Coastal Dynamics Research Articles

Comment on Souza and Perez Filho (2019) "Late Holocene Coastal Dynamics, Climate Pulses and Low Terraces in the Coast of the State of São Paulo, Southeast Brazil"

Comment on Souza and Perez Filho (2019) "Late Holocene Coastal Dynamics, Climate Pulses and Low Terraces in the Coast of the State of São Paulo, Southeast Brazil"

Coastline Dynamics Analysis in Dakar Region, Senegal from 1990 to 2040

In the context of climate change, the study of shoreline dynamics is a critical issue concerning economic losses in coastal countries. Therefore, since it is an important parameter to study the impacts of climate change in coastal areas, scientists are more interested in littoral studies seeking deep existential knowledge. This study aims to depict separately the coastal dynamics from 1990 to 2020 in Dakar region. The difference in terms of geologic, geomorphologic and hydrodynamic conditions within the three different coasts of Dakar and the prediction until 2040 have been taken into account in comparison to the previous studies. To achieve this purpose, the Geographic Information System (GIS) approach which is among the most current methods to determine the coastline dynamics is used. Historical Landsat images from the USGS, QGIS 3.12.0, Arc GIS 10.4 and DSAS software have been used for the Landsat images pre-processing and coastline dynamic computation. After obtaining the coastline velocity rate, some predictions of future coastline position have been estimated using the formula of velocity. The results showed that the Dakar region is characterized by an average rate of retreat about −0.44 m/year on the northern coast. The western and southern coasts record respectively a rate of about 0.21 and −0.11 m/year. In 2030, the average rates of retreat of −4.4, 2.1 and −1.1 m/year were estimated respectively in the northern, western and southern coasts.

The Effect of Human Activities Towards Coastal Dynamics and Sustainable Coastal Management

One of the disasters that often occur in coastal areas is abrasion. Abrasion causes coastal dynamics, including the East Coast of Rembang, Kragan Village, Kragan District, Rembang Regency. From 1975 to 1990, at least 50 meters of land from this area has been lost due to abrasion. This dynamic may become one of the causes of unsustainable management of the coastal environment and its natural resources. Various efforts have been made to overcome abrasion, but abrasion continues to hit this area, even until 2020. Qualitative and quantitative approaches were carried out in this study to discover the coast dynamics and various human activities that may trigger abrasion. Image interpretation, observation, interviews, and questionnaires were used as data collection techniques at three observation points in the Kragan Village area. This study concludes that the beach in Kragan Village has experienced dynamics with a total land loss of 46 meters from 2003 to 2020. Harmful activities carried out by humans resulted in abrasion so that the coast experienced dynamics. Human activities also affect coastal management, namely the basic principles of integrated coastal management and processes in the management of coastal areas.

BEACH PROFILE EVOLUTION IN URBAN AND PERI-URBAN AREAS IN THE VILLA GESELL DISTRICT, BUENOS AIRES, ARGENTINA

The coastal villages with the greatest touristic affluence of the province of Buenos Aires, Argentina, are located on the Eastern Sand Barrier. The characteristics of the beaches of Villa Gesell, one of the most visited districts, have been studied before but there is no recent data available. The present work represents an update of the state of the beaches of this district, comparing data collected between 1994 and 2004 with sporadic measurements taken up to 2010. In 2021, two new seasonal surveys were carried out with the completion of four beach profiles distributed throughout the district and covering urban and peri-urban areas. It was observed that beaches in urban areas, where coastal dunes have been deteriorated or eliminated as a result of urban development and some anthropic practices, presented smaller beach widths and lower slopes. Beaches in peri-urban areas, with less building occupation on the waterfront, had greater beach widths and slopes, as well as larger volumes and sediment balances. Seasonal winter/summer cycles, episodic storm cycles and anthropogenic action have been identified as modifying processes of these beaches. Coastal urbanization and practices linked to sun and sea tourism affect coastal dynamics. Thus, sustained monitoring over time is a necessary tool to evaluate possible changes and preserve the beaches that represent a fundamental tourist resource for these localities.

Damming the wood falls.

Rivers historically transported unquantified volumes of driftwood to the ocean. Driftwood alters coastal sediment dynamics and provides food and habitat for diverse organisms. Floating driftwood supports open-ocean organisms. Sunken wood sustains seafloor communities. Centuries of deforestation, flow regulation, and channel engineering have substantially reduced riverine large wood fluxes to the oceans. Here, we use contemporary records of wood flux to reservoirs and coastal regions to estimate the magnitude of potential contemporary global wood fluxes. We estimate that 4.7 million m3 of large wood could enter the oceans each year (the 95% prediction interval range is ~300,000 to 70 million m3). This represents an upper bound for contemporary wood fluxes to the oceans because of wood removal from rivers and reservoirs and a lower bound for historical wood fluxes because of deforestation and river engineering. Substantial reduction of this wood flux likely negatively affects coastal and marine environments.

Assessment of Storm Surge History as Recorded by Driftwood in the Mackenzie Delta and Tuktoyaktuk Coastlands, Arctic Canada

The southern Beaufort coastline in Canada experiences significant storm surge events that are thought to play an important role in coastal erosion and influence permafrost dynamics. Unfortunately, many of these events have not been documented with tide gauge records. In this paper, we evaluate coastal driftwood accumulations as a proxy for estimating maximum storm surge heights and the history of these events. We use historical air photos and data derived from Unoccupied Aerial Vehicle (UAV) imagery to resurvey four coastal stranded driftwood study sites that were first appraised in 1985–86 and assess two new regional sites in the Mackenzie Delta. Maximum storm surge heights were found to be similar to observations carried out in the 1980s, however, we refine the elevations with more accuracy and reference these to a vertical datum appropriate for incorporating into sea level hazard assessments. Detailed mapping, historical air photo comparisons and the UAV acquired imagery at a site close to Tuktoyaktuk demonstrate that the highest storm surge at this site (1.98 m CGVD2013) occurred in association with a severe storm in 1970. This event shifted driftwood and floated material slightly upslope from an older event thought to occur in 1944 that reached 1.85 m (CGVD2013) elevation. The quality and accuracy of the high-resolution Digital Surface Model (DSM) and orthophoto derived from Structure from Motion (SfM) processing of the UAV photographs allowed mapping of four distinct stratigraphic units within the driftwood piles. Based on variations in anthropogenic debris composition, weathering characteristics and history of movement on aerial photographs, we conclude that no storm surge events at Tuktoyaktuk have exceeded ∼1.3 m (CGVD2013) since 1970. While there has been some speculation that ongoing climate change may lead to more frequent large magnitude storm surges along the Beaufort coast, our study and available tide gauge measurements, suggest that while moderate elevation storm surges may be more frequent in the past several decades, they have not approached the magnitude of the 1970 event.

Nearshore sandbar switching episodes and their relationship with coastal erosion at the Curonian Spit, Baltic Sea

The longshore realignment of nearshore sandbars is a morphodynamic phenomenon of multiple sandbar systems that has been known about for several decades. However, it is unknown how switching-related nearshore changes influence the evolution of subaerial beaches. This study aims to define the relationship between sandbar switching episodes and the dynamic state of the beach-foredune system along the Curonian Spit coast (Baltic Sea) using decadal satellite-derived and beach profiling data. To define this connection, sandbar switching locations, sandbar cross-shore positions, shoreline positions, and sand volume changes in the beach-foredune system were assessed on interannual and storm-related time scales. Twenty-seven sandbar switching episodes were observed with an average duration of 14.3 months. Most of the switching episodes occurred at preferred locations, coinciding with breaking points of different shoreline orientations where oblique waves and longshore currents prevailed. Shoreline retreat at an average rate of –14.2 m was observed within most of the sandbar switching zones. During major storm events, the average rate of erosion within the sandbar switching zones was significantly higher than the rate outside them. On an interannual time scale, a moderate average rate of erosion was observed within the sandbar switching zones compared to a small accretion rate outside them. Additional case studies of coastal evolution within the switching zones indicated well-correlated rates of switching-determined outer sandbar positions, shoreline positions, and sand volume on the beach and foredune during the switching episodes. The results of this study could be important for the identification of erosional hot spots and coastal prediction.

Along‐Shore Movement of Groundwater and Its Effects on Seawater‐Groundwater Interactions in Heterogeneous Coastal Aquifers

AbstractStudies of coastal groundwater dynamics often assume two‐dimensional (2D) flow and transport along a shore‐perpendicular cross‐section. We show that along‐shore movement of groundwater may also be significant in heterogeneous coastal aquifers. Simulations of groundwater flow and salt transport incorporating different geologic structure show highly three‐dimensional (3D) preferential flow paths. The along‐shore movement of groundwater on average accounts for 40%–50% of the total flowpath length in both conduit‐type (e.g., volcanic) heterogeneous aquifers and statistically equivalent (e.g., deltaic) systems generated with sequential indicator simulation (SIS). Our results identify a critical role of three‐dimensionality in systems with connected high‐permeability geological features. 3D conduit features connecting land and sea cause more terrestrial groundwater flow through the inland boundary and intensify water exchange along the land‐sea interface. Therefore, conduits increase the rate of SGD compared to equivalent homogeneous, SIS and corresponding 2D models. In contrast, in SIS‐type systems, less‐connected high‐permeability features produce mixing zones and SGD nearer to shore, with comparable rates in 3D and 2D models. Onshore, 3D heterogeneous cases have longer flowpaths and travel times from recharge to discharge compared to 2D cases, but offshore travel times are much shorter, particularly for conduit‐type models in which flow is highly preferential. Flowpath lengths and travel times are also highly variable in 3D relative to 2D for all heterogeneous simulations. The results have implications for water resources management, biogeochemical reactions within coastal aquifers, and subsequent chemical fluxes to the ocean.

Interdisciplinary approach for qualitatively monitoring coastline dynamics in North Java Coast, Case study: Karawang Regency Indonesia

The coast of north Java is the most rapid development area among other parts of Indonesia. Since the North Java Coast is dominated by mild slope, soft-loose quaternary sediment and provoked by the sea thus the vulnerability of it is the most challenging issue to be assessed. Karawang is the representative area to investigate the scientific reason of coastal dynamics. This study aims to reveal the coastline changing based on RBI (1210-211, 1210-212, 1210-221, 1210-542, 1210-543, 1210-544 and 1210-631) and LPI (1210-04 and 1209-01) maps, hydrodynamics simulation and field measurements associated with abrasion and accretion. The equalizing procedure has been applied for a benchmark of zero coastlines that LPI and RBI data were used to observe the back and forth of coastline changing throughout 2000 and 2018. The results show five districts, Tirtajaya, Pakisjaya, Cilebar, Cibuaya and Pedes have the highest abrasion with an average magnitude of 11.3 m/year, 9.1 m/year, 6.9 m/year, 5.1 m/year and 3.7 m/year respectively within a total 489 ha disappear area. By all integrated analysis data so we can conclude that the dominated monsoonal longshore current is east to west and working on the dominantly terrigenous coastal alluvium and intercalated by carbonatic marine sediment.

Coastal dynamics of the Gulf of Kalamita (Western Crimea)

The performed research showed that since the first third of the 20th century until today the beach width at various sections of the Gulf of Kalamita has decreased two-to fourfold, and at some of them beaches have totally disappeared. The average coast erosion rate for the last 100 years has been 1.3 m/yr, with the maximum being 7.8 m/yr. These processes are accompanied with depletion of debris on the beach and underwater slope, erosion of bench deposits, and destruction of coastal structures. This is due to deficiency of beach-forming material resulted from intense economic management in the coastal area. Implementation of scientifically and technically sound coastal protection projects is essential to preserve the beaches of the Gulf of Kalamita.

Vertical pore pressure variations and geotechnical sediment properties at a sandy beach

The role of geotechnical properties and soil behavior for beach dynamics has been recognized before, but geotechnical field measurements in energetic beach environments are still rare. This study focused on two days of field measurements along a cross-shore transect reaching from the foot of the dunes to the upper subtidal zone at the western sandy beach of the island of Sylt, Germany, just south of the city of Westerland. Sediment properties and geotechnical parameters were obtained from sediment sampling and limited in-situ testing. Pore pressure measurements were conducted along a vertical array in the upper 55 cm of the beach surface in the lower intertidal zone. Pore pressure recordings were then analyzed using a one-dimensional-vertical (1DV) model based on Biot (1956) and Mei and Foda (1981). Laboratory testing results demonstrated slight trends of increasing grain size and friction angles from the subaerial to the lower intertidal zone. In-situ sediment strength testing using a portable free fall penetrometer supported the trends in friction angles for the subaerial and intertidal zone. Additionally, a significant increase in sediment resistance was observed in the swash zone and upper subtidal zone. Pore pressure recordings showed a consistent trend associated with the tidal water elevations. However, data collected during low tide suggested a decoupling of surface water effects and groundwater, possibly associated with gas content and negative pore pressures in the vadose zone. Pore pressure recordings also suggested a more pronounced wave damping in the upper sediment layers and a minor phase lag. The 1DV pore pressure model succeeded to simulate the observed pressures at all sediment depths well, and suggested no liquefaction events during the measurement period, but a reduction of effective weight that may affect sediment dynamics.

Investigating the physical and chemical characteristics of construction and demolition wastes as filler to regenerate beaches

Currently, many countries around the world face serious problems related to coastal erosion. The use of natural fillers extracted from shallow areas as well as from rivers for coastal regeneration and beach nourishment generates additional environmental impacts that affect plants and animal communities, water circulation and coastal dynamics, amongst others. On the other hand, construction and demolition wastes (CDW) are becoming more abundant worldwide, generating additional environmental impacts related to water pollution due to leaching of contaminants, as well as loss of landscape quality. In this work it is proposed that CDW can be better suited to replace natural gravel for coastal erosion management. In addition, the use of CDW for beach regeneration will help to reduce the use of natural sources and thus to reduce the environmental impacts produced by extraction. This study investigates the physical characteristics of some fractions of construction and demolition wastes (CDW), particularly concrete, ceramics, asphaltic, and mixture material, to be used as filler to regenerate beaches, replacing the traditional filler generally used elsewhere. A wet ball milling method was used to adequate the physical characteristics (i.e. such as sphericity, roundness, and roughness) of the aggregates of CDW to be used for beach regeneration. The effects of the water mass to solid mass ratio (W/S), mass of sample to the mass of the balls (S/B), as well as ball milling time on the shape of CDW aggregates were studied. The optimum conditions to generate the required aggregates were W/S = 1, S/B = 0.5 and 1 h of ball milling. As particle size is considered an important parameter to avoid water turbidity, it is recommended to use particles with size greater than 2 mm, and the shape of the generated aggregates was calculated and compared to natural beach gravel. Wet ball milling significantly increased their roundness and contributed to a decrease of surface roughness, thus the final material presented high similarity with standard beach gravel aggregates. The durability of the material was also studied and compared to commercial gravel and beach gravel. The results show that weight loss during durability tests mainly depends on chemical composition of the CDW aggregates assayed. The chemical composition and mineralogical phase identification of CDW show the absence of hazardous elements and the presence of dolomite, quartz and calcite as principal phases. Inorganic composition of the CDW was also determined in order to comply with the Spanish Technical Instruction for the Environmental Management of Marine Extractions to obtain sand. Additionally, leaching tests of organic and inorganic substances were carried out according the European Standard EN12457/4 which specifies a compliance test providing information on leaching of granular wastes and sludges under specified experimental conditions, particularly a liquid to solid ratio of 10 L/kg dry matter for materials with a particle size below 10 mm (without or with limited size reduction). All generated aggregates complied with standard requirements, thus based on the satisfactory results produced by wet ball milling treatment on the physicals characteristics of CDW aggregates as well as on their chemical composition and results of the leaching tests, it is proposed the use of CDW as filler in beach and coastal regeneration.

Satellite Image Processing for the Coarse-Scale Investigation of Sandy Coastal Areas

In recent years, satellite imagery has shown its potential to support the sustainable management of land, water, and natural resources. In particular, it can provide key information about the properties and behavior of sandy beaches and the surrounding vegetation, improving the ecomorphological understanding and modeling of coastal dynamics. Although satellite image processing usually demands high memory and computational resources, free online platforms such as Google Earth Engine (GEE) have recently enabled their users to leverage cloud-based tools and handle big satellite data. In this technical note, we describe an algorithm to classify the coastal land cover and retrieve relevant information from Sentinel-2 and Landsat image collections at specific times or in a multitemporal way: the extent of the beach and vegetation strips, the statistics of the grass cover, and the position of the shoreline and the vegetation–sand interface. Furthermore, we validate the algorithm through both quantitative and qualitative methods, demonstrating the goodness of the derived classification (accuracy of approximately 90%) and showing some examples about the use of the algorithm’s output to study coastal physical and ecological dynamics. Finally, we discuss the algorithm’s limitations and potentialities in light of its scaling for global analyses.

On the influence of ENSO complexity on Pan-Pacific coastal wave extremes

Wind-generated waves are dominant drivers of coastal dynamics and vulnerability, which have considerable impacts on littoral ecosystems and socioeconomic activities. It is therefore paramount to improve coastal hazards predictions through the better understanding of connections between wave activity and climate variability. In the Pacific, the dominant climate mode is El Niño Southern Oscillation (ENSO), which has known a renaissance of scientific interest leading to great theoretical advances in the past decade. Yet studies on ENSO's coastal impacts still rely on the oversimplified picture of the canonical dipole across the Pacific. Here, we consider the full ENSO variety to delineate its essential teleconnection pathways to tropical and extratropical storminess. These robust seasonally modulated relationships allow us to develop a mathematical model of coastal wave modulation essentially driven by ENSO's complex temporal and spatial behavior. Accounting for this nonlinear climate control on Pan-Pacific wave activity leads to a much better characterization of waves' seasonal to interannual variability (+25% in explained variance) and intensity of extremes (+60% for strong ENSO events), therefore paving the way for significantly more accurate forecasts than formerly possible with the previous baseline understanding of ENSO's influence on coastal hazards.

Coastal Image Classification and Pattern Recognition: Tairua Beach, New Zealand.

The study of coastal processes is critical for the protection and development of beach amenities, infrastructure, and properties. Many studies of beach evolution rely on data collected using remote sensing and show that beach evolution can be characterized by a finite number of “beach states”. However, due to practical constraints, long-term data displaying all beach states are rare. Additionally, when the dataset is available, the accuracy of the classification is not entirely objective since it depends on the operator. To address this problem, we collected hourly coastal images and corresponding tidal data for more than 20 years (November 1998–August 2019). We classified the images into eight categories according to the classic beach state classification, defined as (1) reflective, (2) incident scaled bar, (3) non-rhythmic, attached bar, (4) attached rhythmic bar, (5) offshore rhythmic bar, (6) non-rhythmic, 3-D bar, (7) infragravity scaled 2-D bar, (8) dissipative. We developed a classification model based on convolutional neural networks (CNN). After image pre-processing with data enhancement, we compared different CNN models. The improved ResNext obtained the best and most stable classification with F1-score of 90.41% and good generalization ability. The classification results of the whole dataset were transformed into time series data. MDLats algorithms were used to find frequent temporal patterns in morphology changes. Combining the pattern of coastal morphology change and the corresponding tidal data, we also analyzed the characteristics of beach morphology and the changes in morphodynamic states.

Glukhoye Lake: Middle to Late Holocene environments of Kunashir Island (Kuril Archipelago, Russian Far East)

A multiproxy analysis of a sediment core from Glukhoye Lake in the southern Kuril Islands indicates that the basin originated c. 8.2 cal. ka BP as a brackish lagoon with the subsequent development of a freshwater lake (c. 4.0 to 3.3 cal. ka BP), a bog (c. 3.3 to 2.4 cal. ka BP) and a second lake (c. 2.4 cal. ka BP to present). The basin history primarily reflects local coastal dynamics and is not related to proposed Archipelago‐wide changes in sea level. Between c. 8.2 and 8.0 cal. ka BP, the vegetation of southern Kunashir Island was characterized by Betula–Quercus forest with a secondary component of temperate broadleaf trees. Quercus broadleaf forest established c. 8.0 to 6.5 cal. ka BP and represents the Holocene thermal maximum. The remainder of the record shows a gradual decrease in temperate and an increase in conifer taxa, indicating a gradual cooling from the Holocene thermal maximum to c. 2.3 cal. ka BP. Maxima in Picea and Abies pollen between c. 2.3 and 1.1 cal. ka BP suggest conditions that were slightly cooler than present. Palaeovegetation changes in the Kuril Islands as inferred from lake and section data differ in the timing and/or composition of the vegetation communities, although results from the two types of sites become more similar as the number of sections increases. The lake results do not support a previous conceptual model developed for the southern Russian Far East, which linked changes in sea levels to Holocene climate fluctuations. Rather the depositional environments in the lake cores seem more related to coastal dynamics that are independent of fluctuations in sea levels or climate. The difficulty in developing accurate age models for sites with multiple depositional environments may be the most important obstacle for documenting and understanding the Archipelago’s vegetation and climate histories.

Holocene coastal environmental changes inferred by multi-proxy analysis from Lago Formoso sediments in Maranhão State, northeastern Brazil

Little is known about the history of the coastal environment in the northern part of northeastern Brazil and the role of sea level and climate change, as well as the human impact during the past. In order to shed more light on coastal ecosystem dynamics and its influencing factors, a 300 cm long sediment core has been taken from Lago Formoso (LF), located around 150 km distance from the present-day coast in Maranhão State. The core has been radiocarbon dated and analyzed by pollen, spores, charcoal, X-Ray Fluorescence (XRF), X-ray Powder Diffraction (XRPD), LOI, and sedimentary characteristics. During the period from 7520 to 6230 cal yr BP occurred a dominance of mangrove vegetation, and a high relative sea level (RSL), indicating that the coast of the Atlantic Ocean was very close to the study area. The following period is characterized by an increased input of marine sediment into LF and vegetational succession, indicating a highstand of RSL between 5500 and 5020 cal yr BP. From 5020 to 2580 cal yr BP, dominant sandy sediments show chemical and mineralogical characteristic typical of continental sources. The study area was represented mainly by herbaceous and arboreal vegetation, while mangroves were absent, indicating an RSL decrease. The period between 2580 and 1350 cal yr BP is marked by the lower water table and the stronger presence of rainforest vegetation, and an increasing presence of palm trees, indicating the beginning of the human settlement. The last period, after 1350 cal yr BP, is marked by an even stronger anthropogenic influence in the study area, as the records of the stilt-house settlements also evidence it. These records together with others from the same region are the only evidence of stilts-houses from the pre-colonial period in South America.

Urban pocket-beach morphodynamics along the wave-dominated southwest coast of Lake Michigan: An analysis of shoreline and sand volumetric changes

Many of the world’s beaches are embayed, but while a large body of work addresses the geomorphology of pocket beaches in oceanic settings, little is known about urban analogs, especially within the Great Lakes of North America. Groins and jetties shelter these systems from direct interaction with littoral processes, which elsewhere can influence how changes in lake level, winter-ice cover, and wave climate impact beach evolution. We address the direct controls of these forcing parameters on beach morphodynamics over a 33-yr period at North Point Beach, which is confined to an engineered ‘container’ along Lake Michigan’s wave-dominated SW margin. Analysis of near-annual beach change suggests lake-level change is the dominant geomorphic driver over inter-annual to decadal timeframes, with winter ice playing a secondary role. Pocket-beach shoreline positions were found to be unreliable indicators of sand volumetric changes. Lake-level rise facilitated shoreline retreat and overwash-induced beach accretion while high lake levels created the accommodation for additional sands to enter the embayment. This is important for coastal managers to consider when developing mitigation strategies for ongoing lake-level fluctuations and anticipated regional climate impacts. This foundational assessment has implications for embayed beaches of the greater Chicago coastal margin (n > 20), where many other site-specific variables (e.g., groin orientations and shoreline aspect) may factor into nearshore and onshore beach morphodynamics. Continued research into urban pocket beaches of the Great Lakes stands to offer useful information on the impacts of littoral fragmentation on coastal sediment routing during different lake-level phases and degrees of littoral interconnectivity.

The Making of a Gravel Beach (Cavo, Elba Island, Italy)

This paper presents the history and evolution of the different projects carried out from 1999 to 2008 at Cavo beach in the Elba Island, Italy. The village of Cavo almost completely lost its beach in the 1970s due to the reduction of sedimentary input, and the backing coastal road was defended by a revetment and two detached breakwaters. Such severe erosion processes continued in the following years and impeded any possibility of beach tourist development. In 1999, a project based on the removal of existing breakwaters and beach nourishment works based on the use of gravel as borrow sediment and the construction of two short groins to maintain nourished sediment, raised environmental concern and did not find the approval of the stakeholders. They were worried about the characteristics of the sediments, i.e., waste materials from iron mining rich in red silt and clay. Such sediment fractions made the sea red during the nourishment and deposited on the Posidonia oceanica meadow in front of the beach, with a potential environmental impact. Furthermore, they cemented the gravel fraction forming a beach rock. Between 2006 and 2008, these materials were covered with better quality gravel, extending and raising the beach profile, which required the elevation and lengthening of the two existing groins. Beach evolution monitoring following the second project, based on morphological and sedimentological data acquired before, during and after the works, demonstrated the great stability of the newly created beach. The wider beach has allowed the construction of a promenade and the positioning, in summer, of small structures useful for seaside tourism, increasing the appeal of this village. Data presented in this paper shows an interesting study case, since few examples exist in international literature regarding gravel nourishment projects monitoring and evolution.

Short-term seasonal changes of the Dzita beach of Ghana using geographic information system and photogrammetry

Coastal erosion has become an issue globally. As the sea level continues to rise due to global warming, projections are that erosion would increase. To address the issue sustainably, relevant scientific information such as sediment transport and shoreline dynamics is required at local scales. Over the years, erosion at the eastern coast of Ghana has been mainly evaluated using low-resolution imagery due to the challenges in retrieving high-resolution data in the nearshore region. An unmanned aerial vehicle (UAV) approach was used to assess beach evolution on a seasonal and short-term basis between May 2018 and December 2019. Using the UAV approach, shoreline changes, sediment volume changes, and profile elevation parameters were extracted for the Dzita beach of Ghana. Shoreline changes indicated the dominance of erosion during the first and third phases (May 2018–December 2018 and June 2019–December 2019, respectively) at a rate of −7.23 ± 0.23 and −4.85 ± 0.23 m/yr, whereas the second phase (January 2019–June 2019) showed accretion of +8.44 ± 0.23 m/yr. Beach profiles from the first, second, and third phases had steep and gentle slopes, respectively. From these observations, it was recommended that soft engineering approaches such as beach nourishment should be implemented to protect the shoreline and strict prevention of nearshore sand mining and gravel mining. It is also possible that the beach could go through a cycle of changes. Further studies using this same approach should be done as well as probing into other parameters such as nearshore bathymetry to have a better understanding of beach dynamics as envisaged.