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article de 13 p.; International audience; Maintenance operations in regulated rivers are often implemented as preventive measure to maintain wide, smooth channels and to limit the risk of flooding. By clearing vegetation, removing roots and lowering sediment bar elevation, these works can recreate pioneer habitats and related plant communities. Using a before-after-control-impact design with monitoring of riparian vegetation over 10 years, we evaluated the effects of fluvial maintenance works on plant richness and composition in an island complex located in a Nature Reserve along the Middle Loire River. Our results showed that artificial rejuvenation operations had a significant short-term negative effect on richness. However, in the few years following the work, the riparian communities established on the rejuvenated island became more diverse, with a large proportion of annual plants, contributing to the increased species pool of the Nature Reserve. In addition, we found that temporal changes in species richness were strongly influenced by hydrological conditions, with a peak in biodiversity observed during prolonged summer low water. This highlights the importance of considering flow variations to more accurately assess the ecological benefit of restoration operations on riparian vegetation. Overall, as successional stages were more advanced at the island complex scale, fluvial maintenance works have allowed the recreation of sandy pioneer habitats exposed to flooding. These habitats have promoted the establishment of species-rich communities without favoring the installation of invasive alien species. From this view, the maintenance works have increased the mosaic of habitats within the Nature Reserve and have restored environmental conditions favorable to early-successional species.

In a dynamic coastal environment, the morphology of a sandbar is anticipated to change regularly, particularly when there is a large annual sediment supply. The study explored the nature and magnitude of a developing sandbar’s morphological changes between 1972 and 2006 in Sonadia Island, Bangladesh, using five different satellite images. The sandbar’s changes across the shoreline were calculated using field survey data and manual-drawing outlines of overlaid maps. The study revealed continuous and rapid morphological changes of the sandbar along the Island’s shoreline. The net annual rate of shoreline displacement ranges between 3.94 m and 7.79 m during the period. These might directly result from the Island being exposed to huge wave and tidal action and excessive sediment supply around the Island. Transect 3 represents the sandbar’s head and appears to be the most active zone with the most significant annual shoreline displacement of 22.00 m. The sandbar’s far end around Transect 7 is more stable with a yearly shoreline displacement of 0.50 m. Changes were more drastic between 1999 and 2006 than between 1972 and 1999. These rapid changes after 1999 could indicate that the sandbar is becoming increasingly vulnerable to anthropogenic changes and the adverse effects of sea-level rise.

Formation of spawning redds for ayu fish can be affected by both environmental factors and morphological factors at spring water channel. Thus, regression analysis of presence of spawning redds and each factor allows for the identification of the underlying effects at both local and sandbar scales. To evaluate the directly or indirectly effects of water quality, physical variables, meso-scale riverbed configuration and sandbar variations on spawning redds, we examined the relationships between distribution of spawning redds and environmental factors. The logistic regression model indicated that the distribution of redds is affected by turbidity, velocity, depth, meso-scale rived parameters and several sandbar variation parameters but not affected by water temperature, number of channels and number of sandbar variations. Recognition of the distribution pattern of spawning redds at a sandbar scale at spring water channel may be useful to determine areas on which to focus both future river and reservoir sediment management strategies.

Field observations of small scale seabed morphology were obtained over 4 weeks at two locations separated 66 m along a cross-shore transect during the 2014 MEGAPEX Experiment conducted as part of the longer term Sand Engine mega-nourishment project along the North Sea Coast of The Netherlands. The seafloor was continuously covered by dynamic bedforms with amplitudes ranging 0.02–0.40 m and wavelengths ranging 0.20–2.5 m. Ripple migration rates were up to 3.6 m/h, dependent on the energy of the waves and currents. Under the assumption of bedload dominant transport, cross-shore and alongshore sediment volume flux by ripples was estimated from observations at the spatially separated imaging locations. The average and maximum ripple sediment volume flux was found to be 0.22 and 1.7 m3/m/day, respectively, with larger fluxes during spring flood tides and storm wave conditions. The daily averaged fluxes were usually oriented about 30° north of shore-normal, moving in the same direction as a nearby transverse sandbar migration direction. Estimated gradients in the sediment flux within the surfzone were computed from bed level change measurements of the inner surfzone including a larger scale transverse sandbar measured from subsequent jetski surveys. We find that the estimated gradients in surfzone sediment flux are conceivably driven by small variations in the sediment flux driven by sand ripple migration, supported by our observations of ripple driven sediment flux at the two ripple imaging stations. A simple conceptual model is presented that shows how small scale bedforms may contribute to the growth and decay of larger scale bathymetric features, such as sandbars. Results suggest that sediment flux by small scale sand ripples and megaripples could significantly contribute to larger scale morphologic development in the surfzone.

Sandbars are commonly observed on sandy coasts, and they can prevent erosion on the beach face. Better prediction of sandbar evolution is necessary for coastal management and beach nourishment. In this study, a process-based morphodynamic model is used to reproduce the barred beach profile evolution in the Duck94 field experiments. The importance of the wave roller slope parameter in the model is revisited. Six idealized numerical experiments are set to investigate the effect of wave heights, wave periods and sea levels on sandbar migrations. By implementing two recent cross-shore varying roller slope formulas, the models achieved fair-to-good performances. It was found that the variations of sandbar morphological evolution are mainly controlled by the cross-shore varying roller slope. An increase in the wave height or a decrease in the wave period would lead to a more rapid and further-offshore migration of the sandbar. When the sea level variations are much smaller than the water depth over the sandbar, the effect of sea level changes on the sandbar migration is negligible, though a lower sea level would cause more erosion on the beach face.

Artificial beach nourishment is one of the most important environmentally friendly coastal protection methods since it protects the aesthetic and recreational values of the beach and increases its protective properties. Therefore, the main aim of the current study is to assess the accuracy of multivariate adaptive regression splines (MARS) in predicting the parameters, namely sediment transport coefficients (K) and the diffusion rate (omega), which affect beach nourishment performance. The performance of the MARS was determined by comparison of the models using exponential, linear, and power regression equations trained by conventional regression analyses (CRA) and the teaching-learning based optimization (TLBO) algorithm. In all models, two different input data obtained from the experimental study were used, one dimensional and one non-dimensional. The results presented that the MARS models gave lower error values than the CRA and TLBO models according to the root mean square error, mean absolute error, and scattering index criteria. When the models were evaluated, it was revealed that dimensional and non-dimensional models gave approximate results. We proved that the dimensional and non-dimensional MARS models can be used to estimate the (K) and (omega) values.

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 Ltd

Long-term persistence of turbid water has become an environmental issue in downstream reaches in a lot of dams. Turbid water causes degradation of river landscape, load of water treatment process, burden on the hydraulic power plant and degradation of biodiversity. In this paper, we focus on sandbars as a place of purification of the turbid water. We evaluated the influence of sandbars on qualitative and quantitative change of turbid water in the Tenryu river. Regarding quantitative change of turbid water, turbidity in the river water at downstream of the sandbar showed a 52.8% reduction by drifting through the survey section of 23.7km in total length. However, the concentration of suspended solids in the river water was not significantly reduced, and fluctuated between 3.4 and 5.0 mg L-1. As for qualititative change, proportion of dam POM in SFPOM at downstream of sandbar declined as downstream and varied between 0.01 and 0.94. The reduction rate slope of Dam POM was higher in the double row bars section than the point bars section. Therefore, it is necessary to evaluate the turbid water purification function with attention to various characteristic values of sandbar.

Cross-shore sediment transport is one of the effective factors in erosion and sedimentation, and affects dynamics of the beach profile in coastal areas. Furthermore, sandbar migration due to cross-shore sediment transport mostly effects beach nourishment, displacement of pollutions trapped in sediments, and organism and plants’ lives. In this manuscript, sandbar migration due to cross-shore sediment transport is studied and results have been compared to field data. Field data used here have been measured at the southern Caspian Sea, Noshahr coasts, Iran. During the measurement period, two high-energy events with significant wave height of approximately 1.4 m have been measured. All simulations have been done based on a one dimensional cross-shore transect. Wave transformation during propagation toward the coast has been modeled using the third generation model SWAN, and long-shore wave-induced current has been simulated by solving alongshore momentum equilibrium equation. To include the morphological change, the cross-shore sediment transport rate has been estimated using Bagnold [1966], Bowen [1980], and Bailard’s [1981] (BBB) energetic sediment transport model, and results has been compared to the model developed by Plant et al. [2001], which itself is an energetic model based on Bagnold [1966]. Finally, bathymetric changes has been forecasted by solving cross-shore mass conservation equation which indicated slight outperform of BBB rather than Plant et al. model in this study area.

Micro-estuaries in semi-arid areas, despite their small size (shallow depth of a few meters, length of a few kilometers, and a surface area of less than 1 km2) are important providers of ecosystem services. Despite their high abundance, tendency to suffer from eutrophication and vulnerability to other anthropogenic impacts, such systems are among the least studied water bodies in the world. In low tidal amplitude regions, micro-estuaries often have limited rate of sea-river water exchange, somewhat similar to fjord circulation, caused by a shallow sandbar forming at the coastline. The long-term study, we report here was inspired by the idea that, due to their small size and low discharges regime, relatively small interventions can have large effects on micro-estuaries. We used a stationary array of sensors and detailed monthly water sampling to characterize the Alexander estuary, a typical micro-estuary in the S.E. Mediterranean, and to identify the main stress factors in this aquatic ecosystem. The Alexander micro-estuary is stratified throughout the year with median bottom salinity of 18 PSU. Prolonged periods of hypoxia were identified as the main stress factor. Those were alleviated by breaching of the sandbar at the estuary mouth by sea-waves or stormwater runoff events (mostly during winter) that flush the anoxic bottom water. Analysis of naturally occurring sandbar breaches, and an artificial breach experiment indicate that the current oxygen consumption rate of the Alexander micro-estuary is too high to consider sandbar breaches as a remedy for the anoxia. Nevertheless, it demonstrates and provides the tools to assess the feasibility of small-scale interventions to control micro-estuaries hydrology and biogeochemistry.

EnvironmentAsia, 12, special, 36-47

A simple methodology to track the displacements of a sandbar from a fixed video camera, extracting its morphological features and deriving the associated fluvial morphology is presented, using a small reach of the Po River in Italy as a case study. A camera fixed on a bridge pier acquired images every twelve hours while hourly water levels are derived from a radar hydrometer located upstream of the study area. The quantification of the fluvial bathymetry is achieved by mapping multiple edge-of-water lines of a sandbar before and after high flow conditions in December 2017. Both from video information and 2-D numerical simulations, it is evident that flooding waves can easily remove sediments that accumulated on bars during low flow conditions in this area, redistributing them across the river channel. This video-based methodology—which confirms to be economically attractive if compared to more traditional monitoring systems—proves to be a valuable system to monitor long-term fluvial processes providing detailed indications on how to better plan river management activities.

В течение 1974-2016 гг. в природных и лабораторных условиях в Самарской области изучались особенности выживания имаго жуков-листоедов в результате паводкового разлива р. Волги, затопления рекой изолированных островных систем, а также миграционные процессы насекомых после схода паводковой воды. За 12-летний период полевых исследований 11 специалистов-энтомологов, используя 2 традиционных и 6 авторских методов, на 11 относительно больших волжских островах (3 из которых периодически затапливаются) и 20 крупных, регулярно затапливаемых отмелях и косах собрали коллекцию из 29 видов жуков-хризомелид. Установлено, что фауна листоедов островов по генезису очень близка к фауне сопредельных побережий. Анализируется происхождение и рельеф типичных островов, уровень паводковых вод, продолжительность затопления поймы р. Волги близ Самарской Луки, механизмы выживания жуков путем адаптации их к условиям местообитаний или особенности их миграций, при вторичном заселении островных систем. Установлено, что, кроме активного перелета и автономного плавания на острова, жуки пользуются доступными «плавсредствами» «плотами» из растительного паводкового шлама, мелкими и достаточно крупными плавающими объектами (от веток и досок до речных судов). Приведены данные по примерным долям участия разных способов передвижения имаго листоедов при их рассредоточении в пространстве. Установлено, что миграции происходят ежегодно, совершенно независимо от успеха перезимовки популяции островных жуков-предшественников., The following paper deals with the study that was carried out during 1974-2016 in natural and laboratory conditions in the Samara Region. The authors studied the features of adults leaf beetles survival as a result of the Volga river flood spill, flooding of the isolated island systems as well as migratory processes of insects. Over a 12year period of field research, 11 entomologists, using 2 traditional and 6 author’s methods, have collected 29 species of Chrysomelidae beetles on 11 large Volga Islands (3 of which are periodically flooded) and 20 large, regularly flooded shallows and braids. It is established that the fauna of the Islands’ leaf beetles is very close to the fauna of adjacent coasts by genesis. The authors analyze the origin and relief of typical Islands, the level of flood waters, the duration of flooding of the Volga river floodplain near Samarskaya Luka, the mechanisms of survival of beetles by adapting them to the conditions of habitats or features of their migrations, with the secondary settlement of island systems. It is established that, in addition to the active flight and autonomous navigation to the Islands, beetles use available «boats» «rafts from vegetable flood sludge», small and fairly large floating objects (from branches and boards to river vessels). It is established that migrations occur annually, completely regardless of the island beetlespredecessors population wintering success.

In its judgment of 2 February 2018 in the joined cases between Costa Rica and Nicaragua, the International Court of Justice held that Harbor Head Lagoon and the sandbar separating it from the Caribbean Sea belonged to Nicaragua, thereby creating an enclave on the Costa Rican coast. Despite this finding, the Court decided to disregard it when establishing the maritime delimitation. This article aims at showing that such a solution is incompatible with the United Nations Convention on the Law of the Sea as well as examining the options left to the Court to remedy the impracticality of the situation in accordance with the applicable law.

This study investigates the impact of individual storms and storm clusters on shoreline recovery for the meso-to macrotidal, barred Biscarrosse beach in SW France, using 6 years of daily video observations. While the study area experienced 60 storms during the 6-year study period, only 36 storms were analysed due to gaps in the video data. Based on the 36 individual storms and 13 storm clusters analysed, our results show that clustering impact is cumulatively weak and shoreline retreat is governed by the first storms in clusters, while the impact of subsequent events is less pronounced. The average post-storm beach recovery period at this site is 9 days, consistent with observations at other beaches. Apart from the dominant effect of present storm conditions, shoreline dynamics are also significantly affected by previous storm influence, while recovery is strongly modulated by tidal range and the bar location. Our results reveal that not only is the storm energy important but also the frequency of recurrence (storms result in greater retreat when time intervals between them are longer), which suggests an interaction between short storm events and longer-term evolution.

The present work investigates cross-shore shoreline migration as well as its alongshore variability (with deformation) on timescales of days to years using 6 years of time-averaged video images. The variability of the shoreline is estimated through empirical statistical methods with comprehensive reference to three scales of variability. At the meso-to macro-tidal barred Biscarrosse beach, shoreline responds in decreasing order at seasonal (winter/summer cycles, 52%), event (storms, 28%) and inter-annual scales. Whereas seasonal evolution is dominated by wave climate modulation, short-term evolution is influenced by tidal range and surf-zone sandbar characteristics. The influence of tide range and sandbars increases when timescale decreases. This is even more the case for the alongshore deformation of the shoreline which is dominated by short-term evolution. An EOF analysis reveals that the first mode of shoreline change time series is associated with cross-shore migration and explains 58% of the shoreline variability. The rest of the modes are associated to deformation which explain 42% of shoreline variability.

The characteristics of spatiotemporal variation of the multiple bar system on the Chirihama and neighboring beach, Japan, have been investigated using a set of field surveys collected over 13 years and aerial photographs during 1947 to 2010. In the north and middle of the study area temporal variation of sandbar configuration is characterized by the presence of cyclic cross-shore migration with approximately 4 to 6 years return period. The direction of systematic inter-annual migration is net offshore. The migration features indicate substantial alongshore variability. On the north part the behavior of bar system is quasi two-dimensional. On the middle to south area several three-dimensional configuration and deformation such as bar switching and bifurcation are observed.

This study analyzes a bathymetric dataset sampled annually for 51 years along the Ishikawa Coast, Japan, where the morphological variation is characterized by the cyclic cross-shore migration of bars with approximately 10-year return period. Five cycles have been identified from 1960 to 2010. The variability of spatial pattern during individual cycle is analyzed to quantify the characteristics of three-dimensional morphological evolutions. Considerable changes in plan shape were observed such as quasi-regular crescentic patterns, parallel alignment of oblique bars, disconnection and realignment of bars. This is in contrast to the quasi two-dimensional progress of net offshore migration (NOM) of sandbars reported in the Netherlands, New Zealand, Denmark, and Japan.

On steep beaches, the cross-shore movement of sand in response to ‘erosive’ storm waves and ‘accretive’ swell waves can lead to temporal changes between a barred winter profile and a non-barred summer profile with a pronounced berm in the upper swash zone. Despite recent improvements in predicting berm formation and evolution within process-based morphodynamic models, substantial demand for improvement in understanding swash processes and associated surf–swash sand exchange remains. Here, we analyze bed level data collected on a near-prototype, 4.5-m high and 75-m wide sandy beach (median grain diameter D50 = 430 μm) with a lagoon situated at its landward side. In particular, we distinguish between surf–swash sand exchange (time scale of tens of minutes to hours), the net effect of single and multiple swash events on the entire beach face (time scale of a few seconds to hours), and instantaneous bed variability at 3 cross-shore locations within individual swashes. During ‘erosive’ waves (Hs = 0.8 m, Tp = 8 s) sand on the initially 1:15 planar profile was predominantly eroded from the inner surf zone to be deposited in the outer surf zone as a sandbar, indicating minimal surf–swash sand exchange. Subsequent ‘accretive’ waves (Hs = 0.6 m, Tp = 12 s) caused substantially larger surf–swash sand exchange: the pre-existing sandbar migrated onshore and decayed, with the sand ending up on the beach face in a prominent (up to 0.7 m high), steep (1:6) berm. We found the dynamics of the berm to be governed primarily by wave conditions and the antecedent morphology, with ground water gradients of additional importance when morphodynamic feedback between swash flow and the berm is small. The observed bed level change within a swash and averaged over a swash event could be substantial (several centimeters) during all wave conditions, but the net (i.e., averaged over multiple swash events) bed level change was strongly suppressed because erosive and accretionary swashes nearly balanced. In addition, the local beach face slope could be instantaneously ≈ 25 % steeper or shallower than the median slope, or the initial or final slope. We anticipate that our data will stimulate new model development, as to increase the range of conditions and settings in which morphodynamic models can be applied realistically and reliably.

International audience; Anglet beach, Basque Coast (SW France), is a 4-km long embayment bounded by a prominent headland in the South and by the southern Adour River training wall in the North. The beach is structurally-engineered with, within the embayment, 6 groins and 3 distinct sectors where the beach is backed by a seawall. The beach is high-energy intermediate, mostly double-barred, composed of medium to coarse sand with a steep beach face (∼1/10). In January 2013, a video system was installed at the Southern end of Anglet beach at about 70 m above mean sea level to monitor about 2 km of the southern beach of Anglet that includes 4 groins extending about 100 m seaward and a 1- km seawall backing the beach. The study period includes the winter 2013/2014 that was outstanding in terms of the available energy arriving at the coast with a 2-month-averaged significant wave height peaking at 3.6 m. Despite the extreme storm wave conditions during the winter 2013/2014, the outer bar crescentic patterns maintained and even further developed. The beach eroded by O(10 m) and, surprisingly and in contrast with the nearby northern open beaches, they recovered to their pre-winter 2013/2014 state within only a few months. Overall, Anglet beach appears to respond predominantly at individual storm frequency rather than at seasonal timescales, with the groins and headland acting as major controlling boundaries influencing beach state and dictating rip channel locations. \textcopyright Coastal Education and Research Foundation, Inc. 2016.

本稿は，堰の部分撤去による上流河道の水理学及び地形学的な応答特性に関する実験的研究である。特に，堰の改変形状及び河床材料の粒径特性について注目した。堰を部分撤去した場合は，堰周辺には局所洗掘，河道上流域には砂州の移動が生じた。堰の改変形状が堰近傍の三次元流れ場及び局所洗掘を促進し，上流砂州の伝播特性にも影響していることが確認された。準平衡状態においては，砂州の特性は堰の改変形状よりも堰の改変面積との関連性は深いことが示された。混合砂での実験では，河床材料の平均粒径及び標準偏差による河道の応答特性に大きいな違いが見られた。また，河道横断方向の流砂分級現象による河道縦断方向にはサンドリボンと呼ばれる細粒径砂による帯が形成され，そのサンドリボンは河床地形に影響を及ぼすことも確認された。, This paper presents an experimental study on the hydraulic and morphological responses of a channel due to partial removal of a weir. In particular, the impacts of the removal shape of the weir and the properties of the bed sediment are focused on. It is found that weir removal promotes local scour and sandbar development in the upstream channel. The removal shape significantly affects the three dimensional flow structure and the local scour around the weir and poses influences on the propagation process of upstream sandbars at the early stage. Nevertheless, the characteristics of the sandbar system at the quasi-equilibrium stage are governed by the removal area rather than the removal shape. The mean grain size and the geometric standard deviation of the bed sediment mixtures are two practical parameters in characterizing the local scour and the sandbar structure in non-uniform sediment beds. Sand ribbons are observed in non-uniform sediment beds due to the lateral sediment sorting and the ribbons also influence the bed morphologies.

This paper studied the development and the underlying physical mechanisms of the large sandbar in Qiantang estuary, China, using an idealized morphodynamic model. The model coupled shallow water equations, cohesive sediment transport and bed level update equations. The model was given a fixed geometry and impermeable boundaries, and forced by M2 tide at mouth and river discharge at the upstream. The sandbar was reproduced on a timescale of 30 years, and the spatial scales of the sandbar were comparable to the real situation. The formation of the sandbar was controlled by the flood dominance due to tide wave deformation and sufficient sediment supply. The morphological development was driven by the nonlinear interaction between hydrodynamics, sediment transport and bed evolution. This morphodynamic model provides a new tool for the analysis of the large-scale morphological behaviour of tidal sandbar.

Aim of works on morphology and morphometry of the coastal zone is identification of qualitative and quantitative changes in the beach-dune strip and in the shoreface in conditions of their natural and anthropogenic transformations. As shore and backshore are essential elements reducing risks from the sea to the adjacent hinterland, this article focuses on evaluation of their parameters. Moreover, elements of the coast are described herein in detail. The research material used for the purposes of this article were records of bathymetric-tacheometric measurements of the Polish coast, made at consistent profiles evenly spaced every 500 m. The measurements did not cover the areas adjacent to the Bay of Gdańsk or the Lagoons. This article presents an analysis of the measurements of components of the coastal zone, which covered four morphodynamical areas (the Hel Peninsula, Jastrzębia Góra – Jarosławiec, Jarosławiec – Sarbinowo, and Sarbinowo – Międzyzdroje), twelve sandbar stretches (the Helska, Karniewska, Sarbska, Łebska, Długie, Gardno, Wicko, Kopań, Bukowo, Jamno, Resko, and Dziwnowska Spits) and thirteen cliff stretches (the cliffs in Chłapowo, Jastrzębia Góra, Rowy, Dębina, Ustka, Jarosławiec, Wicie, Sarbinowo, Ustronie Morskie, Śliwin, Trzęsacz, Pobierowo, and on Wolin Island). The basic linear parameters of the beach-dune and beach-cliff belt were read from 678 printouts of tacheometric profiles. A detailed analysis carried out in this manner made it possible for the endangered sections of the coast to manifest themselves. The obtained data are a basis for further comparative analyses, and assessment of the shore under conditions of implementation of the Act on the Protection of Sea Coasts. Renata Kozak

Basic features of coastal evolution on Chirihama Beach, Japan, have been investigated using a set of field surveys. The results on the shoreline survey show long-term eroding trend during the last twenty years. The cross-shore profile survey records show that the seabed slope has been decreasing more recently. The typical profile configurations are characterized by the presence of multiple bars. An EOF analysis has been conducted on the periodic movements of these bars. The net offshore migrations of bars have been repeated with a return period of approximately 4 years. It is also shown that the transition from double bar to triple bar configuration accompanies the temporal retreat of shoreline. The alongshore variability of the behavior of multiple bar system has also been examined.

The Yoneshiro river has very good and many spawning grounds for ayu. The river experiences snowmelting flood every year from begin of March to end of May. After 2006 snow-melting flood, the river form is extremely changed and the good spawning around 22km from the mouth disappear. We think that that main reason is that the duration of 2006 flood is longer than normal year. Recently, the river researcher indicate that sandbar deformation process is affected the duration time of flood with flume experimental study and theoretic analysis. In this study, the deformation process is reproduced with 2d numerical model for river bed fluctuation to investigate the deference of the duration of flood in natural river. The results of long flood shows that river bed fluctuation is larger than the short flood like normal year., application/pdf

Sandbars are ubiquitous patterns along wave-dominated sandy coastlines and are key elementsin the global evolution of beaches. Cross-shore sandbar migrations are the result of the permanentimbalance between sediment flux driven by wave non-linearity and mean return current. In this thesis,we developed a new process-based beach profile model integrating the recent scientific advancesin term of hydrodynamics and sediment transport developed for beach morphodynamics. The lowcomputing time allows for long-term morphodynamic simulations (O months/years) of natural beachprofiles of diverse characteristics (beach slope, sediment grain size or type of wave breaking). Modelvalidations on several data sets, encompassing natural and experimental beach profile evolutions,highlight the respective contribution of the main hydrodynamic and sediment transport processesinvolved in specific cross-shore sandbar evolution relative to various wave conditions. Finally, all thecross-shore physical processes were integrated in a 2DH morphodynamic model, resulting for the firsttime in the simulation of a quasi-complete down state sequence showing alongshore bar generationwith subsequent spontaneous formation of transverse bar and rip morphology. These very encouragingresults pave the way for using this model to simulate 3-Dimensional evolutions of natural beachesforced by irregular wave conditions; Les barres sableuses pré-littorales ont un rôle fondamental en morphodynamique des plages soumises à l’action des vagues. Le déséquilibre permanent entre les flux sédimentaires induits vers laplage par les non linéarités des vagues et ceux induits vers le large par le courant de retour gouverne lamigration transversale des barres. Dans cette thèse, un nouveau modèle morphodynamique de profilde plage intégrant l’état de l’art des processus hydro-sédimentaires a été développé. Le faible coûten temps de calcul de ce modèle permet de réaliser des simulations à long terme, O(mois/années),de la morphologie de plages réelles ayant des caractéristiques variées (pente, type de déferlement,granularité). La simulation sur plusieurs jeux de données, de plages réelles et expérimentales, a permisd’identifier la contribution respective des principaux processus hydro-sedimentaires dans la dynamiquede la plage suivant les conditions de houle (e.g. Tempête, temps calme). Ces avancées scientifiques ontété intégrées à un modèle 2DH, ce qui a notamment permis de simuler pour la première fois sur des casacadémiques la formation d’une barre sableuse rectiligne à partir d’une plage parfaitement plane, suiviedu développement de corps sableux tridimensionnels. Ces résultats ouvrent la voie vers l’applicationde ce type de modèle aux plages naturelles soumises à une large variabilité de régimes de houle.

Phytosociological classification of the coastal vegetation according to the concept and method of the Zürich-Montpellier School was done for the natural terrestrial vegetation that remains as isolated patches on sandbars parallel to the seashore of Narathiwat, Thailand. Twelve study sites were marked and the vegetation types were discussed. The results show that the plant communities in the study areas can be classified into 3 categories: 1) foredune and dune grassland communities; 2) dune scrub communities; 3) dune woodland communities. This report is the first description of such communities on peninsular Thailand. Profiles of the natural vegetation gradient across the sandbars are proposed.

Sandbars are ubiquitous patterns along wave-dominated sandy coastlines and are key elementsin the global evolution of beaches. Cross-shore sandbar migrations are the result of the permanentimbalance between sediment flux driven by wave non-linearity and mean return current. In this thesis,we developed a new process-based beach profile model integrating the recent scientific advancesin term of hydrodynamics and sediment transport developed for beach morphodynamics. The lowcomputing time allows for long-term morphodynamic simulations (O months/years) of natural beachprofiles of diverse characteristics (beach slope, sediment grain size or type of wave breaking). Modelvalidations on several data sets, encompassing natural and experimental beach profile evolutions,highlight the respective contribution of the main hydrodynamic and sediment transport processesinvolved in specific cross-shore sandbar evolution relative to various wave conditions. Finally, all thecross-shore physical processes were integrated in a 2DH morphodynamic model, resulting for the firsttime in the simulation of a quasi-complete down state sequence showing alongshore bar generationwith subsequent spontaneous formation of transverse bar and rip morphology. These very encouragingresults pave the way for using this model to simulate 3-Dimensional evolutions of natural beachesforced by irregular wave conditions, Les barres sableuses pré-littorales ont un rôle fondamental en morphodynamique des plages soumises à l’action des vagues. Le déséquilibre permanent entre les flux sédimentaires induits vers laplage par les non linéarités des vagues et ceux induits vers le large par le courant de retour gouverne lamigration transversale des barres. Dans cette thèse, un nouveau modèle morphodynamique de profilde plage intégrant l’état de l’art des processus hydro-sédimentaires a été développé. Le faible coûten temps de calcul de ce modèle permet de réaliser des simulations à long terme, O(mois/années),de la morphologie de plages réelles ayant des caractéristiques variées (pente, type de déferlement,granularité). La simulation sur plusieurs jeux de données, de plages réelles et expérimentales, a permisd’identifier la contribution respective des principaux processus hydro-sedimentaires dans la dynamiquede la plage suivant les conditions de houle (e.g. Tempête, temps calme). Ces avancées scientifiques ontété intégrées à un modèle 2DH, ce qui a notamment permis de simuler pour la première fois sur des casacadémiques la formation d’une barre sableuse rectiligne à partir d’une plage parfaitement plane, suiviedu développement de corps sableux tridimensionnels. Ces résultats ouvrent la voie vers l’applicationde ce type de modèle aux plages naturelles soumises à une large variabilité de régimes de houle.

山陰地域の弓ヶ浜砂州では豊富な地下水を用いて農業,特に白ネギの栽培が盛んである.しかし地下水はこのような活動と家庭排水によって汚れてきたと言われている.そこで地下水の水質の現状を評価するため地下水に含まれる地球化学種の分析を行った.27試料の地下水のpHは中性もしくはやや酸性を示す.ECは低いが,300から600μS/cmと変化に富む.水質は窒素の化学種の含有量によって2タイプに分類される.相対的に高いNO_3^- (5mg/l以上)濃度は南東と北西の地域の地下水にみられ,極めて高いNH_4^+ (>0.5mg/l)と鉄化学種(>0.5mg/l)は半島の中部にみられる.両方どちらもPO_4^濃度は変化に富み,最大3mg/lに達する.前者のタイプの水は家庭排水や農業生産によるかなりの汚染をうけていると考えられ,帯水層が酸化的状態にあると予想される.後者は前者と同様に汚染を受けた水が還元的な環境の帯水層に存在していると思われる.それは帯水層の水が停滞していたり,肥料や家庭排水の供給の増加によって生じたと推定される.後者のタイプではヒ素化学種が土壌もしくは堆積物から溶出している.この水は低いDO値(1試料を除いて2mg/l以下)とNO_3^-,を含まないことで特徴づけられる.

There have been significant increases in stream flow in many rivers of the Upper Midwestern United States since 1980. Increased summer flows may negatively impact ecological processes, including aquatic organisms’ life cycles. The smooth softshell (Apalone mutica) and wood turtle (Glyptemys insculpta) are threatened by alteration of stream flow regime and other changes to river ecosystems in the Upper Midwest. We hypothesized that prolonged duration of high summer flows would reduce time available for nesting. We assessed hydrologic change using the Indicators of Hydrologic Alteration program and stream gauge data, characterized physical properties of sandbars, surveyed turtle nesting sites and assessed historical channel change using aerial photos in GIS on five Upper Midwest rivers. A river stage-sandbar area relationship was developed to determine the effect of prolonged summer flow duration on turtle nesting opportunity for the 1940–2009 time period. Suitable water levels have declined since 1980 in the agricultural watersheds of southern Minnesota likely delaying hatching and reducing survival, particularly for aquatic turtles such as A. mutica. In contrast to the agricultural watersheds, there was no significant change in the northern forested rivers’ stream flow and sandbar availability during the nesting season. Management to reduce summer stream flow in agricultural watersheds and protection of known nest sites could benefit threatened aquatic turtle populations.

We analyse a seven-year dataset (1999–2005) of shoreline and sandbar variations derived from video observations at the embayed Tairua Beach, New Zealand, to explore sandbar–shoreline coupling and to determine how this coupling is related to alongshore-averaged sandbar–shoreline separation and beach rotation. Our results quantify the coupling between the sandbar and the shoreline which is directly related to the reduced separation between the sandbar and the shoreline. Using a simple predictive shoreline model, we show that this behaviour is related to the energy of the incoming waves. Our observations are obtained from a headland-enclosed beach and show aspects of the morphological state that relate to the existence of headlands that are not considered in the Wright and Short beach state classification. Both the sandbar and shoreline at Tairua Beach rotate relatively quickly (< 1 month) during the winter storm events, when the storms are accompanied by strong alongshore components, gradually returning during the summer months. The sandbar–shoreline coupling length scale is controlled by this rotation, with large wavelengths occurring when the sandbar is strongly rotated.

International audience; Nearshore sandbars are often characterized by three-dimensional bed patterns. To analyze the influence of wave direction on the morphological response of a double sandbar system, this paper uses the 2DH nonlinear surf zone model MORFO55. Depending on wave direction, different morphologies emerge as free instabilities. These morphological responses differ in terms of geometry (shape of the alongshore rhythmic patterns) and temporal evolution. Nearly shore-normal waves favor the emergence of crescentic patterns along both the inner and outer bars. These instabilities arise from ''bedsurf'' coupling, which is the positive feedback between the bed perturbations and the wave-breaking patterns resulting in rip-cell circulations. The systemis stable for intermediate wave incidence angles because the longshore current shifts the circulation cells alongshore, inhibiting the growth of initial perturbations. For larger angles, the system is again unstable. Two types of oblique bars emerge. The first type forms between the crest of the inner bar and the shoreline and is oriented down-current. The second type is superimposed on the two bars and is oriented up-current. Although previous studies attribute the formation of oblique bars to the deflection of the longshore current (that is a cross-shore process), we show here that this mechanism contributes to the bar formation but the growth rate is mainly governed by a longshore process. Specifically, it is the positive feedback between the bathymetry and the longshore gradient of the sediment concentration. Finally, interactions between the patterns in the two shore-parallel bars are analyzed. In the observed configurations, the influence is always one way as the inner-bar dynamics never influence those of the outer bar. The outer-bar instabilities cause undulations in the inner bar when the outer-bar instabilities grow faster than those of the inner bar.

Most of the Earth coasts recede and 80 % are rocky. Prediction of sea-cliff recession is essential to anticipate future risks for coastal development. However, it is difficult to understand this recession because many parameters control it. In addition, both the space and time scales are too big for the different mechanisms of cliff erosion to be fully analyzed. Experiments in a small-scale wave flume were conducted in which a massif made of wet sand is submitted to wave attack. The aim is to understand how cliff erosion is wave-controlled. The technique of shadow graph measurements was used to detect the time evolution of sand and water surfaces. We have analyzed the influence of wave forcing (F, ξ) (where F is the incident offshore wave energy flux and ξ is the surf similarity parameter) on the cliff recession rate and on collapse event size. The cliff recession rate increases linearly with the wave energy flux F. The eroded cliff materials change the bottom morphology; the types of bottom morphology strongly depend on the surf similarity parameter at the breaker point, or the Dean parameter Ω. Bottom profiles characterized by unsteady self-sustained sandbar oscillation were observed. In addition, we studied how sand granulometry change the system evolution. Finer the sand is, more cohesive is the cliff and bigger are cliff collapses. Contrary to what was expected, cliff recession is more important for finer sand: this could be due to a more dissipative bottom morphology built by fine sands. The sand volume within the system changes following cliff collapses and a sandbar removal during particular experiments. The cliff recession rate is constant when the sandbar is removed and decreases with cliff height. It seems that the unsteadiness of the bottom profile is activated when the volume of eroded sand exceeds a threshold value.; La plupart des côtes de la Terre reculent et 80% sont rocheuses. La prévision du recul des falaises littorales est primordiale afin d'anticiper les risques futurs pour les aménagements littoraux. Cependant, la compréhension de ce recul est difficile car de nombreux paramètres le contrôlent. Des expériences en canal à houle de petite échelle ont été effectuées où nous avons mis en place un massif de sable humide soumis à l'attaque des vagues par sapement. Le but est de comprendre comment l'effet des vagues contrôle l'érosion des falaises. La technique de mesure par ombroscopie a été employée et nous a permis de détecter la surface du sable et la surface libre en fonction du temps. Nous avons ainsi analysé l'influence du forçage des vagues (F, ξ) (où F est le flux d'énergie des vagues incidentes au large et ξ est le paramètre de similitude de "surf") sur la vitesse de recul de la falaise et sur la profondeur des évènements d'effondrement. La vitesse de recul de la falaise augmente linéairement avec le flux d'énergie F. Les débris de falaise érodés changent la morphologie du fond, les types de morphologie du fond dépendent fortement du paramètre de similitude de "surf" au déferlement, ou encore du paramètre de Dean Ω. Des profils du fond instationnaires présentant une oscillation auto-entretenue de la barre sédimentaire ont été observés. Nous avons de plus étudié l'effet de la granulométrie du sable utilisé : pour un sable plus fin, la falaise est plus cohésive et s'effondre au cours d'évènements de plus grande ampleur. Etonnamment, le recul de la falaise est plus important pour du sable fin. Ceci est probablement dû à une modification de la morphologie du fond conduisant à une dissipation de l'énergie des vagues moins importante. Le volume de sable injecté dans le système a finalement été quantifié, la barre sédimentaire a d'abord été prélevée périodiquement et il a été observé que la vitesse de recul de la falaise vr est constante. Puis, la hauteur de falaise a été modifiée, le recul des falaises est plus important pour des petites falaises. Il semblerait que l'instationnarité d'un profil du fond se déclenche à partir d'un volume seuil de sable érodé.

Most of the Earth coasts recede and 80 % are rocky. Prediction of sea-cliff recession is essential to anticipate future risks for coastal development. However, it is difficult to understand this recession because many parameters control it. In addition, both the space and time scales are too big for the different mechanisms of cliff erosion to be fully analyzed. Experiments in a small-scale wave flume were conducted in which a massif made of wet sand is submitted to wave attack. The aim is to understand how cliff erosion is wave-controlled. The technique of shadow graph measurements was used to detect the time evolution of sand and water surfaces. We have analyzed the influence of wave forcing (F, ξ) (where F is the incident offshore wave energy flux and ξ is the surf similarity parameter) on the cliff recession rate and on collapse event size. The cliff recession rate increases linearly with the wave energy flux F. The eroded cliff materials change the bottom morphology; the types of bottom morphology strongly depend on the surf similarity parameter at the breaker point, or the Dean parameter Ω. Bottom profiles characterized by unsteady self-sustained sandbar oscillation were observed. In addition, we studied how sand granulometry change the system evolution. Finer the sand is, more cohesive is the cliff and bigger are cliff collapses. Contrary to what was expected, cliff recession is more important for finer sand: this could be due to a more dissipative bottom morphology built by fine sands. The sand volume within the system changes following cliff collapses and a sandbar removal during particular experiments. The cliff recession rate is constant when the sandbar is removed and decreases with cliff height. It seems that the unsteadiness of the bottom profile is activated when the volume of eroded sand exceeds a threshold value.; La plupart des côtes de la Terre reculent et 80% sont rocheuses. La prévision du recul des falaises littorales est primordiale afin d'anticiper les risques futurs pour les aménagements littoraux. Cependant, la compréhension de ce recul est difficile car de nombreux paramètres le contrôlent. Des expériences en canal à houle de petite échelle ont été effectuées où nous avons mis en place un massif de sable humide soumis à l'attaque des vagues par sapement. Le but est de comprendre comment l'effet des vagues contrôle l'érosion des falaises. La technique de mesure par ombroscopie a été employée et nous a permis de détecter la surface du sable et la surface libre en fonction du temps. Nous avons ainsi analysé l'influence du forçage des vagues (F, ξ) (où F est le flux d'énergie des vagues incidentes au large et ξ est le paramètre de similitude de "surf") sur la vitesse de recul de la falaise et sur la profondeur des évènements d'effondrement. La vitesse de recul de la falaise augmente linéairement avec le flux d'énergie F. Les débris de falaise érodés changent la morphologie du fond, les types de morphologie du fond dépendent fortement du paramètre de similitude de "surf" au déferlement, ou encore du paramètre de Dean Ω. Des profils du fond instationnaires présentant une oscillation auto-entretenue de la barre sédimentaire ont été observés. Nous avons de plus étudié l'effet de la granulométrie du sable utilisé : pour un sable plus fin, la falaise est plus cohésive et s'effondre au cours d'évènements de plus grande ampleur. Etonnamment, le recul de la falaise est plus important pour du sable fin. Ceci est probablement dû à une modification de la morphologie du fond conduisant à une dissipation de l'énergie des vagues moins importante. Le volume de sable injecté dans le système a finalement été quantifié, la barre sédimentaire a d'abord été prélevée périodiquement et il a été observé que la vitesse de recul de la falaise vr est constante. Puis, la hauteur de falaise a été modifiée, le recul des falaises est plus important pour des petites falaises. Il semblerait que l'instationnarité d'un profil du fond se déclenche à partir d'un volume seuil de sable érodé.

Submitted by Fabricia Fialho Reginato (fabriciar) on 2015-06-16T23:24:33Z No. of bitstreams: 1 Crippa.pdf: 92752 bytes, checksum: 705c764746213cbbe4b6d38f8af8384e (MD5) Made available in DSpace on 2015-06-16T23:24:33Z (GMT). No. of bitstreams: 1 Crippa.pdf: 92752 bytes, checksum: 705c764746213cbbe4b6d38f8af8384e (MD5) Previous issue date: 2011 Nenhuma A Lagoa do Peixe situada no Parque Nacional da Lagoa do Peixe – sul do Brasil - tem sua conexão com o mar aberta artificialmente todos os anos no final do inverno. Entretanto, esse manejo vem sendo realizado sem avaliar os impactos da abertura da barra na biodiversidade aquática das áreas úmidas da região. As seguintes questões foram testadas nesse estudo: 1) A riqueza, a abundância e a composição de macroinvertebrados da planície de inundação da Lagoa do Peixe variam temporalmente com a abertura e fechamento da barra? 2) O padrão de variação da comunidade de macroinvertebrados varia com a abertura e fechamento da barra? Um total de quatro coletas foi realizado entre março e outubro de 2008 em três áreas úmidas localizadas na planície de inundação da Lagoa do Peixe que recebiam influência da abertura artificial da barra e em duas áreas úmidas sem a influência da abertura da barra (áreas controle). Um total de 19.333 indivíduos distribuídos em 45 famílias de macroinvertebrados aquáticos foi amostrado nas áreas úmidas estudadas. A riqueza de macroinvertebrados (F1,3= 41, 645, p = 0, 008) e abundancia (F1,3= 1499,37; p < 0, 001) foram maiores nas áreas úmidas que não receberam influência da abertura artificial da barra (áreas controle) do que naquelas sujeitas à abertura da barra. A composição de macroinvertebrados variou significativamente entre as áreas úmidas sujeitas e não sujeitas à abertura da barra (F1,16= 6, 2422, p < 0, 001). Os resultados obtidos nesse estudo sugerem que a abertura artificial da barra da Lagoa do Peixe afeta a dinâmica da comunidade de macroinvertebrados aquáticos em áreas úmidas costeiras no Sul do Brasil. The Lagoa do Peixe located in the Parque Nacional da Lagoa do Peixe – South of Brazil - has its connection with the sea artificially opened every year in the end of winter. However, this management is being accomplished without assessing the impacts of the sandbar opening in the aquatic biodiversity of the region’s humid areas. The following questions were tested in this study: 1) The richness, the abundance and the composition of macroinvertebrates in the wetlands of the Lagoa do Peixe vary temporally with the opening and closing of the sandbar? 2) The macroinvertebrates community range’s pattern varies with the opening and closing of the sandbar? A total of four collections was accomplished between March and October 2008 in three humid areas located in the Lagoa do Peixe flooding plain that were influenced by the artificial opening of the sandbar in two humid areas without being influenced by the opening of the sandbar (control areas). A total of 19,333 individuals distributed in 45 families of aquatic macroinvertebrates was sampled in the humid areas studied. The macroinvertebrates richness (F1,3= 41, 645, p = 0, 008) and abundance (F1,3= 1499,37; p < 0, 001) were superior in the humid areas that weren’t influenced by the artificial opening of the sandbar (control areas) than in those ones subjected to the opening of the sandbar. The macroinvertebrates composition significantly ranged between the humid areas subjected and the ones not subjected to opening of the sandbar (F1,16= 6, 2422, p < 0, 001). The obtained results in this study indicate that the artificial opening of the Lagoa do Peixe sandbar affects the dynamics of the associations of aquatic macroinvertebrates in humid coastal areas in the South of Brazil.

Cross-shore migratory behavior of nearshore sandbars is commonly studied with nearshore bathymetric-evolution models that represent underlying processes of hydrodynamics and sediment transport. These models, however, struggle to reproduce natural cross-shore sandbar behavior on timescales of a few days to weeks and have uncertain skill on longer scales of months to years. One particular concern for the use of models on prediction timescales that far exceed the timescale of the modeled processes is the exponential accumulation of errors in the nonlinear model equations. The relation between cross-shore sandbar migration, sandbar location and wave height has previously been demonstrated to be weakly nonlinear on timescales of several days, but it is unknown how this nonlinearity affects the predictability of long-term (months to years) cross-shore sandbar behavior. Here we study the role of nonlinearity in the predictability of sandbar behavior on timescales of a few days to several months with data-driven neural network models. Our analyses are based on over 5600 daily-observed cross-shore sandbar locations and daily-averaged wave forcings from the Gold Coast, Australia, and Hasaki, Japan. We find that neural network models are able to hindcast many aspects of cross-shore sandbar behavior, such as rapid offshore migration during storms, slower onshore return during quiet periods, seasonal cycles and annual to interannual offshore-directed trends. Although the relation between sandbar migration, sandbar location and wave height is nonlinear, sandbar behavior can be hindcasted accurately over the entire lifespan of the sandbars at the Gold Coast. Contrastingly, it is difficult to hindcast the long-term offshore-directed trends in sandbar behavior at Hasaki because of exponential accumulation of errors over time. Our results further reveal that during periods with low-wave conditions it becomes increasingly difficult to predict sandbar locations, while during high waves predictions become increasingly accurate.

Management of the Dutch embanked floodplains is of crucial interest in the light of a likely increase of extreme floods. One of the issues is a gradual decrease of floodwater accommodation space as a result of overbank deposition of mud and sand during floods. To address this issue, sediment deposits of an undisturbed embanked floodplain near Winssen along the river Waal were studied using ground-penetrating radar (GPR). A number of radar facies units were recognized. Boreholes were used to relate radar facies units to sedimentary facies and to determine radar velocity. The GPR groundwave is affected by differences in moisture and texture of the top layer and probably interferes with the first subsurface reflector. The architectural elements recognized in the GPR transects confirm earlier reported insights on human-influenced river behaviour. This is testified in the development of sand bars during flood regimes that are probably more widespread than previously established.

The temporal evolution of nearshore sandbars (alongshore ridges of sand fringing coasts in water depths less than 10 m and of paramount importance for coastal safety) is commonly predicted using process-based models. These models are autoregressive and require offshore wave characteristics as input, properties that find their neural network equivalent in the NARX (Nonlinear AutoRegressive model with eXogenous input) architecture. Earlier literature results suggest that the evolution of sandbars depends nonlinearly on the wave forcing and that the sandbar position at a specific moment contains ‘memory’, that is, time-series of sandbar positions show dependencies spanning several days. Using observations of an outer sandbar collected daily for over seven years at the double-barred Surfers Paradise, Gold Coast, Australia several data-driven models are compared. Nonlinear and linear models as well as recurrent and nonrecurrent parameter estimation methods are applied to investigate the claims about nonlinear and long-term dependencies. We find a small performance increase for long-term predictions (>40 days) with nonlinear models, indicating that nonlinear effects expose themselves for larger prediction horizons, and no significant difference between nonrecurrent and recurrent methods meaning that the effects of dependencies spanning several days are of no importance.

Management of the Dutch embanked floodplains is of crucial interest in the light of a likely increase of extreme floods. One of the issues is a gradual decrease of floodwater accommodation space as a result of overbank deposition of mud and sand during floods. To address this issue, sediment deposits of an undisturbed embanked floodplain near Winssen along the river Waal were studied using ground-penetrating radar (GPR). A number of radar facies units were recognized. Boreholes were used to relate radar facies units to sedimentary facies and to determine radar velocity. The GPR groundwave is affected by differences in moisture and texture of the top layer and probably interferes with the first subsurface reflector. The architectural elements recognized in the GPR transects confirm earlier reported insights on human-influenced river behaviour. This is testified in the development of sand bars during flood regimes that are probably more widespread than previously established.

石川県千里浜・高松・七塚海岸に対する深浅測量データを基に，多段砂州の周期的沖向移動に伴う変動を抽出し，経験的固有関数(EOF)法に基づく解析を行って，砂州移動の固有モードや岸沖漂砂分布，土砂量変動の解析を行った．砂州の形成・移動・消失から成る地形変動は，EOF第1，第2モードの組合せで表現され，両モードが符号を変えつつ交互に支配的となる4つの型を1サイクル間に推移する．対応する岸沖漂砂分布は，地形変動に対する空間固有関数の空間積分と時間固有関数の時間微分の積により規定される．砂州移動に伴い，汀線での土砂輸送も岸向・沖向に周期変化して汀線付近の地盤高が変動する．前浜との土砂授受により断面内土砂量は周期変動を示すが，1サイクル経過すると元の状態に戻り，土砂量の長期変動には寄与しない．The characteristics of systematic net-offshore migration of the multiple bar system on the Chirihama and neighboring beach, Japan, have been investigated using a set of annual field surveys collected over 11 years. An EOF analysis has been conducted on the periodic movements of the sandbars, and the related cross-shore sediment transport and sediment volume variation were examined. The migration cycle of bars consisting of the successive generation, migration and degeneration were well reproduced by the combination of the 1st and 2nd eigen-modes, and these two modes become dominant alternatively. The principal modes of cross-shore sediment transport are shown to be characterized by the spatial integration of space eigen-function and the temporal derivative of the time eigen-functions. Corresponding to the cyclic movement of sandbars, the direction of sediment transport at the shoreline changes alternatively between seaward and landward directions. The sediment volume over the profile varies accordingly, but on the long-term the net-offshore migration of sandbars does not contribute to the sediment volume variation.

The characteristics of systematic net-offshore migration of the multiple bar system on the Chirihama and neighboring beach, Japan, have been investigated using a set of annual field surveys collected over 11 years. An EOF analysis has been conducted on the periodic movements of the sandbars, and the related cross-shore sediment transport and sediment volume variation were examined. The migration cycle of bars consisting of the successive generation, migration and degeneration were well reproduced by the combination of the 1st and 2nd eigen-modes, and these two modes become dominant alternatively. The principal modes of cross-shore sediment transport are shown to be characterized by the spatial integration of space eigen-function and the temporal derivative of the time eigen-functions. Corresponding to the cyclic movement of sandbars, the direction of sediment transport at the shoreline changes alternatively between seaward and landward directions. The sediment volume over the profile varies accordingly, but on the long-term the net-offshore migration of sandbars does not contribute to the sediment volume variation. 石川県千里浜・高松・七塚海岸に対する深浅測量データを基に，多段砂州の周期的沖向移動に伴う変動を抽出し，経験的固有関数(EOF)法に基づく解析を行って，砂州移動の固有モードや岸沖漂砂分布，土砂量変動の解析を行った．砂州の形成・移動・消失から成る地形変動は，EOF第1，第2モードの組合せで表現され，両モードが符号を変えつつ交互に支配的となる4つの型を1サイクル間に推移する．対応する岸沖漂砂分布は，地形変動に対する空間固有関数の空間積分と時間固有関数の時間微分の積により規定される．砂州移動に伴い，汀線での土砂輸送も岸向・沖向に周期変化して汀線付近の地盤高が変動する．前浜との土砂授受により断面内土砂量は周期変動を示すが，1サイクル経過すると元の状態に戻り，土砂量の長期変動には寄与しない．, 出版者照会後に全文公開

The Sandbar Wildlife Management Area (SWMA) is on the northeast shore of Lake Champlain in Vermont. The wetlands of SWMA are bisected by US Rt. 2, an arterial highway with average daily traffi c (ADT) of 10,200. There are hundreds of acres of wetlands and forested upland on both sides of Rt. 2. Wildlife commonly crosses the highway, which results in a high incidence of roadkill. Northern leopard frogs (Rana pipiens) are a signifi cant portion of the roadkill. The Vermont Agency of Transportation (VTrans) in collaboration with the Vermont Agency of Natural Resources (VANR) installed silt fences as a barrier to keep animals off the highway. This is a short-term solution that also provided a test for the use of temporary fences to direct movement of animals. The long-term solution must include the installation of culverts and permanent fencing. A secondary benefi t of the project was to promote the needs for wildlife crossing in Vermont through media coverage of the project.

We analyse a seven-year dataset (1999–2005) of shoreline and sandbar variations derived from video observations at the embayed Tairua Beach, New Zealand, to explore sandbar–shoreline coupling and to determine how this coupling is related to alongshore-averaged sandbar–shoreline separation and beach rotation. Our results quantify the coupling between the sandbar and the shoreline which is directly related to the reduced separation between the sandbar and the shoreline. Using a simple predictive shoreline model, we show that this behaviour is related to the energy of the incoming waves. Our observations are obtained from a headland-enclosed beach and show aspects of the morphological state that relate to the existence of headlands that are not considered in the Wright and Short beach state classification. Both the sandbar and shoreline at Tairua Beach rotate relatively quickly (< 1 month) during the winter storm events, when the storms are accompanied by strong alongshore components, gradually returning during the summer months. The sandbar–shoreline coupling length scale is controlled by this rotation, with large wavelengths occurring when the sandbar is strongly rotated.

As waves propagate from deep into shallow waters, they begin to interact with the sea floor and undergo through several changes due to non-linear effects. These interactions cause the waves to transform and become non-linear as they decelerate and finally break. These local nonlinearities are reflected on the near-bed oscillatory flow and are inextricably linked to sediment transport, causing erosion-accretion patterns and bar migration. In this work the ability of a practical transport model that includes the effects of velocity and acceleration skewness in the time-varying bed shear stress (Abreu et al., 2011) is assessed to predict sediment transport rates under oscillatory flows and currents. The results are compared with two different data sets obtained under sheet flow conditions, showing a good agreement with the measurements. Moreover, its performance to the undertow and to non-linear characteristics is further assessed. The practical sediment transport model is coupled to a simple bed-evolution model, enabling to evidence the relative strength of mechanisms associated with the wave and current induced sand transports. The results show that the formation of the bar and its migration is affected by a new term introduced in the bed shear stress predictor. This time-varying term accounts for the shape of the wave and is described through two non-linear parameters recently proposed in Abreu et al. (2010).This work provides further insights in the correct prediction of sediment transport modeling and sandbar developments, due to the combined influence of non-linear waves with undertow currents. 1-14pp DHA/NEC 2012

The characteristics of spatiotemporal variation of the multiple bar system on the Ishikawa Coast, Japan, have been investigated using a set of field surveys collected over 51 years. For the time variation, the behavior of sandbars is characterized by the presence of cyclic cross-shore migration of outer bars with approximately 10-year return period. Five cycles have been recognized from 1960 to 2010. The evolution of outermost bar strongly exhibits three-dimensional features. On the contrary to the bar migration patterns observed at many of other sites, the bar position are observed to move landward during the decaying phase.

石川県加越海岸は，福井県境から能登半島付け根の滝崎に位置する砂浜海岸である．本研究では，金沢港以北に位置する延長約32kmの北部加越海岸を対象とし，1998～2010年に取得された深浅測量結果を用いて，海浜地形変動の基本特性を解析し，沿岸方向変化に着目して比較検討を行った．領域南端で金沢港に隣接する内灘地区において急速な堆積が進む一方，その北側では侵食が著しいこと，また，領域北端付近の羽咋地区においても，汀線後退が加速傾向にあることが確認された．海浜単位幅あたりの土砂量変動は，汀線位置変化と全般に対応する形となったが，領域北側においては，汀線の後退傾向に反して土砂量は微増・安定となるなど，汀線近傍と沖側で地盤高変動の傾向に相違が見られた． The characteristics of morphological variation on the northern Kaetsu Coast, Ishikawa, Japan, have been investigated using a set of annual field surveys collected over 13 years for an alonghore stretch of approximately 32 km. Spatiotemporal variation of cross-shore profiles, shoreline location, and sediment volume has been examined for 12 survey lines. The alongshore variability on the study area was substantial: Significant retreat of shoreline was recognized on the middle and north part, while an accelerated accretion occurred on the south end near Kanazawa Port.

The temporal evolution of nearshore sandbars (alongshore ridges of sand fringing coasts in water depths less than 10 m and of paramount importance for coastal safety) is commonly predicted using process-based models. These models are autoregressive and require offshore wave characteristics as input, properties that find their neural network equivalent in the NARX (Nonlinear AutoRegressive model with eXogenous input) architecture. Earlier literature results suggest that the evolution of sandbars depends nonlinearly on the wave forcing and that the sandbar position at a specific moment contains ‘memory’, that is, time-series of sandbar positions show dependencies spanning several days. Using observations of an outer sandbar collected daily for over seven years at the double-barred Surfers Paradise, Gold Coast, Australia several data-driven models are compared. Nonlinear and linear models as well as recurrent and nonrecurrent parameter estimation methods are applied to investigate the claims about nonlinear and long-term dependencies. We find a small performance increase for long-term predictions (>40 days) with nonlinear models, indicating that nonlinear effects expose themselves for larger prediction horizons, and no significant difference between nonrecurrent and recurrent methods meaning that the effects of dependencies spanning several days are of no importance.

International audience; A conceptual analysis of the coupling between bars and infragravity waves is performed combining laboratory experiments and numerical modeling. Experiments are carried out in a wave flume with a barred profile. The Boussinesq fully-nonlinear model SERR1D is validated with the laboratory data and a sensitivity analysis is performed next to study the influence on the infragravity wave dynamics of bar amplitude and location, and swash zone slope. A novel technique of incident and reflected motions separation that conserves temporal characteristics is applied. We observe that changing bar characteristics induces substantial variations in trapped energy. Interestingly, a modification of swash zone slope has a large influence on the reflected component, controlling amplitude and phase time-lag, and consequently on the resonant pattern. Variations of trapped infragravity energy induced by changes of swash zone slope reach 25 %. These changes in infragravity pattern consequently affect short-wave dynamics by modifying the breakpoint location and the breaking intensity. Our conceptual investigation suggests the existence of a morphological feedback through the action of evolving morphology on infragravity structures which modulates the action of short-waves on the morphology itself.