the measurement and modelling of rill erosion at angle of repose slopes in mine spoil the process of rill erosion causes significant amounts of sediment to be moved in both undisturbed and disturbed environments and can be a significant issue for agriculture as well as mining lands rills also often develop very quickly from a single rainfall event to a season and can develop into gullies if sufficient runoff is available to continue their development this study examines the ability of a terrestrial laser scanner to quantify rills that have developed on fresh and homogeneous mine spoil on an angle of repose slope it also examines the ability of the siberia erosion model to simulate the rill s spatial and temporal behaviour while there has been considerable work done examining rill erosion on rehabilitated mine sites and agricultural fields little work has been done to examine rill development at angle of repose sites results show that while the overall hillslope morphology was captured by the laser scanner with the morphology of the rills being broadly captured the characteristics of the rills were not well defined the digital elevation model created by the laser scanner failed to capture the rill thalwegs and tops of the banks therefore delineating a series of ill defined longitudinal downslope depressions these results demonstrate that an even greater density of points is needed to capture sufficient rill morphology nevertheless siberia simulations of the hillslope demonstrated that the model was able to capture rill behaviour in both space and time when correct model parameters were used this result provides confidence in the siberia model and its parameterization the results demonstrate the sensitivity of the model to changes in parameters and the importance of the calibration process copyright 2007 john wiley sons ltd

clustering river profiles to classify geomorphic domains the structure and organization of river networks has been used for decades to investigate the influence of climate and tectonics on landscapes the majority of these studies either analyze rivers in profile view by extracting channel steepness or calculate planform metrics such as drainage density however these techniques rely on the assumption of homogeneity that intrinsic and external factors are spatially or temporally invariant over the measured profile this assumption is violated for the majority of earth s landscapes where variations in uplift rate rock strength climate and geomorphic process are almost ubiquitous we propose a method for classifying river profiles to identify landscape regions with similar characteristics by adapting hierarchical clustering algorithms developed for time series data we first test our clustering on two landscape evolution scenarios and find that we can successfully cluster regions with different erodibility and detect the transient response to sudden base level fall we then test our method in two real landscapes first in bitterroot national forest idaho where we demonstrate that our method can detect transient incision waves and the topographic signature of fluvial and debris flow process regimes and second on santa cruz island california where our technique identifies spatial patterns in lithology not detectable through normalized channel steepness analysis by calculating channel steepness separately for each cluster our method allows the extraction of more reliable steepness metrics than if calculated for the landscape as a whole these examples demonstrate the method s ability to disentangle fluvial morphology in complex lithological and tectonic settings

analysis of gully dimensions and sediment texture from southeast australia for catchment sediment budgeting abstract catchment scale sediment budgeting models are increasingly being used to target remediation works aimed at controlling erosion and improving water quality gully erosion is often a major sediment source and needs to be accounted for in such models in a manner consistent with the scale of analysis and available data using 130 measurements of gully cross sectional area and 45 measurements of gully wall sediment texture the variability in gully dimensions and particle size distribution for the lake burragorang catchment in australia is examined the distribution of gully cross sectional area measurements is log normally distributed and modelling indicates a representative value of 23 m 2 be used in catchment sediment budgeting applications the proportion of gully eroded sediment contributing to the bedload budget defined as particles 63 m diameter of a river link is approximately half though may be higher in igneous landscapes a continental scale spatially distributed subsoil texture dataset provided limited capacity to predict the finer scale spatial variation in the proportion of sediment contributing to bedload from gully erosion within the lake burragorang catchment

towards a protocol for laser scanning in fluvial geomorphology advances in spatial analytical software allow digital elevation models dems to be produced which accurately represent landform surface variability and offer an important opportunity to measure and monitor morphological change and sediment transfer across a variety of spatial scales many of the techniques presently employed aerial lidar edm theodolites gps photogrammetry suffer coverage or resolution limitations resulting in a trade off between spatial coverage and morphologic detail captured this issue is particularly important when rates of spatial and temporal change are considered for fluvial systems this paper describes the field and processing techniques required for oblique laser scanning to acquire 0 01 m resolution digital elevation data of an upland reach of the river wharfe in the uk the study site is variable with rapidly changing morphology diverse vegetation and the presence of water and these are evaluated with respect to laser data accuracy scan location frequency and distance are discussed with reference to survey accuracy and efficiency and a field protocol is proposed scan data cloud merging was achieved with a high degree of precision sub centimetre and positional data are shown to be very accurate for exposed surfaces vegetation and water decrease the accuracy as the laser pulse is often prevented from reaching the ground surface or is not returned copyright 2006 john wiley sons ltd

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

experimental pressure solution in halite the effect of grain interphase boundary structure to investigate the mechanisms and kinetics of pressure solution we measured deformation at contacts between polished convex lenses of halite and polished flat lenses of either halite or fused silica in saturated brine at 50 2 0 2 c and fluid pressures of 0 1 mpa loads applied using small springs ranged from 0 1 4 2 n mean effective normal stresses within the contact zone ranged from 1 14 mpa the geometry and diametric growth rate of the contact spot neck growth and the rate at which the lenses approached one another convergence were monitored during deformation using transmitted and reflected light photomicrography time dependent convergence did not occur at measurable rates when two halite lenses were pressed together in saturated brine but did occur when halite and fused silica lenses were pressed together in brine convergence rates in the halite silica experiments were 0 01 0 05 m day although the initial deformation during loading involved elastic and plastic processes control experiments without brine showed no time dependent convergence indicating that dislocation creep did not contribute to the observed rates no undercutting or cataclasis was observed in any experiments residual fluid inclusions were formed along grain boundaries between two halite lenses loaded in brine indicating non zero wetting angles

dissolution and time dependent compaction of albite sand experiments at 100 c and 160 c in ph buffered organic acids and distilled water abstract aqueous fluids are important in the diagenesis and deformation of crustal rocks both chemical and physical interactions are involved and often they are strongly coupled for example pore waters not only dissolve transport and precipitate chemical species but they also substantially affect the mechanical behavior of the rocks that contain them stresses magnified at grain contacts by differences in pore fluid pressure p p and confining pressure p c can in turn influence the rate and extent of chemical exchange to begin investigation of these coupled systems compaction experiments were conducted using albite sand 250 500 m and distilled water ph 5 8 0 07 m acetate ph 4 7 and 0 07 m acetate 0 005 m citrate ph 4 4 solutions in a hydrothermal flow through system at conditions that simulate diagenesis pore fluid chemistry and pore volume loss were monitored to quantify the effects of organic acids on time dependent compaction rates the effects of stress and fluid chemistry on the dissolution kinetics were also examined albite dissolution rates monitored by steady state fluid chemistry increased when an effective pressure p e p c p p was applied probably due to increases in total surface area caused by grain breakage at contacts these effects were transient in distilled water however si and al concentrations remained elevated in the acetate pore fluid the average si based release rates indicate 35 increase in reactive surface area by application of p e 34 5 mpa at 100 c with p e 34 5 mpa steady state si concentrations were 2 3 times higher in 0 07 m acetate and 5 8 times higher in 0 07 m acetate 0 005 m citrate than in distilled water al increased by even larger factors 3 in the acetate buffer and 10 in the citrate solution these changes in fluid chemistry are attributed to both ph and ligand enhanced reactions albite dissolution appears to be controlled by surface complexation reactions at al sites rapid dissolution of albite in the organic acid solutions is probably due to the ability of organic acid ligands to selectively complex with aluminum time dependent compaction was observed at 100 and 160 c with p e 34 5 mpa strain rates increased with temperature from 10 9 s l at 100 c to 10 8 s l at 160 c and decreased with strain in all pore fluids especially at 100 c compaction rates in distilled water and in the acetate solution had similar magnitudes and strain dependencies however small amounts of citrate species apparently enhance compaction compared to the other fluids at similar strains textural data indicate that time dependent compaction of the albite sand occurred primarily by brittle mechanisms at these temperatures however the deformation is clearly thermally activated and may be chemically assisted by the aqueous pore fluid

a global analysis of the morphology of linear erosion features abstract concentrated flow erosion poses a serious threat to agriculture across the world as it scours soils into linear features that can be wide and large which dramatically decreases land productivity and accessibility and causes serious downslope and downstream impacts despite the widespread occurrence of concentrated flow erosion features across the globe variations in their sizes have received limited attention their morphometric characteristics inform on the amount of fertile soil material eroded and transported to lower parts of landscapes and to river networks the main objective of this study was to elucidate the impacts of climate tropical sub tropical and temperate soil texture clayey loamy silty and sandy and land use cropland forest grassland and urban on the morphology length l width w depth d w d ratio of linear erosion features rills and gullies a total of 769 linear features from 53 published studies across the world were used in the current analysis the average length was 458 2 m for gullies and 114 7 m for rills width averaged 9 5 m for gullies and 1 0 m for rills and w d was respectively 4 0 and 6 7 which corresponded in all cases to significant difference at p

objective landslide detection and surface morphology mapping using high resolution airborne laser altimetry a map of extant slope failures is the most basic element of any landslide assessment without an accurate inventory of slope instability it is not possible to analyze the controls on the spatial and temporal patterns of mass movement or the environmental human or geomorphic consequences of slides landslide inventory maps are tedious to compile difficult to make in vegetated terrain using conventional techniques and tend to be subjective in addition most landslide inventories simply outline landslide boundaries and do not offer information about landslide mechanics as manifested by internal deformation features in an alternative approach we constructed accurate high resolution dems from airborne laser altimetry lidar data to characterize a large landslide complex and surrounding terrain near christchurch new zealand one dimensional circular 2 d and spherical 3 d statistics are used to map the local topographic roughness in the dems over a spatial scale of 1 5 to 10 m the bedrock landslide is rougher than adjacent unfailed terrain and any of the statistics can be employed to automatically detect and map the overall slide complex furthermore statistics that include a measure of the local variability of aspect successfully delineate four kinematic units within the gently sloping lower half of the slide features with a minimum size of surface folds that have a wavelength of about 11 to 12 m and amplitude of about 1 m are readily mapped two adjacent earthflows within the landslide complex are distinguished by a contrast in median roughness and texture and continuity of roughness elements the less active of the earthflows has a surface morphology that presumably has been smoothed by surface processes the laplacian operator also accurately maps the kinematic units and the folds and longitudinal levees within and at the margins of the units finally two dimensional power spectra analyses are used to quantify how roughness varies with length scale these results indicate that no dominant length scale of roughness exists for smooth unfailed terrain in contrast zones with different styles of landslide deformation exhibit distinctive spectral peaks that correspond to the scale of deformation features such as the compression folds the topographic based analyses described here may be used to objectively delineate landslide features generate mechanical inferences about landslide behavior and evaluate relatively the recent activity of slides published by elsevier science b v

spatial structures of stream and hillslope drainage networks following gully erosion after wildfire the drainage networks of catchment areas burned by wildfire were analysed at several scales the smallest scale 1 1000 m2 representative of hillslopes and the small scale 1000 m2 to 1 km2 representative of small catchments were characterized by the analysis of field measurements the large scale 1 1000 km2 representative of perennial stream networks was derived from a 30 m digital elevation model and analysed by computer analysis scaling laws used to describe large scale drainage networks could be extrapolated to the small scale but could not describe the smallest scale of drainage structures observed in the hillslope region the hillslope drainage network appears to have a second order effect that reduces the number of order 1 and order 2 streams predicted by the large scale channel structure this network comprises two spatial patterns of rills with width to depth ratios typically less than 10 one pattern is parallel rills draining nearly planar hillslope surfaces and the other pattern is three to six converging rills draining the critical source area uphill from an order 1 channel head the magnitude of this critical area depends on infiltration hillslope roughness and critical shear stress for erosion of sediment all of which can be substantially altered by wildfire order 1 and 2 streams were found to constitute the interface region which is altered by a disturbance like wildfire from subtle unchannelized drainages in unburned catchments to incised drainages these drainages are characterized by gullies also with width to depth ratios typically less than 10 in burned catchments the regions hillslope interface and channel had different drainage network structures to collect and transfer water and sediment copyright 2005 john wiley sons ltd

badland susceptibility assessment in volterra municipality tuscany italy by means of gis and statistical analysis badlands can be defined as complex and peculiar types of erosional formations that develop in clayey environments and are mainly favoured by lithological and topographic features as well as by markedly seasonal climate this work aims at assessing badland susceptibility in volterra municipality located in tuscany region italy by means of bivariate statistical analysis implemented in a geographic information system the volterra municipality is affected by intense soil erosion processes including rill and gully erosion usually turned out as badland forms mostly occurring on pliocene pleistocene clayey sediments firstly an inventory of 234 badland areas was produced on the basis of an available pre existing database integrated with the interpretation of aerial photographs and supported by a field survey badlands were distinguished in type a and type b according to different evolutional stage vegetation presence and consequently different landforms then nine geoenvironmental factors supposed to be predisposing for badland occurrence were chosen and combined with the spatial frequency of badland areas derived from the inventory through information value statistic approach the result was a badland susceptibility map that highlights a strong control of lithology slope gradient and land use in conditioning badland development in the investigated area the effectiveness of the performed model was demonstrated by a validation test computed through a receiver operating characteristics analysis the outcomes of this work provide an updated badland database that is useful for soil erosion management and further land use planning within the volterra municipality

quantifying temporal changes in gully erosion areas with object oriented analysis abstract mapping gully systems and quantifying their changes over time are essential for implementing soil conservation measures the aim of this study is to analyze the changes in the gully systems in the context of land management image analysis of remotely sensed data in combination with field verification has proven to be a good and practical approach for mapping gully features over large areas given the variability in gully size shape and occurrence recent work has shown object based image analysis also termed as object oriented analysis ooa to be superior to pixel based methods for the identification and characterization of gullies this study presents an improved procedure to map gully features one that has been extended to assess and quantify erosion area dynamics in addition to the convention of using suitable topographic and spectral thresholds in the method the use of contrast and edge filter information and process knowledge of erosion by overland flow was incorporated in the rule set to help recognize potential gullies in ikonos 2 and geoeye 1 data changes in the area enclosed by the gully system boundary estimated for three different sub watersheds sw1 sw2 and sw3 observed over a period of eight years ranged from moderate 11 in sw2 and 21 in sw1 to a very high increase 91 in sw3 however the changes seen in gully system density were much higher than the changes in the area enclosed by the gully system boundary 81 104 and 109 in the respective sws the complex gully systems were better identified semi automatically than was possible by manual digitization in particular the finer edges of the gully systems which in turn led to better quantification of changes in the gully systems the study also determined that the rule set developed for gully feature extraction is more sensitive to the spatial resolution of the imagery used than the quality or resolution of the digital terrain model and its derivatives determining suitable segmentation parameters selecting appropriate object features for the classification the thresholds used retain the trial error aspects in this analysis this limits its application to a regional scale the rule set developed is generic and transferable to other region imagery with adaptation the rule set will be made available on our website www itc nl ooa group

assessing the repeatability of terrestrial laser scanning for monitoring gully topography a case study from aratula queensland australia abstract terrestrial laser scanning tls technology is a powerful tool for quantifying gully morphology and monitoring change over time this is due to the high sampling density sub centimetre positional accuracies x y z flexibility of survey configurations and ability to link multiple tls scans together however to ensure correct interpretation of results research is needed to test the repeatability of tls derived products to quantify the accuracy and separate false from true geomorphic change in this study we use the riegl vz400 scanner to test the repeatability of tls datasets for mapping gully morphology we then quantify change following a rainfall event of approximately 100 mm our study site located in south east queensland australia was chosen to be challenging from a repeatability perspective with high topographic variability the tls data capture involved three sets of linked scans one survey pre rainfall to be compared to two surveys post rainfall acquired on consecutive days change is considered negligible in the two post rainfall scans to test survey repeatability to verify tls accuracy an independent dataset of gully extent and spot heights were acquired using traditional total station techniques results confirm that the tls datasets can be registered multi temporally at sub centimetre levels of accuracy in three dimensions total station and tls elevation samples showed strong agreement with a mean error and standard deviation sd of residuals equal to 0 052 and 0 047 m respectively n 889 significantly our repeatability tests found that return type and pulse deviation influence the accuracy and repeatability of dems in gully environments analysis of consecutive day datasets showed that dems derived from first return data recorded 40 higher sd of residual error than dems using multiple return data a significant empirical relationship between pulse deviation and the variance of residuals for repeat dems is also shown r2 0 95 by accounting for pulse deviation we demonstrate that a spatially variable change detection threshold increased the geomorphic change detected following the rainfall event overall this work supports tls as a tool for monitoring change in gully morphology however consideration of the survey configuration is needed to maximise the change detected and ensure repeatability of results

controls on zero order basin morphology zero order basins are common features of soil mantled landscapes defined as unchanneled basins at the head of a drainage network their geometry and volume control how quickly sediment may re accumulate after landslide evacuation and how water and subsequently pore pressure is delivered to hollow axes they also deliver water and sediment to the uppermost portions of the fluvial network despite this role as the moderator between hillslope and fluvial processes little analysis on their morphology has been conducted at the landscape scale we present a method to identify zero order basins in landscapes and subsequently quantify their geometric properties using elliptical fourier analysis we deploy this method across the coweeta hydrologic laboratory usa properties such as length relief width and concavity follow distinct probability distributions which may serve as a basis for testing predictions of future landscape evolution models surprisingly in a landscape with an orographic precipitation gradient and large hillslope to channel relief we observe no correlation between elevation or spatial location and basin geometry however we find that two physiographic units in coweeta have distinct zero order basin morphologies these are the steep thin soiled high elevation nantahala escarpment and the lower gradient lower elevation thick soiled remainder of the basin our results indicate that basin slope and area negatively covary producing the distinct forms observed between the two physiographic units which we suggest arise through competition between spatially variable soil creep and stochastic landsliding

monitoring sediment source areas in a debris flow catchment using terrestrial laser scanning abstract geomorphic changes caused by three debris flow events in a small mountain catchment moscardo torrent eastern italian alps were investigated by means of multitemporal terrestrial laser scanning tls surveys over three areas exposed to debris flow dynamics for these areas dem of differences dods with a 0 2 m spatial resolution allowed the assessment of elevation uncertainty as spatially variable by applying the fuzzy inference system fis proposed by wheaton et al 2010 along with two commonly used parameters affecting digital elevation model dem accuracy such as terrain slope and point density we developed and employed in the fis a new index named vegetation noise that takes into account the disturbance caused by the vegetation cover on the dem accuracy the results of volumetric budgets of the surveyed sediment source areas derived from the dod analysis were compared with debris flow volumes estimated from flow stage measurements at the instrumented channel reach on the one hand the discrepancies arising from this comparison underline the limitations of tls surveys over morphologically complex areas such as debris flow catchments on the other hand the tls unveils the geomorphic changes at the scale of the single event because a terrestrial survey is usually easier to carry out than an aerial one the analysis of dem quality and uncertainty indexes correlation may help to refine methods for spatializing elevation errors and improving the reliability of the models

effects of dem resolution on the accuracy of gully maps in loess hilly areas abstract gully maps are important prerequisites for the study of gully erosion and land degradation many digital elevation model dem based methods have been proposed to enable automated gully mapping however the accuracy of a gully map derived from a dem is inevitably affected by the dem resolution this study investigates the effects of dem resolution on the accuracy of gully maps a series of dems with resolutions of 0 1 10 m is employed to map gully areas the effects of dem resolution on the error in the mapped gully area and on the position error are described by regression models the results from two catchments in hilly areas of the loess plateau in china are as follows dems with resolutions of 0 5 2 m are the most suitable for gully mapping very high resolution dems increase local position errors and over predict the extents of gullies whereas dems with coarser resolutions cause the downward migration of mapped gully boundaries resulting in the under prediction of gully areas however the effects of dem resolution on gully maps are not constant but vary in space the spatial disparities of the resolution effects are related to the gully morphology the resolution effects on the gully maps in v shaped gullies are stronger than those in u shaped gullies the findings of this study can be used to select a suitable dem resolution for gully mapping in loess hilly areas and contribute to understanding the characterization of gullies by using dems

distribution and occurrence of aliphatic acid anions in deep subsurface waters abstract this study reports 144 new analyses of short chain aliphatic acid anions acetate propionate butyrate and valerate in formation waters from eight localities eastern venezuelan basin denver basin eastern green river basin red desert and washakie basins wamsutter arch san juan basin piceance basin raton basin gulf coast basin and the western overthrust reservoir temperature does not predict total or relative abundance of aliphatic acid anions but does predict maximum total concentrations of these species maximum concentrations increase to 90 c above 90 c maximum concentrations decrease above 250 c maximum concentrations should not exceed 1 mg 1 the general order of dominance is acetate propionate butyrate valerate but for coal associated waters is propionate acetate butyrate valerate lack of longer chain aliphatic acid anion dominance over acetate at low reservoir temperatures may suggest hydrologie communication with deeper reservoirs

loess erosion patterns on a cut slope revealed by lidar scanning abstract erosion is a major environmental issue on the chinese loess plateau although the erosion intensity on the plateau has generally decreased in recent years ongoing mega engineering projects continuously produce large bare and steep loess cut slopes that are prone to erosion therefore investigating loess erosion on cut slopes in this region has practical importance multi temporal high resolution digital elevation model dem analysis has been widely used to quantify surface erosion but has not yet been applied to loess cut slopes this study aims to reveal the spatial and temporal patterns of loess erosion on an artificial cut slope through the analysis of a time series of lidar scans the results showed that the spatial distribution of loess erosion on the study cut slope was constrained by three slope characteristics slope material slope structure and slope hydrology the highest erosion rates were observed in areas with paleosols discontinuities and water accumulation in the temporal domain the variation of the loess erosion rate with rainfall intensity could be described using a power function although this research only focused on one slope findings suggest that it is possible to investigate the complex loess erosion on cut slopes using state of the art high resolution remote sensing techniques such as lidar scanning our results provide useful information for soil conservation on similar engineering loess cut slopes in the loess plateau

monitoring gully change a comparison of airborne and terrestrial laser scanning using a case study from aratula queensland abstract airborne laser scanning als and terrestrial laser scanning tls technologies capture spatially detailed estimates of surface topography and when collected multi temporally can be used to assess geomorphic change the sensitivity and repeatability of als measurements to characterise geomorphic change in topographically complex environments such as gullies however remains an area lacking quantitative research in this study we captured coincident als and tls datasets to assess their ability and synergies to detect geomorphic change for a gully located in aratula southeast queensland australia we initially used the higher spatial density and ranging accuracy of tls to provide an assessment of the digital elevation models dem derived from als within a gully environment results indicated mean residual errors of 0 13 and 0 09 m along with standard deviation sd of residual errors of 0 20 and 0 16 m using pixel sizes of 0 5 and 1 0 m respectively the positive mean residual errors confirm that tls data consistently detected deeper sections of the gully than als we also compared the repeatability of als and tls for characterising gully morphology this indicated that the sensitivity to detect change using als is substantially lower than tls as expected and that the als survey characteristics influence the ability to detect change notably we found that using one als transect mean density of 5 points m2 as opposed to three transects increased the sd of residual error by approximately 30 the supplied classification of als ground points was also demonstrated to misclassify gully features as non ground with minimum elevation filtering found to provide a more accurate dem of the gully the number and placement of terrestrial laser scans were also found to influence the derived dems furthermore we applied change detection using two als data captures over a four year period and four tls field surveys over an eight month period this demonstrated that als can detect large scale erosional changes with head cutting of gully branches migrating approximately 10 m upslope in comparison tls captured smaller scale intra annual erosional patterns largely undetectable by the als dataset with a large rainfall event coinciding with the highest volumetric change net change 46 m3 overall these findings reaffirm the importance of quantifying dem errors and demonstrate that als is unlikely to detect subtle geomorphic changes

assessment of bank gully development and vegetation coverage on the chinese loess plateau abstract gully erosion is a serious environmental problem and the primary source of sediment loss on the loess plateau of china yet previous research focusing on bank gullies is limited an assessment of bank gully development is needed as a basis for predicting erosion rates under the effects of vegetation cover and land use change to estimate bank gully retreat rates under different land uses assess the factors leading to bank gully development and model gully area growth rate at the catchment scale 30 catchments with an average area of 39 0 ha were selected in the southeastern part of the loess plateau quickbird images 0 61 m resolution obtained in 2003 and 2010 were interpreted to delineate bank gully features and a 5 m resolution digital elevation model was used to extract topographic factors the results showed that from 2003 to 2010 the maximum retreat rates of bank gully heads in the 30 investigated catchments ranged between 0 23 and 1 08 m yr 1 with an average of 0 51 m yr 1 the ratio of bank gully growth area to valley area changed from 0 49 to 9 45 depending on land use with average increases of 3 94 4 00 and 2 09 for the three land use types identified i e mixed use grassland and forestland respectively correlation analysis indicated that the effects of topographic factors on bank gullies decreased as vegetation coverage increased in upslope drainage areas and that vegetation coverage exceeding 60 in upslope drainage areas can significantly control bank gully development a model was built to predict the bank gully area growth rate ra m2 yr 1 with upslope drainage area ai m2 local slope gradient s m m 1 and the proportion of the area with vegetation coverage below 60 in upslope drainage areas 0 6 at the catchment scale the regression equation is in the form ra 0 1540 0 6ai 0 24s 3 2588 compared with previous studies vegetation is a factor in this model which would be helpful for assessing the influence of vegetation cover on bank gully development

accuracy constraints of terrestrial lidar data for soil erosion measurement application to a mediterranean field plot abstract applications of terrestrial laser scanning tls to measure soil erosion are yet limited although this topographic mapping method allows for large area coverage with high resolution and reliable precision however restricting factors are accurate and stable references for multi temporal change detection and adverse scanning geometries at agricultural fields the plot is usually situated on gentle slopes provoking low viewing angles of the scanning device onto the surface which inherits the risk of high data noise in this study tls is exploited from a high tripod to measure soil erosion at an andalusian hillslope 2 1000 m2 in the mediterranean sediment yield reveals discontinuous pattern and tls is a promising method to quantify these surface changes a stable reference system is defined resulting in multi temporal registration accuracy better than 7 mm further an mm accurate calibration plot 60 m2 is designed to evaluate scan geometry and radiometry i e incidence angle footprint and intensity in dependence of distance related errors a lookup table is determined to correct systematic errors of the field data the andalusian field plot is captured during a winter season and during single precipitation events estimated erosion rates amount 10 and 2 4 t ha 1 respectively surface changes with magnitudes larger 1 5 cm are reliably measured tls can be implemented to estimate soil erosion with cm resolution if errors are carefully accounted for

mapping and quantifying sediment transfer between the front of rapidly moving rock glaciers and torrential gullies abstract the sedimentary connection which may occur between the front of active rock glaciers and torrential channels is not well understood despite its potential impact on the torrential activity characterizing the concerned catchments in this study dems of difference dods covering various time intervals between 2013 and 2016 were obtained from lidar derived multitemporal dems for three rapidly moving rock glaciers located in the western swiss alps the dods were used to map and quantify sediment transfer activity between the front of these rock glaciers and the corresponding underlying torrential gullies sediment transfer rates ranging between 1500 m3 y and 7800 m3 y have been calculated depending on the sites sediment eroded from the fronts generally accumulated in the upper sectors of the torrential gullies where they were occasionally mobilized within small to medium sized debris flow events a clear relation between the motion rates of the rock glaciers and the sediment transfer rates calculated at their fronts could be highlighted along with the size of the frontal areas rock glacier creep rates influence thus directly sediment availability in the headwaters of the studied torrents the frequency magnitude of debris flow events varied between sites and was mainly related to the concordance of local factors such as topography water availability sediment availability or sediment type

tectonic forcing of evolution and holocene erosion rate of ravines in the marginal ganga plain india abstract understanding the processes of ravine formation and estimates of specific sediment yields ssy of these regions help in formulating mitigation policies significantly upto now in the ganga plain the work done on ravine formation erosion and ssy estimates has been speculative here utilizing i high resolution digital elevation models dems prepared from real time kinematic rtk survey and cartosat images of ravined zones and ii luminescence chronology we provide the first estimate of ssy from the ravines the results indicate that ssy in the marginal ganga plain mgp ravines may range between 600 100 t km 2 yr and 1600 200 t km 2 yr the correspondence between the orientations of fractures and that of first order ravine suggests that the ravine growth is genetically related to extensional stress regime of the peripheral forebulge further the clay sedimentology indicates that besides regional tectonics action of swelling clays may have accelerated development of the badlands the geomorphic relationship between the length of ravined catchments and incision in the trunk channels indicates that the river incision associated base level change is not playing an overarching role in the ravine formation in the mgp

wind driven ageostrophic transport in the north equatorial countercurrent of the eastern pacific at 95 w abstract observations of horizontal velocity from two shipboard acoustic doppler current profilers adcps as well as wind temperature and salinity observations from a cruise during june july 2001 are used to compute a simplified mean meridional momentum balance of the north equatorial countercurrent necc at 95 w the terms that are retained in the momentum balance and derived using the measurements are the coriolis and pressure gradient forces and the vertical divergence of the turbulent stress all terms were vertically integrated over the surface turbulent layer the k profile parameterization kpp prescribed richardson number ri is used to determine the depth of the turbulent boundary layer h at which the turbulent stress and its gradient vanish at the time of the cruise surface drifters and altimeter data show the flow structure of the necc was complicated by the presence of tropical instability waves to the south and a strong costa rica dome to the north nonetheless a consistent simpl

combining airborne and terrestrial laser scanning for quantifying erosion and deposition by a debris flow event abstract we quantified the sediment volume transported by a major debris flow event in the halltal austrian alps using a combination of terrestrial tls and airborne laser scanning als which has rarely been carried out before a digital terrain model dtm derived from als data pre event surface was combined with a dtm derived from tls data post event surface both datasets were aligned and compared in a cut and fill analysis estimating differential volumes the main focus lay on the evaluation and accuracy assessment of the applied method tie point based registration of both datasets proved to be insufficient additional alignment by multi station adjustment was necessary to minimise the averaged height error between both datasets amounting for a volumetric error of less than 10 which is comparable to pure als campaigns larger errors were estimated for complex terrain with low scanning resolutions a particular problem in data processing was the low and dense shrub vegetation in the study area which required a specifically adapted filter algorithm an insufficient ground representation was observed for the als data overestimating ground heights for averaged 70 cm despite these limitations the approach proved to be suitable for accurate extreme event quantification the starting zones of the debris flows lie at the bedrock debris interface where runoff is concentrated volumes of 5000 to 12 000 m3 were assessed volume estimation worked better for the erosional than for the depositional features this is because the erosional gullies are relatively deep and the calculation is not affected by pre event vegetation while erosion and sedimentation are balanced for one of the three catchments investigated the deposited volumes are higher than the detected eroded volumes for the other two the reasons are not fully understood the magnitude of the flows was determined by catchment size topographical characteristics and deforestation by a major wildfire in 1946

using an ultra long range terrestrial laser scanner to monitor the net mass balance of urumqi glacier no 1 eastern tien shan china at the monthly scale we describe the use of a terrestrial laser scanner tls to monitor the net mass balance of urumqi glacier no 1 eastern tien shan we used an ultra long range riegl vz 6000 tls which is specially designed for surveying snow and ice covered terrain to create repeated high spatiotemporal resolution dems focusing on the monthly scale 25 april 28 may 2015 net mass balance according to the tls derived dems the area of urumqi glacier no 1 was 1 558 km 2 on 25 april 2015 and the average surface elevation change was 0 225 m by comparing the results from the use of tls with the conventional glaciological mass balance method the correlation coefficient r 2 between glaciological elevation changes of individual stakes and the tls derived geodetic elevation change of corresponding points was 0 85 considering the uncertainty of both methods this is a promising result using the in situ measured snow densities snow pits of the glacier surface the geodetic net mass balance was 0 074 m w e which is slightly positive the mean uncertainty in the tls derived monthly net mass balance was 0 018 m w e showing that the tls surveying system presented accurate and relevant results and is therefore suitable to monitor mass balance evolution of mountain glaciers

the application of semi quantitative methods and reservoir sedimentation rates for the prediction of basin sediment yield in spain traditionally the problems in predicting sediment yield at the basin scale are related to model s high data requirements the focus on a limited amount of erosion and sediment transport processes and a general lack of systems knowledge here we explore the performance of semi quantitative approaches to predict mean annual area specific sediment yield ssy at the scale of small to medium sized basins the factorial scoring model fsm verstraeten g poesen j de vente j koninckx x 2003 sediment yield variability in spain a quantitative and semiqualitative analysis using reservoir sedimentation rates geomorphology 50 4 327 348 the psiac model psiac 1968 pacific southwest inter agency committee report of the water management subcommittee on factors affecting sediment yield in the pacific southwest area and selection and evaluation of measures for reduction of erosion and sediment yield and some variations of these models were applied to predict ssy for the 60 reservoirs using the reservoir sedimentation rates as published by avendano salas et al avendano salas c sanz montero e gomez montana j l 1997 sediment yield at spanish reservoirs and its relationship with the drainage basin area dix neuvieme congres des grands barrages commission internationale de grands barrages florence pp 863 874 the fsm explained 72 of the variability found in reservoir sedimentation rates which is significantly better than estimates based on basin area alone explaining only 22 the fsm uses five factors i e topography lithology vegetation cover gullies basin shape to characterise a drainage basin in the vicinity 5 km of the reservoir and the main tributaries feeding the reservoir by providing a score an index is calculated by multiplying the scores per factor together with basin area this index is used to predict ssy the psiac model works in a comparable way though some other factors are used i e topography climate runoff lithology soil vegetation land use upland erosion channel erosion basin area is not part of the relation and the index is calculated by summation of all scores psiac explained 58 of the variation in ssy advantages of both models over physically based and other empirical models are that less data are required gully erosion is included and the importance of connectivity in the landscape is recognised this study thus demonstrates that semi quantitative approaches can provide fairly accurate and reliable estimates of ssy at the scale of small to medium sized basins with relatively low data requirements

the evaluation of unmanned aerial system based photogrammetry and terrestrial laser scanning to generate dems of agricultural watersheds article i nfo agricultural watersheds tend to be places of intensive farming activities that permanently modify their microtopography the surface characteristics of the soil vary depending on the crops that are cultivated in these areas agricultural soil microtopography plays an important role in the quantification of runoff and sedi ment transport because the presence of crops crop residues furrows and ridges may impact the direction of water flow to better assess such phenomena 3 d reconstructions of high resolution agricultural watershed to pographyareessential fine resolutiontopographicdatacollectiontechnologiescanbeusedtodiscernhighlyde tailed elevation variability in these areas knowledge of the strengths and weaknesses of existing technologies used for data collection on agricultural watersheds may be helpful in choosing an appropriate technology this study assesses the suitability of terrestrial laser scanning tls and unmanned aerial system uas photogrammetry for collecting the fine resolution topographic data required to generate accurate high resolution digital elevation models dems in a small watershed area 12 ha because of farming activity 14 tls scans 25 points m 2 were collected without using high definition surveying hds targets whic ha re generally used to mesh adjacent scans to evaluate the accuracy of the dems created from the tls scan data 1098 ground control points gcps were surveyed using a real time kinematic global positioning system rtk gps linear regressions were then applied to each dem to remove vertical errors from the tls point elevations errors caused by the non perpendicularity of the scanner s vertical axis to the local horizontal plane and errors correlated with the distance to the scanner s position the scans were then meshed to generate a demtls with a1 1m spatial resolution the agisoft photoscan and micmac software packages were used to process the aerial photo graphsand generate a dempsc agisoftphotoscan anddemmcm micmac respectively with spatial resolutions of 1 1 m comparing the dems with the 1098 gcps showed that the demtls was the most accurate data prod uct with a root mean square error rmse of 4 5 cm followed by the demmcm and the dempsc which had rmse values of 9 0 and 13 9 cm respectively the dempsc had absolute errors along the border of the study area that ranged from 15 0 to 52 0 cm indicating the presence of systematic errors although the derived demmcm was accurate an error analysis along a transect showed that the errors in the demmcm data tended to increase in areas of lower elevation compared with tls uas is a promising tool for data collection because of its flexibility and low operational cost however improvements are needed in the photogrammetric processing of the aerial photographs to remove non linear distortions

experimental diagenesis exploratory results we conducted experiments in which a granular mixture of quartz and labradorite was deformed in compression at elevated temperatures 200 350 c and pressures 100 mpa in the presence of deionized water following initial consolidation of the material by application of the loads at room temperature a second hydrothermal phase of consolidation was observed when the temperature was increased with the loads fixed the strain rate during this hydrothermal consolidation decayed approximately exponentially with time and was accompanied by only minor porosity reduction the sample permeability decreased rapidly during the hydrothermal consolidation and continued to decrease following cessation of the deformation the rate of this self sealing process was a complex function of temperature scanning electron microscopy and microprobe analysis of the indurated post experimental material showed albitization of the feldspar especially in highly deformed regions analysis of post experimental fluids show that si in solution increased with increasing flow and temperature fluid rock equilibrium was not achieved within the short durations of the experiments 50 60 hours our interpretation is that deformation occured by grain boundary sliding aided by solution and reaction at high stress contacts and sealing occurred by precipitation in low stress regions in the throats of pores

detailed recording of gully morphology in 3d through image based modelling abstract the ability to understand gully erosion development is closely related to our ability to quantify the morphology of gullies at present various technologies are at hand to collect data at increasing levels of detail however many of the developed technologies are time consuming difficult to apply or expensive as an alternative image based modelling offers a cost efficient flexible and rapid method to quantify gully morphology from photographs taken in the field in this study the use of image based modelling was tested and fine tuned to quantify the morphology of four gully heads in contrasting biophysical environments prone to gully erosion two bank gullies in central belgium and two permanent gullies in northern ethiopia ground photographs n 88 235 were taken with a reflex canon eos 450d camera having a 20 mm wide angle lens with a fixed focal length the data collection occurred during days of 30 100 cloud cover and after removing excessive vegetation in the gullies processing of the photographs occurred in photoscan 1 0 2 software using the semi automated structure from motion multi view stereo sfm mvs workflow and allowed to produce 3d digital elevation models with accuracies that range from millimetres to centimetres in addition for the same surface 2 5d models were created in arcgis gully morphological properties were derived and included cross sections total volume and volume of undercut walls and soil pipe inlets for the volume calculation optocat software was used cross sections were also quantified by tape meter measurements when compared to 3d models cross sections quantified from tape meter measurements and from 2 5d models underestimate the cross sectional area by

review of earth science research using terrestrial laser scanning abstract the application of advanced remote sensing technologies including terrestrial laser scanning tls to the earth sciences has increased rapidly in the last two decades improving the spatial and temporal resolution of data terrestrial laser scanning units have evolved into a common tool in studies of spectral and structural geology seismology natural hazards geomorphology and glaciology special consideration of the advantages and limitations of tls in each of these fields is discussed in depth in the context of important work published in each field the workflow used in a tls survey is crucial to the success of the survey and field specific earth science workflows are therefore also discussed products based on tls data such as triangulated irregular networks tin and digital surface models dsm are commonplace tools throughout the earth sciences and the use of these tools to measure slip distributions fault geometries aeolian transport river bed morphologies and flows and other research problems is expanded on where appropriate the review concludes with a discussion of recent trends in tls instrument development and their potential impact on the use of tls in the earth sciences in the future

an evaluation of the effectiveness of low cost uavs and structure from motion for geomorphic change detection abstract the measurement of topography and of topographic change is essential for the study of many geomorphic processes in recent years structure from motion sfm techniques applied to photographs taken by camera equipped unmanned aerial vehicles uavs has become a powerful new tool for the generation of high resolution topography the variety of available uav systems continues to increase rapidly but it is not clear whether increased uav sophistication translates into improved quality of the calculated topography to evaluate the lower end of the uav spectrum a simple low cost uav was deployed to calculate high resolution topography in the daan river gorge in western taiwan a site with a complicated 3d morphology and a wide range of surface types making it a challenging site for topographic measurement terrestrial lidar surveys were conducted in parallel with uav surveys in both june and november 2014 enabling an assessment of the reliability of the uav survey to detect geomorphic changes in the range of 30 cm to several meters a further uav survey was conducted in june 2015 in order to quantify changes resulting from the 2015 spring monsoon to evaluate the accuracy of the uav derived topography it was compared to terrestrial lidar data collected during the same survey period using the cloud to cloud comparison algorithm m3c2 the uav generated point clouds match the lidar point clouds well with rms errors of 30 40 cm however the accuracy of the sfm point clouds depends strongly on the characteristics of the surface being considered with vegetation water and small scale texture causing inaccuracies the lidar and sfm data yield similar maps of change from june to november 2014 with the same areas of geomorphic change detected by both methods the sfm generated change map for november 2014 to june 2015 indicates that the 2015 spring monsoon caused erosion throughout the gorge and highlights the importance of event driven erosion in the daan river the results suggest that even very basic uavs can yield data suitable for measuring geomorphic change on the scale of a channel reach

object based gully feature extraction using high spatial resolution imagery abstract gully erosion is responsible for a substantial amount of soil loss and is generally considered an indicator of desertification hence mapping these gully features provides essential information needed on sediment production identification of vulnerable areas for gully formation land degradation and environmental and socio economical effects this paper investigates the use of object oriented image analysis ooa to extract gully erosion features from satellite imagery using a combination of topographic spectral shape geometric and contextual information obtained from ikonos and geoeye 1 data a rule set was developed and tested for a semi arid to sub humid region in morocco the percentage of gully system area indicated negligible overestimations between the reference area and the ooa area in two sub watersheds 0 03 and 1 77 we also observed that finer gully related edges within the complex gully systems were better identified semi automatically than was possible by manual digitization suggesting higher detection accuracy ooa based gully mapping is quicker and more objective than traditional methods and is thus better suited to provide essential information for land managers to support their decision making processes and for the erosion research community

refining the southern extent of the 1872 owens valley earthquake rupture through paleoseismic investigations in the haiwee area southeastern california recent upward revision of the 1872 owens valley earthquake from mw 7 4 7 5 to 7 7 7 9 implies either additional unrecognized rupture length or anoma louslystronggroundmotionsassociatedwiththisevent weinvestigatethefirstpossibility through paleoseismic trenching south of the mapped surface rupture in the haiwee area where historical accounts suggest significant surface deformation following the earth quake trenching focused on a prominent north striking scarp herein termed the sage flat fault expressed in pleistocene alluvial fans east of haiwee reservoir surficial map ping and ground based light detection and ranging lidar surveying suggest that this faultaccommodateseast downnormalmotion andpossiblyacomparableamountofdex tralslip trenchingandluminescencedatingbracketsthetimingofthemostrecentsurface rupturing earthquake between 25 7 and 30 1 ka and provides evidence for an earlier event predating this time in combination with scarp profiling these dates also suggest am aximum rate of normal dip slip fault motion up to 0 1 mm yr over this period although we discovered no evidence for recent surface rupture on the sage flat fault a series of subvertical fractures and fissures cut across young trench stratigraphy consis tentwithsecondarydeformationassociatedwithseismicshaking assuch wesuggestthat possible ground disturbance in the haiwee area during the 1872 event primarily reflected ground shaking or liquefaction related deformation rather than triggered slip in addition we infer a structural and kinematic connection between the owens valley fault and oblique dextral faults north of lower cactus flat in the northwestern coso range rather thanawest stepintonorthernorwesternrosevalley considerationofthesestructuresin the total extent of the owens valley fault suggests a length of 140 km of which at least 113 km ruptured during the 1872 event online material procedural details and expanded results from the osl sample analyses as well as high resolution paleoseismic trench logs

impact of rock fragment size on erosion process and micro topography evolution of cone shaped spoil heaps abstract spoil heaps in sites disturbed by construction cause severe acceleration of erosion threatening environment quality and personal safety rock fragments rfs are a common component of spoil heaps therefore this study was conducted to evaluate the effects of different size classes of rfs on cone shaped spoil heap erosion a 3d laser scanner was used to capture the surface micro topography evolution a multi day rainfall simulation experiment at 1 5 mm min 1 rainfall intensity was conducted with 30 mass percent of rfs of different diameters 1 3 5 3 5 7 7 10 10 15 cm the results showed that rfs reduced runoff by 13 0 relative to the bare soil spoil heap among which the rfs of the 7 10 cm size class performed best only the initial surface micro topography factors increased with rf size the stable micro topography factors of 1 3 5 cm rf treatment were 59 2 larger than those for other rf treatments on average because of the slope slump spoil heaps containing small size 1 3 5 rfs more easily slumped with an area of 0 895 m2 and showed obvious changes in micro topography rfs in different size classes influenced soil loss of spoil heaps via runoff yield and effects on slope stability larger roughness increment and runoff rate were associated with greater soil loss rate r2 0 828 but time varying roughness had no effect on runoff overall the results of this study provide a better understanding of the impact of rfs on spoil heap erosion

the potential of 3d gully monitoring with gis using high resolution aerial photography and a digital photogrammetry system although gully erosion is generally considered a major process of land degradation its contribution to total soil loss by erosion has recently been a subject of much discussion the lack of adequate methods for the documentation and monitoring of gullies resulted in the shortage of quantitative data therefore a high resolution remote sensing system for aerial surveys by blimp or kite has been developed which meets spatial and temporal image resolutions required for short term gully monitoring the objective of this paper is to examine the potential of a method using non metric digital photogrammetry and gis for gully surface modelling and monitoring two bank gullies representing different morphological types of gullies v shaped and u shaped were chosen from a dataset of gully systems in semi arid spain the considerable relief energy and complex topography of the gullies in a natural vegetated landscape were found to be a challenge to digital photogrammetric techniques introducing errors which inhibit fully automated dem generation using a hybrid method combining stereomatching for mass point extraction with manual 3d editing and digitizing high resolution dems 5 and 7 5 cm pixel size were created for the study sites gis analysis of the dems for different monitoring periods 2 to 4 years allowed the computation of gully area and volume as well as their changes with an accuracy and detail sufficient to represent the geomorphological forms and processes involved furthermore the spatially continuous survey of the entire form offered the possibility of distinguishing different zones of activity both at the gully rim and within the gully interior identifying patterns of erosion and deposition which indicate the limited use of headcut retreat rates for the assessment of sediment production on a short term basis

mapping gullies dunes lava fields and landslides via surface roughness abstract gully erosion is a widespread and significant process involved in soil and land degradation mapping gullies helps to quantify past and anticipate future soil losses digital terrain models offer promising data for automatically detecting and mapping gullies especially in vegetated areas although methods vary widely measures of local terrain roughness are the most varied and debated among these methods rarely do studies test the performance of roughness metrics for mapping gullies limiting their applicability to small training areas to this end we systematically explored how local terrain roughness derived from high resolution light detection and ranging lidar data can aid in the unsupervised detection of gullies over a large area we also tested expanding this method for other landforms diagnostic of similarly abrupt land surface changes including lava fields dunes and landslides as well as investigating the influence of different roughness thresholds resolutions of kernels and input data resolution and comparing our method with previously published roughness algorithms our results show that total curvature is a suitable metric for recognising analysed gullies and lava fields from lidar data with comparable success to that of more sophisticated roughness metrics tested dunes or landslides remain difficult to distinguish from the surrounding landscape partly because they are not easily defined in terms of their topographic signature

combining bulk sediment osl and meteoric 10be fingerprinting techniques to identify gully initiation sites and erosion depths deep erosional gullies dissect landscapes around the world existing erosion models focus on predicting where gullies might begin to erode but identifying where existing gullies were initiated and under what conditions is difficult especially when historical records are unavailable here we outline a new approach for fingerprinting alluvium and tracing it back to its source by combining bulk sediment optically stimulated luminescence bulk osl and meteoric 10be 10bem measurements made on gully derived alluvium samples in doing so we identify where gully erosion was initiated and infer the conditions under which such erosion occurred as both 10bem and bulk osl data have distinctive depth profiles in different uneroded and depositional settings we are able to identify the likely incision depths in potential alluvium source areas we demonstrate our technique at birchams creek in the southeastern australian tablelands a well studied and recent example of gully incision that exemplifies a regional landscape transition from unchanneled swampy meadow wetlands to gully incision and subsequent wetland burial by post european settlement alluvium we find that such historic alluvium was derived from a shallow erosion of valley fill upstream of former swampy meadows and was deposited down the center of the valley incision likely followed catchment deforestation and the introduction of livestock which overgrazed and congregated in valley bottoms in the early 20th century during a period of drought as a result severe gully erosion was likely initiated in localized compacted and oversteepened reaches of the valley bottom

comparison of gully erosion estimates using airborne and ground based lidar on santa cruz island california abstract gully erosion removes comparatively large volumes of soil from small areas it is often difficult to quantify the loss of soil because the footprint of individual gullies is too small to be captured by most generally available digital elevation models dems such as the usgs national elevation dataset airborne lidar light detection and ranging has the potential to provide the required data density but an even newer class of ground based sensors may provide better local resolution at lower cost in this study we compared digital elevation models produced by airborne and ground based lidar systems with ground based geomorphic and geodetic survey data to determine their utility in quantifying volumetric soil loss due to gully erosion in a heavily degraded watershed 7 55 10 2 km 2 on southwestern santa cruz island in southern california volumetric estimates of the eroded sediment were produced by comparing the lidar derived dems of the gully system to a modeled pre erosion surface average point densities were significantly higher for the ground based lidar system and provided more detailed information however its limited scanning footprint and side looking orientation presented serious challenges in collecting continuous data from deeply incised gullies making the airborne system preferable for this type of investigation and likely for most applications where heavy topographic shadowing is prevalent

a spatial information technology approach for the mapping and quantification of gully erosion abstract in contrast to the effort during the last decades to investigate sheet interrill and rill soil erosion processes relatively few studies have been focused on quantifying and or predicting gully erosion the extension of the use of modern spatial information technologies such as geographical information systems gis digital elevation modelling dem and remote sensing have created new possibilities for research in this field a key issue to be addressed as the basis for predicting the effects of global changes such as land use and climate changes is the mapping and quantification of gully erosion rates including rate of retreat of gully walls and rate of sediment production this research work presents a method to compute the rate of retreat of gully walls and the associated rate of sediment production caused by gully erosion the proposed method uses multitemporal aerial photographs and multitemporal digital elevation models both of which have been processed using gis techniques the research was applied to a sample catchment of 25 km2 located in catalonia spain aerial photographs at scale of 1 30 000 from 1957 and orthophotos from 1993 were used to map gully erosion and determine erosion rates between 1957 and 1993 the rates of channel incision and sediment production were computed from the subtraction of multitemporal digital elevation models the rate of gully walls retreat was 0 2 m year 1 representing a rate of 0 9 m2 year 1 the maximum rate of channel incision 0 7 0 8 m year 1 occurred at the head of the gully and at meandering zones the rate of sediment production caused by gully erosion was 1322 142 ton ha 1 year 1 in comparison with other methods to compute sediment production caused by gully erosion processes the proposed method integrates the losses due to overland flow mass movements and gully deepening and supposes an improvement to locate the areas within the gullies with higher erosional activity

development of gullies and sediment production in the black soil region of northeastern china abstract gully erosion is an important environmental hazard in the black soil region of northeastern china it is a primary sediment source in the region which needs appropriate soil conservation practices gully incision in rolling hills typical of this region was monitored using real time kinematic gps to assess the rates of gully development and the resultant sediment production from 2002 to 2005 gully heads in the study area retreated between 15 4 and 33 5 m giving an average retreat rate of 8 4 m yr 1 field measurements showed that total sediment production due to gully erosion during the three years ranged between 257 and 1854 m3 yr 1 which is equivalent to 326 to 2355 t yr 1 with gully head retreat accounting for 0 to 21 7 4 4 in average the sediment delivery ratio was especially high during the summer rainy season 56 in average sediment production by ephemeral gullies and permanent gullies was 1 5 times greater than that from surface erosion gully heads retreated faster in the spring freeze thaw period than in the summer the stage of gully development could be identified based on short term changes in the gully erosion rate

computer assisted terrain sketch mapping that considers the geomorphological features in a loess landform abstract in geography a terrain sketch map is necessary to understand the features and internal structures of a landscape due to its ability to depict key information in a geographical scene using as few lines as possible previous computer drawn sketch maps have focused on the artistic effect rather than on depicting terrain features and landform structures and thus they differ considerably from hand drawn sketch maps by geographers or geologists this study develops a dem based method for terrain sketch mapping that considers the typical feature descriptions of a loess landform and the visual hierarchy expression in line with the law of visual perspective the method was tested with experiments on two landforms of chinese loess plateau based on digital elevation models dem with a horizontal resolution of 5 m in the developed method first typical terrain features including the visual outline shoulder line gully and flow lines are extracted from the dem second the map is divided into three visual levels in accordance with the data extension and viewing point then terrain feature lines are assigned to different visual levels finally the visual outlines in the distant view are generalized following the law of visual perspective results are assessed through a questionnaire with specialists experts and students non experts the sketch map was able to characterise loess landforms and is somewhat similar to traditional hand drawn maps the generalisation method realises the near and distant view characteristics of a sketch map which are detailed and simplified respectively the results of the questionnaire also showed that our method presents terrain morphology and geographical scene more accurately and reliably than a hand drawn sketch map

assessment of sidewall erosion in large gullies using multi temporal dems and logistic regression analysis although in the last decades gully erosion has been a thriving research field few studies have specifically addressed the contribution and location of sidewall erosion processes in gullies in this paper sidewall erosion in some large gullies in a mediterranean area anoia penedes ne spain is mapped and assessed for two time intervals 1975 1995 and 1995 2002 using detailed digital elevation models derived from aerial photographs at a scale of 1 5000 to 1 7000 logistic regression analysis is applied to compute the probability of occurrence of gully sidewall erosion from terrain variables the results confirm the complex nature of sidewall processes whose intensity is most probably related to rainfall characteristics prolonged wet soil conditions in the period 1995 2002 together with the large and high intensity rainfall of an extreme event occurred on 10th june 2000 help to explain the different sediment production rates 16 0 4 mg ha 1 year 1 in 1975 1995 and 83 6 3 mg ha 1 year 1 in 1995 2002 the logistic regression analysis revealed that gully wall slope angle was the main factor controlling gully sidewall failure in gully walls with high slope angles tension crack development is the main process promoting wall collapse the application of the logistic regression model showed a high overall accuracy 87 but over 50 of commission and omission errors for the class of interest sidewall erosion in agreement with the variance explained by the model

water rock interaction in tertiary sandstones san joaquin basin california u s a diagenetic controls on water composition three water types are recognized among petroleum associated waters of the southern san joaquin basin 1 meteoric water 2 diagenetically modified connate water and 3 mixed meteoric modified connate water the diagenetically modified connate marine water can be further subdivided into three types 1 fully mg depleted mg 1 mole of the sum of na k ca and mg 2 partially mg depleted and 3 ca enriched enrichment in ca which is the sharpest chemical divide found for the diagenetically modified connate water is the result of feldspar albitization the ca enriched waters are also rich in total dissolved al up to 6 mg l 1 and exhibit lighter 18o values than other diagenetically modified connate waters the total dissolved al abundance in these waters may be due to the presence of organic complexing agents simple and aromatic organic acids and phenolics the lighter 18o values are probably due to both albitization and the lack of substantial clay diagenesis illitization of smectite

gully erosion impacts factors and control gully erosion attracts increasing attention from scientists as reflected by two recent international meetings poesen and valentin eds catena 50 2 4 87 564 li et al 2004 gully erosion under global change sichuan science technology press chengu china 354 pp this growing interest is associated with the increasing concern over off site impacts caused by soil erosion at larger spatial scales than the cultivated plots the objective of this paper is to review recent studies on impacts factors and control of gully erosion and update the review on dgully erosion and environmental change importance and research needst poesen et al 2003 catena 50 2 4 91 134 for the farmers the development of gullies leads to a loss of crop yields and available land as well as an increase of workload i e labour necessary to cultivate the land gullies can also change the mosaic patterns between fallow and cultivated fields enhancing hillslope erosion in a feedback loop in addition gullies tend to enhance drainage and accelerate aridification processes in the semi arid zones fingerprinting the origin of sediments within catchments to determine the relative contributions of potential sediment sources has become essential to identify sources of potential pollution and to develop management strategies to combat soil erosion in this respect tracers such as carbon nitrogen the nuclear bomb derived radionuclide 137 cs magnetics and the strontium isotopic ratio are increasingly used to fingerprint sediment recent studies conducted in australia china ethiopia and usa showed that the major part of the sediment in reservoirs might have come from gully erosion gullies not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess european belt chinese loess plateau north america and sandy soils sahelian zone north east thailand or in soils prone to piping and tunnelling such as dispersive soils most of the time the gullying processes are triggered by

chronology of tectonic geomorphic and volcanic interactions and the tempo of fault slip near little lake california new geochronologic and geomorphic constraints on the little lake fault in the eastern california shear zone reveal steady modest rates of dextral slip during and since the mid to late pleistocene we focus on a suite of offset fluvial landforms in the pleistocene owens river channel that formed in response to periodic interaction with nearby basalt flows thereby recording displacement over multiple time intervals overlap between 40 ar 39 ar ages for the youngest intracanyon basalt flow and 10 be surface exposure dating of downstream terrace surfaces suggests widespread channel incision during a prominent outburst flood through the little lake channel at ca 64 ka older basalt flows flanking the upper and lower canyon margins indicate localization of the owens river in its current position between 212 14 and 197 11 ka coupled with terrestrial light detection and ranging lidar and digital topographic measurements of dextral offset the revised little lake chronology indicates average dextral slip rates of at least 0 6 0 7 mm yr and 4 to 10 5 yr despite previous geodetic observations of relatively rapid interseismic strain along the little lake fault we find no evidence for sustained temporal fluctuations in slip rates over multiple earthquake cycles instead our results indicate that accelerated fault loading may be transient over much shorter periods 10 1 yr and perhaps indicative of time dependent seismic hazard associated with eastern california shear zone faults

the measurement of river bank erosion and lateral channel change a review a detailed review and chronological survey is presented of the various techniques which have been used for the measurement of river bank erosion and channel change the techniques are classified according to the time scales involved long intermediate and short and each is discussed with respect to accuracy and repeatability the methods covered include sedimentological evidence botanical evidence historical sources planimetric resurvey repeated cross profiling erosion pins and terrestrial photogrammetry prospects for future developments are also discussed

from geotechnical analysis to quantification and modelling using lidar data a study on rockfall in the reintal catchment bavarian alps germany in the year 2007 enhanced rockfall activity was observed within the scarp of a 500 bp rockslide in the reintal catchment northern calcareous alps germany the largest of a series of events took place in august when almost 50000 m of rock were detached from the subvertical rock face and deposited on a talus cone in this case study we focus on three aspects of rockfall research first we compile detailed geomorphological and geotechnical findings to explain the causes of the recent events the results of laboratory tests and stability estimations suggest that rockfall activity will persist in the future as the old rockslide scarp still contains unstable rock masses second we use digital elevation data from a pre event airborne lidar survey als and post event terrestrial laserscanning tls to quantify landform changes and the mass balance of the rockfall event s the widespread availability of als elevation data provides a good opportunity to quantify fresh events using a comparatively inexpensive tls survey this approach is complicated by uncertainties resulting from the difficult coregistration of als and tls data and the specific geometric problems in steep als and flat tls terrain it is therefore limited to at least medium sized events third the event s is simulated using the results of the lidar surveys and a modified gis based rockfall model in order to test its capability of predicting the extent and the spatial distribution of deposition on the talus cone results show that the model generally reproduces the process domain and the spatial distribution of topographic changes but frequently under and over estimates deposition heights copyright 2011 john wiley sons ltd

tracking geomorphic signatures of watershed suburbanization with multitemporal lidar abstract urban development practices redistribute surface materials through filling grading and terracing causing drastic changes to the geomorphic organization of the landscape many studies document the hydrologic biologic or geomorphic consequences of urbanization using space for time comparisons of disparate urban and rural landscapes however no previous studies have documented geomorphic changes from development using multiple dates of high resolution topographic data at the watershed scale this study utilized a time series of five sequential light detection and ranging lidar derived digital elevation models dems to track watershed geomorphic changes within two watersheds throughout development 2002 2008 and across multiple spatial scales 0 01 1 km 2 development induced changes were compared against an undeveloped forested watershed during the same time period changes in elevations slopes hypsometry and surface flow pathways were tracked throughout the development process to assess watershed geomorphic alterations results suggest that development produced an increase in sharp topographic breaks between relatively flat surfaces and steep slopes replacing smoothly varying hillslopes and leading to greater variation in slopes examinations of flowpath distributions highlight systematic modifications that favor rapid convergence in unchanneled upland areas evidence of channel additions in the form of engineered surface conduits is apparent in comparisons of pre and post development stream maps these results suggest that topographic modification in addition to impervious surfaces contributes to altered hydrologic dynamics observed in urban systems this work highlights important considerations for the use of repeat lidar flights in analyzing watershed change through time novel methods introduced here may allow improved understanding and targeted mitigation of the processes driving geomorphic changes during development and help guide future research directions for development based watershed studies

analysis of lidar derived topographic information for characterizing and differentiating landslide morphology and activity abstract this study used airborne laser altimetry lidar to examine the surface morphology of two canyon rim landslides in southern idaho the high resolution topographic data were used to calculate surface roughness slope semivariance and fractal dimension these data were combined with historical movement data global positioning systems gps and laser theodolite and field observations for the currently active landslide and the results suggest that topographic elements are related to the material types and the type of local motion of the landslide weak unconsolidated materials comprising the toe of the slide which were heavily fractured and locally thrust upward had relatively high surface roughness high fractal dimension and high vertical and lateral movement the body of the slide which predominantly moved laterally and consists mainly of undisturbed older canyon floor materials had relatively lower surface roughness than the toe the upper block consisting of a down dropped section of the canyon rim that has remained largely intact had a low surface roughness on its upper surface and high surface roughness along fractures and on its west face unrelated to landslide motion the upper block also had a higher semivariance than the toe and body the topographic data for a neighboring older and larger landslide complex which failed in 1937 are similarly used to understand surface morphology as well as to compare to the morphology of the active landslide and to understand scale dependent processes the morphometric analyses demonstrate that the active landslide has a similar failure mechanism and is topographically more variable than the 1937 landslide especially at scales 20 m weathering and the larger scale processes of the 1937 slide are hypothesized to cause the lower semivariance values of the 1937 slide at smaller scales

analysis of the influence of gully erosion in the flow pattern of catchment streams southeastern brazil the baseflow of tributaries to the velhas river in the northwest region of ouro preto county sao francisco basin brazil has been declining in the last years without a simultaneous decrease in the water input this can only be attributed to badly planned human activities which result in soil crusting or compaction erosion among other types of impact such as groundwater overexploitation and wetland drainage almost all of the study area has been eroded by hundreds of large size gullies in order to analyze the influence of erosion in the hydrological behavior of small streams two similar and contiguous catchments were selected the only remarkable difference between them is a gully that occupies circa 42 of one of the catchments eroded catchment rainfall flow rates and chemical data were obtained throughout a hydrological year and the results showed that the eroded catchment presented smaller baseflow rates and bigger but short lived stormflows this contrasting flow regime is attributed to the gully which is causing the partial withdraw of the regolith and the exposure of weathered rock as the regolith has smaller hydraulic conductivities and higher storage coefficients the exposure of weathered rock on the gully floor explains the odd flow behavior of the eroded catchment other studies in the same region confirm the impact caused by the gullies thus the superposition of many gullies can cause decrease of the baseflow and increase of the stormflow as gullies are very common erosion features in brazil they should be much more studied in order to better understand this and other similar types of environmental impact