ultra fine grain landscape scale quantification of dryland vegetation structure with drone acquired structure from motion photogrammetry abstract covering 40 of the terrestrial surface dryland ecosystems characteristically have distinct vegetation structures that are strongly linked to their function existing survey approaches cannot provide sufficiently fine resolution data at landscape level extents to quantify this structure appropriately using a small unpiloted aerial system uas to acquire aerial photographs and processing theses using structure from motion sfm photogrammetry three dimensional models were produced describing the vegetation structure of semi arid ecosystems at seven sites across a grass to shrub transition zone this approach yielded ultra fine

evaluation of various satellite sensors for waterline extraction in a coral reef environment majuro atoll marshall islands abstract the ability of five satellite sensor bands ikonos band 4 terra aster bands 3 and 4 and landsat etm bands 4 and 5 was examined to extract the waterline at coral reef coasts majuro atoll marshall islands using different wavelength regions near infrared nir and shortwave infrared swir and different spatial resolutions 4 15 and 30 m after performing georeferencing and normalization of the images density slicing was used to extract the waterline comparisons of extracted waterline positions with ground level data for eight transects and global positioning system gps tracks of the island shorelines showed that nir bands were superior to swir bands because of the characteristics of the coral reef coasts including a lack of foam and suspended sediments which can affect the nir wavelength region if present and the presence of remnant water on reef flats during low tide which can affect the swir wavelength region a linear relationship was found between the estimation errors of waterline positions and the spatial resolutions of the nir sensors analysis on estimation errors and image costs showed that terra aster band 3 was the most cost effective sensor for extracting waterlines with reasonable accuracy the results serve as general guidelines for using satellite derived data to estimate intertidal topography and detect and monitor shorelines in coral reef environments

quantitative analysis of temporal variations on shoreline change pattern along ganjam district odisha east coast of india this research work describes the shoreline change rate variations of ganjam district of odisha east coast of india for the past 24 years seven shorelines were extracted from multidated satellite images and shoreline change rate has been calculated by using digital shoreline analysis system long term shoreline change rate 1990 2014 of the study area has been calculated using weighted linier regression method short term changes have been computed for different time scales i e 1990 1999 1999 2006 2006 2008 2008 2013 and 2013 2014 using end point rate method the results obtained from the study show that 71 65 of ganjam coast shows accretion pattern and 28 35 of coast falls under erosion category high erosion is mainly noticed in northern side of gopalpur port which is mainly due to recent construction activities short term results reveals that 2006 2008 period shows maximum erosion and 1999 2006 period exhibit maximum accretion in ganjam coast from short term analysis it is observed that shoreline in the study area shows cyclic nature of erosion and accretion pattern the study reveals that tropical cyclones and human activities such as port development construction of breakwaters and groins are the major factors responsible for shoreline erosion in the study area

natural hazards of shoreline bluff erosion a case study of horizon view lake huron abstract assessment of hazard of erosion of shoreline bluffs requires an understanding of the natural processes and human use in these high risk areas as an important component associated with erosion and natural evolution bluff shorelines alongshore sediment transport is an essential process in defining the hazard associated with bluff erosion the objective of this study is the integration of an understanding of alongshore sediment transport into a proposed management framework for cohesive bluff shorelines a study of a ten kilometre area along the southeastern lake huron shoreline at the cottage community of horizon view north of goderich ontario examines the natural and human components which have led to the development of bluff erosion hazards although dominant sediment transport is north to south alongshore the pattern of wave refraction during south and southwest waves suggests frequent northward transport of material from the 30 meter high bluffs at the site examination of beach sediments and bluff conditions support this finding and indicate long term sediment supply and bluff instability planning of future development at this location must appreciate the potential for continued bluff erosion and the study results suggest that when combined with other factors such as wave energy bluff morphology groundwater conditions vegetation cover land uses and impacts of fluctuating lake levels studies of alongshore sediment transport can be a useful tool to assist in management of cohesive coastlines and understanding the natural hazard of bluff erosion in developed coastal areas a management framework for cohesive bluffs attempts to integrate an understanding of natural processes with human uses and land use policies in order to identify assess and select a preferred management option reflecting this understanding

threshold of motion of coarse grained sediment under waves in shallow water this paper considers the threshold of motion of sediment in shallow coastal waters under breaking and non breaking waves a simple model representing conditions at the fluid sediment interface is developed the representation of a breaking wave is based on bore theory and the shear stress at the bed is based on the friction formula of o connor and yoo a threshold formula is presented based on the use of energy dissipation the threshold data is also related to the shields threshold criterion

ultra rapid topographic surveying for complex environments the hand held mobile laser scanner hmls terrestrial laser scanning is the current technique of choice for acquiring high resolution topographic data at the site scale i e over tens to hundreds of metres for accurate volume measurements or process modelling however in regions of complex topography with multiple local horizons restricted lines of sight significantly hinder use of such tripod based instruments by requiring multiple setups to achieve full coverage of the area we demonstrate a novel hand held mobile laser scanning technique that offers particular promise for site scale topographic surveys of complex environments to carry out a survey the hand held mobile laser scanner hmls is walked across a site mapping around the surveyor continuously en route we assess the accuracy of hmls data by comparing survey results from an eroding coastal cliff site with those acquired by a state of the art terrestrial laser scanner tls and also with the results of a photo survey processed by structure from motion and multi view stereo sfm mvs algorithms hmls data are shown to have a root mean square rms difference to the benchmark tls data of 20 mm not dissimilar to that of the sfm mvs survey 18 mm the efficiency of the hmls system in complex terrain is demonstrated by acquiring topographic data covering 780 m2 of salt marsh gullies with a mean point spacing of 4 4 cm in approximately six minutes we estimate that hmls surveying of gullies is approximately 40 times faster than using a tls and six times faster than using sfm mvs 2013 the authors earth surface processes and landforms published by john wiley sons ltd

quantifying the effectiveness of mountain terraces on soil erosion protection with sediment traps and dry stone wall laser scans abstract mountain depopulation in the mediterranean region over the past decades has led to a decline in the use and maintenance of agricultural terraces and consequently the collapsing of dry stone walls which can increase soil erosion rates and downstream sedimentation a field experiment has been set up on a degrading terraced hillslope in the troodos mountains of cyprus to quantify the effectiveness of terrace maintenance on protecting cultivated land against soil erosion the monitored site is cultivated with grapes the terrace riser 22 m long that forms the linear outlet of the hillslope has 11 4 m of standing dry stone wall and 10 6 m of collapsed wall it has been instrumented with seven 1 m wide sediment traps three on standing sections of the wall and four on collapsed sections when dry sediment was collected from the traps after rainfall events from december 2015 to november 2017 uncertainties in the drainage areas of the 31 5 m long slope were quantified both for the terrace wall and for the individual traps through hydrologic delineations based on a detailed topographic survey the sediment data were complemented by laser scanner surveys that were conducted in november 2015 may 2016 and april 2017 on a dry stone terrace wall upslope from the outlet section wall degradation was assessed from the consecutive 3d model reconstructions rainfall was 469 mm in the first year and 515 mm in the second year and the average erosivity was 1148 mj mm ha 1 h 1 y 1 the average soil erosion rate was 2 4 mg ha 1 y 1 when linear drainage areas are considered 693 m2 3 2 mg ha 1 y 1 when the borders are delineated with the topographic data 520 m2 nearly half of the soil erosion 43 occurred during two very intense rainfall events maximum 30 min intensity exceeding 35 mm h 1 out of the 34 monitored events erosion from standing terrace sections was 3 8 less than the erosion from the collapsed sections for the scanned terrace wall soil erosion from the standing sections was 2 2 lower than from the degraded sections the laser scanner surveys identified some preferential erosion paths but failed to recognize single stone collapses whereas possible wall displacement was masked by scanning artifacts the sediment traps were found to be an effective method for understanding and quantifying soil erosion in terraced mountain environments while further research is needed to develop a more rigorous acquisition procedure for laser scanner surveys to derive useful information on wall degradation

propagating bottom pressure signals around antarctica at 1 2 day periods and implications for ocean modes abstract previous studies of barotropic ocean dynamics have shown that several global normal modes are possible at periods between 1 and 2 days the role of these modes in diurnal tidal dynamics is well documented but finding evidence for their direct excitation by atmospheric forcing has remained elusive analyses of a barotropic ocean model and a limited number of bottom pressure records in the southern ocean described here provide evidence for large scale coherent signals propagating westward around antarctica at 1 2 day periods phases are roughly consistent with the fundamental kelvin wave structure underlying a number of normal modes with significant expressions in the southern ocean model and data results suggest the weak excitation of several of these normal modes by atmospheric pressure fluctuations strong dissipation also contributes to their weak amplitudes and makes it difficult to detect a truly global signal in the data

semi empirical treatment of wave transformation outside and inside the breaker line a semi empirical method is developed which predicts the wave height shoaling up to the break point on laboratory and natural beaches linear shoaling is enhanced with empirical curves for the wave shape obtained from field measurements of wave height through the break point and the surf zone made on an ocean beach in southern australia from 1987 to 1989 wave height shoaling breaking and attenuation are unified in a mixed lagrangian eulerian numerical model of random wave height transformation which with the semi analytical enhancements provides improved predictions of the height transformation of individual waves through the surf zone this is demonstrated for a wide variety of cases from the field and laboratory

automatic extraction of shorelines from landsat tm and etm multi temporal images with subpixel precision abstract a high precision geometric method for automated shoreline detection from landsat tm and etm imagery is presented the methodology is based on the application of an algorithm that ensures accurate image geometric registration and the use of a new algorithm for sub pixel shoreline extraction both at the sub pixel level the analysis of the initial errors shows the influence that differences in reflectance of land cover types have over shoreline detection allowing us to create a model to substantially reduce these errors three correction models were defined according to the type of gain used in the acquisition of the original landsat images error assessment tests were applied on three artificially stabilised coastal segments that have a constant and well defined land water boundary a testing set of 45 images 28 tm 10 etm high gain and 7 etm low gain was used the mean error obtained in shoreline location ranges from 1 22 to 1 63 m and the rmse from 4 69 to 5 47 m since the errors follow a normal distribution then the maximum error at a given probability can be estimated the results confirm that the use of landsat imagery for detection of instantaneous coastlines yields accuracy comparable to high resolution techniques showing the potential of landsat tm and etm images in those applications where the instantaneous lines are a good geomorphological descriptor

using dinsar airborne lidar and archival air photos to quantify landsliding and sediment transport 1 we demonstrate the ability of coupled remote sensing tools to characterize large slow moving landslides in the eel river catchment northern california from a stack of alos interferograms we identified 5 large 1 km long landslides that exhibited significant activity from february 2007 to february 2008 for the boulder creek earthflow we used orthorectified air photos taken in 1964 and unfiltered airborne lidar flown in 2006 to map the displacement of trees growing on the landslide surface combining those displacement orientations with stacked dinsar data we observed average downslope velocities of 0 65 m yr 1 through the central transport zone of the landslide given landslide depth estimates minimum sediment transport and denudation rates are estimated to be 4100 m3 yr 1 and 1 6 mm yr 1 respectively our results demonstrate the highly erosive role of large slow moving landslides in landscape evolution and suggest that the superposition of dense ephemeral gully networks and rapidly moving zones within the landslide may facilitate delivery of slide mobilized sediment into adjacent fluvial channels

dynamics of the wind driven sea level variation around antarctica coastal sea level variation around antarctica is characterized by a coherent circumpolarly in phase fluctuation correlated with the antarctic oscillation aao this study addresses the dynamics of the winddriven sea level variation around antarctica a realistic barotropic numerical model reproduced well the observed sea level around antarctica from numerical model experiments the authors demonstrate that the forcing responsible for the coastal sea level is the wind stress at the coastal boundary both the dominant coherent signal and westward propagating signals are identified in the model and these signals are trapped over the shelf and slope around antarctica as a mechanism of these trapped signals the authors consider analytical solutions of the oceanic response to alongshore wind stress over the shelf and slope in the circumpolar domain in these solutions besides the shelf wave mode a wavenumber zero mode appears and characterizes the coastal dynamics around antarctica at periods from 10 to 200 days the coherent sea level can be explained quantitatively by the solution of this wavenumber zero mode with a 5 10 day damping time scale the spectral peaks of the westward propagating signals can be explained by the resonance of the shelf wave mode the wavenumber zero mode can respond to the wavenumber zero forcing at any frequency and the degree of response increases with decreasing frequency in addition the wavenumber zero component of wind stress corresponding to the aao variation is a dominant forcing therefore the coherent sea level variation around antarctica is preferably generated and becomes a dominant feature in the circumpolar domain particularly at lower frequencies

coastal geomorphology through the looking glass abstract coastal geomorphology will gain future prominence as environmentally sound coastal zone management strategies requiring scientific information begin to supplant engineered shoreline stabilization schemes for amelioration of coastal hazards we anticipate substantial change and progress over the next two decades but we do not predict revolutionary advances in theoretical understanding of coastal geomorphic systems paradigm shifts will not occur knowledge will advance incrementally we offer predictions for specific coastal systems delineated according to scale for the surf zone we predict advances in wave shoaling theory but not for wave breaking we also predict greater understanding of turbulent processes and substantive improvements in surf zone circulation and radiation stress models very few of these improvements are expected to be incorporated in geomorphic models of coastal processes we do not envision improvements in the theory of sediment transport although some new and exciting empirical observations are probable at the beach and nearshore scale we predict the development of theoretically based two and three dimensional morphodynamical models that account for non linear time dependent feedback processes using empirically calibrated modules most of the geomorphic research effort however will be concentrated at the scale of littoral cells this scale is appropriate for coastal zone management because processes at this scale are manageable using traditional geomorphic techniques at the largest scale little advance will occur in our understanding of how coastlines evolve any empirical knowledge that is gained will accrue indirectly finally we contend that anthropogenic influences directly and indirectly will be powerful forces in steering the future of coastal geomorphology if you should suddenly feel the need for a lesson in humility try forecasting the future kleppner 1991 p 10

detecting surface changes from an underground explosion in granite using unmanned aerial system photogrammetry efficient detection and high fidelity quantification of surface changes resulting from underground activities are important national and global security efforts in this investigation a team performed field based topographic characterization by gathering high quality photographs at very low altitudes from an unmanned aerial system uas borne camera platform the data collection occurred shortly before and after a controlled underground chemical explosion as part of the united states department of energy s source physics experiments spe 5 series the high resolution overlapping photographs were used to create 3d photogrammetric models of the site which then served to map changes in the landscape down to 1 cm scale separate models were created for two areas herein referred to as the test table grid region and the nearfield grid region the test table grid includes the region within 40 m from surface ground zero with photographs collected at a flight altitude of 8 5 m above ground level agl the near field grid area covered a broader area 90 130 m from surface ground zero and collected at a flight altitude of 22 m agl the photographs processed using agisoft photoscan in conjunction with 125 surveyed ground control point targets yielded a 6 mm pixel size digital elevation model dem for the test table grid region this provided the 3 cm resolution in the topographic data to map in fine detail a suite of features related to the underground explosion uplift subsidence surface fractures and morphological change detection the near field grid region data collection resulted in a 2 cm pixel size dem enabling mapping of a broader range of features related to the explosion including uplift and subsidence rock fall and slope sloughing this study represents one of the first works to constrain both temporally and spatially explosion related surface damage using a uas photogrammetric platform these data will help to advance the science of underground explosion detection

modeling the high frequency barotropic response of the ocean to atmospheric disturbances sensitivity to forcing topography and friction this study examines high frequency sea level variations forced by changes in surface atmospheric pressure and wind and their sensitivity to different forcing mechanisms bottom topography resolution and amount of friction in a barotropic ocean model optimal model performance defined in terms of the explained variance in satellite altimeter and bottom pressure data is found when using relatively strong friction equivalent to a damping timescale of only a few days over the deep ocean and topography with minimal smoothing spatial variations of the optimal friction parameter seem to reflect the roughness of bottom topography the model demonstrates skill in simulating the wind driven response as well as the nonequilibrium response to atmospheric pressure variations

uav based surveying in volcano tectonics an example from the iceland rift abstract in the present work we applied the use of an unmanned aerial vehicle uav a quadcopter and the aerial structure from motion digital photogrammetry image processing technique asfm to study volcano tectonics and tectonic features in an active icelandic rift data have been collected in order to evaluate the holocene deformation in the northern volcanic zone of iceland we mapped 397 structures mainly related to extension fractures and subordinately normal faults in the theistareykir fissure swarm obtaining 1098 and 21 structural data respectively this allowed to reconstruct an overall spreading direction of n108 during holocene times and to calculate a stretch of 1 013 regarding 8 10 ka old lava units deformation in the area is related to both dyke intrusions and extensional tectonics furthermore detailed geological structural field and uav surveys were also performed in two test areas in order to determine data accuracy and the associated reliability of this approach in addition to the above different flight heights were tested suggesting that photo collection with a 12 4 mpx camera at 100 m is efficient to study fracture dilation and kinematics

shoreline changes and morphology of spits along southern karnataka west coast of india a remote sensing and statistics based approach abstract the changes in shoreline positions and morphology of spits along the karnataka coast western india are investigated for the period from 1910 to 2005 using multi dated satellite images and topomaps the study area has been divided into four littoral cells and each cell into a number of transects at uniform intervals the rate of change in shoreline position has been estimated using the statistical linear regression method and cross validated with regression coefficient r 2 and root mean square error rmse methods past and future shoreline positions have been demarcated and future positions of shoreline are estimated for time periods of 10 and 24 years the study reveals that i about 57 of transects exhibit 10 m rmse values indicating better agreement between the estimated and satellite based shoreline positions and ii transects closer to the cell boundaries exhibit about 50 uncertainties in shoreline change rate estimations based on rmse values the influence of natural processes and anthropogenic factors on shoreline changes has been evaluated the cells transects dominated by natural processes reveal low rmse values whereas the cells transects influenced by anthropogenic activities such as sand mining construction of coastal structures exhibit higher rmse values however the variation in rmse values is not significant if the total number of transects is considered significant changes in morphology of spits have been recorded spits demonstrate variations in areal extent i e length and area if 1910 and 1967 are considered separately as base years the present study demonstrates that combined use of satellite imagery and statistical techniques such as linear regression and rmses can be very useful in quantifying shoreline changes and spit morphology

coastal morphodynamics and chenier plain evolution in southwestern louisiana usa a geomorphic model abstract using 28 topographic profiles air photo interpretation and historical shoreline change data coastal processes were evaluated along the chenier plain to explain the occurrence distribution and geomorphic hierarchy of primary landforms and existing hypotheses regarding chenier plain evolution were reconsidered the chenier plain of sw louisiana classified as a low profile microtidal storm dominated coast is located west and downdrift of the mississippi river deltaic plain this late holocene marginal deltaic environment is 200 km long and up to 30 km wide and is composed primarily of mud deposits capped by marsh interspersed with thin sand and shell rich ridges cheniers that have elevations of up to 4 m in this study the term ridge is used as a morphologic term for a narrow linear or curvilinear topographic high that consists of sand and shelly material accumulated by waves and other physical coastal processes thus most ridges in the chenier plain represent relict open gulf shorelines on the basis of past movement trends of individual shorelines ridges may be further classified as transgressive regressive or laterally accreted geomorphic zones that contain two or more regressive transgressive or laterally accreted ridges are termed complexes consequently we further refine the chenier plain definition by otvos and price otvos e g and price w a 1979 problems of chenier genesis and terminology an overview marine geology 31 251 263 and define chenier plain as containing at least two or more chenier complexes based on these definitions a geomorphic hierarchy of landforms was refined relative to dominant process for the louisiana chenier plain the chenier plain is defined as a first order feature 5000 km2 composed of three second order features 30 to 300 km2 chenier complex beach ridge complex and spit complex individual ridges of each complex type were further separated into third order features chenier beach ridge and spit to understand the long term evolution of a coastal depositional system primary process response mechanisms and patterns found along the modern chenier plain coast were first identified especially tidal inlet processes associated with the sabine calcasieu and mermentau rivers tidal prism and quantity of littoral transport mtotal are the most important factors controlling inlet stability greater discharge and or tidal prism increase the ability of river and estuarine systems to interrupt longshore sediment transport maintain and naturally stabilize tidal entrances and promote updrift deposition thus prior to human modification and stabilization efforts the mermentau river entrance would be classified as wave dominated sabine pass as tide dominated and calcasieu pass as tide dominated to occasionally mixed hoyt hoyt j h 1969 chenier versus barrier genetic and stratigraphic distinction am assoc petrol geol bull 53 299 306 presented the first detailed depositional model for chenier genesis and mudflat progradation which he attributed to changes in mississippi river flow direction i e delta switching caused by upstream channel avulsion however hoyt s model oversimplifies chenier plain evolution because it omits ridges created by other means thus the geologic evolution of the chenier plain is more complicated than channel avulsions of the mississippi river and it involved not only chenier ridges i e transgressive but also ridges that are genetically tied to regression beach ridges and lateral accretion recurved spits a six stage geomorphic process response model was developed to describe chenier plain evolution primarily as a function of i the balance between sediment supply and energy dissipation associated with mississippi river channel avulsions ii local sediment reworking and lateral transport iii tidal entrance dynamics and iv possibly higher than present stands of holocene sea level consequently the geneses of three different ridge types transgressive regressive and laterally accreted typically occur contemporaneously along the same shoreline at different locations

monitoring of gully erosion in the central ebro basin by large scale aerial photography taken from a remotely controlled blimp large deep gullies span barrancos are some of the most important sediment sources in the semi arid environment of the central ebro basin they are incised into the quaternary valley bottoms span vales which are characteristic landforms in this area in the research project eprodesert evaluation of processes leading to land degradation and desertification under extensified farming systems the development of a large barranco system is being investigated by different methods including documentation and monitoring by aerial photography geomorphological forms and processes such as sheet wash rill and gully erosion cannot be documented sufficiently by conventional remote sensing methods spatial and temporal resolution of satellite sensors as well as of conventional aerial photography do not correspond to the scale and dynamics of geomorphological processes with a specially designed hot air blimp as a sensor platform large scale aerial photographs were obtained from the barranco de las lenas specifically aimed at the scientific demands very high spatial and temporal resolution the development of the gully is documented and its dynamics are evaluated by a sequence of six aerial photographs taken between 1995 and 1998 d 2003 elsevier science b v all rights reserved

close range digital photogrammetric analysis of experimental drainage basin evolution brasington james smart r m a 2003 close range digital photogrammetric analysis of experimental drainage basin evolution earth surface processes and landforms 28 3 pp 231 247 rae2008 special issue the generation of high quality topographic data for hydrology and geomorphology

testing the utility of structure from motion photogrammetry reconstructions using small unmanned aerial vehicles and ground photography to estimate the extent of upland soil erosion quantifying the extent of soil erosion at a fine spatial resolution can be time consuming and costly however proximal remote sensing approaches to collect topographic data present an emerging alternative for quantifying soil volumes lost via erosion herein we compare terrestrial laser scanning tls and both unmanned aerial vehicle uav and ground photography gp structure from motion sfm derived topography we compare the cost effectiveness and accuracy of both sfm techniques to tls for erosion gully surveying in upland landscapes treating tls as a benchmark further we quantify volumetric soil loss estimates from upland gullies using digital surface models derived by each technique and subtracted from an interpolated pre erosion surface soil loss estimates from uav and gp sfm reconstructions were comparable to those from tls whereby the slopes of the relationship between all three techniques were not significantly different from 1 1 line only for the tls to gp comparison was the intercept significantly different from zero showing that gp is more capable of measuring the volumes of very small erosion features in terms of cost effectiveness in data collection and processing time both uav and gp were comparable with the tls on a per site basis 13 4 and 8 2 person hours versus 13 4 for tls however gp was less suitable for surveying larger areas 127 person hours per ha 1 versus 4 5 for uav and 3 9 for tls annual repeat surveys using gp were capable of detecting mean vertical erosion change on peaty soils these first published estimates of whole gully erosion rates 0 077 m a 1 suggest that combined erosion rates on gully floors and walls are around three times the value of previous estimates which largely characterize wind and rainsplash erosion of gully walls copyright c 2017 john wiley sons ltd

coastal cliff ground motions and response to extreme storm waves coastal cliff erosion from storm waves is observed worldwide but the processes are notoriously difficult to measure during extreme storm wave conditions when most erosion normally occurs limiting our understanding of cliff processes over january february 2014 during the largest atlantic storms in at least 60 years with deepwater significant wave heights of 6 8 m cliff top ground motions showed vertical ground displacements in excess of 50 100 m an order of magnitude larger than observations made previously repeat terrestrial laser scanner surveys over a 2 week period encompassing the extreme storms gave a cliff face volume loss of 2 orders of magnitude larger than the long term erosion rate the results imply that erosion of coastal cliffs exposed to extreme storm waves is highly episodic and that long term rates of cliff erosion will depend on the frequency and severity of extreme storm wave impacts

cost effective erosion monitoring of coastal cliffs abstract structure from motion with multi view stereo sfm mvs methods hold the potential for monitoring and quantifying cliff erosion to levels of accuracy and precision which rival terrestrial laser scanning tls and at a fraction of the cost we benchmark repeat sfm mvs against tls for quantifying rock fall frequency volume and cliff face erosion rates for a 1 km section of coastal cliffs where cliff top infrastructure is threatened by erosion first we address a major unknown in these techniques the number and configuration of control points surveys demonstrate that a sparse configuration along the cliff base and top at spacing equivalent to the cliff height provides suitable accuracy at acceptable logistic time and expense second we show that sfm mvs models match equivalent tls data to within 0 04 m and that the correlation between intersecting tls and sfm derived rock fall volumes improves markedly above a detection threshold of 0 07 m3 rock falls below this size threshold account for 77 7 of detected rock falls but only 1 9 of the calculated annual eroded volume annual erosion rates for the 1 km cliff face as calculated by repeat tls and sfm differencing are 0 6 10 2 m a 1 and 0 7 10 2 m a 1 respectively kilometre scale patterns of cliff erosion are dominated by localised zones of high magnitude episodic failure that are over an order of magnitude greater than background rates the ability of non specialist engineers geologists geomorphologists and managers to rapidly capture high quality accurate erosion data in a cost effective manner through repeat sfm mvs has significant potential to inform coastal managers and decision makers to further empower coastal authorities and communities policy frameworks must be developed to incorporate and interpret these data

mean bed friction of combined wave current flow abstract bijker s model for evaluating the wave period mean bed friction of combined wave current flow has been modified to account for the current velocity reduction as well as the wave boundary layer near the sea bed a method of estimating the bed frictional dissipation rate of the combined flow is also presented the results obtained by the present approach are compared with several sets of experimental data and confirm its accuracy and usefulness

spot shallow water bathymetry of a moderately turbid tidal inlet based on field measurements the determination of shallow water depth in high energy tidal inlets is essential to model and to forecast the navigation channel position or the short term topographic evolution of beaches colour satellite imagery provides at low cost complete maps of areas that are difficult to map by traditional hydrographic means due to their size and their rough underwater morphology in order to calibrate spot images to derive bathymetric maps a simple method applied to shallow waters of a moderately turbid tidal inlet has been carried out its development is based on a set of field measurements including the reflectance of the water and of the bottom sediment the vertically averaged diffuse attenuation coefficient and the concentrations of inorganic particles in suspension of chlorophyll a and pheopigments and of dissolved organic carbon doc from these data it appears first that the water reflectance is directly linked to the depth and second that the water reflectance varies slowly with the turbidity in this area for total suspended matter sm concentrations lower than 9 mg l 1 the extinction of light with depth has been characterized in the inlet the relationship obtained is slightly different from that observed in clear waters the bathymetric models established for the clearest waters do not calculate the depth accurately in the contrary reflectance code adapted to case ii water type calibrated with in situ measurements allows us to retrieve depth down to 6 m and for total sm concentrations ranging from 0 2 to 9 mg l 1 this relationship has been applied to five spot images of the mouth of arcachon lagoon the accuracy of the derived map has been assessed by in situ depth measurements the mean difference between measured depths and computed depths is about 20 this accuracy is adequate to assess the inlet morphodynamics quantitatively which is necessary for middle term to short term mathematical modeling of the 3d inlet evolution

wave set up on coral reefs 2 set up on reefs with various profiles abstract all available laboratory data for wave set up on two dimensional reef profiles of various shapes have been compared with data from an idealised horizontal reef with a steep reef face gourlay 1996 the data is generally well represented by a relationship between the relative set up parameter gh r t o and the submergence parameter g h r h r h o and the relative set up on reef profiles of natural form is found to be less than that observed on the idealised horizontal reef the important influences of reef rim slope and variable water depths on the reef top have been investigated and some methods for allowing for them are suggested comparison of data for irregular waves with that for regular waves has led to the development of a simple method for estimating the effects of wave groups upon the magnitude of the steady state mean wave set up gh r the results of the analyses are applied to the determination of wave set up and its effects at three specific coral reef sites

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

short term beach dune sand budgets on the north sea coast of france sand supply from shoreface to dunes and the role of wind and fetch abstract three experimental plots covering the transition from the upper beach to the dune on the north sea coast of france were monitored at various intervals over a period of 18 24 months via high resolution terrain surveys in order to determine inter site sand budget variability as well as patterns and processes involved in sand exchanges between the upper beach and dune the wind regime consists of a fairly balanced mix of moderate 80 of winds are below 8 m s onshore offshore and shore parallel winds sustained dune accretion over several years depends on the periodic local onshore welding of shoreface tidal banks that have developed in the storm and tide dominated setting of the southern north sea the only site where this has occurred in the recent past is calais where bank welding has created a wide accreting upper beach sand flat at this site significant sand supply from the subtidal sand bank reservoir to the upper beach flat occurred only once over the 18 month survey following a major storm the bulk of the sand deposited over this large flat is not directly integrated into the adjacent embryo dunes by onshore winds but is progressively reworked in situ into developing dunes or transported alongshore by the balanced wind regime thus resulting in alongshore stretching of the embryo dune system the leffrinckoucke site near belgium shows moderate beach dune mobility and accretion while the wissant site exhibits significant upper beach bedform mobility controlled by strong longshore currents that result in large beach budget fluctuations with little net budget change to the detriment of the adjacent dunes accretion at these two sites which are representative of the rest of the north sea coast of france is presently constrained by the absence of a shore attached sand bank supply reservoir while upper beach dune sand exchanges are further limited by the narrow wave affected upper beach the intertidal morphology of bars and troughs which segments the aeolian fetch and the moderate wind energy conditions the balanced wind regime limits net sand mobilisation in favour of either the beach or the dune and may explain the relatively narrow longshore morphology of the dune ridges bounding this coast

uav based remote sensing surveys of lava flow fields a case study from etna s 1974 channel fed lava flows during an eruption time scales of topographic change are fast and involve vertical and planimetric evolution of millimeters to meters as the event progresses repeat production of high spatial resolution terrain models of lava flow fields over time scales of a few hours is thus a high value capability in tracking the buildup of the deposit among the wide range of terrestrial and aerial methods available to collect such topographic data the use of an unmanned aerial vehicle uav as an acquisition platform together with structure from motion sfm photogrammetry has become especially useful this approach allows high frequency production of centimeter scale terrain models over kilometer scale areas including dangerous and inaccessible zones with low cost and minimal hazard to personnel this study presents the application of such an integrated uav sfm method to generate a high spatial resolution digital terrain model and orthomosaic of mount etna s january february 1974 lava flow field the sfm method applied to images acquired using a uav platform enabled the extraction of a very high spatial resolution 20 cm digital elevation model and the generation of a 3 cm orthomosaic covering an area of 1 35 km2 this spatial resolution enabled us to analyze the morphology of sub meter scale features such as folds blocks and cracks over kilometer scale areas the 3 cm orthomosaic allowed us to further push the analysis to centimeter scale grain size distribution of the lava surface using these data we define three types of crust structure and relate them to positions within a channel fed a flow system these crust structures are i flow parallel shear lines ii raft zones and iii folded zones flow parallel shear lines are found at the channel edges and are 2 m wide and 0 25 m deep zones running along the levee base and in which cracking is intense they result from intense shearing between the moving channel lava and the static levee lava in zones where initial levees are just beginning to form these subtle features are the only marker that delimits the moving lava from the stagnant marginal lava rafts generally form as the system changes from a stable to a transitional channel regime over this 170 m long zone the channel broadens from 8 to 70 m and rafts are characterized by topographically higher and poorly cracked areas surrounded by lower heavily cracked areas we interpret the rafts as forming due to breakup of crust zones previously moving in a coherent manner in the narrow proximal channel reach folded zones involve arcuate cross flow ridges with their apexes pointing down flow where ridges have relatively small clasts and depressions are of coarser grained breccia our folds have wavelengths of 10 m and amplitudes of 1 m are found towards the flow front down flow of the raft zones and are associated with piling up of lava behind a static or slowly moving flow front the very high spatial resolution topographic data available from uav sfm allow us to resolve surfaces where roughness has a vertical and horizontal scale of variation that is less than 1 m this is the case over p hoehoe and a flow surfaces and thus allows us to explore those new structures that are only apparent in the sub metric data moreover during future eruptions the possibility to acquire such information in near real time will allow a prompt analysis of developing lava flow fields and structures therein such as developing lava channel systems so as to contribute to timely hazard assessment modeling and projections

a geomorphological approach to sustainable planning and management of the coastal zone of kuwait the coastal zone in kuwait has been under a considerable pressure from conflicting land uses since the early 1960s as well as from the destruction and oil pollution caused by the gulf war to avoid further damage and to protect the coastal heritage it is essential to adopt an environmentally sustainable management process this paper shows how the study of coastal geomorphology can provide a sound basis for sustainable planning and management based on coastal landforms sediments and processes the coastline of kuwait was divided into nine geomorphic zones these zones were grouped into two main geomorphic provinces the northern province is marked by extensive muddy intertidal flats and dominated by a depositional and low energy environment the southern geomorphic province is characterised by relatively steep beach profiles rocky sandy tidal flats and a moderate to high energy environment the study has demonstrated that pollution benthic ecology and other environmental conditions of the coast are a function of coastline geomorphology sedimentology and related processes the geomorphological information was used to determine the coastal vulnerability and to assess the environmental impacts of development projects and other human activities several strategies were outlined to integrate the geomorphic approach into the management of the coastal resources

adjustment of the southern ocean to wind forcing on synoptic time scales abstract this study addresses the response of the southern ocean to high frequency wind forcing focusing on the impact of several barotropic modes on the circumpolar transport a suite of experiments is performed with an unstratified model of the southern ocean forced with a stochastic wind stress that contains a large range of frequencies with synoptic time scales the southern ocean adjustment displays a different character for frequencies below and above 0 2 cpd the low frequency range is dominated by an almost free mode response in the region where contours of f h are obstructed by only a few bathymetric features the truly free mode only plays a minor role topographic form stress rather than friction is the dominant decay mechanism of the southern mode it leads to a spindown time scale on the order of 3 days for the high frequency range the circumpolar transport is dominated by the resonant excitation of oscillatory modes the active response of the ocean leads to strong changes and eve

resonant third degree diurnal tides in the seas off western europe abstract third degree diurnal tides are estimated from long time series of sea level measurements at three north atlantic tide gauges although their amplitudes are only a few millimeters or less their admittances are far larger than those of second degree diurnal tides just as cartwright discovered for the m1 constituent the tides are evidently resonantly enhanced owing to high spatial correlation between the third degree spherical harmonic of the tidal potential and a near diurnal oceanic normal mode that is most pronounced in the north atlantic by estimating the ocean tidal response across the diurnal band five tidal constituents plus nodal modulations the period and q of this mode and one nearby mode are estimated

a virtual power function for estimating the alongshore transport of sediment by waves abstract a transport formula is presented which is based upon the rate of energy dissipation in breaking waves it incorporates a dimensionless grain size parameter and has been calibrated against field and laboratory data

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

initial hydro geomorphic development and rill network evolution in an artificial catchment the formation of erosion rills and gullies is a critical step in land surface development but possibilities to study initial unaffected surface development under natural conditions and with well defined initial and boundary conditions are rare the objective of this study was to characterize rill network development from point zero in the artificially created catchment huhnerwasser to ensure unaffected development the study was largely restricted to the analysis of remotely sensed data we analyzed a series of photogrammetry based digital elevation models dems for 10 points in time over a period of five years and beginning with the initial state the evolving erosion rill network was quantitatively described based on mapping from aerial photographs dems and rill network maps were combined to specifically analyze the development of morphometry for different parts of the network and to characterize energy dissipation and connectivity the restriction to remote sensing data did not allow for analyzing specific processes governing rill network development nevertheless two major development phases could be characterized we observed a phase of growth of the rill network along with variations in drainage patterns during the first two years of development and a subsequent phase of reduction of its area along with comparably stable patterns region specific analysis of morphometry indicates that besides effects of changing sediment characteristics and vegetation cover development locally evolving hydro geomorphic feedback cycles influenced this development results show an increasing similarity of overall statistical characteristics e g drainage density for two parts of the catchment but a persistent influence of initial conditions on specific rill geometry the observed development towards higher orderliness and increased connectivity is consistent with experiments and concepts on drainage network evolution across scales however we did not observe major influences of rill piracy and cross grading or a reduction of energy dissipation with network development copyright 2013 john wiley sons ltd

assessing the performance of structure from motion photogrammetry and terrestrial lidar for reconstructing soil surface microtopography of naturally vegetated plots soil microtopography is a property of critical importance in many earth surface processes but is often difficult to quantify advances in computer vision technologies have made image based three dimensional 3d reconstruction or structure from motion sfm available to many scientists as a low cost alternative to laser based systems such as terrestrial laser scanning tls while the performance of sfm at acquiring soil surface microtopography has been extensively compared to that of tls on bare surfaces little is known about the impact of vegetation on reconstruction performance this article evaluates the performance of sfm and tls technologies at reconstructing soil microtopography on 6 m 2 m erosion plots with vegetation cover ranging from 0 to 77 results show that soil surface occlusion by vegetation was more pronounced with tls compared to sfm a consequence of the single viewpoint laser scanning strategy adopted in this study on the bare soil surface elevation values estimated with sfm were within 5 mm of those from tls although long distance deformations were observed with the former technology as vegetation cover increased agreement between sfm and tls slightly degraded but was significantly affected beyond 53 of ground cover detailed semivariogram analysis on meter square scale surface patches showed that tls and sfm surfaces were very similar even on highly vegetated plots but with fine scale details and the dynamic elevation range smoothed out with sfm errors in the tls data were mainly caused by the distance measurement function of the instrument especially at the fringe of occlusion regions where the laser beam intersected foreground and background features simultaneously from this study we conclude that a realistic approach to digitizing soil surface microtopography in field conditions can be implemented by combining strengths of the image based method simplicity and effectiveness at reconstructing soil surface under sparse vegetation with the high accuracy of tls like technologies copyright 2015 john wiley sons ltd

shoreline change analysis and its application to prediction a remote sensing and statistics based approach abstract shoreline change analysis and prediction are important for integrated coastal zone management and are conventionally performed by field and aerial surveys this paper discusses an alternative cost effective methodology involving satellite remote sensing images and statistics multi date satellite images have been used to demarcate shoreline positions from which shoreline change rates have been estimated using linear regression shoreline interpretation error uncertainty in shoreline change rate and cross validation of the calculated past shorelines have been performed using the statistical methods namely regression coefficient r 2 and root mean square error rmse this study has been carried out along 113 5 km of coast adjoining bay of bengal in eastern india over the time interval 1973 to 2003 the study area has been subdivided into seven littoral cells and transects at uniform interval have been chosen within each cell the past and future shoreline positions have been estimated over two time periods of short and long terms in three modes viz transect wise littoral cell wise and regionally the result shows that 39 of transects have uncertainties in shoreline change rate estimations which are usually nearer to cell boundaries on the other hand 69 of transects exhibit lower rmse values for the short term period indicating better agreement between the estimated and satellite based shoreline positions it is also found that cells dominated by natural processes have lower rmse when considered for long term period while cells affected by anthropogenic interventions show better agreement for the short term period however on regional considerations there is not much difference in the rmse values for the two periods geomorphological evidence corroborates the results the present study demonstrates that combined use of satellite imagery and statistical methods can be a reliable method for shoreline related studies

kelvin waves around antarctica abstractthe southern ocean allows circumpolar structure and the antarctic coastline plays a role as a waveguide for oceanic kelvin waves under the cyclic conditions the horizontal wavenumbers and frequencies for circumpolarly propagating waves are quantized with horizontal wavenumbers 1 2 and 3 corresponding to periods of about 32 16 and 11 h respectively at these frequencies westward propagating signals are detected in sea level variation observed at antarctic coastal stations the occurrence frequency of westward propagating signals far exceeds the statistical significance and the phase speed of the observed signal agrees well with the theoretical phase speed of external kelvin waves therefore this study concludes that the observed westward propagating sea level variability is a signal of the external kelvin waves of wavenumbers 1 2 and 3 around antarctica a series of numerical model experiments confirms that kelvin waves around antarctica are driven by surface air pressure and that th

guidelines on the use of structure from motion photogrammetry in geomorphic research as a topographic modelling technique structure from motion sfm photogrammetry combines the utility of digital photogrammetry with a flexibility and ease of use derived from multi view computer vision methods in conjunction with the rapidly increasing availability of imagery particularly from unmanned aerial vehicles sfm photogrammetry represents a powerful tool for geomorphological research however to fully realize this potential its application must be carefully underpinned by photogrammetric considerations surveys should be reported in sufficient detail to be repeatable if practical and results appropriately assessed to understand fully the potential errors involved to deliver these goals robust survey and reporting must be supported through i using appropriate survey design ii applying suitable statistics to identify systematic error bias and to estimate precision within results and iii propagating uncertainty estimates into the final data products

coastline change of the yellow river estuary and its response to the sediment and runoff 1976 2005 abstract the dramatic decreases in runoff and sediment have great impacts on erosion deposition variation in the yellow river estuary this study extracted mean high tide lines of the yellow river estuary from mss tm and etm data from 1976 to 2005 and explored relationships between the accretion erosion of land and the runoff and sediment load of the yellow river the results showed that the general pattern of accretion erosion of the entire estuary was divided into four stages rapid accretion stage 1976 1986 accretion erosion adjustment stage 1986 1996 slow erosion stage 1996 2003 and slow accretion stage 2003 present for maintaining the annual balance of the entire estuary 1976 2005 and q8 estuary most recent course of the qingshuigou estuary from 1996 to 2005 critical annual runoff and sediment load are 140 36 108 m3 year 1 and 3 31 108 t year 1 and 85 0 108 m3 year 1 and 1 63 108 t year 1 respectively in the future decades the q8 estuary is likely to maintain its shape and area balance or have a little accretion but the entire estuary could be in an eroding state

evidence of a 4 6 day barotropic planetary oscillation of the pacific ocean abstract spectral analysis of scattered island and coastal tide gage records from the pacific ocean reveals the presence of a coherent sea level fluctuation at 4 6 days period the oscillation is distinct from baroclinic inertia gravity wave fluctuations of sea level at the same periods that are trapped to the central pacific equatorial zone concomitant spectral analysis of island surface weather data demonstrates that sea level is forced by surface atmospheric pressure but does not respond statically like an inverted barometer the basinwide character and uniform westward propagation of the oscillation suggest the presence of a barotropic planetary wave s however the oscillation is strongly attenuated with an estimated energy e folding time of less than three days

normal modes of the world ocean part iv synthesis of diurnal and semidiurnal tides abstract diurnal and semidiurnal tides of second and third degree are synthesized from 60 normal modes with period in the range 8 to 96 h diurnal tides especially those of second degree can be represented by remarkably few modes the principal lunar diurnal constituent for example consists almost entirely of a single forced mode excited mainly in the pacific and indian oceans semidiurnals are spectrally more heterogeneous and more resonant than diurnals but some specific features can be attributed to individual modes several of the most energetic modes in the principal lunar semidiurnal constituent are prominent in the atlantic ocean together with the fact that diurnally excited modes are relatively weak in that region this presumably accounts for the observed tendency for the total tide to be predominantly semidiurnal in the atlantic but mixed diurnal and semidiurnal in many parts of the pacific and indian oceans

spatial patterns of erosion in a bedrock gorge understanding the physical processes driving bedrock channel formation is essential for interpreting and predicting the evolution of mountain landscapes here we analyze bedrock erosion patterns measured at unprecedented spatial resolution mm over 2 years in a natural bedrock gorge these spatial patterns show that local bedrock erosion rates depend on position in the channel cross section height above the streambed and orientation relative to the main streamflow and sediment path these observations are consistent with the expected spatial distribution of impacting particles the tools effect and shielding by sediment on the bed the cover effect vertical incision by bedrock abrasion averaged 1 5 mm a lateral abrasion averaged 0 4 mm a and downstream directed abrasion of flow obstacles averaged 2 6 mm a however a single plucking event locally exceeded these rates by orders of magnitude 100 mm a and accounted for one third of the eroded volume in the studied gorge section over the 2 year study period hence if plucking is spatially more frequent than we observed in this study period it may contribute substantially to long term erosion rates even in the relatively massive bedrock at our study site our observations demonstrate the importance of bedrock channel morphology and the spatial distribution of moving and static sediment in determining local erosion rates

waterline extraction from landsat tm data in a tidal flat a case study in gomso bay korea waterline extraction is potentially one of the most effective satellite remote sensing tools for studying changes in tidal flat environment and coastlines however its application to the study of tidal flats has not been investigated in detail the waterline in a tidal flat in gomso bay korea is characterized and evaluated using 27 sets of landsat thematic mapper tm and earth observing system terra eos terra advanced spaceborne thermal emission and radiometer aster data ground truth data including grain size soil moisture content ground levelling and waterline tracking have been obtained the choice of spectral bands in terms of tidal conditions turned out to play a key role in locating the waterline while the waterlines extracted from near infrared nir short wavelength infrared swir and thermal infrared tir data are commonly reliable on the flood tide the discrepancies between different bands become large on the ebb tide the bands tir nir and swir are in that order decreasingly effective in extracting the waterline while ebb tides are in progress the effect of turbid water on nir can be reduced by a ratioing of nir and the visible band the location of the waterline is also an important factor to consider the discrepancy is largest on the middle tidal flat selection of the proper band for waterline extraction under various conditions is suggested however no single band can accommodate all aspects of the tidal flat environment a schematic model associated with the spectral reflectance of the tidal flat is proposed in which the remnant water scattered on the surface after exposure is emphasized as an additional factor

recent deep seated coastal landsliding at san onofre state beach california abstract airborne lidar collected during the period 1998 2010 and differential gps surveys conducted over 2008 2013 show recent reactivation and movement of a large deep seated coastal landslide at san onofre state beach san diego county california the overall slide complex extends about 700 m alongshore 150 m inland and an unknown distance offshore differencing digital elevation models and tracking field monuments benchmarks provide time series of quantitative topographic landslide changes and new insight in to the slide motion sequences and mechanics the slide contains several distinct primary and secondary regions moving and deforming at different rates primary slide motion includes slow seaward translational motion rotational slipping and upward offshore movement secondary processes of basal wave erosion and new inland cliffline failures contribute to primary landslide destabilization the landslide exhibits lithologic and structural controls is driven by a combination of marine and subaerial processes influences local beach morphology and deviates from typical southern california coastal cliff processes which mostly involve shallow landslides and topples large scale cross shore slide rotation has recently created new nearshore reefs eroded cliff sediments provide a local beach sand source and probably influence local nearshore ecosystems all known time periods of major historical landslide activity were preceded by elevated seasonal rainfall and analysis suggests elevated rainfall generated primary slide motion as opposed to wave action as of spring 2013 landslide activity has slowed but continued positive feedbacks including toe removal by wave activity suggest that future landsliding will probably threaten coastal infrastructure

normal modes of the world ocean part ii description of modes in the period range 8 to 80 hours abstract we have calculated normal modes with period between 8 and 80 h for a domain consisting of the arctic atlantic indian and pacific oceans in this period range the numerical model has 56 modes of which 13 are topographic vorticity waves all slower than 30 h the trapping sites for these modes are the siberian shelf the icelandic plateau the grand banks the falkland plateau and patagonian shelf the kerguelen plateau the new zealand and fiji plateaus and the hawaiian ridge predominantly planetary vorticity waves do not appear in the model at periods less than 80 h the 41 modes found between 30 and 8 h include basin modes in the north atlantic indian and equatorial pacific quarter wave resonances in the arabian sea bay of bengal and gulf of guinea and kelvin waves on the antarctic coast the pacific north american coast and the new zealand coast several vorticity and gravity modes exhibit an eastward circumglobal flow of energy that is confined to equatorial latitudes except where defl

structure from motion photogrammetry a low cost effective tool for geoscience applications abstract high resolution topographic surveying is traditionally associated with high capital and logistical costs so that data acquisition is often passed on to specialist third party organisations the high costs of data collection are for many applications in the earth sciences exacerbated by the remoteness and inaccessibility of many field sites rendering cheaper more portable surveying platforms i e terrestrial laser scanning or gps impractical this paper outlines a revolutionary low cost user friendly photogrammetric technique for obtaining high resolution datasets at a range of scales termed structure from motion sfm traditional softcopy photogrammetric methods require the 3 d location and pose of the camera s or the 3 d location of ground control points to be known to facilitate scene triangulation and reconstruction in contrast the sfm method solves the camera pose and scene geometry simultaneously and automatically using a highly redundant bundle adjustment based on matching features in multiple overlapping offset images a comprehensive introduction to the technique is presented followed by an outline of the methods used to create high resolution digital elevation models dems from extensive photosets obtained using a consumer grade digital camera as an initial appraisal of the technique an sfm derived dem is compared directly with a similar model obtained using terrestrial laser scanning this intercomparison reveals that decimetre scale vertical accuracy can be achieved using sfm even for sites with complex topography and a range of land covers example applications of sfm are presented for three contrasting landforms across a range of scales including an exposed rocky coastal cliff a breached moraine dam complex and a glacially sculpted bedrock ridge the sfm technique represents a major advancement in the field of photogrammetry for geoscience applications our results and experiences indicate sfm is an inexpensive effective and flexible approach to capturing complex topography

compartmentalisation of beachface sediments along the southwestern coast of australia abstract identification of littoral cells is a prerequisite for the determination of sediment budgets on sandy coasts in this context the aims of the project were first to investigate the applicability of statistical techniques particularly auto correlation and cluster analysis to the definition of littoral cell boundaries second add detail to sedimentological and environmental observations previously reported for the southwestern australian coast and third provide a basis for future examination of sediment transport in a nearshore environment that is generally subject to low wave energy the alongshore component of sediment compartmentalisation has been determined for the sandy beaches of the study area and relationships between environmental parameters and beachface sediment characteristics have been established using data describing textural and compositional attributes the systematic alongshore variation in sediments was determined from the cluster analysis and auto correlation results from the grouping of sediments were then used in conjunction with geomorphic variables to determine boundaries of six sediment compartments littoral cells are better developed on the southern sector of the coast where shoreline salients and headlands are larger and act as boundaries these barriers limit but do not prevent inter compartment sediment transport the findings of this study provide a context for further investigation of littoral cell dynamics and coastal sediment transport the statistical techniques applied to data describing the alongshore distribution of sediments are readily repeatable in other contexts and have general applicability and offer a rigorous procedure for definition of coastal regions

straightforward reconstruction of 3d surfaces and topography with a camera accuracy and geoscience application topographic measurements for detailed studies of processes such as erosion or mass movement are usually acquired by expensive laser scanners or rigorous photogrammetry here we test and use an alternative technique based on freely available computer vision software which allows general geoscientists to easily create accurate 3d models from field photographs taken with a consumer grade camera the approach integrates structure from motion sfm and multi view stereo mvs algorithms and in contrast to traditional photogrammetry techniques it requires little expertise and few control measurements and processing is automated to assess the precision of the results we compare sfm mvs models spanning spatial scales of centimeters a hand sample to kilometers the summit craters of piton de la fournaise volcano with data acquired from laser scanning and formal close range photogrammetry the relative precision ratio achieved by sfm mvs measurement precision observation distance is limited by the straightforward camera calibration model used in the software but generally exceeds 1 1000 i e centimeter level precision over measurement distances of 10s of meters we apply sfm mvs at an intermediate scale to determine erosion rates along a 50 m long coastal cliff seven surveys carried out over a year indicate an average retreat rate of 0 70 0 05 m a 1 sequential erosion maps at 0 05 m grid resolution highlight the spatio temporal variability in the retreat with semivariogram analysis indicating a correlation between volume loss and length scale compared with a laser scanner survey of the same site sfm mvs produced comparable data and reduced data collection time by 80

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

monitoring changing position of coastlines using thematic mapper imagery an example from the nile delta coastline movement due to erosion and deposition is a major concern for coastal zone management very dynamic coastlines such as sections of the nile delta coast pose considerable hazards to human use and development and rapid replicable techniques are required to update coastline maps of these areas and monitor rates of movement the synoptic capability of landsat thematic mapper imagery enables monitoring of large sections of coastline at relatively coarse 30 m spatial resolution by comparing positions of the nile delta coast in 1984 1987 and 1990 1991 mapped using a region growing image segmentation technique areas of rapid change can be identified and targeted for more detailed monitoring in the field or using higher resolution images rates of erosion and deposition can be estimated crudely and areas where change appears to be accelerating can also be identified areas of severe erosion along the nile delta coast are found to be confined to the promontories of the present day mouths of the nile at rosetta and damietta eroding shorelines are mostly flanked by accreting shorelines showing that some of the eroded material is redistributed along the coast the technique outlined here has potential to augment conventional field based surveying for monitoring shoreline changes over short timescales

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

soil surface roughness measurement methods applicability and surface representation abstract in a laboratory rainfall simulator study soil surface roughness was measured using contact roller chain pin meter and noncontact devices laser scanner photogrammetry soil surfaces with two initial roughness conditions aggregates as for the contact methods resolution cm range and precision mm range is limited which constrains their application to calculation of simple surface parameters resolution and precision in the sub millimeter range could be obtained with the laser scanner while for the photogrammetric method the measurement uncertainty was approximately 1 2 mm measurement time was highest 90 min for the pin meter technique though data were ready to use for analyses laser scanner measurements took 34 min several steps of data post processing required 30 more minutes data acquisition was fastest for photogrammetry 5 min but expert knowledge as well as special hard and software were necessary for time consuming photo analyses taking about 120 min the chain and pin meter were compared using a profile index profile lengths matched well for smooth surfaces on rough surfaces the chain meter gave shorter profile lines between profile index from chain measurements and the random roughness derived from pin meter data a polynomial regression could be found parameters of distributions of elevations as well as inclinations and depressions were used to compare the laser scanner and the photogrammetric technique generally the laser scanner was able to reproduce small aggregates as well as voids in between them while dem from stereophotos was smoothed between major aggregates this led to skewed distributions of elevations and inclinations as well as to a lower surface area up to 39 and a lower depression volume up to 68 shapes of depressions were significantly different as well the used photogrammetric technique is supposed to be successful in producing adequate dems for already smoothed surfaces e g after rainfall events the study revealed different fields of application and limitations of the compared devices using a non adequate technique for certain situations will definitely have implications on further analyses concerning connectivity of runoff pathways surface protection from raindrop impact or runoff detachment and sediment transport

spatial and temporal shoreline changes of the southern yellow river huanghe delta in 1976 2016 abstract in this study 364 landsat satellite images were utilized to study the spatial and temporal shoreline changes of the southern yellow river delta in 1976 2016 and a new method revised and improved after zhang et al 2016 was proposed by employing that method the calculated sea levels calculated from simulated tidal heights and instantaneous shoreline positions rather than simulated tidal heights were used to correct fluctuations in instantaneous shoreline positions caused by tidal height and seasonal sea level changes and other random sea level fluctuations when calculating the shoreline erosion rates and beach slopes a statistical analysis of a large number of corrected shoreline positions was used to reduce the influence of random errors that were mainly caused by waves and other casual factors the shoreline erosion rates and beach slopes presented in this paper are therefore more precise and reliable than those derived in previous studies which only used two satellite images the results of this study show that the shoreline of the southern yellow river delta primarily experienced gradual erosion during 1976 2016 with an average erosion rate of 26 9 m year the average shoreline erosion rate increased from 24 9 m year in 1976 1996 to 34 9 m year in 1996 2016 an increase of 40 probably due to the reduction in sediment discharge and shifting northward course of the yellow river after 1996 the shoreline erosion rate of the central coast decreased from 50 2 m year in 1976 1996 to 27 1 m year in 1996 2016 a decrease of 46 probably due to the protection offered by coastal hard structures the average shoreline erosion rate caused by relative sea level rise was 8 5 m year or 32 of the total average shoreline erosion rate relative sea level rise plays an important role in the erosion of the southern yellow river delta due to its flat beach the beach slope of the southern yellow river delta was flat and stable in 1976 2016 and the average slope over most of the beach was 0 043

modeling the topography of shallow braided rivers using structure from motion photogrammetry abstract recent advances in computer vision and image analysis have led to the development of a novel fully automated photogrammetric method to generate dense 3d point cloud data this approach termed structure from motion or sfm requires only limited ground control and is ideally suited to imagery obtained from low cost non metric cameras acquired either at close range or using aerial platforms terrain models generated using sfm have begun to emerge recently and with a growing spectrum of software now available there is an urgent need to provide a robust quality assessment of the data products generated using standard field and computational workflows to address this demand we present a detailed error analysis of sub meter resolution terrain models of two contiguous reaches 1 6 and 1 7 km long of the braided ahuriri river new zealand generated using sfm a six stage methodology is described involving i hand held image acquisition from an aerial platform ii 3d point cloud extraction modeling using agisoft photoscan iii georeferencing on a redundant network of gps surveyed ground control points iv point cloud filtering to reduce computational demand as well as reduce vegetation noise v optical bathymetric modeling of inundated areas and vi data fusion and surface modeling to generate sub meter raster terrain models bootstrapped geo registration as well as extensive distributed gps and sonar based bathymetric check data were used to quantify the quality of the models generated after each processing step the results obtained provide the first quantified analysis of sfm applied to model the complex terrain of a braided river results indicate that geo registration errors of 0 04 m planar and 0 10 m elevation and vertical surface errors of 0 10 m in non vegetation areas can be achieved from a dataset of photographs taken at 600 m and 800 m above the ground level these encouraging results suggest that this low cost logistically simple method can deliver high quality terrain datasets competitive with those obtained with significantly more expensive laser scanning and suitable for geomorphic change detection and hydrodynamic modeling