exploring the role of humans and climate over the balkan landscape 500 years of vegetational history of serbia abstract we present the first well dated high resolution record of vegetation and landscape change from serbia which spans the past 500 years biological proxies pollen spores and charcoal geochemical analysis through x ray fluorescence xrf and a detailed chronology based on ams 14c dating from a western serbian sinkhole core suggest complex woodland grassland dynamics and strong erosional signals throughout the little ice age lia an open landscape with prominent steppe vegetation e g poaceae chenopodiaceae and minor woodland exists during 1540 1720 ce early lia while the late lia 1720 1850 ce in this record shows higher tree percentages possibly due to increased moisture availability the post lia era 1850 2012 ce brings a disturbed type of vegetation with the presence of weedy genera and an increase in regional woodland anthropogenic indicators for agricultural pastoral and fire practices in the region together attest to the dominant role of humans in shaping this balkan landscape throughout the interval the changing nature of human interference potentially as a response to underlying climatic transitions is evident through large scale soil depletion resulting from grazing and land clearance during the early lia and stabilization of arable lands during the late and post lia eras

influence of cohesion on river bed scour in the wake region of piers abstractstudies on scour in the wake region of piers in cohesive sediments containing gravel were not reported in literature to the best of our knowledge results from the laboratory experiments based study on the process of wake scour are presented here the sediment used for the experiment were of two types 1 fine gravel mixed with clay in proportions varying from 20 to 60 by weight and 2 fine gravel and fine sand in equal proportion by weight mixed with clay in proportions varying from 20 to 60 by weight the experiments revealed that the process of scour as well as depth shape and geometry of scour hole developed in such cohesive sediment were significantly different from that of cohesionless sediments proportion of clay fraction and unconfined compressive strength of cohesive sediment mixture were found to be the most significant variables controlling the depth of scour in the wake of piers on the basis of dimensional considerations relationships have been proposed for the estimation

annual climate variability in the holocene interpreting the message of ancient trees abstract over vast areas of the world s landmasses where climate beats out a strong seasonal rhythm tree growth keeps unerring time in their rings trees record many climate melodies played in different places and different eras recent years have seen a consolidation and expansion of tree ring sample collections across the traditional research areas of north america and europe and the start of major developments in many new areas of eurasia south america and australasia from such collections are produced networks of precisely dated chronologies records of various aspects of tree growth registered continuously year by year across many centuries their sensitivities to different climate parameters are now translated into ever more detailed histories of temperature and moisture variability across expanding dimensions of time and space with their extensive coverage high temporal resolution and rigid dating control dendroclimatic reconstructions contribute significantly to our knowledge of late holocene climates most importantly on timescales ranging from 1 to 100 years in special areas of the world where trees live for thousands of years or where subfossil remnants of long dead specimens are preserved work building chronologies covering many millennia continues apace very recently trees have provided important new information about major modes of general circulation dynamics linked to the el nino southern oscillation and the north atlantic oscillation and about the effect of large volcanic eruptions as for assessing the significance of 20th century global warming the evidence from dendroclimatology in general supports the notion that the last 100 years have been unusually warm at least within a context of the last two millennia however this evidence should not be considered equivocal the activities of humans may well be impacting on the natural growth of trees in different ways making the task of isolating a clear climate message subtly difficult

experimental investigation on the longitudinal evolution of landslide dam breaching and outburst floods abstract accurate prediction of the evolution of a landslide dam that is breached due to overtopping failure is necessary to estimate the outflow hydrograph and the resulting inundation in this study physical flume tests on the breaching of landslide dams were conducted a wide grain size distribution with unconsolidated dam material was used dam breaching was initiated by cutting a notch across the crest of the dam adjacent to the side wall of the flume this allowed water to escape from the dam while a steady inflow of water was continuously supplied upstream the effects of upstream inflow on the timescales and magnitudes of the peak discharges and the time to inflection point were also investigated experimental results reveal that the whole hydrodynamic process of dam breaching can be divided into three stages defined by clear inflection points and peak discharge a new longitudinal evolution model is proposed this model captures the initial increase of the soil erosion rate of landslide dam and its subsequent decrease along the longitudinal direction in addition a linear relationship between the soil erosion rate and shear stress of water flow was observed and this is similar to that observed in large scale natural landslide dams furthermore soil erosion resistances of landslide dam against water flow above are observed to increase with the concentration of entrained sediments along the flow direction

vertical roughness of mars from the mars orbiter laser altimeter the vertical roughness of the martian surface at 250 m spatial scales has been determined in two global latitude bands an equatorial and a high northern band acquired from 18 tracks of data by the mars orbiter laser altimeter mola during the fall of 1997 the distribution of rms vertical roughness as derived from mola pulse widths for the equatorial band is non gaussian with an overall mean of 2 8 m rms but with secondary populations at 1 5 m and 2 6 m rms the higher latitude northern plains of mars are almost uniformly 1 m rms in their vertical roughness characteristics suggesting that they are smoother than virtually any terrestrial deserts we suggest that dust mantling has muted the local topography of mars rendering it as smooth as 1 2 m rms heavily cratered uplands near the martian equator are noticeably rougher indicating more rugged and less mantled local topography

through water terrestrial laser scanning of gravel beds at the patch scale acquiring high resolution topographic data of natural gravel surfaces is technically demanding in locations where the bed is not exposed at low water stages often the most geomorphologically active surfaces are permanently submerged gravel beds are spatially variable and measurement of their detailed structure and particle sizes is essential for understanding the interaction of bed roughness with near bed flow hydraulics sediment entrainment transport and deposition processes as well as providing insights into the ecological responses to these processes this paper presents patch scale laboratory and field experiments to demonstrate that through water terrestrial laser scanning tls has the potential to provide high resolution digital elevation models of submerged gravel beds with enough detail to depict individual grains and small scale forms the resulting point cloud data requires correction for refraction before registration preliminary validation shows that patch scale tls through 200 mm of water introduces a mean error of less than 5 mm under ideal conditions point precision is not adversely affected by the water column the resulting dems can be embedded seamlessly within larger sub aerial reach scale surveys and can be acquired alongside flow measurements to examine the effects of three dimensional surface geometry on turbulent flow fields and their interaction with instream ecology dynamics copyright 2011 john wiley sons ltd

volcanism on mars more than 15 years of planetary exploration of mars have given insight into the geologic processes that have shaped its surface the newly acquired viking data have shown that volcanism is one of the most important geologic processes operating on mars throughout its history in situ chemical analyses of martian soil by the viking lander spacecraft indicate mafic to ultramafic source rocks this is consistent both with available remote sensing data which indicate the presence of mafic minerals such as pyroxene and olivine and with petrologic modeling based on available geophysical data which suggest that martian lavas are probably iron rich and ultramafic these data strongly suggest that basaltic volcanism is widespread on mars and much of the photogeological data may be studied in this context photogeological analysis of the martian surface has shown two main types of volcanic morphologies the first type is central volcanoes which are volcanic landforms developed by continued and prolonged eruption from a point source vent this category includes 1 shields the classic low profile volcanic mountains of which olympus mons is the most spectacular example 2 domes steep sided constructs such as tharsis tholus that may represent lower rates of eruption than the shields or possibly more silicic lava compositions 3 highland patera radially textured low profile volcanoes that occur in the cratered terrain and are interpreted as ash shields 4 alba patera an apparently unique volcanic landform consisting of a vast volcanic center over 1500 km across with flank slopes of less than a tenth of a degree and 5 various small features such as cinder cones the second major category is volcanic plains which are units recognized by several criteria of which the presence of mare ridges and flow lobes are the most useful volcanic plains are subdivided into four main groups 1 simple flows broad smooth to rolling plains that contain numerous mare type ridges but no flow lobes interpreted as being composed of thick single cooling units 2 complex flows displaying multiple overlapping flow lobes interpreted to be indicative of thin multiple cooling units 3 undifierentiated flows plains that typically lack any morphologic identifying feature but are considered to be volcanic partly on the basis of their association with large volcanic centers and 4 questionable plains volcanic units heavily modified by other processes erosion tectonism etc so that their origins are uncertain when these categories of volcanic morphologies are combined with relative age data provided by crater statistics a volcanic history for mars can be derived as follows early heavy bombardment of mars was accompanied and followed by small scale fluvial channeling extensive flood volcanism the plateau plains and ash shield volcanism in the cratered terrain shortly after this time less extensive flood volcanism continued to resurface the planet during formation of the northern southern hemisphere dichotomy central volcanism became more prominent with the development of the alba patera center as well as the older shields and domes of the northern hemisphere early tharsis and elysium regions the development of the tharsis and elysium uplifts may have triggered the release of large scale catastrophic floods producing large channels continued uplift and lithospheric thinning concentrated volcanic activity in the tharsis region producing large shield volcanoes and extensive lava plains both central vent and plains volcanism have been active throughout martian history but the volumes of extrusion have gradually decreased with time this is consistent with a moonlike thermal history involving a lithosphere of increasing thickness with time gradually turning off the volcanism although many questions remain regarding martian volcanism the viking data have provided a remarkable detailed overview of the probable nature of the volcanic history of mars

analysis of a detention basin impact on dike failure probabilities and flood risk for a channel dike floodplain system along the river elbe germany highly concentrated asset values are often protected by dikes stretching along the river course during extreme floods dikes may fail due to various breach mechanisms and cause considerable damage therefore detention basins are often additionally installed to reduce the flood risk for downstream communities in such situations however the systemic performance of dikes and spatial redistribution of inundation patterns are often unknown intuitively expected effects such as more probable breaches downstream due to fewer breaches upstream and consequently higher conveyance of upstream reaches lack evidential proof with a coupled probabilistic deterministic 1d channel dike breach 2d inundation flood damage model chain the impact of a detention basin on losses to residential buildings and agricultural crops is investigated we demonstrate the changes in dike performance due to systemic load and relief along the river course on the middle elbe germany considering three breach mechanisms overtopping piping and slope micro instability the reduction of overtopping failures due to the detention basin resulted in the slightly increased breach probabilities due to piping and micro instability farther downstream finally the uncertainty in hazard and damage estimations are analysed using the monte carlo simulation and applying several damage models despite high uncertainties in flood hazard and damage estimations we conclude that the risk reduction to residential buildings downstream of the detention basin exceeds the higher losses to agricultural crops within the filled detention area

borehole climate reconstructions spatial structure and hemispheric averages 1 ground surface temperature gst reconstructions determined from temperature profiles measured in terrestrial boreholes when averaged over the northern hemisphere estimate a surface warming of 1 k during the interval ad 1500 2000 other traditional proxy based estimates suggest less warming during the same interval mann et al 2003a have raised two issues with regard to borehole based reconstructions the first focuses on the need for spatial gridding and area weighting of the ensemble of borehole based gst reconstructions to yield an average hemispheric reconstruction the second asserts that application of optimal detection techniques show that the gst only weakly displays the spatial structure of the surface air temperature sat we demonstrate the consistency of gst warming estimates by showing that over a wide range of grid element area and occupancy weighting schemes the five century gst change falls in the range of 0 89 1 05 k we examine the subhemispheric spatial correlation of gst and sat trends at various spatial scales in the 5 degree grid employed for optimal detection we find that the majority of grid element means are determined from three or fewer boreholes a number that is insufficient to suppress site specific noise via ensemble averaging significant spatial correlation between sat and gst emerges in a 5 degree grid if low occupancy grid elements are excluded and also in a 30 degree grid in which grid element means are better determined through higher occupancy reconstructions assembled after excluding low occupancy grid elements show a five century gst change in the range of 1 02 1 06 k index terms 1645 global change solid earth 1699 global change general or miscellaneous 3309 meteorology and atmospheric dynamics climatology 1620 3322 meteorology and atmospheric dynamics land atmosphere interactions 3344 meteorology and atmospheric dynamics paleoclimatology keywords boreholes paleoclimate spatial analysis surface temperature

drought reconstructions for the continental united states abstract the development of a 2 lat 3 long grid of summer drought reconstructions for the continental united states estimated from a dense network of annual tree ring chronologies is described the drought metric used is the palmer drought severity index pdsi the number of grid points is 154 and the reconstructions cover the common period 1700 1978 in producing this grid an automated gridpoint regression method called point by point regression was developed and tested in so doing a near optimal global solution was found for its implementation the reconstructions have been thoroughly tested for validity using pdsi data not used in regression modeling in general most of the gridpoint estimates of drought pass the verification tests used in addition the spatial features of drought in the united states have been faithfully recorded in the reconstructions even though the method of reconstruction is not explicitly spatial in its design the drought reconstructions show that the 1930s dust bow

nao signal recorded in the stable isotopes of greenland ice cores 1 the winter 18o signal is extracted from 7 greenland ice cores covering the past 700 years to filter out noise and local variations in the 7 isotope records a principal component analysis is carried out on the ice core data a comparison between the time series of the first principal component pc1 with 67 years of winter december to march temperature measurements from 3 southern greenland synoptic stations shows highly significant correlations southern greenland winter temperatures are known to be greatly influenced by the north atlantic oscillation nao a good proxy for southern greenland temperatures is therefore expected to reveal at least parts of the nao signal it is shown that the pc1 time series indeed is significantly correlated to the nao during the winter months the inclusion of ice core winter season 18o time series in future multiproxy nao reconstructions is therefore recommended

lateral outflow over side weirs note 66 reference lch article 1987 011 record created on 2007 04 24 modified on 2016 08 08

laboratory experiments on failure characteristics of non cohesive sediment natural dam in progressive failure mode natural dam failure may cause disastrous floods in the downstream especially for dam outbursts in progressive failure mode until now researches about the characteristics of progressive failure are still completely unclear in this paper a series of flume tests were conducted to investigate the formation mechanism of progressive failure of natural dam the breaching characteristics and the effect of outburst flood on the channel bed according to the results three typical features in the progressive failure process of natural dams were observed seepage on downstream slope slide of the downstream slope and overtopping with phreatic line rising continuously seepage occurred on the downstream slope which caused slide of downstream slope of the dam the breaching discharge hydrographs were asymmetric on both sides of peak discharge which was similar to the breaching discharge of overtopping the relationship between breach width and depth was like a shape of s which followed a logistic function in the breaching process sediment in the channel bed near the dam was first deposited and then scoured where the flow velocity was large with strong turbulence while flow on channel bed far away from the dam showed lower velocity and the flow regime transferred from supercritical flow to subcritical flow sediment deposited at first and then scoured gradually on channel bed but only deposited at a large distance from the dam the outburst flood eroded the channel bed continuously the erosion mechanism was from tractive erosion to backward erosion and returned to tractive erosion finally in addition the further away from the dam the weaker the erosion intensity was the results of this paper enriched the understanding of the failure mechanism of progressively outburst natural dam which is helpful to predict breaching parameters in progressive failure mode and to provide some reference about flood prevention

overtopping induced failure of noncohesive homogeneous fluvial dikes accurate predictions of breach characteristics are necessary to reliably estimate the outflow hydrograph and the resulting inundation close to fluvial dikes laboratory experiments on the breaching of fluvial sand dikes were performed considering a flow parallel to the dike axis the breach was triggered by overtopping the dike crest a detailed monitoring of the transient evolution of the breach geometry was conducted providing key insights into the gradual and complex processes involved in fluvial dike failure the breach develops in two phases 1 the breach becomes gradually wider and deeper eroding on the downstream side along the main channel and 2 breach widening controlled by side slope failures continuing in the downstream direction only increasing the inflow discharge in the main channel the breach formation time decreases significantly and the erosion occurs preferentially on the downstream side the downstream boundary condition has a strong influence on the breach geometry and the resulting outflow hydrograph

geologic conditions underlying the 2005 17th street canal levee failure in new orleans a careful program of subsurface sampling and cone penetration test soundings was employed to characterize the geologic conditions beneath the failed portion of the 17th street canal levee in new orleans where a 150 m long section of the levee and floodwall translated up to 16 m when flood waters rose to 1 2 m of the wall s crest on august 29 2005 during hurricane katrina the subsurface conditions are characterized by discrete layers of fill placed upon the historic cypress swamp which is underlain by a deeper prehistoric cypress swamp these swamp deposits were consolidated beneath the levee and in the area of the 2005 failure the swamp materials infilled a natural depression believed to be an old slough which dipped below the sheetpile tips for a distance of about 50 m which corresponds to where the breach appears to have initiated detailed examination of the recovered soils suggest that recent hurricanes periodically inundated the swamps with saline and or brackish water which cause a mass

last millennium summer temperature variations in western europe based on proxy data we present a method of multiproxy reconstruction of the climate of europe during the last millennium the proxies used comprise long tree ring width series grape harvest dates greenland ice oxygen isotope series and temperature indices based on historical documents the proxies are calibrated using gridded april to september mean temperatures for western europe i e between 10 degrees w and 20 degrees e and between 35 degrees n and 55 degrees n they are calibrated also using the long instrumental summer temperature series of the marseilles observatory of longchamp which begins in the mid eighteenth century the method is a combination of an analogue technique which is able to deal with missing data an artificial neural network technique for an optimal non linear calibration and a bootstrap technique for calculating error bars on the reconstruction about 70 of the temperature variance is reconstructed the amplitude of the past temperature variations is particularly well reconstructed which is important when considering whether the recent temperature trend is or is not within the natural variability it appears that the temperature of the last decade of the twentieth century was reached only 14 times during the last millennium the reconstruction is discussed with respect to other multiproxy and borehole temperature reconstructions we conclude that a reconstruction such ours with a specific regional focus as opposed to the larger northern hemisphere is more reliable and is in better agreement with borehole results even allowing for the fact that only a part of the long term variance is reconstructed little ice age c ad 1560 1930 summers were 0 2 0 5 degrees c cooler than the 1961 1990 period borehole temperatures indicate a cooling of 0 4 degrees c which falls in the 95 confidence interval of our reconstructions

geostatistical estimations of bathymetric lidar errors on rivers the geometry of river channels is a key descriptive element for hydromorphology hydraulics and hydroecology gravel bed rivers usually have a mean water depth of 0 5 m for such shallow waters the accuracy of bathymetric lidar data has to be precisely assessed alongside this accuracy investigation methodological questions arise how to assess the data quality of elevation lidar when comparing reference topographic points on river beds to laser beam footprints of several square metres at different locations what are the consequences of uncertainties and scaling in accuracy estimations in this study we designed a methodology to assess the quality of lidar topographical data within rivers using a specific geostatistical method that conducts upscaling as well as interpolation of reference data that takes into account uncertainties this method uses an anisotropic block kriging from dgps points on lidar footprint areas within a channel fitted coordinate system this assessment focused on a 1 5 km long reach of the gardon gravel bed river in the south of france dgps points pseudo regularly located along the river were acquired at the same time as the lidar survey with the hawkeyeii system lidar accuracy results for river bottom elevation show a negative bias for high depth added to that bias a random error with 0 32 m standard deviation was found by considering upscaling and uncertainties in reference data and a 0 20 m standard deviation was found if they were not considered consequently if lidar bias can be corrected measuring a water depth less than 32 cm i e for 28 of the river area is unrealistic however this experiment shows that lidar provides an accurate representation of the riverbed forms it also provided a useful continuous topographic surface from the underwater river bed up to riparian areas copyright 2010 john wiley and sons ltd

numerical modeling of breach erosion of river embankments the process of breach erosion of river embankments depends on the interaction among flow sediment transport and the corresponding morphological changes levees often consist of noncohesive material with a wide range of grain sizes the dam material is mainly eroded due to the transport capacity of the overtopping water both bed load and suspended load are of importance for breach formation the lateral erosion due to slope instabilities has a significant impact a depth averaged two dimensional numerical model was developed to account for these processes the sensitivity of the discharge through the breach related to different processes and material parameters was investigated and compared to experimental and field data the results show that the most sensitive parameter of an erosion based dike breach simulation is the breach side slope angle which determines the lateral erosion the application of the described model 2dmb to different embankment failures at the elbe river illustrates its capability in simulating overtopping breaching

a new methodology for flood hazard assessment considering dike breaches 1 this study focuses on development and application of a new modeling approach for a comprehensive flood hazard assessment along protected river reaches considering dike failures the proposed inundation hazard assessment model iham represents a hybrid probabilistic deterministic model it comprises three models that are coupled in a dynamic way 1 1d unsteady hydrodynamic model for river channel and floodplain between dikes 2 probabilistic dike breach model which determines possible dike breach locations breach widths and breach outflow discharges and 3 2d raster based inundation model for the dike protected floodplain areas due to the unsteady nature of the 1d and 2d models and runtime coupling the interdependence between the hydraulic loads on dikes at various locations along the reach is explicitly considered this ensures a more realistic representation of the fluvial system dynamics under extreme conditions compared to the steady approaches the probabilistic dike breach model describes dike failures due to three failure mechanisms overtopping piping and slope instability caused by seepage flow through the dike core micro instability the 2d storage cell model computes various flood intensity indicators such as water depth flow velocity and inundation duration iham is embedded in a monte carlo simulation in order to account for the natural variability of the input hydrograph form and the randomness of dike failures besides binary wet dry inundation patterns iham generates new probabilistic flood hazard maps for each intensity indicator and the associated uncertainty bounds furthermore the novel probabilistic dike hazard maps indicate the failure probability of dikes for each considered breach mechanism

discharge coefficient for sharp crested side weir in subcritical flow to estimate the outflow over a rectangular sharp crested side weir the discharge coefficient in the weir equation needs to be known although this type of structure has been designed and used extensively by hydraulic engineers a universally acceptable discharge coefficient does not exist in this study over 250 laboratory tests were conducted and the results were analyzed to find the influence of the flow hydraulics and the geometric channel and weir shapes on the coefficient the results show that for subcritical flow the de marchi assumption of constant energy is acceptable and the weir discharge can therefore be used furthermore it was discovered that the de marchi coefficient of discharge is a function of the upstream froude number and the ratios of weir height to upstream depth and weir length to channel width whereas the channel slope in subcritical flow can be ignored hence an accurate equation for the coefficient of discharge is introduced

the applicability of microbially induced calcite precipitation micp for internal erosion control in gravel sand mixtures seepage induced internal erosion in earth filled embankment dams has been attracting the attention of civil engineering researchers and practitioners for decades microbially induced carbonate prec

numerical and experimental modeling of levee breach including slumping failure of breach sides abstractthe overtopping failure of noncohesive earthen levees was investigated by considering sediment transport by flowing water and including slumping failure due to slope instability the breach

breaching parameters for earth and rockfill dams dam risk analysis is at the heart of dam failure prevention and mitigation in order to assess dam risk it is essential to conduct a quantitative analysis of the process of a dam breach which can be described by such parameters as breach geometry breaching duration and peak outflow rate the main objective of this paper is to develop robust empirical formulas with physical meaning for predicting dam breaching parameters based on past dam failure data a database of 182 earth and rockfill dam failure cases has been compiled among these cases nearly one half are for large dams higher than 15 m a multiparameter nonlinear regression model is recommended to develop empirical relationships between five breaching parameters breach depth breach top width average breach width peak outflow rate and failure time and five selected dam and reservoir control variables dam height reservoir shape coefficient dam type failure mode and dam erodibility the relative importance of each control variable is evaluated the dam erodibility is found to be the most important factor influencing all five breaching parameters the reservoir shape coefficient and the failure mode also play an important role in the prediction models two case studies are presented to show the application of the empirical models developed in this paper

dike failure mechanisms and breaching parameters abstractdike risk management requires breaching parameters that can be estimated rapidly to support the prediction of inundation zones and decision making the objectives of this paper are to compile a database of dike breaching cases study common dike failure mechanisms and develop a set of empirical equations for estimating breaching length depth and peak discharge a database of over 1 000 dike failure cases was collected with information on pre breach dike geometry materials type of dike failure mechanisms breaching length depth and peak discharge a set of regression models are formulated using five control variables dike height width material type of dike and failure mechanism the standard error is set as a selection criterion and the akaike information criterion is used to optimize the proposed empirical models the new models are validated using independent cases and compared with available empirical equations for dikes and man made dams

climate variability in se europe since 1450 ad based on a varved sediment record from etoliko lagoon western greece to achieve deeper understanding of climate variability during the last millennium in se europe we report new sedimentological and paleoecological data from etoliko lagoon western greece the record represents the southernmost annually laminated i e varved archive from the balkan peninsula spanning the little ice age allowing insights into critical time intervals of climate instability such as during the maunder and dalton solar minima after developing a continuous ca 500 year long varve chronology high resolution xrf counts stable isotope data measured on ostracod shells palynological including pollen and dinoflagellate cysts and diatom data are used to decipher the season specific climate and ecosystem evolution at etoliko lagoon since 1450 ad our results show that the etoliko varve record became more sensitive to climate change from 1740 ad onwards we attribute this shift to the enhancement of primary productivity within the lagoon which is documented by an up to threefold increase in varve thickness this marked change in the lagoon s ecosystem was caused by i increased terrestrial input of nutrients ii a closer connection to the sea and human eutrophication particularly from 1850 ad onwards and iii increasing summer temperatures integration of our data with those of previously published paleolake sediment records tree ring based precipitation reconstructions simulations of atmospheric circulation and instrumental precipitation data suggests that wet conditions in winter prevailed during 1740 1790 ad whereas dry winters marked the periods 1790 1830 ad dalton minimum and 1830 1930 ad the latter being sporadically interrupted by wet winters this variability in precipitation can be explained by shifts in the large scale atmospheric circulation patterns over the european continent that affected the balkan peninsula e g north atlantic oscillation the transition between dry and wet phases at etoliko points to longitudinal shifts of the precipitation pattern in the balkan peninsula during the little ice age

evaluation and prediction of 17th street canal i wall stability using numerical limit analyses numericallimitanalyseshavebeenusedtoevaluatethestabilityofthe17thstreetcanali wallleveeduringhurricanekatrina the potential formation of a water filled gap along the canal side soil wall interface at failure is included in both the lower and upper bound for mulations the analyses replicate published two dimensional 2d cross sections and soil properties developed in forensic investigations car ried out by the interagency performance evaluation task force ipet and by the independent levee investigation team ilit the current results provide anindependent basis forunderstanding andevaluating the proposedfailure mechanisms anddemonstrate that awater filled gap is a necessary condition for the critical i wall failure mechanism further limit analysis calculations produce credible estimates of the surge elevation that caused failure of the 17th street canal i wall as well as predictions of a consistent failure mechanism the numerical limit anal yses show clearly how differences in the stability of the i wall are linked to different interpretations of the stratigraphy and undrained shear strengths by ipet and ilit the analyses also show that effects of a thin layer of weak organic clay as postulated by ilit are not necessary to explain the i wall failure doi 10 1061 asce gt 1943 5606 0000814 2013 american society of civil engineers ce database subject headings drainage walls clays lateral loads levees and dikes louisiana hurricanes structural stability author keywords upper and lower bound limits undrained stability walls clays limit equilibrium lateral loading

on the spatial variation of resistance to flow in upland channel networks 1 detailed field measurements of channel properties and flow characteristics collected in the ashley and cropp catchments new zealand are used to investigate the spatial variation of resistance to flow across upland channel networks the application of the darcy weisbach equation and semilogarithmic flow resistance relationships reveals that mean flow velocities calculated from local measurements of bed material particle size hydraulic depth and channel bed slope may be inaccurate the manning gauckler strickler equation with resistance coefficient independent of bed material particle size is found to be relatively more reliable but not sufficiently general to reproduce the spatial variation of resistance to flow across a complex channel network a new methodology is developed by combining a hydraulic equation of the manning gauckler strickler type a flow discharge upstream drainage area relationship and geomorphological fluvial relationships for mean flow velocity gauckler strickler resistance coefficient hydraulic depth and friction slope this methodology is found to improve the reproduction of the spatial variation of mean flow velocity across the ashley catchment and appears of general applicability for the parameterization of resistance to flow in distributed catchment models

artificial neural networks and dendroclimatic reconstructions an example from the front range colorado usa the feasibility of reconstructing total spring precipitation for the south platte river basin from tree ring chronologies using artificial neural networks is explored the use of artificial neural networks allows a comparison of reconstructions resulting from both linear and nonlinear models both types of models produced reconstructions that explained more than 40 of the variation in spring precipitation and were well verified with independent data although the nonlinear models produced higher r2 values than did the linear model for the calibration period they performed less well in the independent period this result and other model evaluation statistics suggest that in this study the nonlinear models contain a greater degree of overfit than the linear model and thus do not offer a clear improvement over the linear model for the reconstruction of spring precipitation in this region however neural networks offer an alternative approach to linear regression techniques and may provide improved den

modeling river bed morphology roughness and surface sedimentology using high resolution terrestrial laser scanning 1 recent advances in technology have revolutionized the acquisition of topographic data offering new perspectives on the structure and morphology of the earth s surface these developments have had a profound impact on the practice of river science creating a step change in the dimensionality resolution and precision of fluvial terrain models the emergence of hyperscale survey methods including structure from motion photogrammetry and terrestrial laser scanning tls now presents the opportunity to acquire 3 d point cloud data that capture grain scale detail over reach scale extents translating these data into geomorphologically relevant products is however not straightforward unlike traditional survey methods tls acquires observations rapidly and automatically but unselectively this results in considerable noise associated with backscatter from vegetation and other artifacts moreover the large data volumes are difficult to visualize require very high capacity storage and are not incorporated readily into gis and simulation models in this paper we analyze the geomorphological integrity of multiscale terrain models rendered from a tls survey of the braided river feshie scotland these raster terrain models are generated using a new computationally efficient geospatial toolkit the topographic point cloud analysis toolkit topcat this performs an intelligent decimation of point cloud data into a set of 2 5 d terrain models that retain information on the high frequency subgrid topography as the moments of the locally detrended elevation distribution the results quantify the degree of terrain generalization inherent in conventional fluvial dems and illustrate how subgrid topographic statistics can be used to map the spatial pattern of particle size grain roughness and sedimentary facies at the reach scale

laboratory experiments on the failure of coarse homogeneous sediment natural dams on a sloping bed we present the results of a systematic series of 168 laboratory experiments that examine the critical conditions for the failure of landslide dams which obstruct the course of mountain rivers the experiments were carried out by using three different sediment materials with a quasiuniform grain size distribution and with a flume bed slope angles that ranged between 0 and 5 71 0 10 three main typologies of dam failure were observed for increasing values of the dam s downstream face angle 1 overtopping 2 headcutting which led to the formation of an erosion channel on the dam s downstream face that progressively migrated up to the dam crest and 3 initial slide of large part of superficial layer of the dam s downstream face which was followed by headcutting the experiments focused on the second type of failure to provide a safety criterion based on the upstream reservoir level the quantities that govern this phenomenon have been identified and a functional relationship is proposed based on

proxy based northern hemisphere surface temperature reconstructions sensitivity to method predictor network target season and target domain abstract results are presented from a set of experiments designed to investigate factors that may influence proxy based reconstructions of large scale temperature patterns in past centuries the factors investigated include 1 the method used to assimilate proxy data into a climate reconstruction 2 the proxy data network used 3 the target season and 4 the spatial domain of the reconstruction estimates of hemispheric mean temperature are formed through spatial averaging of reconstructed temperature patterns that are based on either the local calibration of proxy and instrumental data or a more elaborate multivariate climate field reconstruction approach the experiments compare results based on the global multiproxy dataset used by mann and coworkers with results obtained using the extratropical northern hemisphere nh maximum latewood tree ring density set used by briffa and coworkers mean temperature reconstructions are compared for the full nh tropics and extratropics land and ocean and ext

five hundred years of gridded high resolution precipitation reconstructions over europe and the connection to large scale circulation we present seasonal precipitation reconstructions for european land areas 30 w to 40 e 30 71 n given on a 0 5 0 5 resolved grid covering the period 1500 1900 together with gridded reanalysis from 1901 to 2000 mitchell and jones 2005 principal component regression techniques were applied to develop this dataset a large variety of long instrumental precipitation series precipitation indices based on documentary evidence and natural proxies tree ring chronologies ice cores corals and a speleothem that are sensitive to precipitation signals were used as predictors transfer functions were derived over the 1901 1983 calibration period and applied to 1500 1900 in order to reconstruct the large scale precipitation fields over europe the performance quality estimation based on unresolved variance within the calibration period of the reconstructions varies over centuries seasons and space highest reconstructive skill was found for winter over central europe and the iberian peninsula precipitation variability over the last half millennium reveals both large interannual and decadal fluctuations applying running correlations we found major non stationarities in the relation between large scale circulation and regional precipitation for several periods during the last 500 years we identified key atmospheric modes for southern spain northern morocco and central europe as representations of two precipitation regimes using scaled composite analysis we show that precipitation extremes over central europe and southern spain are linked to distinct pressure patterns due to its high spatial and temporal resolution this dataset allows detailed studies of regional precipitation variability for all seasons impact studies on different time and space scales comparisons with high resolution climate models as well as analysis of connections with regional temperature reconstructions

reconstruction of precipitation in morocco since 1100 a d based on cedrus atlantica tree ring widths annual october through september precipitation from 1100 a d to modern times is reconstructed for morocco using cedrus atlantica endl carriere tree ring chronologies both multiple regression on principal components and the bootstrap method are used to calibrate tree ring width with precipitation precipitation variation is reconstructed for three climatically distinct areas the humid subhumid and arid regions of morocco a series of successive wet and dry periods is identified for the past 1000 years the maximum length of the 13 dry periods during which precipitation was at least 1 sigma below normal is six years twenty one years are identified during which precipitation fell more than 2 sigma below normal there is no significant correspondence in climatic variation in morocco europe and the sahel during this time period

topography of the moon from the clementine lidar range measurements from the lidar instrument carried aboard the clementine spacecraft have been used to produce an accurate global topographic model of the moon this paper discusses the function of the lidar the acquisition processing and filtering of observations to produce a global topographic model and the determination of parameters that define the fundamental shape of the moon our topographic model a 72nd degree and order spherical harmonic expansion of lunar radii is designated goddard lunar topography model 2 gltm 2 this topographic field has an absolute vertical accuracy of approximately 100 m and a spatial resolution of 2 5 the field shows that the moon can be described as a sphere with maximum positive and negative deviations of 8 km both occurring on the farside in the areas of the korolev and south pole aitken s p aitken basins the amplitude spectrum of the topography shows more power at longer wavelengths as compared to previous models owing to more complete sampling of the surface particularly the farside a comparison of elevations derived from the clementine lidar to control point elevations from the apollo laser altimeters indicates that measured relative topographic heights generally agree to within 200 m over the maria while the major axis of the lunar gravity field is aligned in the earth moon direction the major axis of topography is displaced from this line by approximately 10 to the east and intersects the farside 24 north of the equator the magnitude of impact basin topography is greater than the lunar flattening 2 km and equatorial ellipticity 800 m which imposes a significant challenge to interpreting the lunar figure the floors of mare basins are shown to lie close to an equipotential surface while the floors of unflooded large basins except for s p aitken lie above this equipotential the radii of basin floors are thus consistent with a hydrostatic mechanism for the absence of significant farside maria except for s p aitken whose depth and lack of mare require significant internal compositional and or thermal heterogeneity a macroscale surface roughness map shows that roughness at length scales of 10 1 10 2 km correlates with elevation and surface age

experimental investigation of the effects of soil properties on levee breach by overtopping abstractlevee failure due to overtopping during floods is a common phenomena an experimental study was conducted in the hydraulics laboratory university of south carolina to develop an understanding of the effects of soil properties on the breaching process of earthen levees a total of eight experiments were conducted a new methodology to measure the subaqueous breach evolution has been developed and validated measurements of breach width evolution and headcut migration are shown to be related to soil properties inclusion of noncohesive silt size crushed silica in the levee material 45 by weight significantly reduced the peak discharge and breach evolution time compared to a levee constructed with sand alone increase in kaolin clay in the levee material led to an increase in unconfined compressive strength which in turn increased resistance to levee failure nondimensional equations relating the breach width evolution and headcut migration to the soil properties have been developed by performi

satellite laser altimetry of terrestrial topography vertical accuracy as a function of surface slope roughness and cloud cover analysis of the sensitivity of laser ranging errors to surface conditions indicates that predicted single shot range errors are primarily dependent on surface slope range errors are less sensitive to variations in surface roughness or reflectivity values of total surface slope and roughness for nine terrestrial landforms derived from digital elevation data at a 186 m length scale vary from 2 spl deg to 40 spl deg and 0 8 to 15 m respectively at a 90 frequency of occurrence this range of surface morphologies yields a variation in single shot laser ranging error from 0 4 to 8 m assuming system parameters for the proposed topographic mapping laser altimeter tmla and a nominal 30 surface reflectivity the total elevation accuracy of data obtained via satellite laser altimetry although dominated by the range error is also a function of additional error sources including orbit ephemeris atmospheric and calibration errors averaging of multiple laser measurements improves the vertical accuracy of the elevation data by statistical reduction of random errors during a three year mission two to three laser measurements will be acquired on average for each 200 m footprint at low to moderate latitudes accounting for the latitudinal variation of ground track spacing and cloud cover for high latitude regions the narrow spacing of satellite ground tracks in a polar orbit will provide frequent repeat observations yielding on average 4 to 25 measurements of each footprint over the antarctic and greenland ice sheets averaging of these multiple repeat observations at high latitude will yield an improvement in vertical accuracy by a factor of two to five

embankment dam breach parameters and their uncertainties potential flood hazards that would be created by breached embankment dams need to be evaluated to select spillway design floods and to prepare emergency action plans the breaches are often modeled simply usually in the shape of a trapezoid that is defined by its final height base width or average width and side slopes along with the time needed for the opening to form completely data collected from 74 embankment dam failures were used to develop mathematical expressions for the expected values of the final width and side slope of a trapezoidal breach along with its formation time information is provided that allows variances of the predicted quantities to be calculated as well the findings of the statistical analysis were then applied in a monte carlo simulation to estimate the degree of uncertainty of predicted peak flows and water levels downstream from breached embankment dams

ranging performance of satellite laser altimeters topographic mapping of the earth moon and planets can be accomplished with high resolution and accuracy using satellite laser altimeters these systems employ nanosecond laser pulses and microradian beam divergences to achieve submetre vertical range resolution from orbital altitudes of several hundred kilometres in this paper the authors develop detailed expressions for the range and pulsewidth measurement accuracies and use the results to evaluate the ranging performances of several satellite laser altimeters currently under development by nasa for launch during the next decade the analysis includes the effects of the target surface characteristics spacecraft pointing jitter and waveform digitizer characteristics the results show that ranging accuracy is critically dependent on the pointing accuracy and stability of the altimeter especially over high relief terrain where surface slopes are large at typical orbital altitudes of several hundred kilometres single shot accuracies of a few centimetres can be achieved only when the pointing jitter is on the order of 10 mu rad or less

modeling gradual dam breaches a simulation model of the gradual failure of an earth dam has been formulated developed and tested with real life data a significant feature of the model is its ability to account for the growth of the breach and the eventual draining of the reservoir concepts of water and sediment routing are used in conjunction with a channel geometry descriptor to arrive at a self contained mathematical model of the breach enlargement and the ensuing flood wave unsteady flow elements of the simulation are an implicit numerical solution of the complete saint venant equations coupled with a sequential sediment routing technique this approach provides an increased rational basis for determining outflow hydrographs from postulated earth dam breaches

modeling sea dike breaching induced by breaking wave impact laboratory experiments and computational model abstract sea dikes are of crucial importance for the defense systems of low lying coastal areas in countries such as germany the netherlands denmark etc as sea dike breaching induced by storm surges is regarded as one of the main causes of coastal flood disasters reliable predictions of both the breach initiation formation and breach development is urgently needed although a simple preliminary model for the simulation of sea dike breaching initiated from the seaside was developed stanczak et al 2006 its limitations showed the necessity for further research and for the development of a more detailed model this paper therefore provides a summary of the results of laboratory experiments on the erosion of grass and clay revetment of a sea dike induced by breaking wave impact and describes the new detailed computational model including an uncertainty analysis

1200 years of decadal scale variability of mediterranean vegetation and climate at pantelleria island italy a new sedimentary sequence from lago di venere on pantelleria island located in the strait of sicily between tunisia and sicily was recovered the lake is located in the coastal infra mediterranean vegetation belt at 2 m a s l pollen charcoal and sedimentological analyses are used to explore linkages among vegetation fire and climate at a decadal scale over the past 1200 years a dry period from ad 800 to 1000 that corresponds to the medieval warm period wmp is inferred from sedimentological analysis the high content of carbonate recorded in this period suggests a dry phase when the ratio of evaporation precipitation was high during this period the island was dominated by thermophilous and drought tolerant taxa such as quercus ilex olea pistacia and juniperus a marked shift in the sediment properties is recorded at ad 1000 when carbonate content became very low suggesting wetter conditions until ad 1850 1900 broadly this period coincides with the little ice age lia which was charact

new orleans levee system performance during hurricane katrina 17th street canal and orleans canal north centrifuge modeling of the 17th street canal and orleans canal north levees was performed in this study during hurricane katrina the levees on the 17th street canal failed leading to breaches in the outfall canal in the city two mechanisms were observed in the centrifuge modeling that could cause a breach first a water filled crack formed in front of the floodwall as the water in the canal rose above the top of the levee the levees on the 17th street canal which were supported on clay foundations failed when this cracking led to a translational sliding failure in the clay layer commencing at the toe of the floodwall the levees at orleans canal north where failure did not occur were also modeled to demonstrate that the model tests could successfully simulate failure and nonfailure conditions the centrifuge model tests identified the importance of the crack formation in relation to the stability of the floodwall these tests also confirmed that levee geometry floodwall depth of penetration and the underlying soil profile were all critical to the performance of the system under flood loading

low frequency temperature variations from a northern tree ring density network we describe new reconstructions of northern extratropical summer temperatures for nine subcontinental scale regions and a composite series representing quasi northern hemisphere temperature change over the last 600 years these series are based on tree ring density data that have been processed using a novel statistical technique age band decomposition designed to preserve greater long timescale variability than in previous analyses we provide time dependent and timescale dependent uncertainty estimates for all of the reconstructions the new regional estimates are generally cooler in almost all precalibration periods compared to estimates obtained using earlier processing methods particularly during the 17th century one exception is the reconstruction for northern siberia where 15th century summers are now estimated to be warmer than those observed in the 20th century in producing a new northern hemisphere series we demonstrate the sensitivity of the results to the methodology used once the number of regions with data and the reliability of each regional series begins to decrease we compare our new hemisphere series to other published large regional temperature histories most of which lie within the 1 confidence band of our estimates over most of the last 600 years the 20th century is clearly shown by all of the palaeoseries composites to be the warmest during this period

high resolution palaeoclimatology of the last millennium a review of current status and future prospects this review of late holocene palaeoclimatology represents the results from a pages clivar intersection panel meeting that took place in june 2006 the review is in three parts the principal high resolution proxy disciplines trees corals ice cores and documentary evidence emphasizing current issues in their use for climate reconstruction the various approaches that have been adopted to combine multiple climate proxy records to provide estimates of past annual to decadal timescale northern hemisphere surface temperatures and other climate variables such as large scale circulation indices and the forcing histories used in climate model simulations of the past millennium we discuss the need to develop a framework through which current and new approaches to interpreting these proxy data may be rigorously assessed using pseudo proxies derived from climate model runs where the answer is known the article concludes with a list of recommendations first more raw proxy data are required from the diverse disciplines and from more locations as well as replication for all proxy sources of the basic raw measurements to improve absolute dating and to better distinguish the proxy climate signal from noise second more effort is required to improve the understanding of what individual proxies respond to supported by more site measurements and process studies these activities should also be mindful of the correlation structure of instrumental data indicating which adjacent proxy records ought to be in agreement and which not third large scale climate reconstructions should be attempted using a wide variety of techniques emphasizing those for which quantified errors can be estimated at specified timescales fourth a greater use of climate model simulations is needed to guide the choice of reconstruction techniques the pseudo proxy concept and possibly help determine where given limited resources future sampling should be concentrated

tree ring width and density data around the northern hemisphere part 2 spatio temporal variability and associated climate patterns patterns of summer temperature over the northern hemisphere obtained from a calibration of a treering network are presented for every year from 1600 to 1877 the network of tree ring density chronologies is shown to exhibit spatially coherent modes of variability these modes closely match summer half year tempera ture variations in terms of similar spatial patterns and similar temporal evolution during the instrumental period they can therefore be considered to be proxies for the temperature patterns and time series for the eight most dominant patterns are presented back to the late seventeenth century the first pattern represents spatially coherent warming or cooling and it appears to respond to climate forcings especially volcanic erup tions most other patterns appear to be related to atmospheric pressure anomalies and they can be partially explained by heat advection associated with anomalous atmospheric circulation this provides the potential for reconstructing past variations in atmospher

uncertainty of predictions of embankment dam breach parameters risk assessment studies considering the failure of embankment dams often require the prediction of basic geometric and temporal parameters of a breach or the estimation of peak breach outflows many of the relations most commonly used to make these predictions were developed from statistical analyses of data collected from historic dam failures the prediction uncertainties of these methods are widely recognized to be very large but have never been specifically quantified this paper presents an analysis of the uncertainty of many of these breach parameter and peak flow prediction methods application of the methods and the uncertainty analysis are illustrated through a case study of a risk assessment recently performed by the bureau of reclamation for a large embankment dam in north dakota

on the long term context for late twentieth century warming 1 previous tree ring based northern hemisphere temperature reconstructions portray a varying amplitude range between the medieval warm period mwp little ice age lia and present we describe a new reconstruction developed using largely different methodologies and additional new data compared to previous efforts unlike earlier studies we quantify differences between more traditional std and regional curve standardization rcs methodologies concluding that rcs is superior for retention of low frequency trends continental north american versus eurasian rcs series developed prior to merging to the hemispheric scale cohere surprisingly well suggesting common forcing although there are notable deviations e g fifteenth to sixteenth century results indicate clear mwp warm lia cool and recent warm episodes direct interpretation of the rcs reconstruction suggests that mwp temperatures were nearly 0 7c cooler than in the late twentieth century with an amplitude difference of 1 14c from the coldest 1600 1609 to warmest 1937 1946 decades however we advise caution with this analysis although we conclude as found elsewhere that recent warming has been substantial relative to natural fluctuations of the past millennium we also note that owing to the spatially heterogeneous nature of the mwp and its different timing within different regions present palaeoclimatic methodologies will likely flatten out estimates for this period relative to twentieth century warming which expresses a more homogenous global fingerprint therefore we stress that presently available paleoclimatic reconstructions are inadequate for making specific inferences at hemispheric scales about mwp warmth relative to the present anthropogenic period and that such comparisons can only still be made at the local regional scale

inundation of a dutch river polder sensitivity analysis of a physically based inundation model using historic data 1 the inundation model delft flooding system delft fls was applied to simulating the historical flood of 1805 in the polder land van maas en waal netherlands delft fls is a two dimensional 2 d hydrodynamic model that simulates overland flow sensitivity analyses show a large influence of floodplain topography and hydraulic friction on the propagation of the inundation because of the typical topography of dutch polders a virtually flat floodplain bordered by high dikes the extent of the inundated area alone cannot be used for evaluating the model performance therefore the inundation time and water levels within the inundated area were used to test the model capabilities this study shows that using historic data has a potential advantage over using contemporary data historic data allow evaluation of a model for real flood disasters that have long return periods and fortunately have not occurred in modern times

2d process based morphodynamic model for flooding by noncohesive dyke breach abstractinundation models based on the shallow water equations swe have been shown to perform well for a wide variety of situations even at the limit of their theoretical applicability and arguably somewhat beyond one of these situations is the catastrophic event of floods induced by dyke breach and consequent dyke erosion the dyke collapse is often not sudden as assumed by many flood simulations in which the dyke boundary is treated as a dam break the dyke erosion is a gradual and complex process that delays the onset of the flood affecting the hydrograph of the flow to simulate correct temporal passage of a flood it is important to understand the rate at which these dykes collapse in this paper an overtopping flood event combined with dyke erosion is simulated the model is built upon the two dimensional 2d shallow water equations together with sediment flow interactions and incorporates a sediment transport equation the model is solved using a second order godunov type finite volume me

seasonality variations in the central mediterranean during climate change events in the late holocene abstract holocene rapid climate change rcc events such as the little ice age lia are thought to have influenced average annual temperatures only marginally but to have affected winter temperatures relatively strongly with summer temperatures relatively unaffected reconstructing climate change at a seasonal resolution is crucial to fully capture holocene climate variability mediterranean climate is highly seasonal being influenced by the subtropical high pressure belt in summer and the mid latitude westerlies combined with outbreaks of polar winds in winter we identified events of high and low detrital input to the gulf of taranto central mediterranean sea anticipated to be linked to humid and dry conditions respectively and thereby potentially reflecting seasonal contrasts these events represent the bronze age ba roman humid period rhp medieval climate anomaly mca lia and present day and were selected for the analysis of single specimen globigerinoides ruber white carbonate chemistry mg ca 18o and 13c the dynamic range found for these parameters for the measured single individuals in the most recent interval reflects the present day seasonal contrasts in temperature and precipitation albeit with a bias towards the summer season these results are compared with high resolution 15 years sample sea surface temperature sst and bottom water temperature bwt reconstructions based on the 18o of g ruber white and mg ca of benthic foraminifer hyalinea balthica although the seasonal temperature contrast remains relatively stable significant winter cooling is observed during the ba and lia connections between high latitude climate winter conditions and low latitude climate summer conditions appear not straightforward during rcc events this results in changes in the moisture balance and in shifts in seasonal dominance between rccs during the lia winter like conditions cold and humid prevail throughout the year in contrast winters are dry and cold during the ba and are accompanied by dry and warm summers suggesting year round aridity and a relatively high seasonal temperature contrast this could have had a profound impact on early agriculture in southern italy

application of structure from motion photogrammetry in laboratory flumes abstract structure from motion sfm photogrammetry has become widely used for topographic data collection in field and laboratory studies however the relative performance of sfm against other methods of topographic measurement in a laboratory flume environment has not been systematically evaluated and there is a general lack of guidelines for sfm application in flume settings as the use of sfm in laboratory flume settings becomes more widespread it is increasingly critical to develop an understanding of how to acquire and process sfm data for a given flume size and sediment characteristics in this study we 1 compare the resolution and accuracy of sfm topographic measurements to terrestrial laser scanning tls measurements in laboratory flumes of varying physical dimensions containing sediments of varying grain sizes 2 explore the effects of different image acquisition protocols and data processing methods on the resolution and accuracy of topographic data derived from sfm techniques and 3 provide general guidance for image acquisition and processing for sfm applications in laboratory flumes to investigate the effects of flume size sediment size and photo overlap on the density and accuracy of sfm data we collected topographic data using both tls and sfm in five flumes with widths ranging from 0 22 to 6 71 m lengths ranging from 9 14 to 30 48 m and median sediment sizes ranging from 0 2 to 31 mm acquisition time image overlap point density elevation data and computed roughness parameters were compared to evaluate the performance of sfm against tls we also collected images of a pan of gravel where we varied the distance and angle between the camera and sediment in order to explore how photo acquisition affects the ability to capture grain scale microtopographic features in sfm derived point clouds a variety of image combinations and sfm software package settings were also investigated to determine optimal processing techniques results from this study suggest that sfm provides topographic data of similar accuracy to tls at higher resolution and lower cost we found that about 100pixels per grain are required to resolve grain scale topography we suggest protocols for image acquisition and sfm software settings to achieve best results when using sfm in laboratory settings in general convergent imagery taken from a higher angle with at least several overlapping images for each desired point in the flume will result in an acceptable point cloud

tree ring based drought reconstruction for the central tien shan area in northwest china 1 a robust ring width chronology developed from two sites of picea schrenkiana in the central tien shan area of northwest china was employed to study regional drought variability our analyses demonstrate both temperature and precipitation have significant effects on tree growth thus both should be considered for climate reconstruction regional drought history 1675 2002 a d was therefore reconstructed by calibrating with the palmer drought severity index pdsi our reconstruction not only captured well those extreme drought events recorded in local historical archives but also revealed the long term pattern of drought variability especially the trend of increasing moisture during the 20th century multi taper method spectral analysis indicates the existence of some low and high frequency cycles 146 171 11 5 10 6 9 7 6 1 3 9 3 4 3 2 2 4 and 2 1 yr overall our study indicates the feasibility of combining tree rings and the pdsi to reconstruct large scale drought patterns over this area

first assessment of gps based reduced dynamic orbit determination on topex poseidon the reduced dynamic gps tracking technique has been applied for the first time as part of the gps experiment on topex poseidon this technique employs local geometric position corrections to reduce orbit errors caused by the mismodeling of satellite forces results for a 29 day interval in early 1993 are evaluated through postfit residuals and formal errors comparison with gps and laser doris dynamic solutions comparisons on 6 hr overlaps of adjacent 30 hr data arcs altimetry closure and crossover analysis reduced dynamic orbits yield slightly better crossover agreement than other techniques and appear to be accurate in altitude to about 3 cm rms

discussion of laboratory study on 3d flow structures induced by zero height side weir and implications for 1d modeling by giovanni michelazzo hocine oumeraci and enio paris

venus topography and kilometer scale slopes during the first 8 months of the magellan mission the radar altimeter has made some three million measurements of the surface of venus covering the latitude range from 85 n to 80 s methods involving range correlation doppler filtering multi burst summation and range migration are used to focus the observations and to achieve high surface resolution results are presented as maps of the global distribution of topography meter scale roughness and power reflection coefficient the results are similar to those reported in previous experiments surface heights exhibit a unimodal distribution with more than 80 of the surface lying within 1 km of the 6051 84 km mean radius but the higher resolution of the magellan altimeter has disclosed several surprisingly steep features e g the southwest face of the maxwell montes the southern face of the danu montes and the chasmata to the east of thetis regio where average kilometer scale slopes of greater than 30 are not uncommon this conclusion is corroborated by close inspection of synthetic aperture radar imagery

more intense more frequent and longer lasting heat waves in the 21st century a global coupled climate model shows that there is a distinct geographic pattern to future changes in heat waves model results for areas of europe and north america associated with the severe heat waves in chicago in 1995 and paris in 2003 show that future heat waves in these areas will become more intense more frequent and longer lasting in the second half of the 21st century observations and the model show that present day heat waves over europe and north america coincide with a specific atmospheric circulation pattern that is intensified by ongoing increases in greenhouse gases indicating that it will produce more severe heat waves in those regions in the future

surface subsurface flow modeling with path based runoff routing boundary condition based coupling and assimilation of multisource observation data received 21 october 2008 revised 2 september 2009 accepted 16 september 2009 published 13 february 2010 1 a distributed physically based model incorporating novel approaches for the representation of surface subsurface processes and interactions is presented a path based description of surface flow across the drainage basin is used with several options for identifying flow directions for separating channel cells from hillslope cells and for representing stream channel hydraulic geometry lakes and other topographic depressions are identified and specially treated as part of the preprocessing procedures applied to the digital elevation data for the catchment threshold based boundary condition switching is used to partition potential atmospheric fluxes into actual fluxes across the land surface and changes in surface storage thus resolving the exchange fluxes or coupling between the surface and subsurface modules nested time stepping allows smaller steps to be taken for typically faster and explicitly solved surface runoff routing while a mesh coarsening option allows larger grid elements to be used for typically slower and more compute intensive subsurface flow sequential data assimilation schemes allow the model predictions to be updated with spatiotemporal observation data of surface and subsurface variables these approaches are discussed in detail and the physical and numerical behavior of the model is illustrated over catchment scales ranging from 0 0027 to 356 km 2 addressing different hydrological processes and highlighting the importance of describing coupled surfacesubsurface flow

the mars observer laser altimeter investigation the primary objective of the mars observer laser altimeter mola investigation is to determine globally the topography of mars at a level suitable for addressing problems in geology and geophysics secondary objectives are to characterize the 1064 nm wavelength surface reflectivity of mars to contribute to analyses of global surface mineralogy and seasonal albedo changes to assist in addressing problems in atmospheric circulation and to provide geodetic control and topographic context for the assessment of possible future mars landing sites the principal components of mola are a diode pumped neodymium doped yttrium aluminum garnet laser transmitter that emits 1064 nm wavelength laser pulses a 0 5 m diameter telescope a silicon avalanche photodiode detector and a time interval unit with 10 ns resolution mola will provide measurements of the topography of mars within approximately 160 m footprints and a center to center along track foot print spacing of 300 m along the mars observer subspacecraft ground track the elevation measurements will be quantized with 1 5 m vertical resolution before correction for orbit and pointing induced errors mola profiles will be assembled into a global 0 2 deg x 0 2 deg grid that will be referenced to mars center of mass with an absolute accuracy of approximately 30 m other data products will include a global grid of topographic gradients corrected individual profiles and a global 0 2 deg x 0 2 deg grid of 1064 nm surface reflectivity

rapid profiling of an evolving bed form using planar laser sheet illumination traditional methods of measuring the profile of a scour hole or bed form have poor temporal resolution and may require the temporary cessation of the flow in order to be executed these are undesirable characteristics since many hydraulic flows have unsteady water sediment interfaces that can display considerable differences between their dynamic flow on and static flow off states the present technical note discusses the application of planar laser sheet illumination to the erosion of a cohesionless granular bed due to a planar turbulent wall jet the measurements allow for the quantitative study of the evolution of the bed in its earliest stages in some cases an ephemeral bed form is observed to form prior to the development of the main bed form additionally the measurements illustrate the oscillatory nature of the bed form under certain conditions the experiments therefore demonstrate the great potential of this experimental technique for gaining previously inaccessible information on scour processes

detection and characterization of animal burrows within river embankments by means of coupled remote sensing and geophysical techniques lessons from river panaro northern italy abstract the damage and the eventual breach of river embankments may be due to internal erosion and instability processes in the waterside and landside slopes beside the progressive degradation of soil properties different types of macro pores inside the levee body can influence its short and long term performance among macro pores burrows are a widespread form of biologic erosion of earthen structures potentially producing damage or even their collapse in fact animal burrows are erosion tunnels which can lead to piping phenomena thus the emergent risk connected to burrowing animals in earthen levees has to be tackled given also the environmental changes driven by human activity and climate remote sensing and geophysical surveys can complement data from in situ investigation campaigns in the definition of the real embankment model as well as in the imaging of local defects which may influence its local and or global stability several techniques were integrated in the study area of the panaro river where an active animal burrow was detected in spring 2015 two campaigns were carried out survey 1 in june 2015 just after the relocation of the animals and survey 2 in december 2015 after the filling of the burrow with a cement bentonite slurry here we highlight the peculiarity of each method and the choice of an integrated multi technique approach the results allowed the known burrow as well as two other tunnels to be imaged in 3d providing specific guidelines for the best integrated strategy to detect and characterize these macro pores in a fluvial levee the proposed approach can advance our knowledge of embankments in space and time so that effective remedial actions in flood risk and wildlife management can be identified

mass movement in the himalaya new insights and research directions abstract ongoing studies that relate tectonics to the processes at the surface of earth show that many more sources of information about agents of shallow denudation such as mass movement are required to comprehend the long term erosion that leads to deep denudation over geologic time mass movement in the himalaya is scale dependent from the massive extension of whole mountain ranges gravity tectonics through the sackung failure of single peaks to the smallest slope failures generally denudation of the himalayan orogen begins with slope failure onto glaciers and into river valleys and continues by glacial and fluvial transport the maximum size of stable slopes and mean angles of slope that are produced by these failures are complex and controlled by a variety of factors including mass strength of the rocks stress fields angles of internal friction controlled by rock type cohesion that includes the control of rock temperature bulk unit weight of rock and discontinuities the processes of mass movement in the himalaya have been described many times for the past two centuries recently developments in a variety of fields have been introduced to assess the character of mass movement geomorphometry remote sensing digital elevation models and geographic information system technology are revolutionizing the study of mass movement in the himalaya

a 1052 year tree ring proxy for alpine summer temperatures a june august alpine temperature proxy series is developed back to ad 951 using 1 527 ring width measurements from living trees and relict wood the reconstruction is composed of larch data from four alpine valleys in switzerland and pine data from the western austrian alps these regions are situated in high elevation alpine environments where a spatially homogenous summer temperature signal exists in an attempt to capture the full frequency range of summer temperatures over the past millennium from inter annual to multi centennial scales the regional curve standardization technique is applied to the ring width measurements correlations of 0 65 and 0 86 after decadal smoothing with high elevation meteorological stations since 1864 indicate an optimal response of the rcs chronology to june august mean temperatures the proxy record reveals warm conditions from before ad 1000 into the thirteenth century followed by a prolonged cool period reaching minimum values in the 1820s and a warming trend into the twentieth century this latter trend and the higher frequency variations compare well with the actual high elevation temperature record the new central alpine proxy suggests that summer temperatures during the last decade are unprecedented over the past millennium it also reveals significant similarities at inter decadal to multi centennial frequencies with large scale temperature reconstructions however deviating during certain periods from h h lamb s european north atlantic temperature history

examination of the seepage face boundary condition in subsurface and coupled surface subsurface hydrological models a seepage face is a nonlinear dynamic boundary that strongly affects pressure head distributions water table fluctuations and flow patterns its handling in hydrological models especially under complex conditions such as heterogeneity and coupled surface subsurface flow has not been extensively studied in this paper we compare the treatment of the seepage face as a static dirichlet versus dynamic boundary condition we assess its resolution under conditions of layered heterogeneity we examine its interaction with a catchment outlet boundary and we investigate the effects of surface subsurface exchanges on seepage faces forming at the land surface the analyses are carried out with an integrated catchment hydrological model numerical simulations are performed for a synthetic rectangular sloping aquifer and for an experimental hillslope from the landscape evolution observatory the results show that the static boundary condition is not always an adequate stand in for a dynamic seepage face boundary condition especially under conditions of high rainfall steep slope or heterogeneity that hillslopes with layered heterogeneity give rise to multiple seepage faces that can be highly dynamic that seepage face and outlet boundaries can coexist in an integrated hydrological model and both play an important role and that seepage faces at the land surface are not always controlled by subsurface flow the paper also presents a generalized algorithm for resolving seepage face outflow that handles heterogeneity in a simple way is applicable to unstructured grids and is shown experimentally to be equivalent to the treatment of atmospheric boundary conditions in subsurface flow models

mediterranean drought fluctuation during the last 500 years based on tree ring data a 2 5 x 2 5 degrees gridded summer april september drought reconstruction over the larger mediterranean land area 32 5 degrees 47 5 degrees n 10 degrees w 50 degrees e 152 grid points is described based on a network of 165 tree ring series the drought index used is the self calibrated palmer drought severity index and the period considered is 1500 2000 the reconstruction technique combines an analogue technique for the estimation of missing tree ring data with an artificial neural network for optimal non linear calibration including a bootstrap error assessment tests were carried out on the various sources of error in the reconstructions errors related to the temporal variations of the number of proxies were tested by comparing four reconstructions calibrated with four different sized regressor datasets representing the decrease in the number of available proxies over time errors related to the heterogeneous spatial density of predictors were tested using pseudo proxies provided by the global climate model echo g finally the errors related to the imperfect climate signal recorded by tree ring series were tested by adding white noise to the pseudo proxies reconstructions pass standard cross validation tests nevertheless tests using pseudo proxies show that the reconstructions are less good in areas where proxies are rare but that the average reconstruction curve is robust finally the noise added to proxies which is by definition a high frequency component has a major effect on the low frequency signal but not on the medium frequencies the comparison of the low frequency trends of our mean reconstruction and the gcm simulation indicates that the detrending method used is able to preserve the long term variations of reconstructed pdsi the results also highlight similar multi decadal pdsi variations in the central and western parts of the mediterranean basin and less clear low frequency changes in the east the sixteenth and the first part of the seventeenth centuries are characterized by marked dry episodes in the west similar to those observed in the end of the twentieth century in contrast the eighteenth and nineteenth centuries little ice age are characterized by dominant wet periods in the eastern part of the mediterranean basin the observed strong drought period of the end of the twentieth century seems to be the strongest of the last 500 years

calibration and multi source consistency analysis of reconstructed precipitation series in portugal since the early 17th century a calibration of reconstructed winter spring and autumn precipitation series in portugal from 1600 onwards is undertaken in the present study using new instrumental sources for the period of 1815 2012 as summer precipitation in portugal is scarce and irregular it is not considered a consistency analysis of the calibrated time series is then undertaken using 1 precipitation indices for portugal in 1675 1799 2 teleconnections between seasonal precipitation and large scale atmospheric flow 3 two paleoclimatic experiments erik1 and erik2 generated from a global regional climate model chain echo g mm5 and 4 tree ring records from oak trees in portugal serra do bucaco these are the first multi centennial records of tree ring growth in portugal the earliest series begin in 1675 general agreement is found between indices and calibrated precipitation for their common period on an annual basis overall the atmospheric teleconnection patterns are dynamically coherent between the instrumen

little ice age glacier variations in jotunheimen southern norwvay a study in regionally controlled lichenometric dating of recessional moraines with implications for climate and lichen growth rates a new approach to regional lichenometric dating is developed and applied to little ice age moraine ridge sequences on 16 glacier forelands in jotunheimen southern norway lichenometric dating curves based on the rhizocarpon subgenus are constructed independently for west central and east jotunheimen although there are differences between the subregions a composite regional moraine chronology for jotunheimen identifies 12 episodes of moraine formation in ad 1743 1750 the regional little ice age glacier maximum 1762 1771 1782 1790 1796 1802 1811 1818 1833 1838 1845 1854 1860 1868 1871 1879 1886 1898 1915 1922 and 1927 1934 spatial and temporal patterns in glacier behaviour between the subregions and between jotunheimen and the neighbouring jostedalsbreen are explained in terms of the interaction of annual to decadal variations in summer temperature and winter precipitation glacier advances and moraine formation events driven primarily by winter precipitation variations exhibit subregio

evidence of an emerging levee failure mechanism causing disastrous floods in italy a levee failure occurred along the secchia river northern italy on 19 january 2014 resulting in flood damage in excess of 500 million in response to this failure immediate surveillance of other levees in the region led to the identification of a second breach developing on the neighboring panaro river where rapid mitigation efforts were successful in averting a full levee failure the paired breach events that occurred along the secchia and panaro rivers provided an excellent window on an emerging levee failure mechanism in the secchia river by combining the information content of photographs taken from helicopters in the early stage of breach development and 10 cm resolution aerial photographs taken in 2010 and 2012 animal burrows were found to exist in the precise levee location where the breach originated in the panaro river internal erosion was observed to occur at a location where a crested porcupine den was known to exist and this erosion led to the collapse of the levee top this paper uses detailed numerical modeling of rainfall river flow and variably saturated flow in the levee to explore the hydraulic and geotechnical mechanisms that were triggered along the secchia and panaro rivers by activities of burrowing animals leading to levee failures as habitats become more fragmented and constrained along river corridors it is possible that this failure mechanism could become more prevalent and therefore will demand greater attention in both the design and maintenance of earthen hydraulic structures as well as in wildlife management

formulas for the peak discharge from breached earthfill dams abstractalthough advanced physically based models have been presented in the last years there is still much interest in equations for predicting the peak discharge indeed simple relations are very useful for technical purposes especially when rough calculations are acceptable this paper presents new equations for assessing the peak discharge of the flood hydrograph caused by the gradual erosion of earth dams the equations are obtained by a regression analysis carried out on the peak discharges provided by a physically based numerical model the approach proposed in this paper has the advantage of taking into account some parameters usually neglected by common best fit equations that have strong influence on the peak discharge in particular the equations discussed in this paper take into account the susceptibility to erosion of the dam the shape of the reservoir and the ratio of filling of the reservoir for failures caused by piping the usefulness of the equations is shown through a comparison w