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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): w0=4.248d+0.174. 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. [ABSTRACT FROM PUBLISHER]

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, w 0) to shear velocity, the von Kármán 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 vertical flux profiles obtained from fourteen wind tunnel and field experiments reported in the literature, for a total of 110 profiles. The analyses show that the performance of the Rouse model is not sensitive to changes in the range of variability we can expect to observe in values of fall velocity, shear velocity and the von Kármán constant but is very sensitive to changes in the values of the Schmidt number. First, the Rouse model was applied to vertical flux profiles using the common Schmidt number value of 1.0 in the Rouse number exponent. The model performed poorly in predicting the shape and magnitude of the vertical flux distributions (38% and 18% of the observed transport rate in field and wind tunnels, respectively). Alternative values were derived by adapting the profiles to equivalent concentration Rouse-type ratios and obtaining the slope values of the fitted power functions. With this approach, in field and wind tunnel experiments, the values of the Schmidt number ranged from 4.46 - 19.10 and 0.68 - 23.24, respectively, and predicted, on average, 82% and 90% of the observed transport rate. We tested a third method that does not require measuring vertical flux profiles. We found a strong relationship between the Schmidt number and a shear velocity - fall velocity ratio ( r 2= 0.65), with values ranging from 6.11 - 14.80 and 0.86 - 17.83, for field and wind tunnel experiments, respectively. These modified values of the Rouse exponents also resulted in vertical profiles that predicted similar distributions to the observed flux data and provide good predictions of the total transport rates (86% and 81% in field and wind tunnels experiments, respectively). To our knowledge, these are the first values of the Schmidt number derived for aeolian sand transport and the first successful application of the Rouse model to vertical flux profiles of saltation. [ABSTRACT FROM AUTHOR]

Estuarine beaches often lack well developed surf zones; incident waves break and convert directly to swash on the steep foreshore, resulting in greater influence of the swash zone in generating longshore flows and sediment transport. This study was conducted to evaluate longshore sediment transport in the swash zone of an eroding estuarine beach and relate transport rates to changes in beach position and volume downdrift of a shore-perpendicular structure. Field data were gathered on a sandy beach on the bay side of Fire Island, New York, USA in a short fetch (12–15 km) microtidal (mean range 0.21 m) environment. Wave and swash processes, beach changes and sediment tracer and trapping experiments were conducted during strong onshore winds in March and April 2012. Daily topographic surveys of the beach revealed pulses of sediment movement alongshore at small temporal (daily) and spatial (5 m) scales. The mid foreshore retreated 2.75 m from the beginning to the end of the 24 days of monitoring. This retreat was associated with a loss of 2.1 m 3 of sediment per meter of shoreline length. The greatest amount of foreshore retreat during a single storm event was 1.27 m, associated with a volume loss of 0.9 m 3 of sediment per meter. Mean wind speed on that day was 11.3 m s − 1 with a maximum of 18.2 m s − 1 ; significant offshore wave height at the time of maximum wind speed was 0.30 m. Mean significant wave heights ranged from 0.12 to 0.26 m during the five times when trapping occurred, resulting in mean longshore swash velocities of 0.08 to 0.23 m s − 1 and transport rates ranging from 0.413 to 1.516 m 3 h − 1 . The longshore sediment transport rates are similar to rates gathered under similar longshore current velocities on microtidal low energy beaches. Transport rates on beaches in sheltered environments can differ from rates calculated using existing formulas that may be more appropriate for high-energy beaches, where a greater proportion of sediment is transported in the surf zone than in the energetic swash zone under plunging breakers. Transport rates calculated from three existing formulae (Bagnold, 1963, CERC, 1984, Kamphuis, 2002) revealed that estimates from Bagnold compared most favorably with measured rates because of direct measurements of longshore current velocities. Rates of erosion on beaches in short fetch environments can be high despite low wave energies because the low, narrow beaches have little volume, magnifying the importance of seemingly low rates of transport in the swash. [ABSTRACT FROM AUTHOR]

Shoreline erosion is often exacerbated by reduction of sediment inputs because of interference with sediment transport by human structures. We evaluate use of sediment dredged from a navigation channel to establish a feeder beach adjacent to a bulkhead as a solution for addressing erosion of landforms and habitats on sandy estuarine shores. The objectives are to determine how beach volume, position and shape within and downdrift of the fill area change and whether the volumes supplied by dredging match sediment losses caused by human actions. The fill was placed along a 75 m length of shoreline adjacent to a marina in Great South Bay at Fire Island, New York, USA. Changes in beach shape and volume were determined from topographic surveys conducted before and after fill and at half year intervals for 18 months. The quantity of fill was 1747 m 3 . Maximum shoreline advance due to fill emplacement was 20.7 m. The maximum volume placed at any transect was 28.6 m 3 m − 1 of shoreline length. Erosion of the fill occurred rapidly, with landward migration of a conspicuous scarp. The edge of the upland 18 months after the fill was placed was up to 4.6 m farther landward than prior to the fill. Movement of sediment alongshore downdrift of the fill occurred as wave-like pulses, extending the active foreshore bayward, causing accretion of the inner low tide terrace, burying saltmarsh peat outcrops on the foreshore and creating a higher and wider overwash platform over portions of the saltmarshes. Landforms downdrift of the fill area underwent successive stages including erosion (pre-nourishment), accretion, stability (with throughput of sediment) and then erosion. Beach nourishment compensates for human-induced sediment losses. The volume of sediment added from maintenance dredging can slow the rate of erosion but may not prevent long-term shoreline retreat. Restoration and maintenance of coastal landforms and habitats to specific target states at a given location is difficult, but augmenting longshore sediment inputs can allow those locations to undergo cycles of erosion and accretion, creating a variety of landforms and habitats where only erosional forms existed previously. Alternatively, nourishment could occur more frequently and in smaller volumes to reduce fluctuations in accretion-erosion cycles. [ABSTRACT FROM AUTHOR]

One area where climate adaptation policies are proving difficult to design and implement is at the coast. On one hand, some of the most severe impacts of climate change are being recorded at the coast – especially through erosion and flooding – whilst on the other hand, these areas represent complex land-sea planning and policy interfaces. This paper analyses the coherency of policies along Ireland's coast from a climate adaptation perspective. Results suggest that many policies are developed in an ad-hoc fashion around the needs of single sectors. Improved policy coherence at all levels of governance is required to address this. [ABSTRACT FROM AUTHOR]

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 ratecs 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. [ABSTRACT FROM AUTHOR]

Sherman, D.J., Houser, C., Ellis, J.T., Farrell, E.J., Li, B., Davidson-Arnott, R.G.D., Baas, A.C.W., and Maia, L.P., 2013. Characterization of aeolian streamers using time-averaged videography. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.) 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. [ABSTRACT FROM AUTHOR]