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Aeolian sediment transport has major repercussions for global climatic variations, air quality, human health, agricultural areas, air and ground transportation, civil structures and infrastructures. This led to the development of models to understand the involved physical process, and to predict the dynamics of aeolian sediment transport. The sedimentation velocity is one of the key model parameters characterizing sediment behavior. It allows the prediction of the mode of transport, the distribution of particles above the ground, and the sediment transport rate. Despite its importance, there is substantial discrepancy among the sedimentation velocity laws for natural particles, also due to the large dispersion of experimental data. This study proposes the statistical characterization of the experimental measurements of sedimentation velocity available from the literature. 1812 experimental measurements were recovered from 11 studies. Their variability was discussed, providing an aerodynamic reading. Nonlinear regression was carried out on the consolidated dataset in order to assess the average value. Two well-known laws initially conceived for spheres were refitted to natural particles providing high coefficients of determination equal to 0.90 and 0.93. Then, copula-based regression was performed in order to seize the variability of sedimentation velocity. Finally, the results from the two approaches were compared and critically discussed.

Sherman, D.J., 2018. Megaripple/flat bed transition in rip current channels. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 246–250. Coconut Creek (Florida), ISSN 0749-0208.Megaripple and flat bed conditions are common bed configurations in energetic nearshore environments. Their existence is controlled by shear stresses associated with wave orbital motion, superimposed net flows, and water depth, representing flow regimes. This is based on the premise of a characteristic set of flow conditions associated with particular bed configurations. A simple flow regime sequence for surf zones is ripples, megaripples (or dunes), and flat bed. Each of these bed configurations may include several secondary characteristics. Despite the importance of understanding flow regime ranges and transitions, there have been few detailed studies for characteristic megaripple and flat bed conditions. This paper presents the results of a field experiment designed to acquire flow, sedimentological, and bedform data from rip current feeder channels in an inner surf zone of a barred nearshore. Waves and water depths were measured with pressure transducers, and currents were measured with bidirectional current meters. Sand samples were gathered and bed configurations were measured and photographed by divers. Analysis indicates that the mobility number, as calculated with a number of characteristic velocities, provides first-order bedform discrimination. Observations indicate that bedform transitions can occur over sub-hour time spans, although the response times are slower as combined wave and current velocities are reduced. Under the latter conditions, especially, non-equilibrium configurations may persist.

The quantification of saltation intermittency—the proportion of time when sand transport occurs—provides valuable information about the nature of aeolian systems, including insights concerning thre...

There remains a need for an efficient, low-cost, portable, passive sand trap, which can provide estimates of vertical sand flux over topography and within vegetation and which self-orients into the wind. We present a design for a stacked vertical trap that has been modelled (computational fluid dynamics, CFD) and evaluated in the field and in the wind tunnel. The ‘swinging’ trap orients to within 10° of the flow in the wind tunnel at 8 m s−1, and more rapidly in the field, where natural variability in wind direction accelerates orientation. The CFD analysis indicates flow is steered into the trap during incident wind flow. The trap has a low profile and there is only a small decrease in mass flow rate for multiple traps, poles and rows of poles. The efficiency of the trap was evaluated against an isokinetic sampler and found to be greater than 95%. The centre pole is a key element of the design, minimally decreasing trap efficiency. Finally, field comparisons with the trap of Sherman et al. (2014) yielded comparable estimates of vertical sand flux. The trap described in this paper provides accurate estimates of sand transport in a wide range of field conditions.

Hurricanes and tropical storms are severe threats to coastal properties, settlements, and infrastructure. Airborne light detection and ranging lidar surveys conducted before and after storm events allow detailed analysis of coastal geomorphologic and sediment volumetric changes and have been proved very useful in the study of coastal changes. Traditionally, most studies use the pixel-based differencing method to quantify the spatial extent and magnitude of coastal changes based on sequential lidar surveys. This research presents a graph theory-based approach and associated software tools for representing and quantifying storm-induced damages to buildings, beaches and sand dunes, coastal vegetation canopy, and infrastructure. Generation of elevation difference grids, construction of local contour trees, and derivation of semantic properties are key components of the new algorithm for change object detection and extraction. An ontology and taxonomy are proposed to classify change objects into different types of coastal damages in terms of their semantic properties. This method has been successfully applied to assess damages of Hurricane Ike to the Bolivar Peninsula on the Texas Gulf Coast based on pre-and post-storm airborne lidar data and colour infrared aerial photographs.

The study of aeolian geomorphological systems over the last half century has advanced along several important fronts, supported by developments in technologies and analytic methods and the evolution of modeling approaches. Remote sensing has led to a wealth of knowledge concerning the distribution and dynamics of dunes on Earth and elsewhere, and wind tunnels have elucidated the roles of aeolian processes in reshaping surfaces. Improvements in laboratory and field instrumentation allow measurement of aeolian sand transport systems at levels of detail unimaginable when the Binghamton Geomorphology Symposium began. We have seen, for example, the advent of large, sophisticated field campaigns and advanced modeling approaches using cellular automata and computational fluid dynamics methods. Select avenues of development, especially concerned with depositional environments, are briefly summarized. Advances in many fields have not been matched with proportional advances in our ability to predict rates of sand transport in natural environments, one of the most fundamental challenges. At least eight, commonly cited, sand transport-rate models do not agree with each other and do not replicate field observations even under near-ideal conditions. This review focuses on select reasons why that might be so, and categorizes those reasons into six, principal theoretical and empirical vexations that have made sand transport an intractable problem: predicting rates of transport; characterizing grain size; characterizing fluid and sand densities; estimating shear velocity; predicting the threshold of motion, including the effects of sand moisture content; and understanding granular electrification. The examination of potential sources of error in the rate of transport and threshold of motion models leads to a point-by-point consideration of our current assumptions and protocols (or lack thereof). The objective is to help us identify the hard targets and the soft targets for future research.

Shuster, R.; Sherman, D.J.; Lorang, M.S.; Ellis, J.T., and Hopf, F., 2020. Erosive potential of recreational boat wakes. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1279–1283. Coconut Creek (Florida), ISSN 0749-0208.Recreational boat wakes are important sources of erosive energy in many sheltered coastal and estuarine environments. The energy content of a wake depends on boat speed, length, hull-shape and displacement and the energy delivered to an adjacent shoreline is also a function of the distance traveled by the wake. In this study that was conducted in the estuarine waters of Georgiana Slough, which is a distributory channel of the Sacramento River in California, basic geometries and speeds of common recreational boats were recorded along with the height and period of the wakes they generated. A site was instrumented with a motion-sensing video camera and pressure transducer to record boat passages and resulting wakes. Regression analysis using a curated data set produced a coefficient of determination of 0.87 linking index wave energy and boat length cubed. These results suggest that the length of a boat traveling at typical cruising speeds is a useful predictor of wake energy when a passage is within about 30 m of the shoreline. Further research is required to quantify the effects of greater distances on wake attenuation. This method could be used to monitor boat traffic in sensitive coastal environments, assess possible erosion risk from boat wakes, and inform management responses.

Growing concern regarding the geomorphic and associated biotic effects of dune management practises has led to an increase in the number of dune restoration projects globally. Most recent projects aim to enhance the efficiency of aeolian sediment dynamics and increase dune mobility by decreasing vegetation cover, but we lack objective measures to evaluate such projects. Here we demonstrate the use of landscape metrics to quantify the evolution of foredune texture following the removal of vegetation. A long-term program of marram grass ( Ammophila arenaria ) eradication in southern New Zealand (Doughboy Bay, Stewart Island) is examined. Four metrics: bare sand area, patch adjacency, complexity, and the range of proximity, are used to classify a series of foredune textures beginning with the pre-restoration state through the phases of marram removal, to the current state. Foredune texture at Doughboy Bay has evolved from a semi-stable to an active state as the consequence of restoration. Two metrics, bare sand and adjacency, appear to be particularly good measures of change following marram removal. Patterns and rates of change for these metrics are consistent with ground observations of increased ‘naturalness’ (native plant communities, sand mobility) over the same period. The set of landscape metrics derived for Doughboy Bay were compared to similar sets measured for a nearby foredune system where marram invasion has not occurred, and where conditions presumably represent equilibrium foredune texture. Since the removal of marram at Doughboy Bay and the consequent remobilization of the sand surface, the foredune texture has increased in similarity to that of the reference site, indicating a favourable shift in plant cover as a result of the restoration program. We conclude that landscape metrics can be used to track changes in foredune morphology following restoration. Second, the planning, management, and monitoring of coastal dune restoration programs will benefit by the routine use of reference sites to evaluate the appropriateness and success of restoration actions.

This paper reviews literature on the aerodynamics and morphodynamics of sand fences. We consider both wind fences for reducing wind erosion, and sand-trapping fences for controlling sand deposition. There has been substantial trial-and-error research based upon installations of sand fences, but only limited research on the fence and site attributes that provide the main aerodynamic and morphodynamic controls of interactions between aeolian systems and the fences. Such attributes include: fence porosity, height, length, width, opening size and geometry, porosity distribution, and external factors such as incoming flow characteristics, roughness length, atmospheric stability, grain size and local landform change. Considerations for the optimal design for both wind fences and sand-trapping fences are presented.

The fall velocity of natural sand grains is a fundamental attribute of sediment transport in fluid environments where particles may become partially or fully suspended. Several formulae have been proposed to calculate the fall velocity of particles in air, but there is considerable uncertainty about which is the most accurate or appropriate for a given set of environmental conditions. Five experiments that reported observations of fall velocity of different types of particles in air are described, evaluated, and compared. The experiment data were quality-controlled using four criteria: (1) particles had to have sufficient drop heights to attain their terminal fall velocity; (2) particles had to be in the range of sand sizes; (3) data identified as being problematic by the original authors were removed; and (4) particles comprise natural, irregular shaped sediments. The quality-controlled data were aggregated and analyzed using linear regression to obtain a relationship between grain size ( d, in mm) and fall velocity ( w0, in ms-1): [Formula: see text]. This is a statistically strong relationship with a coefficient of determination of 0.89 ( p < 0.001). This relationship can be regarded as a universal fall velocity model for natural, sand-sized particles falling through a static column of air. In terms of predictive analyses, our heuristic method outperforms alternative formulae and yields a better fit to the experimental data over the full range of sand sizes.

Coastal dunes are sensitive ecosystems because of their location at the juncture of terrestrial, marine, and atmospheric environments. This is especially the case for foredunes and the vegetation they support. Considerable attention is paid to the characteristics of foredunes and dune vegetation, but there has been no systematic study of patterns of bare sand on foredune surfaces—foredune textures—and the climate variables controlling those patterns. We used landscape metrics to quantify foredune textures for twenty-two coastal locations in the contiguous United States and cluster analysis to classify textures using those metrics. Four types of texture were identified: (1) active, where bare sand averages more than 80 percent of the dune surface and sand patches are close together; (2) composite, with about 50 percent bare sand area and sand patches that are close together and of minimal complexity; (3) aggregated, where bare sand is about 23 percent of the surface and the sand patches are moderately adja...

We present a design for an aeolian sand trap that is based on the streamer trap concept used in sediment transport studies. The trap is inexpensive, has excellent trapping efficiency, is durable, and easy to use. It is fabricated from stainless steel that is cut and bent to form a frame to support a fine nylon mesh. Typical trap openings are 100 mm wide and 25, 50, or 100 mm high. Traps are 250 mm long, and are stackable to measure vertical characteristics of saltation. The nylon mesh has 64 μm openings that comprise 47% of the area of the material. Aerodynamic efficiency was tested in a wind tunnel, and sediment trapping efficiency evaluated in field deployments. Both evaluations support the use of this trap for short-term measurements.

Li, B., Ellis, J. T., Sherman, D. J., 2014. Estimating the Impact Threshold for Wind-Blown Sand. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 627–632, ISSN 0749-0208. In many aeolian studies, it is commonplace to use Bagnold's (1936) equation to calculate threshold shear velocity (u*t), which includes an empirical constant, A, typically set at about 0.082 for maintaining saltation (the dynamic, or impact, threshold). Here, we present data from a pilot study to assess the variability of A to improve estimations of u*t, which in turn, should improve transport rate predictions. Using field data from three coastal environments, we measured or calculated all parameters within the Lettau and Lettau (1978) model and u*t equation. In Jericoacoara, Brazil (BRA), Inch, Ireland (IRE), and Esposende, Portugal (POR) wind velocities were measured with cup anemometer towers and transport...

This paper describes a bedload trap designed to separate bedload from saltation load in aeolian environments. The trap is installed below the sand surface and features a chimney that can be adjusted to the height of the surface. The chimney houses an internal wall to separate saltation load from bedload. Bedload particles are funneled to a piezo-electric sensor that converts grain impacts to voltages that can be sampled at very high frequencies (44,000 Hz in this example). Grains are then collected in a container that is easily retrieved so that sand samples can be obtained for weighing and subsequent grain size analysis. An algorithm to isolate single grain impacts is described. The version of the trap presented here is intended for the study of the initiation of grain motion.

Aeolian streamers are common in prototype saltation systems. Streamers are elongate, flow-aligned features within which the concentrations of saltating grains are large relative to a spanwise average concentration. The occurrence of streamers introduces substantial spatial and temporal variability in local sand transport rates. There have been few studies to attempt to characterize the scales of streamers, and the results of those studies have been constrained because they use Eulerian approaches to measure an inherently Lagrangian process. We describe the results from a field experiment designed to address this methodological problem. Field experiments were conducted at Jericoacoara, Ceará, Brazil, in October, 2011. The wind field was measured with ultrasonic anemometers and ruggedized thermal probes. Transport rates were measured using Miniphones, Wenglor Particle Counters, and hose traps. A set of three video cameras, deployed in a triangular array, was used to capture images of streamers. The field of vision for the central, upwind-facing camera was a minimum of about 15 m, expanding to more than 100 m in the middle distance. Video images were time-averaged over a number of intervals, ranging from 1-64 seconds, to establish characteristic path lengths and spatial and temporal scales. The results of these analyses show that this methodological approach is technically sound. Streamer characteristics are center-to-center spacings of about 1 m, length-scales exceeding 50 m and time scales of individual streamers exceeding 64 s. © Coastal Education & Research Foundation 2013.

Farrell, E.J. and Sherman, D.J., 2013. Estimates of the Schmidt Number for vertical flux distributions of wind-blown sand. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.) From studies of suspended sediments in water or dust in air it is recognized that the Rouse profile represents a theoretically sound, first approximation of characteristic sediment concentration gradients. Rouse (1938) combined the influence of grain size and shear velocity changes into a universal equation. The Rouse number relates sediment size (in the form of settling velocity, w0) to shear velocity, the von Karman constant (0.4) and the Schmidt Number, typically assumed to be equal to 1.0 but with much larger values reported. The shape of the Rouse concentration profile is controlled by the Rouse number exponent. We applied the Rouse profile model to 14 vertical flux profiles of wind-blown sand measured during a field experiment in Jericoacoara, Brazil in 2008. These data were supplemented with 96 vert...

Grain size-sorting characteristics from twenty-five vertical, mass-flux profiles for a mixed grain population are presented from a field study conducted in Jericoacoara, Brazil. The vertical mass flux profile is best described using an exponential decay function. An analysis of the grain-size statistics shows that a reverse in grain-size trends occurs at an inflection zone located 0.05–0.15 m above the bed. Below this inflection, mean grain-size decreases steeply with elevation in the near bed region dominated by reptation and saltation modes of transport. Above the inflection there is a coarsening of grain size with elevation. Sorting improves with elevation above the surface. There is not a strong relationship between skewness and kurtosis with elevation. The grain-size inflection above the surface is a characteristic of saltation in some natural environments, with important implications for numerical modeling of grain trajectories.

A quality-controlled data set comprising measurements of aeolian sand transport rates obtained at three disparate field sites is used to evaluate six commonly employed transport rate models (those of Bagnold, Kawamura, Zingg, Owen, Hsu, and Lettau and Lettau) and to recalibrate the empirical constants in those models. Shear velocity estimates were obtained using the von Karman constant and an apparent von Karman parameter. Models were recalibrated using non-linear regression and non-linear regression with least-squares lines forced through axes origins. Recalibration using the apparent von Karman parameter and forced regression reduced the empirical constants for all models. The disparity between the predictions from the different models is reduced from about an order of magnitude to about a quarter of an order of magnitude. The recalibrated Lettau and Lettau model provided the greatest statistical agreement between observed and predicted transport rates, with a coefficient of determination of 0·77. Evaluation of the results suggests that our estimations of threshold shear velocity may be too slow, causing errors in predicted transport rates. Copyright © 2012 John Wiley & Sons, Ltd.

Horizontal variability is often cited as one source of disparity between observed and predicted rates of aeolian mass flux, but few studies have quantified the magnitude of this variability. Two field projects were conducted to evaluate meter-scale spatial and temporal in the saltation field. In Shoalhaven Heads, NSW, Australia a horizontal array of passive-style sand traps were deployed on a beach for 600 or 1200 s across a horizontal span of 0.80 m. In Jericoacoara, Brazil, traps spanning 4 m were deployed for 180 and 240 s. Five saltation sensors (miniphones) spaced 1 m apart were also deployed at Jericoacoara. Spatial variation in aeolian transport rates over small spatial and short temporal scales was substantial. The measured transport rates ( Q ) obtained from the passive traps ranged from 0.70 to 32.63 g/m/s. When considering all traps, the coefficient of variation ( CoV ) values ranged from 16.6% to 67.8%, and minimum and maximum range of variation coefficient ( RVC ) values were 106.1% to 152.5% and 75.1% to 90.8%, respectively. The miniphone Q and CoV averaged 47.1% and 4.1% for the 1260 s data series, which was subsequently sub-sampled at 60–630 s intervals to simulate shorter deployment times. A statistically significant ( p CoV and between Q and CoV , the latter relationship also considering data from previous studies.

Eight aeolian sand-transport models are evaluated using a field data set and a new approach to estimating shear velocity. The models are those of Bagnold, 1937 , Kawamura, 1951 , Zingg, 1953 , Owen, 1964 , Kadib, 1965 , Hsu, 1971 , Lettau and Lettau, 1978 , Sorensen, 2004 . All of these models predict transport as a function of shear velocity to the third power. Shear velocities are estimated using wind profile data (log-linear slope) with the von Karman constant and with the apparent von Karman parameter and the results of the different approaches are evaluated based on comparison of regression statistics and RMS error. The models were not adjusted to account for sediment moisture content or local surface slope effects. All of the models have about the same statistical explanatory power, so evaluations were made by comparing slopes and intercepts of best fit (least-squares) lines and RMSE. From this basis, we conclude that predictions made with the Bagnold (1937) model best match our observations, with the models of Kadib, 1965 , Hsu, 1971 performing nearly as well. The Lettau and Lettau, 1978 , Kawamura, 1951 model predictions match observations least.

We report the results of field experiments designed to compare four types of aeolian saltation sensors: the Safire; the Wenglor® Particle Counter; the Miniphone; and the Buzzer Disc. Sets of sensors were deployed in tight spatial arrays and sampled at rates as fast as 20 kHz. In two of the three trials, the data from the sensors are compared to data obtained from sand traps. The Miniphone and the Buzzer Disc, based on microphone and piezoelectric technologies, respectively, produced grain impact counts comparable to those derived from the trap data. The Safire and the Wenglor® Particle Counter produce count rates that were an order of magnitude too slow. Safires undercount because of their large momentum threshold and because its signal is saturated at relatively slow transport rates. We conclude that the Miniphone and the Buzzer Disc are appropriate for deployment as grain counters because their small size allows them to be installed in closely-spaced sets.

This paper presents algorithmic components and corresponding software routines for extracting shoreline features from remote sensing imagery and LiDAR data. Conceptually, shoreline features are treated as boundary lines between land objects and water objects. Numerical algorithms have been identified and de-vised to segment and classify remote sensing imagery and LiDAR data into land and water pixels, to form and enhance land and water objects, and to trace and vectorize the boundaries between land and water ob-jects as shoreline features. A contouring routine is developed as an alternative method for extracting shore-line features from LiDAR data. While most of numerical algorithms are implemented using C++ program-ming language, some algorithms use available functions of ArcObjects in ArcGIS. Based on VB .NET and ArcObjects programming, a graphical user’s interface has been developed to integrate and organize shoreline extraction routines into a software package. This product represents the first comprehensive software tool dedicated for extracting shorelines from remotely sensed data. Radarsat SAR image, QuickBird multispectral image, and airborne LiDAR data have been used to demonstrate how these software routines can be utilized and combined to extract shoreline features from different types of input data sources: panchromatic or single band imagery, color or multi-spectral image, and LiDAR elevation data. Our software package is freely available for the public through the internet.

The centennial volume of Geographical Review marks a distinct milestone for the discipline of geography in North America. Great editorial leadership, landmark articles, recognition as a flagship journal: all traditions tagged to the Geographical Review. It has been my privilege, as a member of the Editorial Board, to have been part of that enterprise for most of the last quarter-century. I have worked with inspirational editors--Doug McManis (still my favorite, with apologies to), Paul Starrs, Douglas Johnson and Viola Haarmann, and Craig Colten--and learned much from them. But, a la Christopher Keylock (2007), I already knew the difference between "whither" and "wither." Many of the legendary physical geographers and several leading geologists of the twentieth century published in the Geographical Review. The honor roll includes such luminaries as William Morris Davis (both in the Geographical Review and in its predecessor, the Bulletin of the American Geographical Society; see, for example, Davis 1919, 1934), Harlan Bretz (1928), Richard Joel Russell (Russell and Howe 1935), John Hack (1941), Warren Thornthwaite (1948), Luna Leopold (1951), and Kenneth Hare (Hare and Ritchie 1972). However, the work of physical geographers, as the central focus of a research article, has been virtually missing from the pages of the Geographical Review for the last several decades. By my quick count, using titles or abstracts, only 19 of the 382 articles in volumes 86-99 (1986-2009) are on physical geography. Surprisingly, even in the special issue on "Doing Fieldwork" (DeLyser and Starrs 2001), only one of the fifty-six essays deals primarily with physical geography. Slightly more contributions by physical geographers appeared in the mid-1980s and early 1990s, as Doug McManis supported a thematic issue on "Coastal Geomorphology" in 1988 and a short-lived series of essays on philosophy and concepts in physical geography (Sherman 1988; see, for example, Nordstrom 1993). And for most of the last twenty-five years only one or two physical geographers at a time have served on the Editorial Board, which currently comprises thirteen members, not including the editor, the two associate editors, and the book review editor, all of whom are human geographers. So the modern circumstance raises several questions that I will attempt to address here: Was there once a stronger presence of physical geography in the Geographical Review? If so, why has that presence waned? And what might the answers to the preceding questions portend for the journal's future? Much of the change of content in the pages of the Geographical Review is reflected from larger disciplinary forces that altered the landscape of North American geography through the mid-twentieth century. This stems from the disciplinary autophobia espoused by Richard Hartshorne in 1939 under the guise of chorography and regional geography (neatly, but unfortunately not fatally, taken to task in Sauer 1956, 294-295). The decades-long focus on regionalism did great damage to the discipline as a whole (see, for example, Hartshorne 1962), but it dramatically undermined physical geography in general and geomorphology in particular (Butzer 1989). For instance, Hartshorne rejected the study of geomorphological processes as being nongeographical ([1939] 1961, 423-424), and many geography departments in the United States endorsed that rejection via their hiring policies. Therefore, that part of the physical geography community that might have been especially well poised to exploit the quantitative revolution was largely absent from academic geography. It is noteworthy that Hartshorne considered both climatology and biogeography--plant geography in the original--to be safely in the realm of his systematic geography ([1939] 1961, 78-79). Nevertheless, the middle of the twentieth century must be considered a dark period for physical geography in general. Certainly there was a marked distinction in the content of academic geography journals, including the Geographical Review and the Annals of the Association of American Geographers, as physical geography appeared less and less often in their pages. …

We analyzed the HadCRUT3 reconstruction of the instrumental global temperature record for 1850 through 2008 to decompose thirty-year temperature trends into signal and noise components. The signal ...

This paper describes a protocol for characterizing and analyzing the vertical mass-flux profiles above erodible beds in natural aeolian environments. Three main areas of methodological inconsistencies are explored, using two field data sets, to demonstrate the variability of results caused by methodological choices associated with: (1) inconsistent representation of sediment trap elevations; (2) erroneous or sub-optimal regression analysis; and (3) inadequate or ambiguous bed elevation measurements. The recommended methodology is physically based, produces results that most closely represent the measured data, and will permit results from different field and laboratory studies to be compared using a standardized convention. The recommended protocol suggests the following: (1) measure vertical flux profiles with as many traps as feasible with shorter traps near the bed; (2) measure bed elevation before, during, and after data collection; (3) use the geometric mean to represent trap centers; (4) use the saltation-enhanced aerodynamic roughness length when approximating the bottom elevation of traps deployed at the bed (0 mm); (5) plot vertical mass-flux data with height above the bed as the independent variable; and (6) fit vertical mass-flux curves using non-linear, exponential curve fitting.

Photo-Electronic Erosion Pins (PEEPs) can be used to measure short-term fluctuations in swash zone (foreshore) profiles. Because the sensors depend upon ambient light for the detection of bed elevation change, their signal indicates false changes during swash inundation. A method is presented to mitigate this source of noise and to allow a reconstruction of bed changes at swash frequencies. The protocol is illustrated with a sample data set.

This research presents a segmentation-based, image processing method to automate the extraction of tidal datum referenced shorelines from airborne light detection and ranging (LIDAR) data. The method first segments a LIDAR digital elevation model (DEM) into a binary image, consisting of land and water pixels, by intersecting the LIDAR DEM and the tidal datum surface. A chain of image processing algorithms, including region grouping and labeling, two passes of image region scanning, a mathematical morphology operation, line tracing, and vectorization, is sequentially applied to the segmented binary image. Our applications to the upper Texas gulf coast show that the method is efficient, accurate, objective, and replicable. Spatially detailed shorelines can be derived from the LIDAR data with minimal human intervention. The method is a substantial technical improvement over standard cross-shore profile and contouring methods. We also examine and quantify the effects of vertical measurement error of ...

Acoustic sensors are frequently used to measure aeolian saltation. Different approaches are used to process the signals from these instruments. The goal of this paper is to describe and discuss a method to measure aeolian saltation with acoustic sensors. In a laboratory experiment, we measured the output from an advanced signal processing scheme on the circuit board of the saltiphone. We use a software implementation of this processing scheme to re-analyse data from four miniphones obtained during a field experiment. It is shown that a set of filters remove background noise outside the frequency spectrum of aeolian saltation (at 8 kHz), whereas signals within this frequency spectrum are amplified. The resulting analogue signal is a proxy of the energy. Using an AC pulse convertor, this signal can be converted into a digital and analogue count signal or an analogue energy signal, using a rectifier and integrator. Spatio-temporal correlation between field deployed miniphones increases by using longer integration times for signal processing. To quantify aeolian grain impact, it is suggested to use the analogue energy output, as this mode is able to detect changes in frequency and amplitude. The analogue and digital count signals are able to detect an increase in frequency, but are not able to detect an increase in signal amplitude. We propose a two-stage calibration scheme consisting of (1) a factory calibration, to set the frequency spectrum of the sensor and (2) a standardized drop-test conducted before and after the experiment to evaluate the response of the sensor.

This chapter introduces the Sea and Ocean Hazards, Risks, and Disasters volume in the Hazards and Disasters series. The chapters in this volume summarize numerous aspects of our knowledge of a suite of coastal and marine hazards and disasters. A common theme is the persistence and increase of the global threat to coastal populations driven by environmental change and continued population growth. Here, coastal hazards are organized according to two main themes: threats to human systems (mainly) from the geophysical hazards such as tsunami, storm surge, sea ice, sea level rise, shoreline change, rip currents, and threats to humans and loss of ecosystem services caused by biological/ecological systems such as mangroves, corals, marshes, and harmful algal blooms.

Journal article Sediment transport on the lee sides of aeolian dunes involves a combination of grain-fall deposition on the upper portion of the slip face until a critical angle is exceeded, transport of a portion of those sediments down the slip face by grain flows and, finally, deposition at an angle of repose. We measured the mean critical and repose angles and the rate of slip-face avalanching using terrestrial laser scanning (TLS) on two barchans of different size in Jericoacoara, Brazil. Wind speeds and sand fluxes were measured simultaneously at the dune crests. We found that the mean critical decreased with increasing wind speed. We attribute this effect to turbulent shear stresses, the magnitude of which we quantified using 3-D large eddy simulation modeling, that randomly act down the slip face (i.e., in the direction of gravity) to trigger grain flows at lower angles than would be possible with gravity stresses alone. We developed and tested a new predictive model for the frequency of avalanching that depends on both the sediment flux delivered to the slip face and changes in the critical angle with time. In this model, increasing turbulent shear stresses drive avalanching even in the absence of sand flux delivered to the slip face if the critical angle decreases below the slope angle. We also document that the mean critical angle decreases slightly with increasing slip-face height. These results have important implications for aeolian dune evolution, interpretations of aeolian stratigraphy, and granular mechanics. NSF peer-reviewed

Aeolian sand transport on beaches and in dune environments shows a great spatial and temporal variability that has important implications for modeling and monitoring of coastal systems. Yet there have been few quantifications or statistical characteristics of transport variability in natural environments. Transport variability can result from bed surface control in the form of differentiation in grain size, surface moisture, and microtopography, or can be induced by fluid forcing in the form of gusts, burst-sweep events, and streamwise vortices. A field experiment was conducted on a coastal dune near Guadalupe, California, to quantify transport variability over spatial scales of 0.1–4.0 m and temporal scales of 1–120 seconds. Results show that spanwise (lateral) variability increases with spatial scale and decreases with temporal scale. Minimum transport variability over the smallest distances and longest time scales is on the order of 30%, providing error margins for transportrate measurements a...

Sediment transport across a foredune and beach at Ocean City, New Jersey, was examined to identify the effect of houses, dune topography, sand fences, vegetation, and wrack lines during an offshore wind. Houses are as close as 18 m from the crest of the 2- to 3-m-high foredune and are up to 9.0 m high and 12.8 m wide and spaced 4.0 to 5.0 m apart. Data were gathered during a 1-day study on 3 March 2003 with the use of 15 vertical sand traps, 13 erosion pins, and eight sets of anemometers placed 0.3, 0.6, and 0.9 m above the ground surface. Wind speeds 0.9 m above the ground ranged from 1.61 to 3.75 m/s. Trapping rates were negligible on the vegetated dune crest and up to 2.03 kg m−1 h−1 near mid foreshore. The highest rate of trapping was 2.4 kg m−1 h−1 at a

Much of America's coastline is threatened by overdevelopment and coastal erosion, driven by global sea-level rise, a problem that is attracting the attention of researchers around the world. Although we have now acknowledged the impending risks, little is known about the response of spatially dependent dune plant communities to the loss or restriction of their habitat. In order to study this development, a spatially explicit model of sand dune plant succession on Galveston Island, Texas, was created, using sea-level rise as the primary mechanism causing local erosion. Simulations of sea-level rise scenarios developed by the Intergovernmental Panel on Climate Change demonstrated that beach erosion constrained plants to a narrow area, resulting in a breakdown of the successional process. The loss of late-succession plants along coastlines, their dependent faunal species, and possible solutions are discussed. This model and example serves as a harbinger of the future for many of the US's sandy beaches and co...

Recent investigations of aeolian transport have focused on increasingly short time scales because of growing recognition that wind unsteadiness is a major factor in the dynamics of sediment transport. However, the statistical reliability of shear velocity ( u * ) estimates becomes increasingly uncertain as averaging interval is decreased. This study provides an empirical assessment of the influence of averaging interval on the reliability of u * estimates. The data consist of 15-min wind-speed profiles (1 Hz sampling) collected at four coastal sites. Each profile was subdivided into progressively shorter fixed-length time intervals, and estimates of u * and the 95% confidence interval for u * were determined for each time-block using standard statistical techniques. The logarithmic model accurately represents the measured wind-speed profiles, even with relatively brief averaging intervals. Mean r 2 values remain robust down to block lengths as short as 10–20 s, typically retaining better than 98% of the r 2 value found for the full-length data sets. Fewer than 2% of the individual 10-s blocks had r 2 values less than 0.9. However, mean confidence intervals typically expanded by 70–80% of the full-record value as block length decreased from 900 to 10 s. For highly log-linear profiles, this amounted to an absolute increase from about ±8% to only ±14% of u * , so that the additional information gained through the use of shorter averaging intervals may outweigh the increase in statistical uncertainty. Nevertheless, given that rates of aeolian transport are generally modeled as a function of u * 3 , this increase in uncertainty may be significant for transport modeling. Thus, very short averaging intervals should be used with caution when predicting aeolian sediment flux. It is proposed that transport modeling should incorporate the shear velocity confidence interval as an indicator of the potential error associated with this source of uncertainty.