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A field campaign was carried out at a sheltered sandy beach with the aim of gaining new insights into the driving processes behind sheltered beach morphodynamics. Detailed measurements of the local hydrodynamics, bed level changes and sediment composition were collected at the man-made beach on the leeside of the barrier island Texel, bordering the Marsdiep basin that is part of the Dutch Wadden Sea. The data set consists of (1) current, wave and turbidity measurements from a dense cross-shore array and a 3 km alongshore array, (2) sediment composition data from beach surface samples, (3) high-temporal-resolution RTK-GNSS beach profile measurements, (4) a pre-campaign spatially covering bathy-topo map and (5) meteorological data. This manuscript outlines how these measurements were set up and how the data have been processed, stored and can be accessed. The novelty of this data set lies in the detailed approach to resolve forcing conditions on a sheltered beach, where sediment transport is governed by a strong interplay between tidal currents, waves and bed composition, primarily due to the low-energy (near-threshold) forcing. [ABSTRACT FROM AUTHOR]

Beach erosion at the unprotected downdrift end of a groin is common with waves approaching the structure obliquely. This phenomenon has often occurred on the downdrift side of natural groins on the east coast of South Korea during high waves in winter months. The resulting planform assumes a distinctive crenulate shape with a maximum indentation point landward of the erosion. An analytical model is employed to study the beach erosion at the downdrift end of a natural rock groin at Jeongdongjin Beach in Korea, using mathematical equations derived from the parabolic model for headland-bay beaches in static equilibrium, to predict the downdrift control point and maximum indentation of the eroded shoreline. These equations are solved using the prevailing wave height, wave angle at breaking and wave direction derived from analyzing NOAA's wave data over 40 years and the longshore sediment transport rate calculated from the wave data. The location of the calculated maximum indentation is also verified using shoreline video monitoring data and compared with the result of a one-line numerical model for shoreline change. The limitation of the proposed analytical model is discussed as is the effect of sediment bypassing the groin. [ABSTRACT FROM AUTHOR]

In many parts, coastal erosion is severe due to human-induced coastal zone development and storm impacts, in addition to climate change. In this study, the beach erosion risk was defined, followed by a quantitative assessment of potential beach erosion risk based on three components associated with the watershed, coastal zone development, and episodic storms. On an embayed beach, the background erosion due to development in the watershed affects sediment supply from rivers to the beach, while alongshore redistribution of sediment transport caused by construction of a harbor induces shoreline reshaping, for which the parabolic-type equilibrium bay shape model is adopted. To evaluate beach erosion during storms, the return period (frequency) of a storm occurrence was evaluated from long-term beach survey data conducted four times per year. Beach erosion risk was defined, and assessment was carried out for each component, from which the results were combined to construct a combined potential erosion risk curve to be used in the environmental impact assessment. Finally, the proposed method was applied to Bongpo–Cheonjin Beach in Gangwon-do, South Korea, with the support of a series of aerial photographs taken from 1972 to 2017 and beach survey data obtained from the period commencing in 2010. The satisfactory outcomes derived from this study are expected to benefit eroding beaches elsewhere. [ABSTRACT FROM AUTHOR]

Dune height is an important predictor of impact during a storm event given that taller dunes have a lower likelihood of being overtopped than shorter dunes. However, the temporal dominance of the wave collision regime, wherein volume loss (erosion) from the dune occurs through dune retreat without overtopping, suggests that dune width must also be considered when evaluating the vulnerability of dunes to erosion. We use XBeach, a numerical model that simulates hydrodynamic processes, sediment transport, and morphologic change, to analyze storm-induced dune erosion as a function of dune aspect ratio (i.e., dune height versus dune width) for storms of varying intensity and duration. We find that low aspect ratio (low and wide) dunes lose less volume than high aspect ratio (tall and narrow) dunes during longer and more intense storms when the beach width is controlled for. In managed dune scenarios, where sand fences are used to construct a "fenced" dune seaward of the existing "natural" dune, we find that fenced dunes effectively prevent the natural dune behind them from experiencing any volume loss until the fenced dune is sufficiently eroded, reducing the magnitude of erosion of the natural dune by up to 50 %. We then control for dune morphology to assess volume loss as a function of beach width and confirm that beach width exerts a significant influence on dune erosion; a wide beach offers the greatest protection from erosion in all circumstances while the width of the dune determines how long the dune will last under persistent scarping. These findings suggest that efforts to maintain a wide beach may be effective at protecting coastal communities from dune loss. However, a trade-off may exist in maintaining wide beaches and dunes in that the protection offered in the short-term must be considered in concert with potentially long-term detrimental effects of limiting overwash, a process which is critical to maintaining island elevation as sea level rises. [ABSTRACT FROM AUTHOR]

The 2004 Indian Ocean tsunami and the 2011 Tōhoku earthquake and tsunami caused large-scale topographic changes in coastal areas. Whereas much research has focused on coastlines that have or had large human populations, little focus has been paid to coastlines that have little or no infrastructure. The importance of examining erosional and depositional mechanisms of tsunami events lies in the rapid reorganization that coastlines must undertake immediately after an event. A thorough understanding of the pre-event conditions is paramount to understanding the natural reconstruction of the coastal environment. This study examines the location of sediment erosion and deposition during the 2004 Indian Ocean tsunami event on the relatively pristine Phra Thong Island, Thailand. Coupled with satellite imagery, we use numerical simulations and sediment transportation models to determine the locations of significant erosion and the areas where much of that sediment was redeposited during the tsunami inundation and backwash processes. Our modeling approach suggests that beaches located in two regions on Phra Thong Island were significantly eroded by the 2004 tsunami, predominantly during the backwash phase of the first and largest wave to strike the island. Although 2004 tsunami deposits are found on the island, we demonstrate that most of the sediment was deposited in the shallow coastal area, facilitating quick recovery of the beach when normal coastal processes resumed. [ABSTRACT FROM AUTHOR]

Estonia is a small country with remarkably long coastline (ca. 4,000 km). Naturally changeable, strongly indented by peninsulas and bays, and rich in islands (over 1,500 islands) coastline of Estonia is an attractive environment for eco-tourism, human settlements, economic activity and also for coastal researchers. Notably, an increasing activity in seashore dynamics in recent decades has been detected in many countries worldwide including Estonia. Particularly rapid changes occur on depositional (sand, gravel, pebble, till, silt) shores. For example, sandy beaches high in recreation value often suffer from erosion, the areas of erosion and accumulation are shifting, the waterways to harbours need frequent dredging due to siltation, etc. Additionally, an increasing pressure by human activities might be also the cause of erosion in a number of locations. Finally, the impact of climate change combined with increasing human pressure is causing even more rapid changes. The main aim of this poster is to introduce some of the most spectacular findings of this monitoring program and discuss how these results help to increase awareness of people on climate change impacts on the coast and what might be the consequences of mismanagement. This study is based on the results obtained during the fieldwork in the study sites in different parts of Estonia as well as on the analysis of existing maps and datasets. During the fieldworks, we took GPS and RTK-GPS measurements to ascertain short-time changes in shoreline position, contours of beach ridges and location of scarps over the last two decades. Topographic survey (using levelling technique and RTK_GPS) was conducted to assess the beach profiles and the volumes of lost/gained sediments. At present, the modernization of the methodology of coastal monitoring is ongoing. The preliminary measurements are carried out in underwater sections of the monitoring sites using geophysical (acoustic-seismic) methods.In this poster, we present three cases to show different ways of impacts to the coastal zone: a) rapid shore erosion caused by climatic changes; b) gradually worsening erosion-accumulation problem related to unsuitable harbour location and mismanagement of surrounding coastal areas; c) loss of public beach as a result of combination of climate change and wrong coastal protection measures.The natural shoreline retreat in well exposed sandy shores at Harilaid Peninsula may reach over 10 m/year. Primary cause of these changes are shifts in the climatic condition, while direct human impact can be neglected. We have also proved that Lehtma harbour in Hiiumaa, which was established about 100 years ago in the middle of an active zone of longshore sediment transport, is causing massive lack of sediments a few kilometres down-drift resulting in over 60 m of shoreline retreat over the last half century. Our calculations show that an annual loss of the sediment budget is approximately 1500m3. Finally, rebuilding a cafeteria on Valgeranna beach after the extreme storm in 2005 and protecting it from erosion by using stone-walls has resulted in the loss of sandy beach down-drift from this cafeteria. [ABSTRACT FROM AUTHOR]

Blowouts are acknowledged as highly effective transport pathways. Their morphological form is indicative of aeolian transport and the propensity of their topography to modify airflow sufficiently to support transport has been extensively researched. As the evolution of sandy coastlines is governed by sediment exchanges between sub-units of the cross shore profile, blowouts located at the beach-dune interface may play a significant role in evolution through enhancing the landward transfer of sediment into the dune field. Although there is a growing number of studies detailing blowout transport, those which encompass synchronous measurement of flow and sediment exchange from the beach into the dune field remain extremely rare.This study, conducted at Sefton dunes, northwest England, details airflow and sediment transport dynamics at the beach-dune interface of a trough blowout. A dense array of 3D sonic anemometers, co-located with transport sensors were deployed during an oblique onshore wind event. Instantaneous flow and transport dynamics were measured on the back beach, the adjacent upwind foredune and within the throat of the blowout. Additionally, the morphological response was captured via pre and post event TLS surveys.The importance of alongshore deflected airflow in delivering sediment to the blowout throat area was highlighted by a linear trend of high magnitude transport intensity across the upwind foredune. Within the throat, levels of transport intensity displayed extremely high spatial and temporal variability across a relatively confined area. Multiple topographically forced flow modifications were observed. Although incident wind speed remained relatively constant, a sharp 15° onshore directional shift during the experiment resulted in a step change in transport intensity within the blowout, providing insight into how sediment is first delivered to the throat area and then driven landwards. [ABSTRACT FROM AUTHOR]