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

High‐Energy Surf Zone Currents and Headland Rips at a Geologically Constrained Mesotidal Beach

International audienceWe analyze Eulerian and Lagrangian measurements of wave-induced circulation collected during a 3-week field experiment at a high-energy mesotidal barred beach with the presence of a 500-m headland and a submerged reef. Small changes in wave and tide conditions were found to largely impact circulation patterns. Three main regimes were identified depending on offshore wave obliquity: (1) Under shore-normal configuration, the flow was dominated by cross-shore motions, except for moderate waves at low tide, with the presence of a quasi-steady circulation cell on the reef. (2) Under shadowed configuration, an onshore-directed current flowing away from the headland and a weak oscillating eddy were present outside and inside the shadow region, respectively. (3) Under deflection configuration, a deflection rip flowing against the headland and extending well beyond the surf zone was present, with activity maximized around low tide for moderate waves. Under 4-m oblique waves, the deflection rip was active regardless of the tide with mean depth-averaged velocities up to 0.7 m/s 800-m offshore in 12-m depth, with energetic low-frequency fluctuations. Our results emphasize the ability of deflection rips to transport materials far offshore, suggesting that such rips can transport sediment beyond the depth of closure. This study indicates that a wide variety of wave-driven circulation patterns can occur and sometimes coexist on beaches with prominent geological settings. Changes in the dominant driving mechanism can occur as a result of small changes in wave and tide conditions, resulting in more spatially and temporally variable circulation than along open sandy beaches. Plain Language Summary Most field experiments about wave-induced circulation patterns have been conducted along open sandy beaches, while experiments in geologically constrained environments are scarce. We performed intensive field measurements at a high-energy beach with the presence of a 500-m headland and a submerged natural reef. Three main circulation patterns were identified depending on the offshore wave obliquity. For shore-normal waves, cross-shore motions dominated the nearshore region, while oblique wave configurations resulted in more complex horizontal circulation. In particular, under intense headland-directed longshore current, the flow was deflected seaward against the headland. This deflection resulted in an intense seaward flowing jet (deflection rip) extending well beyond the surf zone edge, particularly during storm conditions. Such findings highlight the ability of these deflection rips to dominate water and sediment exchanges between the nearshore and the inner shelf region. Our study further outlines the more spatially and temporally variable circulation patterns occurring along geologically constrained beaches compared to open sandy beaches, ranging from small recirculating cells across the reef to a large deflection rip extending hundreds of meters beyond the surf zone

Quantification of surface water volume changes in the Mackenzie Delta using satellite multi-mission data

Quantification of surface water storage in extensive floodplains and their dynamics are crucial for a better understanding of global hydrological and biogeochemical cycles. In this study, we present estimates of both surface water extent and storage combining multi-mission remotely sensed observations and their temporal evolution over more than 15 years in the Mackenzie Delta. The Mackenzie Delta is located in the northwest of Canada and is the second largest delta in the Arctic Ocean. The delta is frozen from October to May and the recurrent ice break-up provokes an increase in the river's flows. Thus, this phenomenon causes intensive floods along the delta every year, with dramatic environmental impacts. In this study, the dynamics of surface water extent and volume are analysed from 2000 to 2015 by combining multi-satellite information from MODIS multispectral images at 500 m spatial resolution and river stages derived from ERS-2 (1995–2003), ENVISAT (2002–2010) and SARAL (since 2013) altimetry data. The surface water extent (permanent water and flooded area) peaked in June with an area of 9600 km2 (±200 km2) on average, representing approximately 70 % of the delta's total surface.\ud Altimetry-based water levels exhibit annual amplitudes ranging from 4 m in the downstream part to more than 10 m in the upstream part of the Mackenzie Delta. A high overall correlation between the satellite-derived and in situ water heights (R > 0.84) is found for the three altimetry missions. Finally, using altimetry-based water levels and MODIS-derived surface water extents, maps of interpolated water heights over the surface water extents are produced. Results indicate a high variability of the water height magnitude that can reach 10 m compared to the lowest water height in the upstream part of the delta during the flood peak in June. Furthermore, the total surface water volume is estimated and shows an annual variation of approximately 8.5 km3 during the whole study period, with a maximum of 14.4 km3 observed in 2006. The good agreement between the total surface water volume retrievals and in situ river discharges (R =  0.66) allows for validation of this innovative multi-mission approach and highlights the high potential to study the surface water extent dynamics

Field Observations of Wave-induced Headland Rips

Mouragues, A.; Bonneton, P.; Castelle, B.; Marieu, V.; Barrett, A.; Bonneton, N.; Detand, G.; Martins, K.; McCarroll, J.; Morichon, D.; Poate, T.; Rodriguez Padilla, I.; Scott, T., and Sous, D., 2020. Field observations of wave-induced headland rips. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 578-582. Coconut Creek (Florida), ISSN 0749-0208. Most of rip-current field experiments have focused on persistent rips along rip-channeled sandy beaches or transient rips along reasonably alongshore-uniform surf-zone morphology, while experiments on rip flowing against structures are scarce. In October 2018, a 3-week field experiment was performed at Anglet beach, SW France, aiming at examining the dynamics of high-energy rip currents in complex settings. The beach is barred with prominent inherited geology, characterized by the presence of a 500-m headland and a natural submerged reef. A large array of in-situ instruments was deployed to capture the temporal and spatial variability of rip flow circulations, including ADCPs, surf-zone drifters and video monitoring. The latter allowed to identify a wide range of rip-flow patterns. Among these patterns, a high-intensity rip current flowing against the headland was a dominant feature for obliquely incident waves. Such a boundary rip current was driven by the deflection of the longshore current against the headland, peaking at 0.7 m/s (5-min time- and depth-averaged) 800-m offshore in 12-m depth for a moderate storm event with 4-m obliquely incident waves. Very-low-frequency (O(1h) and O(30min)) fluctuations of this rip current were observed around low tide. Measurements of the vertical structure of the rip reveal that the deflection rip was more vertically-sheared as the water depth increases, with higher velocities near the surface, which is typical of a theoretical rip head structure

Use of optical and radar data in synergy for mapping intertidal flats and coastal salt-marshes (Arcachon lagoon, France)

International audienceThis paper explores the potential of high-resolution spaceborne Synthetic Aperture Radar data for mapping intertidal coastal areas as a complement of high-resolution optical imagery (e.g. SPOT, Formosat-2). Classification algorithms based on optical imagery alone fail to accurately discriminate a series of relevant habitats, in particular seabeds of benthic fauna (oysters), low-density Zostera noltii seabeds and salt-marsh vegetation species. Firstly, the paper addresses the benefits from TerraSAR-X data by investigating SAR signatures over intertidal wetlands which have been poorly described in the literature. Secondly, a supervised classification algorithm is run based on the fused SAR-optical bands. A statement of the mapping performance is finally carried out using field observations

Use of optical and radar data in synergy for mapping intertidal flats and coastal salt-marshes (Arcachon lagoon, France)

International audienceThis paper explores the potential of high-resolution spaceborne Synthetic Aperture Radar data for mapping intertidal coastal areas as a complement of high-resolution optical imagery (e.g. SPOT, Formosat-2). Classification algorithms based on optical imagery alone fail to accurately discriminate a series of relevant habitats, in particular seabeds of benthic fauna (oysters), low-density Zostera noltii seabeds and salt-marsh vegetation species. Firstly, the paper addresses the benefits from TerraSAR-X data by investigating SAR signatures over intertidal wetlands which have been poorly described in the literature. Secondly, a supervised classification algorithm is run based on the fused SAR-optical bands. A statement of the mapping performance is finally carried out using field observations

Mapping coastal habitats over the Arcachon Lagoon using high-resolution optical and SAR

International audienceThis study explores the potential of high-resolution spaceborne Synthetic Aperture Radar data for mapping intertidal coastal areas as a complement of high-resolution optical imagery (e.g. SPOT, Formosat-2). Classification algorithms based on optical imagery alone fail to accurately discriminate a series of relevant habitats, in particular seabeds of benthic fauna (oysters), low-density Zostera noltii seabed and salt-marsh vegetation species. Firstly, the benefits from TerraSAR-X data by investigating SAR signatures over intertidal wetlands which have been poorly described in the literature were addressed. Secondly, a supervised classification algorithm is run based on the fused SAR-optical bands. A statement of the mapping performance is finally carried out using field observations

High resolution optical and radar data for mapping intertidal flats and salt marshes

International audienceThe main objective of this study is to define relevant data to improve land-cover maps of the Arcachon bay. With this aim, the authors introduce the use of radar data by assessing their potential for mapping intertidal flats and salt-marshes. In addition, the potential of using images acquired at different seasons is evaluated in order to derive the wavebands useful to test a multi-temporal classification strategy. For this purpose, hyperspectral field measurements carried out seasonally are analyzed. Then, the most discriminating SAR and optical wavebands are concatenated and the resulting muti-sensor multi-temporal composite images are classified. The validation of the resulting maps is performed on a regularly surveyed site. Image data selection, map production and validation are detailed in the present poster

Cartographie des habitats intertidaux du bassin d’Arcachon par imagerie optique et radar

National audienceObjectifs : - Exploitation en synergie de données radar et optiques ; - Discrimination, identification et cartographie exhaustive des substrats durs et meubles ainsi que des principales espèces végétales micro à macroscopiques ; - Quantification optique/radar de paramètres biologiques (composition, abondance spécifique, répartition surfacique) et sédimentaires (minéralogie, teneur en eau) ; - Validation d’une ou plusieurs stratégies de cartographie valorisables par des services GMES (Programme INFOLITTORAL-1, programme Territoire de Démonstration), implicitement adaptées aux exigences des missions de gestion des domaines naturels et exploités

Modélisation de l’évolution des profils de plage sableuse sur plusieurs mois et apports de l’assimilation de données

Dans ce papier nous présentons un nouveau modèle de profil de plage sableuse réalisant le couplage vagues/transport sédimentaire/évolution bathymétrique avec une approche à phase moyennée. Nous utilisons une paramétrisation récente des effets non-linéaires des vitesses orbitales des vagues au fond permettant d’améliorer les flux sédimentaires vers la côte. Nous validons le modèle numérique pour un cas de migration de barres sableuses vers le bord (Duck, Caroline du Nord) et vers le large (Egmond, Pays-Bas) sur une période de plusieurs jours. Nous montrons que le modèle reproduit avec fidélité l’évolution des profils mesurés en termes de migration et de morphologie, confirmée par des indices de performance (Brier skill) supérieures à 0.5 en fin de chaque simulation. Certaines limitations comme les erreurs en domaine intertidal sont discutées ainsi qu’un cas synthétique d’apport de l’assimilation de données. This paper presents the development of a simple coupled, wave-averaged, cross-shore waves-currents-bathymetry evolution model. A recent parameterization of the freestream nonlinear wave orbital motion is used to improve onshore sediment transport. We compare the model with data gathered at two natural beaches where sandbars move onshore (Duck) and offshore (Egmond) on the timescales of weeks. Reliable simulations of observed sandbar behavior (migration and shape) are obtained, despite mismatch at the upper part of the beach. Synthetic assimilation test cases are performed to overcome missing swash-processes, and are further discussed