer massive ground ice was detected in the interpreted gpr images with a thickness of 2 5 m the gpr investigation results were consistent with the borehole drilling records and ground temperatures observation the borehole logs and ground temperatures profile in the borehole indicates that permafrost at honhor basin is characterized by high ground temperature and high ice content which implies that ongoing climatic warming would have great influence on permafrost dynamics the research results are of great importance to further assess permafrost dynamics to climatic change in the boundary of discontinuous and sporadic permafrost regions in mongolia in the future

the origin of horizontal alternating bedding in weichselian aeolian sands in northwestern europe abstract periglacial acolian sands of weichselian age are widespread in the lowlands of western and central europe one facies of this sediment type corresponding to the coversand sensu stricto is characterised by a wavy parallel bedding and a generally horizontal position of the strata since this layering results from an alternation of finer and coarser grained beds horizontal alternating bedding is the appropriate designation for it by a detailed analysis of representative lacquer peels eight characteristic stratification types could be distinguished these units are the smallest fundamental building blocks constituting the sediment under consideration an idealised annual cycle of sedimentation is proposed in summer light and variable winds carry silt in suspension to the site of deposition whilst the sandy saltation load is left behind in a throughput zone farther upwind upon settling the fines adhere to the surface which is wet or damp due to the thawing of the seasonally frozen ground in winter wind strength is generally greater so that deposition of sand prevails in the area whereas the fine grained suspension load settles downwind deposition by snow free winds results in the accretion of patches of well sorted sand snow flurries on the other hand produce niveo aeolian strata of generally more poorly sorted sand in the cycle it is implied that 1 the aeolian sedimentation basin must have been large and uniform enough to permit areal separation of sand and loess like material and 2 a seasonal shift in the centres of sand and silt deposition was inherent to the atmospheric pressure system of the formative period the exposed part of the northern and eastern north sea floor as it existed around the middle weichselian glacial climax assumedly was the principal source area for the deposits the relationships between the periglacial aeolian sands with horizontal alternating bedding loess and their integrades as described from the belgian lowlands and niedersachsen can be interpreted in the context of the proposed depositional cycle

paleoflood hydrology on the lower green river upper colorado river basin usa an example of a naturalist approach to flood risk analysis abstract through a comprehensive paleoflood hydrological investigation we document natural evidence for at least 27 high magnitude paleofloods at six sites on the lower green river utah hydraulic analysis using the sedimentation and river hydraulic 2d model srh 2d shows that the responsible peak paleoflood discharges ranged between 500 and 7500 m3 s at least 14 of these paleoflood discharge peaks exceed a level twice that of the maximum systematic record of gauged flows 1929 m3 s geochronological analyses employing optically stimulated luminescence osl and radiocarbon dating techniques demonstrate that these 14 largest paleoflood peaks occurred during the past 700 years integration of the paleoflood data into flood frequency analyses ffa reveals considerably higher values for the upper tails of the flood distribution than does a ffa based solely on the systematic gauged record indicating that extreme floods are larger and more frequent than implied by the relatively short gauged record through examination of three approaches to extreme flood estimation conventional ffa probable maximum flood estimation pmf and paleoflood hydrology pfh we show the significance of the natural evidence for advancing scientific understanding of extreme floods that naturally occur in the colorado river system we argue that this kind of scientific understanding is absolutely essential for achieving a credible evaluation of extreme flood risk in a watershed of immense importance to economic prosperity of the southwestern u s

measuring thaw depth beneath peat lined arctic streams using ground penetrating radar in arctic streams depth of thaw beneath the stream channel is likely a significant parameter controlling hyporheic zone hydrology and biogeochemical cycling as part of an interdisciplinary study of this system we conducted a field investigation to test the effectiveness of imaging substream permafrost using ground penetrating radar gpr we investigated three sites characterized by low energy water flow organic material lining the streambeds and water depths ranging from 0 2 to 2 m we acquired data using a 200 mhz pulsed radar system with the antennas mounted in the bottom of a small rubber boat that was pulled across the stream while triggering the radar at a constant rate we achieved excellent results at all three sites with a clear continuous image of the permafrost boundary both peripheral to and beneath the stream our results demonstrate that gpr can be an effective tool for measuring substream thaw depth copyright 2005 john wiley sons ltd

sedimentology and development of parabolic dunes grande prairie dune field alberta the grande prairie dune field in northwest central alberta is composed of parabolic and dome dunes presently inactive but which had developed under westerly winds two parabolic dune types are rec