geomorphometry and landform mapping what is a landform abstract starting from a concept of the land surface its definition and subdivision from digital elevation models dems is considered high resolution dems from active remote sensing form a new basis for geomorphological work which is moving on from consideration of whether data are accurate enough to how the surface of interest can be defined from an overabundance of data discussion of the operational definition and delimitation of specific landforms of varying degrees of difficulty from craters to mountains is followed by the applicability of fuzzy boundaries scaling usually allometric is shown to be compatible with the scale specificity of many landforms this is exemplified by glacial cirques and drumlins classification of a whole land surface is more difficult than extraction of specific landforms from it well dissected fluvial landscapes pose great challenges for areal analyses these are tackled by the delimitation of homogeneous elementary forms and or land elements in which slope position is considered the boundaries are mainly breaks in gradient or aspect but may also be in some type of curvature breaks in altitude are rare elementary forms or land elements are grouped together into functional regions landforms such as hill sheds it may often be useful to recognise fuzziness of membership or core and periphery of a surface object plains and etched or scoured surfaces defy most of these approaches and general geomorphometry remains the most widely applicable technique it has been applied mainly within arbitrary areas and to some extent to drainage basins but more experimentation with mountain ranges and other landforms or landform regions is needed geomorphological mapping is becoming more specialised and its legends are being simplified its incorporation into geographical information systems gis has required greater precision with definitions and the separation of thematic layers so that it is converging with specific geomorphometry and becoming more flexible and more applicable with a broader range of visualisation techniques

major disturbance to aquatic ecosystems in the south island new zealand following human settlement in the late holocene lake sediment records from three lakes in the south island of new zealand were examined to determine the effects of human m ori and european impacts on the lake catchments during the late holocene major changes in lake biota occurred in the early to middle holocene 11 000 6000 cal yr bp but there were no major changes between c 6000 cal yr bp and the time of human impact intensive m ori forest clearance occurred here between c ad 1200 and 1600 which is consistent with other new zealand records catchment erosion and increased sedimentation probably occurred in all of the studied lakes but the most obvious changes occurred in lake clearwater and the m ori lakes there was evidence for gravity induced slumping of the littoral sediments in lake clearwater due to increased sediment loading and the outflow from the m ori lakes was blocked by a migrating alluvial fan the erosion of sediment and nutrients from the lake catchments led to eutrophication but increases in lake depth were just as important in two of the lakes increased water depth was caused by damming of the m ori lakes outflow by a migrating alluvial fan reduced evapotranspiration following deforestation would also have led to increased water yield in lake catchments european impacts were minor compared with the impacts of m ori deforestation and all lakes display different levels of recovery towards pre human impact conditions complete recovery is prevented by permanent changes in catchment hydrology and probable internal feedback mechanism such as wind induced sediment re suspension in the larger lakes

on the prediction of channel heads in a complex alpine terrain using gridded elevation data 1 threshold conditions for channel initiation are evaluated by using gridded elevation data derived from a lidar survey a reliable algorithm for the determination of surface flow paths and field observations of channel heads for a study area located in the eastern italian alps these threshold conditions are determined by considering the channel heads observed across a portion of the study area and computing the related values of 1 drainage area a 2 area slope function as2 with s being the local slope and 3 strahler order of surface flow paths extracted from gridded elevation data attention is focused on the dependence of the obtained threshold values on the size of grid cells involved and on the ability of the identified threshold conditions to provide reliable predictions of channel heads across the entire study area the results indicate that the threshold values of a as2 and are all significantly dependent on grid cell size and the uncertainty in the determination of threshold values of is significantly smaller than that affecting the determination of threshold values of a and as2 the comparison between predicted and observed channel heads indicates that the considered methods display variable reliability and sensitivity over different drainage basins and grid cell sizes with a general tendency to predict more channel heads than can be observed in the field acceptable predictions are normally obtained where channel heads are formed essentially by surface runoff more comprehensive methods seem however to be needed to predict channel heads affected by groundwater seeping upward

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

distribution of local landforms at head and end points of gullies on different grid spacing abstract local landforms described by signs of curvatures can be considered as potential indicators of gully formation however the role of these landforms is not generally investigated in literature hence the goals of the present research are i identification of the relationships of land surface attributes at the head and end points of gullies with the size of these gullies at different grid spacings of a digital elevation model dem ii explanation of the frequency of occurrence fo of local landforms investigations were conducted on the example of 439 gullies of the hronska pahorkatina hill land in slovakia the sizes of the gullies were described by their area and perimeter altitude slope steepness maximal catchment area mca and curvatures were calculated at the head and end points of these gullies 12 types of main local landforms mllfs were identified by the signs of six curvatures for calculation of land surface attributes a set of dems with grid spacings at every 10 m interval from 10 m to 100 m was prepared at the head points of gullies significant spearman s rank correlation coefficients rs show that mca and curvatures related with gully size at dem grid spacings from 10 m to 30 m at the end points such relationships are observed at all grid spacings a negative rs between gully size and slope steepness is obtained at the head points it is demonstrated that the large gullies reached more flat locations in comparison with small gullies at the end points negative rs indicates that large gullies are characterized by flatter outlets in comparison with small gullies the fo of mllfs at the head and end points of gullies relative to their frequency for the whole dem indicate that only four types of mllf are systematically related to gully occurrence

downstream hydraulic geometry relationships gathering reference reach scale width values from lidar abstract this paper examines the ability of lidar topography to provide reach scale width values for the analysis of downstream hydraulic geometry relationships along some streams in the dolomites northern italy multiple reach scale dimensions can provide representative geometries and statistics characterising the longitudinal variability in the channel improving the understanding of geomorphic processes across networks starting from the minimum curvature derived from a lidar dtm the proposed algorithm uses a statistical approach for the identification of the scale of analysis and for the automatic characterisation of reach scale bankfull widths the downstream adjustment in channel morphology is then related to flow parameters drainage area and stream power with the correct planning of a lidar survey uncertainties in the procedure are principally due to the resolution of the dtm the outputs are in general comparable in quality to field survey measurements and the procedure allows the quick comparison among different watersheds the proposed automatic approach could improve knowledge about river systems with highly variable widths and about systems in areas covered by vegetation or inaccessible to field surveys with proven effectiveness this research could offer an interesting starting point for the analysis of differences between watersheds and to improve knowledge about downstream channel adjustment in relation for example to scale and landscape forcing e g sediment transport tectonics lithology climate geomorphology and anthropic pressure

experimental investigation of morphological characteristics of rill evolution on loess slope abstract the development of rill is the result of a complex interaction of soil properties with high spatial and temporal variability the rill morphology may act as a determinant as well as a stochastically driven process the description of their complex morphology requires geostatistics and nonlinear theories a study of the morphological characteristics of rill evolution was performed via indoor soil pan rainfall simulations experiments were run with loessial soil bulk density of 1 25 g cm 3 under a rainfall intensity of 90 mm h with a 20 slope gradient a detailed scan of the slope topographic analysis and statistical analyses were the main methods utilized in the study statistical analyses showed that characteristic parameters exhibited differences in the expression of the dynamic change of soil loss according to the comparison of quantitative methods we found that the fractal dimension can reflect the complexity of rill network but it is not able to reflect the dynamic changes of the erosion process perfectly in contrast geomorphologic comentropy is sensitive to the dynamic changes of soil erosion intensity and its variation can reflect the dynamic changes of erosion perfectly the topological parameters can reflect the degree of stability in the rill network structure but it is not suitable for reflecting the dynamic changes of erosion intensity the geomorphologic comentropy was evaluated as the most appropriate characterization parameter for the rill morphology description

field study on drainage densities and rescaled width functions in a high altitude alpine catchment this paper addresses the effect of accurately mapping spatially heterogeneous drainage densities in high altitude alpine basins on rescaled width functions rwfs used in some applications as a minimalist model of the hydrologic response the channel network and 373 of its channel heads were mapped in the field in a high mountain catchment in the swiss alps the mapped channel network is characterized by highly uneven drainage density here described by the distribution of the length to the first channelized site computed along steepest descent from any unchannelled site various channel networks were extracted from a 1 m lidar derived digital terrain model and compared with the field mapped channel network using geomorphologic parameters hillslope to channel distance and rwfs our results show that the channel network derived by statistical analysis of surface morphology is consistent with the field mapped network larger discrepancies were observed when the channel network was obtained with classical threshold based approaches relying on cumulative drainage area and local slope the actual arrangement of the drainage densities has a significant impact on the rwfs the discrepancy was largest between rwfs derived from classical extraction methods and rwfs derived with the field mapped network indicating an inappropriate extraction of the channelled portion of the high altitude catchment that is a reflection of the variety of channel initiation processes our results suggest that spatial heterogeneity of the drainage density might play an important role in modelling streamflow generation

surficial patterns of debris flow deposition on alluvial fans in death valley ca using airborne laser swath mapping data debris flows are a common event in mountainous environments they often possess the greatest potential for destruction of property and loss of lives in these regions delimiting the spatial extent of potential damage from debris flows relies on detailed studies of the location of depositional zones current research indicates debris flow fans have two distinct depositional zones however the two zones were derived from studies containing detailed analyses of only a few fans high resolution airborne laser swath mapping alsm data is used to calculate profile curvature and surface gradient on 19 debris flow fans on the eastern side of death valley the relationship between these parameters is assessed to 1 identify if debris flow fans are accurately represented by two depositional zones and 2 to assess how these terrain parameters relate to one another at the individual fan scale the results show at least three zones of deposition exist within the sampled fans these zones do not hold consistent when individual fan morphometry is analyzed in conjunction with localized fan surface gradients fans with consistently shallower gradients exhibit numerous depositional zones with more subtle changes in profile curvature steeper gradient fans exhibit significantly fewer zones with more pronounced local changes in profile curvature the surface complexity of debris flow fans is evident from these analyses and must be accounted for in any type of hazard studies related to these features

suitability of lidar point density and derived landform curvature maps for channel network extraction this study uses landform curvature as an approach for channel network extraction we considered a study area located in the eastern italian alps where a high quality set of lidar data was available and where channel heads and related channel network were mapped in the field in the analysis we derived 1 m dtms from different ground lidar point densities and we used different smoothing factors for the landscape curvature calculation in order to test the suitability of the lidar point density and the derived curvature maps for the recognition of channel network this methodology is based on threshold values of the curvature calculated as multiples 1 3 times of the standard deviation of the curvature our analyses suggested that i the window size for curvature calculations has to be a function of the size of the features to be detected ii a coarse ground lidar point density could be as useful as a finer one for the recognition of main channel network features and iii rougher curvature maps are not optimal as they do not explore a sufficient range at which features occur while smoother curvature maps overcome this problem and are more appropriate for the extraction of surveyed channels copyright 2010 john wiley sons ltd

gradual catastrophic and human induced environmental changes from a coastal lake southern new zealand abstract cores obtained from a coastal freshwater lake lake waihola south island new zealand show a 4000 year history of environmental changes driven by significant variations in marine influence and anthropogenic modification of the catchment and minor contributions such as possible palaeotsunami inundation all taking place against a background of sea level and landscape change a marked shift from estuarine conditions salinity 14 ppt to a predominantly freshwater state occurred around the mid holocene this shift is recorded as a distinct change in diatom assemblages and by the disappearance of the estuarine bivalve austrovenus stutchburyi from the sedimentary record more recently a marked change in sediment characteristics and changes in the pollen record correlate with rapid anthropogenic land clearance and conversion of the catchment to intensive agriculture in the mid 1800 s the mean rate of sediment accumulation between c 4000 yr bp and the start of major european settlement c ad1860 were around 0 18 0 01 mm yr 1 from c ad1860 onwards this has increased markedly by about 30 fold following major land use changes in the catchment based on current predictions of sea level rise and sediment accumulation various future sea level rise scenarios will more than compensate for infilling resulting in the persistence of this aquatic system which is expected to revert to an estuarine state

assessing levee stability with geometric parameters derived from airborne lidar abstract a methodology to assess levee structural integrity using high resolution airborne light detection and ranging lidar data is investigated for a 16 km reach of the sacramento river within the sacramento san joaquin river delta california levee geometric parameters levee crown width height and water and landside slopes were extracted from 0 5 m resolution lidar derived digital ground models deviation of these parameters from minimum levee design standards was used to calculate a levee stability index stability maps were generated and those areas that did not meet usace geometric shape standards were identified results show that 2 out of the 4 geometric parameters do not meet the minimum value required in 48 and 43 of profiles on the east urban adjacent and west farmland adjacent margins respectively most importantly the crown width in 99 of the levee profiles located on the urban side was below the minimum required the paper also points out the importance of evaluating all four geometric parameters not just the elevation of the levee by assessing its level of performance through a geometric assessment

identifying the probabilistic structure of drained areas as a function of hypsometry in river networks classical morphological descriptors of river networks have been developed in 2d planar system the third z dimension elevation however is necessary to model landscape evolution particularly in a mountainous region when taking into account transport processes such as in glaciology and erosion this paper aims at analyzing 3d morphometric properties of channel networks on the basis of probabilistic relationships relating the drained area and the elevation the methodology is an extension of the fundamental planar power law description proposed by rodriguez iturbe et al 1992a representing the probability that the drained area a is higher than a threshold area a p a a a where is constant and represents an invariant property of natural river networks a new scaling factor taking into account hypsometry is introduced in the previous power law relationship as where f is a scaling function and is a measure of the system scale and a function of hypsometry the new power law has one empirical parameter a procedure was developed to calibrate this parameter and to calculate the corresponding uncertainty for applications on a single basin and then extended to a set of 70 basins in the southern rocky mountains the results show that the 3d power law exhibits scale invariance properties with respect to when applied to a single basin looking at the entire set of 70 basins the criterion value associated with the uncertainty model shows a moderate loss in scaling quality compared with the basin per basin description but nevertheless remains acceptable this 3d power law provides a geomorphologic basis for applications in mountainous regions where the relation between drained area and hypsometry has to be considered copyright 2014 john wiley sons ltd

channel initiation and the problem of landscape scale since the 1940s it has been proposed that landscape dissection into distinct valleys is limited by a threshold of channelization that sets a finite scale to the landscape this threshold is equal to the hillslope length that is just shorter than that necessary to support a channel head a field study supports this hypothesis by showing that an empirically defined topographic threshold associated with channel head locations also defines the border between essentially smooth undissected hillslopes and the valley bottoms to which they drain this finding contradicts assertions that landscapes are scale independent and suggests that landscape response to changes in climate or land use depends on the corresponding changes in the threshold of channelization

chironomids as a tool for inferring holocene climate an assessment based on six sites in southern scandinavia abstract chironomid subfossil assemblages from six low alpine and sub alpine holocene stratigraphies are presented and compared they are from five lakes in mid southern and western norway and one in central sweden when comparing the chironomid inferred july air temperatures there are many time segments with a poor among lake fit in inferred temperatures possible environmental variables influencing the fossil chironomid assemblages are discussed using a modern norwegian calibration data set to indicate taxon environment relationships these analyses indicate that local changes in ph water chemistry and productivity at times may have overridden the regional temperature signal in addition other causes of poor among site temperature fit are discussed in particular those related to chronological uncertainties holocene temperature inferences from single cores based on chironomids may not always be able to provide a reliable regional temperature signal but can act as a guide from which hypotheses about past environmental conditions can be tested with the aid of chironomid inferred temperatures from several sites and from other environmental proxies we have obtained a regional picture of holocene summer temperature change by developing a consensus reconstruction based on the overall temperature signal from all six sites this consensus is developed by fitting a smoother through all 330 site specific temperature deviations from the holocene mean the consensus temperature deviations vary from 0 8 c at 8800 cal years bp to 0 8 c at 6500 cal years bp

the topographic signature of a major typhoon in august 2009 the typhoon morakot characterized by a cumulative rainfall up to 2884 mm in about three days triggered thousands of landslides in taiwan the availability of lidar surveys before 2005 and after 2010 this event offers a unique opportunity to investigate the topographic signatures of a major typhoon the analysis considers the comparison of slope area relationships derived by lidar digital terrain models dtms this approach has been successfully used to distinguish hillslope from channelized processes as a basis to develop landscape evolution models and theories and understand the linkages between landscape morphology and tectonics climate and geology we considered six catchments affected by a different degree of erosion three affected by shallow and deep seated landslides and three not affected by erosion for each of these catchments 2 m dtms were derived from lidar data the scaling regimes of local slope versus drainage area suggested that for the catchments affected by landslides i the hillslope to valley transitions morphology for a given value of drainage area is shifted towards higher value of slopes thus indicating a likely migration of the channelized processes and erosion toward the catchment boundary the catchment head becomes steeper because of erosion ii the topographic gradient along valley profiles tends to decrease progressively the valley profile becomes gentler because of sediment deposition after the typhoon the catchments without any landslides present a statistically indistinguishable slope area scaling regime these results are interesting since for the first time using multi temporal high resolution topography derived by lidar we demonstrated that a single climate event is able to cause significant major geomorphic changes on the landscape detectable using slope area scaling analysis this provides new insights about landscape evolution under major climate forcing copyright 2015 john wiley sons ltd

application of a multi temporal lidar derived digital terrain model in a landslide volume estimation sediments produced by landslides are crucial in the sediment yield of a catchment debris flow forecasting and related hazard assessment on a regional scale however it is difficult and time consuming to measure the volumes of such sediment this paper uses a lidar derived digital terrain model dtm taken in 2005 and 2010 at 2 m resolution to accurately obtain landslide induced sediment volumes that resulted from a single catastrophic typhoon event in a heavily forested mountainous area of taiwan the landslides induced by typhoon morakot are mapped by comparison of 25 cm resolution aerial photographs taken before and after the typhoon in an 83 6 km2 study area each landslide volume is calculated by subtraction of the 2005 dtm from the 2010 dtm and the scaling relationship between landslide area and its volume are further regressed the relationship between volume and area are also determined for all the disturbed areas vl 0 452al1 242 and for the crown areas of the landslides vl 2 510al1 206 the uncertainty in estimated volume caused by use of the lidar dtms is discussed and the error in absolute volume estimation for landslides with an area 105 m2 is within 20 the volume area relationship obtained in this study is also validated in 11 small to medium sized catchments located outside the study area and there is good agreement between the calculation from dtms and the regression formula by comparison of debris volumes estimated in this study with previous work it is found that a wider volume variation exists that is directly proportional to the landslide area especially under a higher scaling exponent copyright 2013 john wiley sons ltd

reconstructing holocene water tables in new zealand using testate amoebae differential preservation of tests and implications for the use of transfer functions testate amoebae analysis is used to provide the e rst quantitative reconstruction of holocene surface wetness changes from a southern hemisphere ombrogenous bog water table depth and surface moisture are the dominant environmental factors ine uencing testate amoebae species composition in a modern training set of 62 surface samples from 19 bogs in new zealand a transfer function based on partial least squares pls performed well in cross validation of modern samples but produced unrealistic predictions of water table depth and moisture for fossil samples this resulted from poor overlap of species composition between modern and fossil samples peat humie cation data is used to examine decay related species diversity trends and ordination is used to explore the differences between modern and fossil assemblages poor overlap can be explained by differential preservation in the fossil assemblages of those taxa with more robust tests this enhances their abundance and reduces the overall diversity of the fossil assemblages human activities over the last 150 years have also ine uenced the surface environments and hydrology of the sampled bogs in this situation weighted average wa and tolerance downweighted weighted average wa tol models were more robust than pls and were applied along with semi quantitative scoring to reconstruct more realistic holocene surface wetness changes selection of the best model for reconstruction of surface wetness changes should be based on the characteristics of the fossil data rather than the predictive power of the model in cross validation of the modern data alone

range imaging a new method for high resolution topographic measurements in small and medium scale field sites topographic measurements are essential for the study of earth surface processes three dimensional data have been conventionally obtained through terrestrial laser scanning or photogrammetric methods however particularly in steep and rough terrain high resolution field measurements remain challenging and often require new creative approaches in this paper range imaging is evaluated as an alternative method for obtaining surface data in such complex environments range imaging is an emerging time of flight technology using phase shift measurements on a multi pixel sensor to generate a distance image of a surface its suitability for field measurements has yet not been tested we found ambient light and surface reflectivity to be the main factors affecting error in distance measurements low reflectivity surfaces and strong illumination contrasts under direct exposure to sunlight lead to noisy distance measurements however regardless of lighting conditions the accuracy of range imaging was markedly improved by averaging multiple images of the same scene for medium ambient lighting shade and a light coloured surface the measurement uncertainty was approximately 9 mm to further test the suitability of range imaging for field applications we measured a reach of a steep mountain stream with a horizontal resolution of approximately 1 cm in the focal plane of the camera allowing for the interpolation of a digital elevation model on a 2 cm grid comparison with an elevation model obtained from terrestrial laser scanning for the same site revealed that both models show similar degrees of topographic detail despite limitations in measurement range and accuracy particularly at bright ambient lighting range imaging offers three dimensional data in real time and video mode without the need of post processing therefore range imaging is a useful complement or alternative to existing methods for high resolution measurements in small to medium scale field sites copyright 2012 john wiley sons ltd

quantifying riparian zone structure from airborne lidar vegetation filtering anisotropic interpolation and uncertainty propagation summary advances in remote sensing technology notably in airborne light detection and ranging lidar have facilitated the acquisition of high resolution topographic and vegetation datasets over increasingly large areas whilst such datasets may provide quantitative information on surface morphology and vegetation structure in riparian zones existing approaches for processing raw lidar data perform poorly in riparian channel environments a new algorithm for separating vegetation from topography in raw lidar data and the performance of the elliptical inverse distance weighting eidw procedure for interpolating the remaining ground points are evaluated using data derived from a semi arid ephemeral river the filtering procedure which first applies a threshold either slope or elevation to classify vegetation high points and second a regional growing algorithm from these high points avoids the classification of high channel banks as vegetation preserving existing channel morphology for subsequent interpolation 2 90 9 21 calibration error 4 53 7 44 error in evaluation for slope threshold eidw which accounts for surface anisotropy by converting the remaining elevation points to streamwise co ordinates can outperform isoptropic interpolation idw on channel banks however performs less well in isotropic conditions and when local anisotropy is different to that of the main channel a key finding of this research is that filtering parameter uncertainty affects the performance of the interpolation procedure resultant errors may propagate into the digital elevation model dem and subsequently derived products such as canopy height models chms consequently it is important that this uncertainty is assessed understanding and developing methods to deal with such errors is important to inform users of the true quality of laser scanning products such that they can be used effectively in hydrological applications

hillslope to valley transition morphology new opportunities from high resolution dtms abstract the search for the optimal spatial scale for observing landforms to understand physical processes is a fundamental issue in geomorphology topographic attributes derived from digital terrain models dtms such as slope curvature and drainage area provide a basis for topographic analyses the slope area relationship has been used to distinguish diffusive hillslope from linear valley processes and to infer dominant sediment transport processes in addition curvature is also useful in distinguishing the dominant landform process recent topographic survey techniques such as lidar have permitted detailed topographic analysis by providing high quality dtms this study uses lidar derived dtms with a spatial scale between 1 and 30 m in order to find the optimal scale for observation of dominant landform processes in a headwater basin in the eastern italian alps where shallow landsliding and debris flows are dominant the analysis considered the scaling regimes of local slope versus drainage area the spatial distribution of curvature and field observations of channel head locations the results indicate that i hillslope to valley transitions in slope area diagrams become clearer as the dtm grid size decreases due to the better representation of hillslope morphology and the topographic signature of valley incision by debris flows and landslides is also best displayed with finer dtms ii regarding the channel head distribution in the slope area diagrams the scaling regimes of local slope versus drainage area obtained with grid sizes of 1 3 and 5 m are more consistent with field data and iii the use of thresholds of standard deviation of curvature particularly at the finest grid size were proven as a useful and objective methodology for recognizing hollows and related channel heads

channel network extraction from high resolution topography using wavelets 1 the availability of high resolution topography from lidar offers new opportunities for objectively extracting the channels directly from a dem using local topographic information instead of inferring them indirectly based on global criteria such as area or area slope threshold relationships here we introduce the use of wavelet filtering to delineate threshold curvatures for defining valleys and threshold slope direction change for defining probable channeled portions of the valleys this approach exploits the topographic signatures uniquely found in high resolution topography and reveals the fuzzy topographic transition in which local weakly convergent areas lie at the transition between hillslopes and valleys

high resolution topography for understanding earth surface processes opportunities and challenges abstract in the last decade a range of new remote sensing techniques has led to a dramatic increase in terrain information providing new opportunities for a better understanding of earth surface processes based on geomorphic signatures technologies such as airborne and terrestrial lidar light detection and ranging to obtain high resolution topography have opened avenues for the analysis of landslides hillslope and channellization processes river morphology active tectonics volcanic landforms and anthropogenic signatures on topography this review provides an overview of the recent flourishing literature on high resolution topographic analyses underlining their opportunities and critical issues such as their limitations the goal is to provide answers to questions such as what kind of processes can be analyzed through high resolution topographic data and how to do it the review focuses on two different environments natural and engineered landscapes in both contexts high resolution topography offers opportunities to better understand geomorphic processes from topographic signatures particular attention is given to engineered landscapes in which the direct anthropic alteration of processes is significant the last part of the review discusses future challenges

hydraulic characterization of river networks based on flow patterns simulated by 2 d shallow water modeling scaling properties multifractal interpretation and perspectives for channel heads detection

formal subdivision of the holocene series epoch a discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommission on quaternary stratigraphy international commission on stratigraphy this discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommision on quaternary stratigraphy sqs of the international commission on stratigraphy ics considers the prospects for a formal subdivision of the holocene series epoch although previous attempts to subdivide the holocene have proved inconclusive recent developments in quaternary stratigraphy notably the definition of the pleistocene holocene boundary and the emergence of formal subdivisions of the pleistocene series epoch mean that it may be timely to revisit this matter the quaternary literature reveals a widespread but variable informal usage of a tripartite division of the holocene early middle or mid and late and we argue that this de facto subdivision should now be formalized to ensure consistency in stratigraphic terminology we propose an early middle holocene boundary at 8200 a bp and a middle late holocene boundary at 4200 a bp each of which is linked to a global stratotype section and point gssp should the proposal find a broad measure of support from the quaternary community a submission will be made to the international union of geological sciences iugs via the sqs and the ics for formal ratification of this subdivision of the holocene series epoch copyright 2012 john wiley sons ltd

late quaternary palaeoecology palynology and palaeolimnology of a tropical lowland swamp rawa danau west java indonesia abstract sedimentological limnological and palynological analyses of a sediment core from a lowland site in west java indonesia provide a detailed palaeoenvironmental record for the late glacial and the holocene the record suggests open vegetation under inferred drier climatic conditions for the late glacial however there is no unequivocal evidence for cooler conditions at this time the onset of the holocene coincides with a change to more humid climatic conditions with the development of a fern rich closed forest vegetation type dramatic changes in diatom community composition provide a striking record of habitat change associated with lake shallowing but this process appears to be a result of basin in filling rather than variations in precipitation evaporation balance associated with climatic fluctuations evidence for human impact on the vegetation development is restricted to the last few hundred years

analysing the influence of upslope bedrock outcrops on shallow landsliding abstract a model for the prediction of topographic and climatic control on shallow landsliding in mountainous terrain is enhanced to analyse the impact of upslope rocky outcrops on downslope shallow landsliding the model uses a generalised quasi dynamic wetness index to describe runoff propagation on bare rock surfaces connected to downslope soil mantled topographic elements this approach yields a simple enhanced model capable of describing the influence of upslope bedrock outcrops on the pattern of downslope soil saturation the model is applied in both diagnostic and predictive modes to a small catchment in the eastern italian alps for which a detailed inventory of shallow landslides in areas dominated by rocky outcrops is available in the diagnostic mode the model is used with satisfactory results to reproduce the pattern of instability generated by an intense short duration storm occurred on 14 september 1994 which triggered a large percentage of the surveyed landslides in the predictive mode the model is used for hazard assessment and the return time of the critical rainfall needed to cause instability for each topographic element is determined modelling results obtained in the predictive mode are evaluated against all the surveyed landslides it is revealed that the generalised quasi dynamic model offers considerable improvement over the non generalised quasi dynamic model and the steady state model in predicting existing landslides as represented in the considered landslide inventory

characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data 1 range front alluvial fan deposition in arid environments is episodic and results in multiple fan surfaces and ages these distinct landforms are often defined by descriptions of their surface morphology desert varnish accumulation clast rubification desert pavement formation soil development and stratigraphy although quantifying surface roughness differences between alluvial fan units has proven to be difficult in the past high resolution airborne laser swath mapping alsm digital topographic data are now providing researchers with an opportunity to study topography in unprecedented detail here we use alsm data to calculate surface roughness on two alluvial fans in northern death valley california we define surface roughness as the standard deviation of slope in a 5 m by 5 m moving window comparison of surface roughness values between mapped fan surfaces shows that each unit is statistically unique at the 99 confidence level furthermore there is an obvious smoothing trend from the presently active channel to a deposit with cosmogenic 10be and 36cl surface exposure ages of 70 ka beyond 70 ka alluvial landforms become progressively rougher with age these data suggest that alluvial fans in arid regions smooth out with time until a threshold is crossed where roughness increases at greater wavelength with age as a result of surface runoff and headward tributary incision into the oldest surfaces

persistent homology on lidar data to detect landslides abstract landslides can result in loss of lives cause damage to property infrastructure utilities and residential structures and can block transportation routes landslide inventory maps can provide spatial temporal information about past and recent landslides and are used for analysis to create models that can characterize susceptibility as such these maps are considered an essential source for risk management tasks in this paper we propose a persistent homology method applied on lidar derived digital terrain model data to detect landslides for landslide inventory maps in testing the hypothesis that persistent homology a method for computing topological features of a space at different resolutions can be used to accurately detect landslides we applied the method on lidar derived digital terrain models to detect shapes and patterns that are indicative of landslide surface expressions we validated our test results by comparing them to currently available landslide inventory maps for selected locations in pennsylvania oregon colorado and washington the results show a different performance for each state the accuraces were 0 79 0 71 0 53 0 69 and 0 77 for five study areas variations in performance are linked to varying surface roughness between different types of landslides their size shape ages composition and a possible history of reactivations of landslides that would further pronounce surface expressions to overcome some of these challenges that may hinder performance of our method we recommend that other datasets containing landslides be considered as additional nth order dimensions beyond the spatial and elevation dimensions inherent in topographic datasets

airborne laser scanning of forested landslides characterization terrain model quality and visualization abstract mapping complex landslides under forested terrain requires an appropriate quality of digital terrain models dtms which preserve small diagnostic features for landslide classification such as primary and secondary scarps cracks and displacement structures flow type and rigid type optical satellite imagery aerial photographs and synthetic aperture radar images are less effective to create reliable dtms under tree coverage here we utilized a very high density airborne laser scanning als data with a point density of 140 points m 2 for generating a high quality dtm for mapping landslides in forested terrain in the barcelonnette region the southern french alps we quantitatively evaluated the preservation of morphological features and qualitatively assessed the visualization of als derived dtms we presented a filter parameterization method suitable for landslide mapping and compared it with two default filters from the hierarchical robust interpolation hri and one default filter from the progressive tin densification ptd method the results indicate that the vertical accuracy of the dtm derived from the landslide filter is about 0 04 m less accurate than that from the ptd filter however the landslide filter yields a better quality of the image for the recognition of small diagnostic features as depicted by expert image interpreters several dtm visualization techniques were compared for visual interpretation the openness map visualized in a stereoscopic model reveals more morphologically relevant features for landslide mapping than the other filter products we also analyzed the minimal point density in als data for landslide mapping and found that a point density of more than 6 points m 2 is considered suitable for a detailed analysis of morphological features this study illustrates the suitability of high density als data with an appropriate parameterization for the bare earth extraction used for landslide identification and characterization in forested terrain

geomorphometric feature analysis using morphometric parameterization and artificial neural networks this paper presents a semi automatic method using an unsupervised neural network to analyze geomorphometric features as landform elements the shuttle radar topography mission srtm provided detai

assessment of drainage network extractions in a low relief area of the cuvelai basin namibia from multiple sources lidar topographic maps and digital aerial orthophotographs abstract accurate delineation of drainage networks dns is crucial for hydrological or hydraulic modelling and the comprehension of fluvial processes this task presents challenging aspects in complex lowland terrains with subtle relief and particularly for data poor areas like the cuvelai river basin crb namibia where the present study takes place in the crb standard methods of drainage network extraction from low resolution gridded digital elevation models dems are unsuitable hence airborne light detection and ranging lidar solutions have been utilized however lidar also presents challenges to large areal applications especially with a surface roughness exceeding the capacity of numerous algorithms indeed lidar based dems 2 and 50 m resolutions need to be hydrologically corrected and smoothed to enable the extraction of scale relevant geomorphologic features such as dns in the present contribution channels from topographic maps blue lines were compared to those from hydrologically corrected and uncorrected lidar dems heads up digitized channels from high resolution digital aerial orthophotographs field mapped channels and auxiliary data the maximum gradient deterministic eight d8 gis algorithm was applied to the corrected and uncorrected lidar dems using two network extraction methods area threshold support and curvature drop analysis different progressive flow accumulation threshold values 12 were used to delineate channels with these methods validation was performed between the field mapped channels the modelled channels and those derived from multiple sources additionally spatial and quantitative analyses were performed on geomorphologic parameters and indices the results have shown that hydrologically corrected lidar dems offer useful details for identifying low order stream segments in headwaters while blue lines derived from the national hydrography datasets for watersheds located in elevated and low lying areas of the study area underestimated total stream lengths for field mapped channels by 15 3 and 88 5 respectively this study also confirmed that dns can be extracted from complex low terrain areas with standard gis algorithms and accurate field data the results will aid national mapping agencies in data poor regions to modernize their national hydrography datasets and to account for changing land surface conditions that can affect channel spatial arrangements over time

extraction of multithread channel networks with a reduced complexity flow model quantitative measures of channel network geometry inform diverse applications in hydrology sediment transport ecology hazard assessment and stratigraphic prediction these uses require a clear objectively defined channel network automated techniques for extracting channels from topography are well developed for convergent channel networks and identify flow paths based on land surface gradients these techniques even when they allow multiple flow paths do not consistently capture channel networks with frequent bifurcations e g in rivers deltas and alluvial fans this paper uses multithread rivers as a template to develop a new approach for channel extraction suitable for channel networks with divergences multithread channels are commonly mapped using observed inundation extent and i generalize this approach using a depth resolving reduced complexity flow model to map inundation patterns for fixed topography across an arbitrary range of discharge a case study for the platte river nebraska reveals that 1 the number of bars exposed above the water surface bar area and the number of wetted channel threads i e braiding index peak at intermediate discharge 2 the anisotropic scaling of bar dimensions occurs for a range of discharge 3 the maximum braiding index occurs at a corresponding reference discharge that provides an objective basis for comparing the planform geometry of multithread rivers mapping by flow depth overestimates braiding index by a factor of two the new approach extends channel network extraction from topography to the full spectrum of channel patterns with the potential for comparing diverse channel patterns at scales from laboratory experiments to natural landscapes

slope area relationships and sediment dynamics in two alpine streams the paper focuses on the channel network of alpine basins attempting to interpret channel reaches in terms of response to erosion and deposition processes two basins in the dolomites north eastern italy were considered the rio cordon 5 km2 and the upper boite river 163 km2 the channel network was extracted from raster type digital elevation models dem using a slope area threshold criterion a contribution area index cai which combines drainage area a and local slope s cai a0 5s was used to identify channel heads the channel network extracted from the dem was then analysed to recognize cells showing a value of cai lower than the threshold adopted for channel initiation contiguous cells with low values of cai define channel reaches with low transport efficiency field surveys carried out for some selected cases showed a good agreement between prevailing sediment deposition predicted by the analysis of the channel network and observed channel morphological features sediment sources mapped in two study basins were also analysed in relation to the location of channels with high potential for sediment deposition this made it possible to classify the potential role of different types of sediment sources with regard to basin sediment yield topographic characteristics of the channel network expressed by cai were compared with a classification of channel morphology in the rio cordon it was found that cells with low values of cai frequently occur in the riffle pool reaches whereas the percentage significantly decreases in step pool and bedrock channels copyright 2003 john wiley sons ltd

how to make robust splitting measurements for single station analysis and three dimensional imaging of seismic anisotropy summary we quantify errors on splitting intensity measurements produced by incoherent noise on horizontal components through a detailed analysis of synthetic seismograms and of sks and skks waves recorded by four permanent broad band stations we find that these errors are quite significant even on high quality records because the measurement procedure involves the comparison of radial and transverse components which are both contaminated by noise to decrease the level of noise in the data it is thus recommended to average splitting intensities from waves coming from the same backazimuth alternatively one can analyse stacked radial and transverse components after applying a wiener filter which standardizes the waveforms this is found to be equivalent because the measure of splitting intensity is a linear process the utilization of wiener filters reduces variations of apparent splitting resulting from differences in frequency content of the waveforms it is possible to determine splitting parameters splitting delays and fast directions from azimuthal variations of splitting intensity at a particular station tests on synthetic seismograms demonstrate that this approach gives unbiased and robust estimates of splitting parameters in contrast to the silver and chan method which only works on the rare records that have very large signals on their transverse components the wolfe and silver method does not suffer from this limitation and gives the same results as the multichannel splitting intensity method analysis of splitting intensities at stations bdfb bgca can and erm gives fast directions that are generally in excellent agreement with those determined with the wolfe and silver method however at some stations azimuthal variations of splitting intensities reveal features that are not well captured by the sinusoidal variation representing the average anisotropy beneath the station this suggests that smallscale lateral variations of anisotropy are present in the subcontinental mantle which remain to be imaged in detail

revisiting scaling laws in river basins new considerations across hillslope and fluvial regimes 1 increasing availability of high resolution 1 m topography data and enhanced computational processing power present new opportunities to study landscape organization at a detail not possible before here we propose the use of directed distance from the divide as the scale parameter instead of horton s stream order or upstream contributing area for performing detailed probabilistic analysis of landscapes over a broad range of scales this scale parameter offers several advantages for applications in hydrology geomorphology and ecology in that it can be directly related to length scale dependent processes it can be applied seamlessly across the hillslope and fluvial regimes and it is a continuous parameter allowing accurate statistical characterization higher order statistical moments across scales application of this scaling formalism to three basins in california demonstrates the emergence of three distinct geomorphic regimes of divergent highly convergent and moderately convergent fluvial pathways with notable differences in their scaling relationships and in the variability or spatial heterogeneity of topographic attributes in each regime we show that topographic attributes such as slopes and curvatures conditional on directed distance from the divide exhibit less variability than those same attributes conditional on upstream contributing area thus affording a sharper identification of regime transitions and increased accuracy in the scaling analysis

combining geomorphometry feature extraction techniques and earth surface processes research the way forward abstract in recent years the wealth of technological development revolutionised our ability to collect data in geosciences due to the unprecedented level of detail of these datasets geomorphologists are facing new challenges giving more in depth answers to a broad er range of fundamental questions across the full spectrum of the earth s and planetary processes this contribution builds on the existing literature of geomorphometry the science of quantitative land surface analysis and feature extraction translate land surface parameters into extents of geomorphological elements it provides evidence of critical themes as well as emerging fields of future research in the digital realm supporting the likely effectiveness of geomorphometry and feature extractions as they are advancing the theoretical empirical and applied dimension of geomorphology the review further discusses the role of geomorphometric legacies and scientific reproducibility and how they can be implemented in the hope that this will facilitate action towards improving the transparency and efficiency of scientific research and accelerate discoveries in geomorphology in the current landscape substantial changes in landforms ecosystems land use hydrological routing and direct anthropogenic modifications impact systems across the full spectrum of geomorphological processes although uncertainties in the precise nature and likelihood of changes exist geomorphometry and feature extraction can aid exploring process regimes and landscape responses taken together they can revolutionise geomorphology by opening the doors to improved investigations crossing space and time scales blurring the boundaries between traditional approaches and computer modelling and facilitating cross disciplinary research ultimately the exploitation of the available wealth of digital information can help to translate our understanding of geomorphic processes which is often based on observations of past or current conditions into the rapidly changing future

analysis of topographic and climatic control on rainfall triggered shallow landsliding using a quasi dynamic wetness index abstract a model for the prediction of both topographic and climatic control on shallow landslide initiation processes in hilly mountainous terrain is proposed the model develops upon a theory for coupled shallow subsurface flow and landsliding of the soil mantle previously proposed by montgomery and dietrich water resour res 30 1994 1153 the model uses a quasi dynamic wetness index to predict the spatial distribution of soil saturation in response to a rainfall of specified duration the rainfall predicted to cause instability in each topographic element is characterised by duration and frequency of occurrence the incorporation of a rainfall frequency duration relationship into assessment of landslide hazard provides a practical way to include climate information into estimation of the relative potential for shallow landsliding the model is applied to a mountain experimental basin where high resolution digital elevation data are available the cordon catchment 5 km2 in north eastern italy an inventory of landslide scars is used to document sites of instability and to provide a test of model performance by comparing observed landslide locations with model predictions the model reasonably reproduces the observed distribution of landslides although spatial variability of soil properties and hydrologic complexities not accounted for by the model complicate prediction of where landslides occur within areas of similar topographic climatic control model predictions from the quasi dynamic model are compared with those provided by the steady state model water resour res 30 1994 1153 these results suggest that the quasi dynamic model offers significant improvement over the steady state model in predicting existing landslides as represented in the considered landslide inventory

quantitative analysis of land surface topography land surface topography significantly affects the processes of runoff and erosion a system which determines slope aspect and curvature in both the down slope and across slope directions is developed for an altitude matrix also the upslope drainage area and maximum drainage distance are determined for every point within the altitude matrix a fortran 66 program performs the analysis

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

lidar derived slopes for headwater channel network analysis abstract slope is one of the most important distinguishing features for channel morphology variations in the computation of slope from a digital elevation model can affect a wide range of hydrogeomorphically derived applications we compare different methods for computing channel slope using lidar derived digital terrain models dtms with varying resolutions we chose a headwater basin of the eastern italian alps characterized by a dense ephemeral colluvial network and a main alluvial channel as our study area the identified alluvial morphologies are characteristic of steep mountain streams namely cascades and step pools field surveys were carried out along the main channel and in some small tributaries results indicate that a single method for slope calculation cannot estimate channel slope at the hydrographic network scale the differential geometry approach for slope calculation tends to overestimate field surveyed channel slope values for all the dtm resolutions 1 2 5 m when a trigonometric approach for slope calculation is applied 2 and 5 m dtm resolutions give more consistent results nevertheless a reliable channel slope can be derived from a dtm with an appropriate resolution by choosing a suitable method only after considering the channel width

geomorphological mapping of glacial landforms from remotely sensed data an evaluation of the principal data sources and an assessment of their quality abstract this paper presents the results of an experiment to compare glacial geomorphology mapped from remotely sensed imagery with 1 10 000 scale field mapping the field mapping was validated against high resolution lidar imagery of an area glacierized during the younger dryas and found to provide an essentially reliable if not complete representation of the glacial geomorphology the experiment consists of comparing the field mapping with digital elevation models shuttle radar topography mission c band landmap os panorama os profile nextmap and satellite imagery landsat thematic mapper of a 100 km2 region of central scotland north of glasgow that was last glaciated during the last glacial maximum and during the younger dryas respectively c 14 5 and 11 5 cal ka bp for the purposes of this exercise we concentrated on glacial lineaments flutes drumlins and crag and tail but attention was also given to moraine ridges and eskers qualitative and quantitative comparisons are performed and the results show that of the remotely sensed data sets only nextmap great britain provided results that showed any approximation to the field mapping os panorama and os profile provided very poor approximations and the other methods fail to provide any information of value attention is given to the issues of scale and the differences between a small scale detailed study such as this experiment in which a high resolution glacial geomorphological reconstruction is required and the small scale studies where the remote sensing techniques used here provide important evidence of regional significance when glaciers formed the largest elements of the landscape the paper concludes with a consideration of protocols for future geomorphological mapping exercises and outlines some of the requirements that must be adopted as these protocols are developed