topographical changes revealed by high resolution airborne lidar data the 1999 tsaoling landslide induced by the chi chi earthquake abstract the 1999 chi chi earthquake triggered the catastrophic tsaoling landslide in central taiwan we mapped the landslide area and estimated the landslide volume using a high resolution digital elevation model from airborne lidar light detection and ranging aerial photographs and topographic maps the comparison between scar and deposit volumes about 0 126 km3 and 0 150 km3 respectively suggests a coseismic volume increase of 19 due to decompaction during landsliding in july 2003 the scar and deposit volumes were about 0 125 km3 and 0 110 km3 respectively these estimates suggest that 4 years after the event the volume of landslide debris removed by river erosion was nearly 0 040 km3 these determinations are confirmed by direct comparison between the most accurate topographic models of the post landslide period indicating a very high erosion rate at the local scale 0 01 km3 year for the deposit area of the landslide such a large value highlights the importance of landslide processes for erosion and long term denudation in the taiwan mountain belt

the role of the sediment budget in understanding debris flow susceptibility this study proposes a sediment budget model to predict the temporal variation of debris volume stored in a debris flow prone watershed the sediment budget is dominated by shallow landslides and debris outflow the basin topography and the debris volume stored in the source area of the debris flow prone watershed help evaluating its debris flow susceptibility the susceptibility model is applied to the tungshih area of central western taiwan the importance of the debris volume in predicting debris flow susceptibility is reflected in the standardized coefficients of the proposed statistical discriminant model the high prediction rate 0 874 for the occurrence of debris flows justifies the capability of the proposed susceptibility models to predict the occurrence of debris flows this model is then used to evaluate the temporal evolution of the debris flow susceptibility index the analysis results show that the numbers of watershed which are classified as a debris flow group correspond well to storage of sediment at different time periods these numbers are 10 before the occurrence of chi chi earthquake 13 after the occurrence of chi chi earthquake 16 after the occurrence of landslides induced by typhoon mindulle typhoon m and 14 after the occurrence of debris flows induced by typhoon m it indicates that the occurrence of 7 6 chi chi earthquake had significant impact on the debris flow occurrence during subsequent typhoons copyright 2009 john wiley sons ltd

multi temporal analysis of the role of check dams in a debris flow channel linking structural and functional connectivity abstract check dams represent one of the most common hydraulic engineering solution to manage debris flow risk however the design of these structures only rarely considers their impact on sediment connectivity and sediment fluxes both at the channel reach and catchment scale in the last two decades high resolution topography hrt provided fundamental data to analyse the morphology evolution of landscapes through the realization of sequential dtms digital terrain models and dtms of difference dods in the context of mountain catchments hrt offers essential information on the evolution of erosion and deposition patterns and allows the application of multi temporal geomorphometric indexes that can enrich the dods analysis with important data as the assessment of sediment connectivity in this research multi temporal lidar derived dtms were used to derive dods and to perform a multi temporal analysis of an index of sediment connectivity ic in three reaches of a debris flow channel moscardo torrent eastern italian alps where several check dams have been built over time the research aims at outlining the effects of torrent control works on sediment dynamics in steep channels affected by frequent debris flows the integration of the difference of ic with dod maps allowed quantifying the impact of newly built check dams on changes in sediment pathways and related erosion processes highlighting a close relationship between structural and functional connectivity in areas where erosive processes prevailed there were increases in connectivity while deposition areas showed a decrease of ic the geomorphometric analyses show that the new check dams have affected the sediment transfer along the main channel but also the hillslope to channel connectivity by altering sediment pathways in the moscardo torrent however the strong impact of these structures on sediment transfer is not matched by long term effectiveness in debris flow control

estimating bedding orientation from high resolution digital elevation models a high resolution digital elevation model dem generated from airborne light detection and ranging lidar remote sensing data is used here to estimate the 3 d orientation of bedding planes methods for enhancement manual identification and extraction of lineaments and estimation of best fit planes representing bedding are presented and evaluated for a study area in folded metasedimentary rocks in northeast tasmania australia estimated bedding plane dip directions are shown to be accurate and reliable when compared with field based observations the same cannot be said for dip angle estimates it is likely that small errors in the location of a manually digitized lineament will affect dip estimation more than dip direction estimation particularly for steeply dipping structures fold axis orientations calculated from the stereographic analysis of estimated bedding closely correspond to orientations determined from field data the mean absolute differences pm standard error for 12 of the 14 regularly spaced domains located within the study area were 8 7 circ pm 1 2 circ for the fold plunge and 4 9 circ pm 0 9 circ for the fold trend the techniques described here for the extraction of bedding plane orientations from high resolution dems complement field based geological mapping and can assist structural interpretations

very high spatial resolution imagery for channel bathymetry and topography from an unmanned mapping controlled platform the increasing availability of aerial photography and satellite imagery offers new possibilities for characterizing river morphology the precision of new very high resolution vhr images allows smaller scale objects within river corridors to be studied high survey frequencies provide increased opportunities for the monitoring of river restoration following this evolution in platform technology a small radio controlled motorized vehicle flying at low altitude was used to study both channel water depth and gravel bar geometry the vhr imagery provided by this equipment allowed both channel bathymetry and a high accuracy photogrammetric digital elevation model dem to be realized using case studies from the ain and the drome rivers in france the accuracy of the results is presented and the various challenges associated with the new platform are discussed one significant issue is that due to the low elevation of the survey the coverage of a target area is usually based on several photographs which leads to variations in illumination conditions that stem from atmospheric changes the images were processed to minimize this source of error but a number of issues have yet to be resolved bathymetric models with r2 values between 0 59 and 0 90 were created in spite of the lack of channel bed homogeneity at the various sites the gravel bar was also effectively mapped and the photogrammetrically predicted dem provided a 5 10 cm pixel resolution with a vertical precision between 2 and 40 cm according to the position within the image this paper shows that despite unstable image acquisition unmanned radio controlled platforms provide significant advantages for the study of river processes offering a flexible very high resolution data source for both channel bathymetry and gravel bar topography copyright 2007 john wiley sons ltd

upper crustal folding of the 2013 lushan earthquake area in southern longmen shan china insights from late quaternary fluvial terraces abstract a thrust earthquake of mw6 6 occurred on april 20 2013 near lushan county in the southern longmen shan at the east margin of tibetan plateau this earthquake did not produce a surface rupture zone and the late quaternary activities of the outcropped faults in the earthquake area were not obvious which increased the difficulty of studying the seismogenic structure this article took as the research target the middle reach of the qingyijiang river which traverses the earthquake area by surveying correlating the fluvial terraces studied quantitatively the late quaternary tectonic deformation and further discussed the seismotectonics the longitudinal profile of river terraces along the middle reach of the qingyijiang river reveals that the principal deformation style in the late quaternary was anticline type folding the folding is a typical fault bend fold involving the basement which is controlled by the newest flat ramp flat structure possibly formed in the pliocene or the early pleistocene across the fold the average shortening rate in the late quaternary is 0 6 1 3 mm yr about one third of the crustal shortening rate by gps data across the longmen shan fold and thrust belt and its foreland the foreland thin skinned structure developed in the cretaceous to paleogene strata in the earthquake area was passively involved into the fault bend folding in the late quaternary which commend the thrust ramp developing in a piggyback style the newest ramp appears to have controlled the rupture and the surface deformation of the 2013 lushan earthquake in the process of thrust sheet sliding toward foreland along the flat ramp flat detachment the ramp acts as a locking structure where earthquake ruptures the coseismic surface deformation seems to be passive folding of the thrust sheet climbing the ramp

developing sub 5 m lidar dems for forested sections of the alpine and hope faults south island new zealand implications for structural interpretations abstract kilometre wide airborne light detection and ranging lidar surveys were collected along portions of the alpine and hope faults in new zealand to assess the potential for generating sub 5 m bare earth digital elevation models dems from ground return data in areas of dense rainforest bush cover as an aid to mapping these faults the 34 km long franz whataroa lidar survey was flown along the densely vegetated central most portion of the transpressive alpine fault six closely spaced flight lines 200 m apart yielded survey coverage with double overlap of swath collection which was considered necessary due to the low density of ground returns 0 16 m 2 or a point every 6 m2 under mature west coast podocarp broadleaf rainforest this average point spacing 2 5 m allowed for the generation of a robust high quality 3 m bare earth dem the dem confirmed the zigzagged form of the surface trace of the alpine fault in this area originally recognised by norris and cooper 1995 norris and cooper 1997 and highlights that the surface strike variations are more variant than previously mapped the 29 km long hurunui hope lidar survey was flown east of the main divide of the southern alps along the dextral slip hope fault where the terrain is characterised by lower rainfall and more open beech forest flight line spacings of 275 m were used to generate a dem from the ground return data the average ground return values under beech forest were 0 27 m 2 and yielded an estimated cell size suitable for a 2 m dem in both cases the lidar revealed unprecedented views of the surface geomorphology of these active faults lessons learned from our survey methodologies can be employed to plan cost effective high gain airborne surveys to yield bare earth dems underneath vegetated terrain and multi storeyed canopies from densely forested environments across new zealand and worldwide

effects of realistic surface topography on seismic ground motion in the yangminshan region of taiwan based upon the spectral element method and lidar dtm we combine light detection and ranging lidar digital terrain model dtm data and an improved mesh implementation to investigate the effects of high resolution surface topography on seismic ground motion based upon the spectral element method in general topography increases the amplitude of shaking at mountain tops and ridges whereas valleys usually have reduced ground motion as has been observed in both records from past earthquakes and numerical simulations however the effects of realistic topography on ground motion have not often been clearly characterized in numerical simulations especially the seismic response of the true ground surface here we use lidar dtm data which provide two meter reso lution at the free surface and a spectral element method to simulate three dimensional 3d seismic wave propagation in the yangminshan region in taiwan incorporating the effects of realistic topography a smoothed topographic map is employed beneath the model surface in order to decrease mesh distortions due to steep ground surfaces numerical simulations show that seismic shaking in mountainous areas is strongly affected by topography and source frequency content the amplification of ground motion mainly occurs at the tops of hills and ridges whilst the valleys and flat topped hills experience lower levels of ground shaking interaction between small scale to pographic features and high frequency surface waves can produce unusually strong shaking we demonstrate that topographic variations can change peak ground accel eration pga values by 50 in mountainous areas and the relative change in pga between a valley and a ridge can be as high as a factor of 2 compared to a flat surface response this suggests that high resolution realistic topographic features should be taken into account in seismic hazard analysis especially for densely populated moun tainous areas

photometrically corrected global infrared mosaics of enceladus new implications for its spectral diversity and geological activity between 2004 and 2017 spectral observations have been gathered by the visual and infrared mapping spectrometer vims on board cassini brown et al 2004 during 23 enceladus close encounters in addition to more distant surveys the objective of the present study is to produce a global hyperspectral mosaic of the complete vims data set of enceladus in order to highlight spectral variations among the different geological units this requires the selection of the best observations in terms of spatial resolution and illumination conditions we have carried out a detailed investigation of the photometric behavior at several key wavelengths 1 35 1 5 1 65 1 8 2 0 2 25 2 55 and 3 6 m characteristics of the infrared spectra of water ice we propose a new photometric function based on the model of shkuratov et al 2011 when combined corrected mosaics at different wavelengths reveal heterogeneous areas in particular in the terrains surrounding the tiger stripes on the south pole and in the northern hemisphere around 30 n 90 w those areas appear mainly correlated to tectonized units indicating an endogenous origin potentially driven by seafloor hotspots

slip distributions on active normal faults measured from lidar and field mapping of geomorphic offsets an example from l aquila italy and implications for modelling seismic moment release surface slip distributions for an active normal fault in central italy have been measured using terrestrial laser scanning tls in order to assess the impact of changes in fault orientation and kinematics when modelling subsurface slip distributions that control seismic moment release the southeastern segment of the surface trace of the campo felice active normal fault near the city of l aquila was mapped and surveyed using techniques from structural geology and using tls to define the vertical and horizontal offsets of geomorphic slopes since the last glacial maximum 15 3 ka the fault geometry and kinematics measured from 43 sites and throw heave measurements from geomorphic offsets seen on 250 scarp profiles were analysed using a modification of the kostrov equations to calculate the magnitudes and directions of horizontal principal strain rates the map trace of the studied fault is linear except where a prominent bend has formed to link across a former left stepping relay zone the dip of the fault and slip direction are constant across the bend throw rates since 15 3 ka decrease linearly from the fault centre to the tip except in the location of the prominent bend where higher throw rates are recorded vertical coseismic offsets for two palaeo earthquake ruptures seen as fresh strips of rock at the base of the bedrock scarp also increase within the prominent bend the principal strain rate calculated by combining strike dip slip direction and post 15 3 ka throw rate decreases linearly from the fault centre towards the tip the strain rate does not increase across the prominent fault bend the above shows that changes in fault strike whilst having no effect on the principal horizontal strain rate can produce local maxima in throw rates during single earthquakes that persist over the timescale of multiple earthquakes 15 3 ka detailed geomorphological and structural characterisation of active faults is therefore a critical requirement in order to properly define fault activity for the purpose of accurate seismic hazard assessment we discuss the implications of modelling subsurface slip distributions for earthquake ruptures through inversion of gps insar and strong motion data using planar fault approximations referring to recent examples on the nearby paganica fault that ruptured in the mw 6 3 2009 l aquila earthquake

stereophotogrammetry of archive data and topographic approaches to debris flow torrent measurements calculation of channel sediment states and a partial sediment budget for manival torrent isere france this paper focuses on a topographic methodology to characterize the amount of sediment stored in channels and the use of historical photographs for aerial survey by stereophotogrammetry as part of wider research on debris flow magnitude prediction the topographic methodology uses equidistant four point cross sections along the long profile of the channel each cross section is representative of a 50 m reach of the channel to calculate the volume of each reach the difference is calculated between a reference level and the topographic surface the reference level is the lowest level where the debris flow can erode and in the current method this level is estimated from fixed points along the long profile of the channel the accuracy of the method has been estimated by comparing results of a detailed topographic survey with a standard deviation corresponding to about 6 per cent of the total calculated sediment volume this topographic methodology has been used on aerial photographs by photogrammetry this tool was applied to photographs taken on 12 past dates the scales of the archive photographs used range from 1 3000 to 1 30 000 but results are consistent and permit us to calculate sediment states of the channel for different past dates with an uncertainty of about 6 per cent of the total volume the application of the technique to the manival debris flow torrent has permitted us to propose some partial sediment budgets and erosion rate estimates copyright 2006 john wiley sons ltd

characterizing the hsincheng active fault in northern taiwan using airborne lidar data detailed geomorphic features and their structural implications abstract we applied newly acquired high resolution airborne lidar data to study a segment of the hsincheng fault a well known active fault near a large industrial park in northern taiwan the hsincheng fault has received much attention and study in the past but high spatial resolution digital elevation models have not previously been applied to the study of the fault and its surrounding structures we processed the acquired lidar data and produced 1 m digital elevation models dems to investigate the active fault adjacent to the densely populated and important infrastructure in taiwan using the lidar dems aerial photographs and topographic maps we show highly detailed geomorphic characteristics around the study area of the hsincheng fault three major characteristics of the study area are defined that include three very well preserved river terraces at varying levels the fault fold scarp of the hsincheng fault and meandering river systems using the lidar dems we were able to detect with precision several fault fold scarps and very gentle ne trending folding of the river terraces in general the lidar dems have provided unprecedented clarity of landforms for one segment of the hsincheng fault which has helped the characterization of subtle but important geomorphic features

utilizing dems derived from lidar data to analyze morphologic change in the north carolina coastline by using digital elevation model dem data derived from light detection and ranging lidar data an approximately 70 km stretch of the southern north carolina coastline was studied the coastline consists of five barrier islands located between masonboro island at the southern extent and topsail island at the northern extent the high resolution dem data allowed for a comprehensive visual quantitative investigation into the spatial patterns of morphologic change that occurred to the barrier islands oceanfront beaches between 1997 and 2000 this study also demonstrated the usefulness of using laser altimetry to examine barrier islands response to level of tropical activity and showed that the coastal process of overwash was recognized as an integral component of barrier island landward migration means of net volumetric change per unit area m 3 m 2 for study areas of different beach management practices characterized as developed undeveloped and nourished beaches on a yearly basis for the period between 1997 and 2000 were derived t test of the means has been conducted and results showed that beaches differed statistically if different management practices were applied to them and the differences were minimized or disappeared if sequential hurricanes or storms affected the beaches d 2002 elsevier science inc all rights reserved

channel scour and fill by debris flows and bedload transport abstract in steep channels debris flows are known to dramatically increase in volume under the effect of channel erosion however the critical factors controlling channel erosion by debris flows are not well documented by field studies this is particularly true for the effect of slope on the depth at which erodible beds are scoured during debris flows and during bedload transport this topic has been addressed by intensive cross section resurveys 54 cross sections of debris flows n 5 and flow events n 9 that occurred in two torrents of the french prealps the manival and real torrents between 2009 and 2012 this study provided evidence that debris flow scouring increases with slope whereas this is not the case for bedload transport no slope effect detected during floods a functional relationship defined from a piecewise regression model is proposed as an empirical fit for the prediction of channel erosion by debris flows with a critical slope threshold at 0 19 95 confidence interval 0 17 0 21 this slope threshold is interpreted as the transition between the transport limited and supply limited regimes associated with the upstream decreasing erodible bed thickness the erodible bed was also characterized by quantifying erosion deposition and surface roughness with multidate terrestrial laser scans tlss in a short reach of high sensitivity of the manival torrent debris flow erosion occurred preferentially on smooth surfaces corresponding to the unconsolidated gravel deposits from bedload transport a 20 cm resolution roughness profile from an airborne laser scan als and a slope profile of the whole channel were used to detect the unconsolidated sediment deposits that can potentially feed future debris flows

debris flows some physical characteristics and behaviour field observations on 449 debris flows in the queen charlotte islands british columbia are summarized movement of debris is classified according to seven characteristic types designated for the purposes of the study data on the physical characteristics of the events are presented an analysis of the data is made with reference to event initiation yield and deposition using both mechanistic and morphological criteria for those events which initiate on an open slope the infinite slope model is used to establish a relationship between field drainage class and slope angle for assumed frictional and cohesive soil strength parameters the field drainage classes are directly related to the postulated location of the groundwater surface within the depth of the rupture plane deposition of channelized events is found to be influenced by the ratio of channel width to channel gradient with the onset of deposition expected when the ratio exceeds unity five classes of depositional area are proposed the mag

geomorphic effectiveness of check dams in a debris flow catchment using multi temporal topographic surveys abstract torrent control works such as grade control dams and sediment retention dams are structural measures for controlling debris flows and debris floods in spite of the widespread presence of such hydraulic structures in steep mountain streams worldwide there are still few studies monitoring the effects of check dams on sediment dynamics the use of repeated topographic surveys allows us to characterize debris flow activity at multiple temporal and spatial scales and its interaction with torrent control works structure from motion sfm technique paired with multi view stereo mvs algorithms represents a low cost opportunity to conduct such multi temporal surveys this enables us to better study the effects of individual debris flows track geomorphic changes and evaluate the effectiveness of torrent control works e g check dams the effect of check dams on sediment dynamics is investigated by means of multi temporal topographic surveys before and after debris flow events in the moscardo torrent eastern italian alps where two check dams have recently been built multi temporal sfm based on images taken from the ground in combination with imagery taken by an unmanned aerial vehicle uav is used to obtain dems and to study topographic changes through the comparison of repeat dems dem of difference i e dod the results show that the new check dams considerably modified sediment dynamics in the studied channel but their performance cannot be considered satisfactory the sediment flowed around the upstream check dam on the right wing while deep erosion observed downstream of the check dam threatened to undermine the foundation s stability moreover debris flow lobes deposited upstream of the check dams could act as sources of sediment further increasing downstream debris flow volume the analysis proposed in this work could help improve design strategies and permitting the identification of a proper site for check dam building

on the pullout resistance of geosynthetics pullout tests are reported on geosynthetic test specimens embedded in a relatively dense coarse sand sample the tests are displacement controlled and are performed at different vertical effective

the contribution of geomorphological mapping to sediment transfer evaluation in small alpine catchments the assessment of sediment transfer processes is necessary to understand the hydro geomorphological functioning of small alpine watersheds prone to channelised debris flows because their occurrence often depends on the amount of debris available in the gully systems therefore sediment budgets should be studied through the identification of erosion transport and deposition processes sediment transfer processes were investigated in a small catchment by field measurements and more specifically through the application of a process based geomorphological mapping method the proposed methodology is based on data directly derived from gis analysis using high resolution dem field measurements and aerial photograph interpretations it has been conceived to estimate sediment transfer dynamics taking into account the role of different sediment stores in the torrential system the proposed geomorphological mapping methodology is quite innovative in comparison with most legend systems that are not adequate for mapping comprehensively active and complex geomorphological systems such as debris flow catchments maps representing the various sediment storages and their relationships can be used for hydro geomorphological hazard mitigation

rates of surface processes on slopes slope retreat and denudation results taken from 270 publications on rates are summarized and collated with those from 149 publications reviewed previously young 1969 1974 the data are classified by major climatic zone normal or steep relief and consolidated or unconsolidated rocks representative rates and their ranges are given for soil creep solifluction surface wash solution chemical denudation rock weathering slope retreat cliff free face retreat marine cliff retreat and denudation the last being compared with representative rates of uplift solifluction is of the order of 10 times faster than soil creep but both cause only very slow ground loss solution is an important cause of ground loss for siliceous rocks on which it may be half as rapid as on limestones total denudation brought about mainly by surface wash reaches a maximum in the semi arid and probably also the tropical savanna zones acceleration of natural erosion rates by human activities ranges from 2 3 times with moderately intense land use to about 10 times with intensive land use and considerably higher still where there is recognized accelerated soil erosion where there is active uplift typical rates are of the order of 10 times faster than denudation although in some high steep mountain ranges these may approach equality

occultation observations of saturn s rings with cassini vims abstract we describe the prediction design execution and calibration of stellar and solar occultation observations of saturn s rings by the visual and infrared mapping spectrometer vims instrument on the cassini spacecraft particular attention is paid to the technique developed for onboard acquisition of the stellar target and to the geometric and photometric calibration of the data examples of both stellar and solar occultation data are presented highlighting several aspects of the data as well as the different occultation geometries encountered during cassini s 13 year orbital tour complete catalogs of ring stellar and solar occultations observed by cassini vims are presented as a guide to the standard data sets which have been delivered to the planetary data system s ring moon systems node hedman and nicholson 2019b

cassini vims observations of the galilean satellites including the vims calibration procedure the visual and infrared mapping spectrometer vims observed the galilean satellites during the cassini spacecraft s 2000 2001 flyby of jupiter providing compositional and thermal information about their surfaces the cassini spacecraft approached the jovian system no closer than about 126 jupiter radii about 9 million kilometers at a phase angle of 90 resulting in only sub pixel observations by vims of the galilean satellites nevertheless most of the spectral features discovered by the near infrared mapping spectrometer nims aboard the galileo spacecraft during more than four years of observations have been identified in the vims data analyzed so far including a possible 13c absorption in addition vims made observations in the visible part of the spectrum and at several new phase angles for all the galilean satellites and the calculated phase functions are presented in the process of analyzing these data the vims radiometric and spectral calibrations were better determined in preparation for entry into the saturn system treatment of these data is presented as an example of the vims data reduction calibration and analysis process and a detailed explanation is given of the calibration process applied to the jupiter data

geomorphic evidence for prior earthquakes lessons from the 1999 chichi earthquake in central taiwan the september 21 1999 mw 7 6 chichi earthquake destroyed several thousand buildings and caused more than 2000 fatalities in central taiwan the earthquake occurred along the chelungpu fault a thrust fault on the western flank of the taiwan fold and thrust belt the surface rupture was more than 90 km long and vertical displacements ranged from 3 to 8 m although pre existing scarps were identified along the chelungpu fault the fault had previously been categorized as a less important active fault owing to the lack of geochronologic evidence and the failure to recognize fault related geomorphic features identifying geomorphic features at active faults in taiwan will permit the delineation of future sur face ruptures and the determination of past magnitudes of past earthquakes thus contributing to hazard assessment