Beach and Dune Erosion: Causes and Interventions, Case Study: Kaulon Archaeological Site

The dune systems are very important from an environmental, landscape, and coastal defense point of view within coastal areas. Currently, dune systems are significantly reduced compared to a few decades ago and, in Europe alone, dune systems have decreased by 70%. During the same period, intense beach erosion processes have often been observed, and, currently, 30% of the world’s coasts are eroding. These processes have various causes, both natural and anthropogenic, and the knowledge of the causes of the erosive processes are very important for an effective planning and management of coastal areas and to correctly plan any interventions on dunes and beaches. The paper, through a case study, analyzes the beach and dune erosive processes, their causes, and the possible interventions. The case study concerns the archaeological site of Kaulon, located on a dune in the Ionian coast of Calabria (Italy). The beach near the site was affected by erosive processes and during the winter of 2013–2014, the site was damaged by two sea storms. To identify the causes of these processes, three erosive factors were analyzed. These factors are anthropogenic pressure, wave climate and sea storms, and river transport. The effects produced by these factors were assessed in terms of shoreline changes and of damage to the beach–dune system, also evaluating the effectiveness of the defense interventions. The main causes of the erosive processes were identified through the cross analysis of erosive factors and their effects. This analysis highlighted that in the second half of the last century the erosive processes are mainly correlated to anthropogenic pressure while, recently, natural factors prevail, especially sea storms. Regarding the interventions, the effects produced by two interventions carried out during the winter of 2013–2014, one built in urgency between the first and second sea storm and the other built a few years after the second sea storm were analyzed. This analysis highlighted that the latter intervention was more effective in defending the site.

Photoprotection and high-light acclimation in semi-arid grassland lichens – a cooperation between algal and fungal partners

In lichens, each symbiotic partner cooperates for the survival of the symbiotic association. The protection of the susceptible photosynthetic apparatus is essential for both participants. The mycobiont and photobiont contribute to the protection against the damaging effect of excess light by various mechanisms. The present study investigated the effect of seasonality and microhabitat exposure on photoprotection and photoacclimation in the photo- and the mycobiont of six lichen species with different thallus morphology in inland dune system in the Kiskunság region (Hungary) with shaded, more humid and exposed, drier dune sides. High-Performance Liquid Chromatography, spectrophotometry, chlorophyll a fluorescence kinetic technique were used, and micrometeorological data were collected. The four years data series revealed that the north-east-facing side was characterized by higher relative humidity and lower light intensities compared to the south-west-facing drier and more exposed sides. The south-west facing side was exposed to direct illumination 3–4 hours longer in winter and 1–2 hours shorter in summer than the north-east facing side of the dune, influencing the metabolism of sun and shade populations of various species. Because rapid desiccation caused short active periods of lichens during bright and drier seasons and on exposed microhabitats, the rapid, non-regulated non-photochemical quenching mechanisms in the photobiont had a significant role in protecting the photosynthetic system in the hydrated state. In dehydrated conditions, thalli were mainly defended by the solar screening metabolites produced by the mycobiont and curling during desiccation (also caused by the mycobiont). Furthermore, the efficacy of light use (higher chlorophyll and carotenoid concentration) increased because of short hydrated periods. Still, a lower level of received irradiation was appropriate for photosynthesis in dry seasons and on sun exposed habitats. In humid seasons and microhabitats, more extended active periods lead to increased photosynthesis and production of solar radiation protectant fungal metabolites, allowing a lower level of photoprotection in the form of regulated non-photochemical quenching by the photobiont. Interspecific differences were more pronounced than the intraspecific ones among seasons and microhabitat types.

Sand Trapping Fences as a Nature-Based Solution for Coastal Protection: An International Review with a Focus on Installations in Germany

Sand trapping fences are a widely used nature-based solution to initiate dune toe growth along sandy shorelines for coastal protection. At present, the construction of sand trapping fences is based on empirical knowledge, since only a few scientific studies investigating their efficiency exist. However, the restoration and maintenance of beach-dune systems along the coast requires knowledge of the interaction between the beach-dune system and the sand trapping fences to provide guidance for coastal managers on how and where to install the fences. First, this review gives an overview of the typical aerodynamic and morphodynamic conditions around a single porous fence and the influence of various fence height and porosity values to understand the physical processes during dune establishment. Second, different approaches for evaluating the efficiency of sand trapping fences to trap sediment are described. This review then highlights significant differences between sand trapping fence configurations, nationally as well as internationally, regarding the arrangement, the materials used, and the height and porosity. In summary, it is crucial to enable an intensive exchange among the respective coastal authorities in order to create uniform or transferable guidelines taking local conditions into account, and thus work collaboratively on the idea of sand trapping fences as a nature-based solution in coastal areas worldwide.

Monitoring the Dynamics of Formby Sand Dunes Using Airborne LiDAR DTMs

Coastal dunes play an important role in coastal erosion risk management, where they act as a dynamic natural sea defence line. Formby coast is part of the Sefton coast in the Northwest of England and is one of the largest and most rapidly evolving sand dune systems in the UK. Such dune systems require continuous comprehensive monitoring activity to understand their dynamics. In this research, we investigate the use of airborne LiDAR digital terrain model DTMs for monitoring the dynamics of the sand dunes at Formby between 1999 and 2020. We found that the rate of elevation change for the beach and the dune areas ranges from −0.78 to 0.02 m/year and −0.92 to 0.73 m/year, respectively. The beach and the frontal dunes have had significant sand erosion, while the inner dunes gained sand during the measurement period. Vegetated areas remained unchanged due to the impact of vegetation in stabilizing the movement of the dunes. Formby beach had a volume loss of about 907,000 m3 in the last 21 years, while the dunes had a volume increase of about 1,049,000 m3 over the same period. The total volume of the entire dune system, consisting of both the beach and dune areas, remained unchanged, which indicates that the growth of the inland dunes is fed by sand from the beach. All the volumetric changes occurred due to sand redistribution within the system, with erosion along the beach, and deposition and erosion in the dune areas.

Soil erosion, reservoir lake infill and coastal erosion in the Mediterranean coast of southern Spain.

The combination of vigorous terrain and millenary human action has produced major changes in vegetation cover, impacting soil losses from slopes and, consequently, sediment production. Increasing focus in the management of water resources led to the widespread construction of dams to generate water flows for iron production, irrigation and to satisfy the increasing demand of the massive urban development along the Costa del Sol. To investigate the connection between soil degradation and loss and river sediment transport retention at a major dam, a first-order sediment yield prediction was established by using a GIS-based model at river basin scale. A quantitative validation of model results is provided by empirical measurements of sedimentation in the main reservoir lake of La Concepción using D_GPS/Echo sounder combination and a Remotely Piloted Aircraft compared with pre-construction blue print topography aimed at documenting spot heights where sediments accumulated or eroded over 50 years. The significant erodibility that we have estimated seems matched by potentially high sediment accumulation rates along selected profiles and spot heights across the bottom of the reservoir lake. Our study discusses that Mediterranean coastal systems may no longer stay in the resilience envelope set by a critically delicate sediment transport balance and without engineering support in the form of direct sediment feeding to the marine system by the permanent nourishment works required. Due to soil loss, sediment entrapment in reservoirs and water management policies, the coastal protection offered by the natural resilience of the beach and dune system is no longer recoverable.

Shoreline Evolution and Environmental Changes at the NW Area of the Gulf of Gela (Sicily, Italy)

Coastal areas are among the most biologically productive, dynamic and valued ecosystems on Earth. They are subject to changes that greatly vary in scale, time and duration and to additional pressures resulting from anthropogenic activities. The aim of this work was to investigate the shoreline evolution and the main environmental changes of the coastal stretch between the towns of Licata and Gela (in the Gulf of Gela, Sicily, Italy). The methodology used in this work included the analysis of: (i) shoreline changes over the long- and medium-term periods (1955–2019 and 1989–2019, respectively), (ii) dune system fragmentation and (iii) the impact of coastal structures (harbours and breakwaters) on coastal evolution. The shoreline change analysis mainly showed a negative trend both over the long- and medium-term periods, with a maximum retreat of 3.87 m/year detected over the medium-term period down-drift of the Licata harbour. However, a few kilometres eastward from the harbour, significant accretion was registered where a set of breakwaters was emplaced. The Shoreline Change Envelope (SCE) showed that the main depositional phenomena occurred during the decade between 1955 and 1966, whereas progressive and constant erosion was observed between 1966 and 1989 in response to the increasing coastal armouring.

Potentiels agronomiques des Niayes de Mboro (littoral Nord du Sénégal) et risques de dégradation mécanique par ensablement : approche par analyse géomorphologique des enjeux socio-économiques

La côte de Mboro, partie intégrante de la Grande Côte du Sénégal, est un creuset de territoires porteurs d’enjeux socio-économiques. Ces territoires sont formés d’écosystèmes supports de l’économie agricole maraîchère en sus des activités inhérentes à la littoralisation de la vie. C’est un espace qui est soumis aux facteurs de la morphodynamique du système de dunes littorales. Ce sont des facteurs agents du risque vecteurs de la dynamique d’ensablement en cours. L’objectif de cet article est de déterminer la granulométrie du substrat dunaire afin d’apprécier sa sensibilité au vent, d’une part, et de mesurer les enjeux socio-économiques du potentiel agronomique maraîcher à Mboro, d’autre part. Dans ce cadre, la méthodologie est basée sur un échantillonnage de sol, l’analyse granulométrique par tamisage et des enquêtes socio-économiques in situ. Compte tenu de la sensibilité granulaire des sédiments à la déflation face au potentiel agronomique des Niayes1 à Mboro, une recherche axée sur l’intensité du risque de dégradation mécanique des profils pédologiques est justifiée dans cet environnement aérologique favorable à la déflation éolienne et sur l’activité économique autour des 1Bas-fonds entre le système de dunes littorales et ogoliennes (cuvettes maraichères).Niayes. Les résultats ont montré une granulométrie globalement fine, soit plus 90 % du poids des échantillons traités susceptibles au mode de transport par saltation et par suspension éolienne, et un potentiel cultural de quelque 14 variétés. Ce qui témoigne des enjeux de la recherche géomorphologique pour les actions d’aménagement du territoire. The coast of Mboro, Great Coast of Senegal, is a melting pot of territories with socio-economic challenges. These territories are made up of ecosystems that support the agricultural market gardening economy in addition to the activities inherent in the coastalization of life. It is a space which is subject to factors of the morphodynamics of the coastal dune system. These are risk factors vectors of the current sand-silting dynamic. This paper focuses on sampling and determining the granulometry of the dune substrate in order to assess its sensitivity to the wind, on the one hand, and to measure the socio-economic issues of the agronomic market gardening potential in Mboro, on the other hand. In this context, the methodology targets soil sampling, particle size analysis by sieving, and socio-economic surveys in situ. Given the granular sensitivity of the sediments to deflation in the face of the agronomic potential of Niayes at Mboro, research focused on the intensity of the risk of mechanical degradation of soil profiles is justified in the aerological environment favorable to wind deflation and on the economic activity around the Niayes. The results showed a medium to fine grain size, i.e., over 90% of the weight of treated samples susceptible to the saltation and wind suspension mode of transport, and a crop potential of some 14 varieties. This testifies to the challenges of geomorphological research for land use planning actions.

Patterns and processes of beach and foredune geomorphic change along a Great Lakes shoreline: Insights from a year-long drone mapping study along Lake Michigan

Coastal storms are an important driver of geomorphic change along Great Lakes shorelines. While there is abundant anecdotal evidence for storm impacts in the region, only a handful of studies over the last few decades have quantified them and addressed system morphodynamics. Annual to seasonal lake-level fluctuations and declining winter-ice covers also influence coastal response to storms, yet relationships between hydrodynamics and geomorphology are poorly constrained. Given this, the Great Lakes region lags behind marine coasts in terms of predictive modeling of future coastal change, which is a necessary tool for proactive coastal management. To help close this gap, we conducted a year-long study at a sandy beach-dune system along the western shore of Lake Michigan, evaluating storm impacts under conditions of extremely high water level and absent shorefast ice. Drone-derived beach and dune topography data were used to link geomorphic changes to specific environmental conditions. High water levels throughout the year of study facilitated erosion during relatively minor wave events, enhancing the vulnerability of the system to a large storm in January 2020. This event occurred with no shorefast ice present and anomalously high winter water levels, resulting in widespread erosion and overwash. This resulted in 20% of the total accretion and 66% of the erosion documented at the site over the entire year. Our study highlights the importance of both antecedent and present conditions in determining Great Lakes shoreline vulnerability to storm impacts.