Coastal Dynamics

Shorelines of sandy beaches are constantly adapting under the forcing of natural and anthropogenic processes. The aim of this study was to develop a methodology to statistically assess the shoreline resilience to storms at different time scales at a storm-dominated mid-latitude meso-to macro barred beach (Biscarrosse, SW France). On a pilot base, storm-free tropical Jamestown beach (Ghana, Gulf of Guinea) was also analysed to explore the potential of using such technique in West Africa.
6-years (2007-2012) of continuous daily video-derived shoreline data and hindcasted hydrodynamics (ECMWF EraInterim) were analysed. Wave climate is dominated by storms (defined as Hs>5% exceedance threshold) and their seasonal fluctuation of intensity and occurrence; 75% of storms occurring in winter with over more than 60 identified storms over the study period. A multi-linear regression on 36 storms shows that whereas current and previous storm intensity have predominant role on current storm impact, tide and sandbar play a major role on the post-storm recovery duration.
An ensemble average on post-storm recovery period shows that Biscarrosse beach recovers rapidly (9 days) to individual storms and sequences of storms (clusters) have a weak cumulative effect. The results therefore point out that rather than individual intensity of storms, their recurrence frequency is key: the beach evolves to an energetic equilibrium state under frequent storms. If the interval between two storms is low compared to the recovery period, the beach becomes more resilient to the following storms; and the first storm in clusters has larger impact than following ones.
Shoreline responds in decreasing order at seasonal, storm event frequency and annual timescales, even though storms are the dominant forcing at Biscarrosse. The use of EOF method shows good skills in separating uniform and non-uniform shoreline dynamics, even at open beaches, and that they have different temporal variability: seasonal and short-term scales dominate first EOF (2D) and second (3D) modes, respectively.
The shoreline at Jamestown was studied on pilot base from 2013-2014 (about 280 days only). Water level fluctuations (astronomical and atmospherical tides) play a predominant role on shoreline location, compared to a rather constant wave forcing. Waves and tide estimates from video are in good agreement with hindcasts. This pioneer study shows the potential of the technique, to be replicated elsewhere in West Africa through a coastal observation network, in order to assess the response of this stretch of coasts, with all its diversity and regional climate variability.

De Waal, M.S., Barbados’ Natural Landscapes. Conditions for Pre-Colonial Settlement, Site Preservation and Archaeological Fieldwork.
In: De Waal, M.S., Finneran, N., Reilly, M.C., Armstrong, D.V. and Farmer, K. (eds) 2019: Pre-Colonial and Post-Contact Archaeology in Barbados. Past, Present, and Future Research Directions, Sidestone Press (Leiden), pp. 43-60.

The article analyzes the contemporary processes of natural and human-induced shoreline dynamics between cape Kaliakra and cape Emine, Bulgarian Black Sea coastal zone. Main accent is put on the anthropogenic impact on beach morphodynamics, coastal erosion, sediment transport and accretion influenced by land use changes and technogenic load. The stages of recent landscape transformations since the beginning of the XX century are discussed chronologically. Assumptions are made with reference to existing relationships among coastal geomorphic processes, land use dynamics, levels of anthropogenization and coastal landscape change at the investigated area. - КиберЛенинка: https://cyberleninka.ru/article/n/recent-trends-in-state-of-landscapes-and-shoreline-dynamics-in-bulgarian-sector-of-the-black-sea

This study analyzes the characteristics of upwelling events during the northeast monsoon, as
well as El-Niño impacts towards upwelling in the northwest Sabah, which is located in southern
part of the South China Sea by combining remote sensing, reanalysis, and modeling data. The
data used in this study obtained from Moderate Resolution Imaging Spectroradiometer (MODIS)
Aqua satellite for the sea surface temperature (SST) and chlorophyll a concentration data, Hybrid
Coordinate Ocean Model (HYCOM) for the vertical cross section of temperature and salinity
data, and European Centre for Medium-range Weather Forecast (ECMWF) Interim Reanalysis
(ERA-Interim) for the wind data, as well as Ekman transport and Ekman pumping analysis during
December to April 2003-2016. The monthly mean of the climatological data were analyzed and
the results showed that the MODIS-Aqua satellite indicates the presence of cooler sea surface
temperature (SST) and higher chlorophyll-a concentration along the inshore region of northwest
Sabah during the northeast monsoon, indicating the existence of upwelling. Cross-sectional
temperature profiles obtained from the HYCOM further confirmed the existence of upwelling as
the thermohaline was uplifted from the deeper layer and reached the surface during the northeast
monsoon. Ekman transport and Ekman pumping derived from the ECMWF showed an upwelling
favorable condition during the northeast monsoon. Comparison between climatological data and
El-Niño year in 2016 represented that El-Niño events somehow increase the upwelling intensity
due to the intensification of Ekman transport and Ekman pumping.

Large, artificial habitation platforms are widely distributed along the southern North Sea coasts. ln this article, we will focus on the less known, small medieval platforms situated further inland, on the edge of the extensive peat bogs which until medieval times covered much of the lowlands of the Netherlands' We have confronted data from the area Eelder-and Peizermaden (northern Netherlands) with existing models on the dynamics of human colonization and exploitation of North Sea coastal wetlands. The evidence from 'peat terps' seems to reflect distinct and successive land-use types or strategies that are associated with at least two colonization phases. Changes in land use are related to environmental changes that are largely human-induced. This is typical for coastal peat landscapes. Land-use patterns display spatio-temporal similarities as well as differences. The observed succession of land-use types and the associated material culture bear a strong resemblance to developments in the western Netherlands IJ estuary a millennium before.

Erosion and accretion rate are found very high in the estuary of an active delta which can be observed by satellite imageries. According to the multispectral satellite imageries it is found that accretion of Domar Char (a little island belongs to Meghna estuary) was more than 1192 hectares in last 25 years. The study was conducted in five years interval from 1990 to 2015 using spatial analyst extension of ArcGIS. It is revealed that accretion rate is about 208 hectares/year and erosion is about 160 hectares/year, which indicates the dynamic nature of the island. According to Landsat imageries about 2500 hectares of land rose in five years (1990 to 1995) and again lost 2300 hectares of land in next five years (1995 to 2000). Though the total area of intertidal zone has decreased, the area of barren land, vegetation and sand dune has increased over the time.

The petrographic composition and grain shape variability of beach gravels in the Pogorzelica-Dziwnów coast section (363.0 to 391.4 km of coastline), southern Baltic Sea, Poland were analyzed herein to characterize the lithodynamics and trends of seashore development. Gravels were sampled at 0.25 km intervals, in the midpart of the berm, following an early-autumn wave storm and before beach nourishment. Individual variations in petrographic groups along the shore were investigated. Gravel data were compared and related to coastal morpholithodynamics, seashore infrastructure, and geology of the study area. The contribution of crystalline rock gravels (igneous and metamorphic) was observed to increase along all coast sections, whereas the amount of less resistant components (limestones, sandstones, and shales) usually declined. This effect is explained by the greater wave crushing resistance of igneous and metamorphic components, compared with sedimentary components. Similarly, the gravel grain shape (mainly elongation or flattening) was observed to change, depending on resistance to mechanical destruction, or due to the increased chemical weathering in mainly the limestones, marbles, and sandstones. Observed increase in contribution of discoid and ellipsoid grains is a potential indicator of depositional trends along the coast sections investigated. On the other hand, increased contents of spheroidal and spindle-shaped grains may be related to erosional trends, where intensive redeposition and mechanical reworking of gravels occurs. However, due to the great number of coastal embankments, the petrographic composition and shape parameters of beach gravels do not always clearly indicate the dominant direction of longshore bedload transport. Increased amount of eroded limestone located east of Pogorzelica indicate increased erosion of glacial tills. These sediments are deposited, building the shallow foreshore, with additional redeposition of morainic material towards the shore.

Sabine Bank, a transgressive shoal located 30 km off the Louisiana-Texas border, USA, has been considered as one of the plausible resources for re-nourishment of the adjacent barrier islands and beaches. Little has been reported on the bottom boundary layer dynamics and sediment transport from this shallow coastal environment. A comprehensive field investigation, coupled with numerical modeling, has been implemented. Wave and bottom boundary layer interactions were strongly associated with the passage of cold fronts across the region. Strong southerly/southeasterly wind regimes also contributed to the re-suspension and transport of sediments, even during summer season. Modification in bulk wave parameters due to two mining scenarios were computed using modified bathymetries and the result shows minimum impact from the proposed mining from the shoal crest. Sediment re-suspension intensity (RI) was computed and found to be high over the inner shelf and shoal during severe storms.

Sabine Bank, a transgressive shoal located 30 km off the Louisiana-Texas border, USA, has been considered as one of the plausible resources for re-nourishment of the adjacent barrier islands and beaches. Little has been reported on the bottom boundary layer dynamics and sediment transport from this shallow coastal environment. A comprehensive field investigation, coupled with numerical modeling, has been implemented.

Summary: An ever growing number of experts and specialists in modern territorial evolution use historical cartography as a primary source. We can say the same for those interested in the evolution of a coastline, not necessarily from an historical point of view, but because they are engaged in counteracting what appears to be an un-restrainable phenomenon of erosion that in 2006 concerned 42% of the low sandy beaches of the Italian coast. We do not have to go too far back in time to see that the intermittent phenomena of an advancing and retreating coastline is not new. Compared to a century or two ago, however, erosion today not only causes severe and immediate economic repercussions, but in the short and intermediate time frame risks the same repercussions on population distribution and settlement at both a national and regional level. Naturally this is all due to global factors: climate change, rising sea levels, greenhouse effect, and others. Few negationists are left, but the p...

Overwash hydrodynamics datasets are mixed in quality and scope, being hard to obtain due to fieldwork experimental difficulties. Aiming to overcome such limitations, this work presents accurate fieldwork data on overwash hydrodynamics, further exploring it to model overwash on a low-lying barrier island. Fieldwork was performed on Barreta Island (Portugal), in December 2013, during neap to spring-tides, when significant wave height reached 2.64 m. During approximately 4 hours, more than 120 shallow overwash events were measured with a video-camera (at 10 Hz), a pressure transducer (at 4 Hz) and a current-meter (at 4 Hz). This high-frequency fieldwork dataset includes runup, overwash number, depth and velocity. Fieldwork data along with information from literature were used to setup XBeach model in non-hydrostatic mode. The baseline model had variable skills over the duration of the overwash each 30 minutes. The baseline model was forced to simulate overwash with different nearshore ...

For morphological behavior of coasts on the long term (years to decades), both storm events and daily conditions can play a role. It can be a challenge to combine the modeling of both types of conditions, because they act on different time scales and the dominant processes are different. This paper presents an assessment of three approaches for long term modeling (5 year), combining different time scales in an integrated modeling framework using the stationary and instationary modes of the XBeach morphological model for a nourishment in The Netherlands. All three methods lead to stable results providing insight in the long term behavior of the nourishment. The results are similar, suggesting the impact of storm events at the study site is limited for the considered period of five years. It was found that nearshore wave height was 20-40% higher using the instationary compared to the stationary mode of the model.

Since 2010, the local press has been reporting an accelerated process of erosion on the sandy beach-es  of  the  Costa  Rican  Caribbean  coast,  it  has  even  been  documented  within  protected  areas.  To  quantify this process and identify coastal erosion hotspots in the Caribbean south, a methodology was proposed for detecting and delineating the shoreline using aerial photographs and high-reso-lution  satellite  imagery  to  determine  the  rate  of  shoreline  retreat,  the  employed  photographs  and  images cover the period between 2005 and 2016. By such means it was possible to identify eleven erosion hotspots, as well as estimation of their retreat rates for the periods 2005-2010 and 2010-2016. The localities that have experienced the greatest erosion of their sandy beaches are Cahuita National Park, Westfalia and Bananito Beach.

Erosion and accretion rate are found very high in the estuary of an active delta which can be observed by satellite imageries. According to the multispectral satellite imageries it is found that accretion of Domar Char (a little island belongs to Meghna estuary) was more than 1192 hectares in last 25 years. The study was conducted in five years interval from 1990 to 2015 using spatial analyst extension of ArcGIS. It is revealed that accretion rate is about 208 hectares/year and erosion is about 160 hectares/year, which indicates the dynamic nature of the island. According to Landsat imageries about 2500 hectares of land rose in five years (1990 to 1995) and again lost 2300 hectares of land in next five years (1995 to 2000). Though the total area of intertidal zone has decreased, the area of barren land, vegetation and sand dune has increased over the time. Asiat. Soc. Bangladesh, Sci. 42(2): 219-228, December 2016

Angular unconformites between Jurassic and Miocene strata are exposed in the sea cliffs of Cala Cigonya on the northwest coast of Menorca in the Balearic Islands of Spain. The geological discontinuities represent rocky shores on opposite sides of a former headland with 15 m of topographic relief. On the east flank, Jurassic dolomite is overlain by Upper Miocene (Tortonian to Messinian) breccia and laminated limestone. Here, a partially exhumed dolomite surface records Miocene bivalve borings of the ichnospecies Gastrochaenolites torpedo and G. lapidicus that achieved a density of >1,000 borings/m2. Other associated traces include sponge borings (Entobia isp.) and polychaete borings (Caulostrepsis isp.). A breccia deposit 0.8 m thick was derived from the underlying dolomite and angular clasts still retain evidence of bivalve borings. Above follows a succession of laminated limestone beds more than 5 m thick, including some levels with dome-shaped stromatolites and other horizons with reworked dolomite clasts. Thin-section analysis of the laminated limestone reveals dark and light couplets 0.2 mm thick consistent with microbial origins. In contrast, the west flank was buried by coarse sandstone and laminated sediments. Here, dwelling structures of regular echinoids (Circolites kotoncensis) are the dominant traces preserved on the dolomite surface, reaching a maximum density of 66 borings/m2. Associated borings include Entobia geometrica as well as rare traces of Gastrochaenolites isp. and Trypanites isp. Notable for the absence of a basal Miocene breccia, the west flank is interpreted as a sheltered rocky shore coeval with an exposed rocky shore on the east flank. Today, heavy surf on the north coast of Menorca is related to the Tramontana winds that blow out of Spain during winter months. Similar atmospheric circulation patterns must have prevailed during the Late Miocene, but the replacement of ichnofacies by microbial build-ups resulted from increased salinity during the Messinian crisis.