The use of video imagery to analyse groundwater and shoreline dynamics on a dissipative beach

Groundwater seepage is known to influence beach erosion and accretion processes. However, field measurements of the variation of the groundwater seepage line (GWSL) and the vertical elevation difference between the GWSL and the shoreline are limited. We developed a methodology to extract the temporal variability of the shoreline and the wet-dry boundary using video imagery, with the overarching aim to examine elevation differences between the wet-dry boundary and the shoreline position in relation to rainfall and wave characteristics, during a tidal cycle. The wet-dry boundary was detected from 10-minute time-averaged images collected at Ngaranui Beach, Raglan, New Zealand. An algorithm discriminated between the dry and wet cells using a threshold related to the maximum of the red, green and blue intensities in Hue-Saturation-Value. Field measurements showed this corresponded to the location where the watertable was within 2 cm of the beachface surface. Timestacks, time series of pixels extracted from cross-shore transects in the video imagery, were used to determine the location of the shoreline by manually digitizing the maximum run-up and minimum run-down location for each swash cycle, and averaging the result. In our test data set of 14 days covering a range of wave and rainfall conditions, we found 6 days when the elevation difference between the wet-dry boundary and the shoreline remained approximately constant during the tidal cycle. For these days, the wet-dry boundary corresponded to the upper limit of the swash zone. On the other 8 days, the wet-dry boundary and the shoreline decoupled with falling tide, leading to elevation differences of up to 2.5 m at low tide. Elevation differences between the GWSL and the shoreline at low-tide were particularly large when the cumulative rainfall in the preceding month was greater than 200 mm. This research shows that the wet-dry boundary (such as often used in video shoreline-finding algorithms) is related to groundwater seepage on low-sloped, medium to fine sand beaches such as Ngaranui Beach (mean grain size~0.27 mm, beach slope ~1:70) and may not be a good indicator of the position of the shoreline

Инновационный фактор совершенствования внешнеэкономической деятельности предприятий Украины: теоретический аспект

Infragravity waves (0.005–0.05 Hz) have recently been observed to dissipate a large part of their energy in the short-wave (0.05–1 Hz) surf zone, however, the underlying mechanism is not well understood. Here, we analyse two new field data sets of near-bed pressure and velocity at up to 13 cross-shore locations in View the MathML source depth on a ≈1:80 and a ≈1:30 sloping beach to quantify infragravity-wave dissipation close to the shoreline and to identify the underlying dissipation mechanism. A frequency-domain Complex Eigenfunction analysis demonstrated that infragravity-wave dissipation was frequency dependent. Infragravity waves with a frequency larger than View the MathML source were predominantly onshore progressive, indicative of strong dissipation of the incoming infragravity waves. Instead, waves with a lower frequency showed the classic picture of cross-shore standing waves with minimal dissipation. Bulk infragravity reflection coefficients at the shallowest position (water depth View the MathML source) were well below 1 (≈0.20), implying that considerable dissipation took place close to the shoreline. We hypothesise that for our data sets infragravity-wave breaking is the dominant dissipation mechanism close to the shoreline, because the reflection coefficient depends on a normalised bed slope, with the higher infragravity frequencies in the mild-sloping regime where breaking is known to dominate dissipation. Additional numerical modelling indicates that, close to the shoreline of a 1:80 beach, bottom friction contributes to infragravity-wave dissipation to a limited extent, but that non-linear transfer of infragravity energy back to sea–swell frequencies is unimportant

Проблеми структурної модернізації регіонального ринку трудових ресурсів АПК в експертній оцінці працівників органів регіонального управління

Barriers and sandbars are ubiquitous natural coastal features, whose variability often determines nearshore morphological evolution. Wave-dominated beach profile evolution results from the interaction between wave non-linearities, wave-breaking induced turbulence, undertow, infragravity motions and swash processes. To explore each of these contributions to the sediment transport, the full-scale Barrier Dynamics Experiment (BARDEX II), performed in the Delta Flume in June 2012, provides a new dataset for the rigorous testing of the performance of beach profile evolution models in the case of steep beaches. This new experiment will improve our knowledge on (1) swash zone processes, including infiltration and exfiltration of water into the sand and subsequent groundwater table response, (2) bore-generated turbulence inducing suspend sediment transport, (3) surfzone sandbar dynamics and (4) overtopping/overwash impact on barrier dynamics. This study aims at testing the ability of the process-based beach profile model 1DBeach in the case of a steep beachface and a predominance of plunging breakers. In this context, we tested the model with a morphological sequence characterised by onshore and subsequent rapid offshore sandbar migration for time-invariant wave forcing and falling tide. A simulated annealing algorithm is used to calibrate the model. In this paper, we discuss the model configuration and associated results, as well as the need of intensive high-frequency full-scale data to further develop and improve process-based models

Observations on decadal sandbar behaviour along a large-scale curved shoreline

Nearshore sandbars are characteristic features of sandy surf zones and have been observed with a variety of geometries in cross-shore (e.g. location) and longshore direction (e.g. planform). Although the behaviour of sandbars has been studied extensively on spatial scales up to kilometres and timescales up to years, it remains challenging to observe and explain their behaviour on larger spatial and temporal scales, especially in locations where coastline curvature can be prominent. In this paper, we study a data set with 38 years of coastal profiles, collected with alongshore intervals of 50 m, along the 34 km-long curved sandy shoreline of Sylt island, Germany. Sylt's shoreline has an orientation difference of ~20° between the northern and southern half of the island. We found that the decadal coastal profiles on the southern half show features of a low-tide terrace and a sandbar located further from the shoreline (~441 m). On the nothern half, the sandbar was located closer to the shoreline (~267 m) and was less pronounced, while the profiles show transverse bar and rip features. The alongshore planform also differed systematically and significantly along the two island sides. The sandbar on the southern island half, with alongshore periodicity on a larger length scale (~2240 m), was coupled out-of-phase to the shoreline, while no phase coupling was observed for the sandbar with periodicity on a shorter length scale (~670 m) on the northern half. We related the observed geometric differences of the sandbars to the difference in the local wave climate along Sylt, imposed by the shoreline shape. Our observations imply that small alongshore variations in wave climate, due to the increasing shoreline curvature on larger spatial scales, can lead to significant alongshore differences in the decadal evolution of coastal profiles, sandbars and shorelines. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Lt

Разработка модели эффективного управления винного туризма

Розглянуто перспективи розвитку винного туризму в АР Крим на базі створення спеціалізованих підприємств у сфері дегустаційного бізнесу і дана оцінка їх економічної ефективності.Рассмотрены перспективы развития винного туризма в АР Крым на базе создания специализированных предприятий в сфере дегустационного бизнеса и дана оценка их экономической эффективности.Outlook of development of testing tourism in the Crimea is studied. The possibility of creating enterprises in the sphere of testing tourism and estimate of economic effectiveness is described

Методические особенности управления туристскими потоками в регионе (на примере Автономной Республики Крым)

Экономическая жизнь, начиная от простых жителей сел и городов, до экономики полуострова в целом зависит от количества туристов, приехавших в Крым на отдых и лечениеЕкономічне життя, починаючи від простих мешканців сіл і міст, до економіки півострова в цілому залежить від кількості туристів, що приїхали до Криму на відпочинок і лікуванн

The effects of bedform roughness on hydrodynamics and sediment transport in Delft3D

To contribute to solving scientific and practical questions, numerical morphodynamic models like Delft3D are often used to predict the hydrodynamics, sediment transport processes and morphological development of coastal systems. In such models, many of the processes are parameterized based on a variety of assumptions. One of the parameterized variables is the bedform-related hydraulic roughness ks, which is often assumed to be related to the ripple height. This roughness affects the magnitude and vertical structure of the flow and, consequently, the magnitude of the sediment transport. Yet, their sensitivity to ks is not well understood

Characteristics and dynamics of crescentic bar events in an open, tideless beach

Crescentic bar events at Castelldefels beach (NW Mediterranean) have been characterised using a 4.25 years dataset (October 2010-December 2014) of time-exposure video images. Crescentic bars are observed during 41% of the study period, with an irregular distribution of the events in the different years. The crescentic bars have a lifetime that varies from 1 to over 100 days, a mean wavelength of 245 m and a mean amplitude of 9 m. The bars are observed in relatively low-energetic wave conditions with a wide variety of wave angles. The formation of crescentic bars also depends on the antecedent bathymetry, in particular crescentic bar events only occur when the sandbar is located at least at 50 m from the shoreline. Crescentic bar destruction at Castelldefels beach is observed in both low- and high energetic wave conditions, but the angle of incidence is always oblique.Peer ReviewedPostprint (published version

Observations of turbulence within a natural surf zone

Here, the Reynolds stresses and , where u′, v′, and w′ are the cross-shore, alongshore, and vertical turbulence velocities, respectively, and the angle brackets represent time averaging, are used to diagnose turbulence dynamics beneath natural breaking surf-zone waves. The data were collected at Truc Vert Beach, France, during a 12-day period in 1–3-m water depth with strong cross-shore and alongshore currents under high-energy wave conditions (offshore significant wave heights ranged between 2 and 8 m). The term is predominantly negative, increases with the ratio of wave height Hs to water depth h (degree of wave breaking), and decreases in magnitude toward the bed. This supports the view that the cross-shore shear stress is due to breaking-induced vortices that transport high-speed cross-shore flow downward and disintegrate close to the bed. The occasional positive sign of within the lower 15%–20% of the water column indicates that sometimes surface-generated turbulence is overwhelmed by bed-generated turbulence, but the conditions when this happens are not clear from the data. The term is persistently of opposite sign to the alongshore mean current and decreases with height above the seabed, implying that is due to bottom boundary layer processes rather than surface-generated turbulence. The bottom drag coefficient amounted to 1.6 × 10−3, similar to earlier observations. As in other high-Reynolds-number geophysical flows, time series of u′w′ and v′w′ comprise intermittently large, short-duration (here, 1 s) stress events that in the data contribute considerably to the net stress in only 3%–15% of the time. The data further show that the turbulent kinetic energy is depth uniform and increases with Hs/h. The depth-averaged Froude-scaled turbulent kinetic energy beneath surf-zone bores is 0.025, a factor of 2 to 3 less than observed beneath regular laboratory waves