Sand Spit Research Articles

Susceptibility of the Climate Resilient Landforms of the Coastal Tract of Odisha and West Bengal, India

Abstract Wide sea beaches, beach ridges, barrier sand spits, sand dunes, and climate-sensitive tidal flats with mangrove forests on the coast of Odisha and West Bengal are the products of coastal process dynamics during the middle to late Holocene epoch under a stable sea level stage. These features are resilient to the global climate change phenomenon under natural conditions with the continuous supply of sediments and the spread of habitats that protect the coastal lowlands behind them against storms and inundations. Both the geomorphological and ecological systems of the depositional features were developed and optimized into matured stages before human intervention into the coastal system. These features were well developed along the storm-affected shoreline of the eastern coast of India with the supply of sediments into the coastal zones by river inputs, longshore current transport, cross-shore transport through storms, transgressive seas during the Holocene epoch, seasonal wind waves, and aeolian deposits. After assessing the climatic sensitivity stress, exposure index, adaptive capacities, and coastal vulnerabilities of the study area, the final result shows high susceptivity scores for the landforms that represent low resilient capacity; whereas, the coastal tracts of Purba Medinipur, and Sundarban represent low resilient capacity; and the coastal tract of Odisha reflects high to moderate resilient capacity. In the perspective of the global climate change phenomenon and human intervention into the coastal systems, the present study was conducted to find out the temporal changes of the coastal depositional features, to estimate the sensitivity of the features, and finally, to enquire about their susceptibility to the impact of cyclonic storms and the rapid rate of sea-level rise process currently occurring in the region of the tropical coast.

Sand Spit Morphology at an Inlet on Phu Quoc Island, Vietnam

Tidal inlets with attached sand spits are a very common coastal landform. Since the evolution of sand spits along coastlines influence the social-economic development of local coastal areas, sand spits have become the objects of numerous studies. However, previous studies have mainly focused on sand spits that are usually in the scale of hundreds of meters in width, whilst knowledge about the evolution of smaller-scale sand spits still remains limited. Therefore, in this study, the morphological change of a small and unexplored sand spit in front of Song Tranh Inlet on the west coast of Phu Quoc Island, Vietnam is investigated. Satellite images are first used to observe the morphological change of the sand spit and calculate the longshore sediment transport rates (LSTR) along the sand spit. Waves and beach sediments are collected at the study site to calculate the longshore sediment transport rate using the CERC formula. It is found that there is a seasonal variation in the evolution of the sand spit at Song Tranh Inlet. The longshore sediment transport rates along the spit calculated by image analysis are 39,000 m3/year, 66,000 m3/year, and 40,000 m3/year, whilst the longshore sediment transport rate calculated by the CERC formula is 72,000 m3/year. This study aims to contribute to the methodology for investigating the evolutions of small sand spits and, specifically, sustainable coastal management for Phu Quoc Island, which is well-known as the Pearl Island of Vietnam.

Sandy shoreline recovery ability after breakwater removal

The removal of coastal structures has emerged as an increasingly considered alternative nature-based solution to sandy coastal erosion due to unsuited structure construction. However, its effectiveness remains uncertain because the ability of natural beach recovery is unclear due to little understanding of shoreline response to the structure removal. In this study, we use a recently developed numerical model to explore the sandy shoreline recovery ability after the removal of an attached breakwater. Both recovery duration and recovery ratio are analyzed concerning various breakwater configurations and environmental settings in a simplified and generalized framework. We find that the sandy shoreline has the ability to naturally recover after breakwater removal but with different recovery durations (years to centuries) and recovery ratios (full to partial). A higher shoreline recovery ability (i.e., shorter duration and larger ratio) is related to shorter effective breakwater length, downdrift inclined breakwater direction, lower angle of wave incidence, and greater longshore sediment transport rate. We reveal that the behavior of sand spit evolution, including the extension and split of the sand spit, is the dominant mechanism for distinct shoreline recovery processes. Two simple formulas are finally proposed to preliminarily estimate shoreline recovery ability for practical purposes. The results of the present study provide new insights into coastal morphological resilience to engineering interventions.

Correction: Geotechnical performance of fine tailings in an oil sands pit lake

Correction: Geotechnical performance of fine tailings in an oil sands pit lake

Psammophilous Grasslands and Other Open Sandy Habitats in the Sandomierz Basin as a Refuge for Threatened Orthoptera in Poland

Psammophilous grasslands are declining in Europe due to ecological succession and anthropogenic pressures, yet they group many specialised invertebrates of early successional biotopes. We investigated the occurrence of six threatened species of Orthoptera in 135 patches of psammophilous grasslands and other open sand-related habitats (dry heaths, sandy roads, sand pits) located in the Sandomierz Basin (SE Poland). The aim was to verify whether these habitats, and especially the active military range, serve as a refuge for any of the selected species. Localities of Podisma pedestris and Calliptamus italicus found in the study area covering 0.7% of Poland’s territory represented a significant proportion (50 and 18%, respectively) of UTM grid squares known to be currently occupied by these species in the country. In the regional scale of southern Poland, studied habitats also accumulated a large proportion (ca. 17%) of the current localities of Oedipoda caerulescens. However, for Aiolopus thalassinus, Psophus stridulus and Sphingonotus caerulans the importance of the Sandomierz Basin as a country wide refuge was rather minor. Five of the six target species were found on the military range, with two (P. pedestris, P. stridulus) recorded only there. These results indicate that sand-related habitats are important refuges for some threatened orthopterans in the region and should be actively protected.

Evaluating resampled and fused Sentinel-2 data and machine-learning algorithms for mangrove mapping in the northern coast of Qeshm island, Iran

Mangrove forests, as an essential component of the coastal zones in tropical and subtropical areas, provide a wide range of goods and ecosystem services that play a vital role in ecology. Mangroves are globally threatened, disappearing, and degraded. Consequently, knowledge on mangroves distribution and change is important for effective conservation and making protection policies. Developing remote sensing data and classification methods have proven to be suitable tools for mapping mangrove forests over a regional scale. Here, we scrutinized and compared the performance of pixel-based and object-based methods under Support Vector Machine (SVM) and Random Forest (RF) algorithms in mapping a mangrove ecosystem into four main classes (Mangrove tree, mudflat, water, and sand spit) using resampled and fused Sentinel-2 images. Additionally, landscape metrics were used to identify the differences between spatial patterns obtained from different classification methods. Results showed that pixel-based classifications were influenced heavily by the effect of salt and pepper noise, whereas in object-based classifications, boundaries of land use land cover (LULC) polygons were smoother and visually more appealing. Object-based classifications, with an excellent level of kappa, distinguished mudflat and sand spit from each other and from mangrove better than the pixel-based classifications which obtained a fair-to-good level of kappa. RF and SVM performed differently under comparable circumstances. The results of landscape metrics comparison presented that the classification methods can be affected on quantifying area and size metrics. Although the results supported the idea that fused Sentinel images may provide better results in mangrove LULC classification, further research needs to develop and evaluate various image fusion approaches to make use of all Sentinel’s fine resolution images. Our results on the mapping of mangrove ecosystems can contribute to the improvement of management and conservation strategies for these ecosystems being impacted by human activities.

A critical review of arsenic occurrence, fate and transport in natural and modified groundwater systems in The Netherlands

Arsenic is a common trace element in groundwater and its fate and transport are controlled by combination of (i) natural processes, including redox conditions, salinity and pH, (ii) sedimentary and geochemical environment, and (iii) anthropogenic influences such as groundwater extraction, managed aquifer recharge (MAR), Aquifer Thermal Energy Storage (ATES), and pollution. We investigated the relative influence of these processes by presenting 10 cases from The Netherlands. Our review showed that the primary controlling factor for arsenic mobility in natural coastal dune systems is the redox state of groundwater, with concentrations between 2 and 10 μg/L. Strongly reduced greensands (containing glauconite and, more importantly, associated minerals) exhibited elevated As concentrations, with concentrations up to 40 μg/L. Groundwater systems modified by MAR or those that are influenced by nitrate pollution (NP) showed elevated As concentrations (20–110 μg/L), as a result of either pyrite oxidation (MAR, NP) or reductive dissolution of iron(hydr)oxides (MAR). Increasing temperature at ATES systems may cause mobilization of As at temperatures beyond 25 °C. The highest As concentrations were observed at sites where muddy sediments were recently deposited in surface water bodies (200–820 μg/L), for example in dammed Rhine River tributaries and sand pit lakes south of the city of Amsterdam. The reduction of arsenate to arsenite and competitive desorption during intrusion of polluted water also form important As mobilizing processes. The data for the Netherlands show that high CH4 and NH4 concentrations may form a risk indicator of elevated As levels in some fresh groundwater systems.

Morphological evolution of paired sand spits at the Fudu river mouth: Wave effects and anthropogenic factors

Sand spits are fragile landforms that have rich values in economic, ecology, landscape and many other respects. They are quite diverse in morphology and their evolution mechanisms are influenced by various hydrodynamic and morphologic factors. Although morphological evolution of sand spits has been well documented, emanative paired sand spits stretching in opposite directions are relatively unexplored. In this study, a pair of emanative sand spits, which have experienced a dramatic evolution in the past decades, at the Fudu river mouth, on the eastern coast of the Bohai Sea, China, are investigated. The shoreline data detected from satellite images between 1984 and 2020 obtained through a free cloud-based platform Google Earth Engine were used to quantify the morphological evolution of the paired sand spits. The offshore wave data derived from a high temporal and spatial resolutions wave hindcast database along the Chinese coast were combined to explore their evolution mechanisms. Results show that the morphological evolution of the paired sand spits is dominated by the different breaking wave characteristics at flanks of the river mouth, which is formed by the geomorphic modulation of the bimodal offshore wave climate. The sand spit at south flank is typically formed by longshore sediment transport like many other cases, while the spit at north flank is fed by intertidal bars through onshore sediment transport and presents good resilience to storm waves and human disturbances. Although several degradation characteristics were caused by storm waves, it is indicated that sediment supply reduction and interception of sediment transport caused by intense human activities are the primary reasons for the degradation of the paired sand spits. The present investigation enriches the maintaining and degradation mechanisms of paired sand spits and suggests that sufficient attention should be paid to the resilience of geomorphic systems in coastal exploitation.

Opak and Bogowonto Coastal Inlet Sand Spit Morphodynamics using Landsat and Sentinel Satellite Images

Sand spits are elongated sand deposits on the beach that often form at the inlet or the headland’s tip. The hydrodynamics of the river flow, waves, storm surge, and tide affect the sand spit formation, which was created by the longshore transport along the coast. Bogowonto and Opak inlets are located in southern coastal Java facing directly to the Indian ocean where micro-tidal, waves, and river flow affecting both inlets, are chosen for this case study. Morphodynamics analysis of sand spit using Landsat 7 and 8, Sentinel 2 image from 2000 to 2020, coastline identification using Modified Normalized Different Water Index (mNDWI). In November 2007 and October 2013, Opak Inlet migratory routes were detected, and closures related to the east season occurred at both of them. Inlet tend to close occur on east season during July until November.

The number of mine surveying service estimation at a sand pit

The number of mine surveying service estimation at a sand pit

Sedimentary evolution of lagoons along the Namibian coast reveals fluctuation in Holocene biogeographic faunal provinces, upwelling intensity and sea level

Within the wave-dominated and high-energy depositional environment of the hyper-arid Namibian coast, lagoons and related saltpans represent one of the few regional settings in which sediments originating from both marine and terrestrial sources can accumulate under sheltered conditions. This allows for an approximately continuous depositional record of mid to late Holocene coastal evolution. For this paleoenvironmental reconstruction, 26 sediment cores from six coastal (paleo-)lagoons were taken and investigated along a 430 km-long latitudinal gradient. Based on 56 age determinations of sediments and shell material, the initial formation of the studied lagoons can be dated back to 6.0–5.3 cal kyr BP. The sediment cores present different types of lithoclastic sediments which can be assigned to five sedimentary facies ranging from sand spit sediments rich in shell material to eolian dune sands and evaporites. From these cores, 221 samples of macrobenthic faunal material have been collected and determined to possess 46 shallow marine species. Biogeographic analyses have resulted in the identification of 10 (sub-)tropical warm water species that are not part of the regional benthic fauna in the present upwelling system. Age determinations of the shell material revealed four phases of biogeographic range expansion/shift into the study area, at 5.3 cal kyr BP, 2.8 cal kyr BP, 1.2–0.9 cal kyr BP, and 0.36–0.12 cal kyr BP from both the northern tropical Angola Current as well as from the southern subtropical Agulhas Current. The combination of datasets from this study with published datasets of regional sea-level fluctuations and upwelling intensities presents an apparent correlation between both processes and presumably an additional linkage to the ENSO and Benguela Niño variability.

From natural river floodplains to sand pits – the role of primary and secondary habitats in the conservation of the rare tiger beetle Cylindera arenaria viennensis (Schrank, 1781) in Poland

Taxa naturally occupying ecosystems spatially restricted by anthropogenic land development sometimes find refuge in secondary habitats, taking advantage of conditions created by human management. One of them is Cylindera arenaria viennensis (Schrank, 1781), a rare tiger beetle originally inhabiting natural river valleys, especially open flat banks and dynamic alluvial zones. Today, these habitats across Europe have been heavily transformed, mostly losing their former natural character. Published data as well as those reported in this study indicate that all nine present-day (recorded no more than 30 years ago) localities of this beetle in Poland are found in secondary habitats. These comprise mainly functioning or abandoned opencast extraction sites of mineral deposits (like sand or gravel), which fits the pattern observed in other central European countries. Nevertheless, such sites, due to vegetation succession, drainage or inadequate management following cessation of extraction, are quickly losing their attractiveness for C. a. viennensis, ultimately driving local populations to disappear, which is likely to have occurred in one of the reported localities. Thereby, it is crucial to search for and then to protect any sites of this species found in primary habitats, as the long-term survival of populations of this beetle seems best ensured by the protection and restoration of original alluvial habitats found in natural river valleys.

Origins and transformations of terrigenous dissolved organic matter in a transgressive coastal system

Hydrogeological, geochemical, and optical approaches were combined to explore how a transgressive coastal system, where 2-kyr-old organic matter is preserved, contributes to dissolved organic matter (DOM) and dissolved organic carbon (DOC) flux to coastal waters. The sand spit system, located on the St. Lawrence shore (Chaleur Bay, Québec, Canada), was mainly composed of saline groundwater from seawater recirculation, and we estimated submarine groundwater discharge (SGD) velocities fluctuating from 0 during the rising tide to 106 cm d−1 during the ebb tide. The radon-222 (222Rn) activities revealed the presence of two distinct water masses in the spit: a surface recirculated saline groundwater cell with a short residence time and low or no 222Rn activity, and a deeper recirculated saline groundwater with a longer residence time, from a few hours to a few days, and thus exhibited higher 222Rn activities. At the falling tide, the upward flow of this 222Rn-rich groundwater contributes to volumetric discharges ranging from ∼6 to ∼17 m3 d−1, corresponding between 10 and 30% of the total SGD. Both DOC and DOM were produced in the subsurface. However, despite the concentrations being high in the discharge zone, the DOC export remained weak, with mean fluxes of 60.7 (±15.5) and 55.8 (±36.5) mol C yr− 1 in 2018 and 2019, respectively. While surface recirculated saline groundwater dominates the SGD, absorbance and fluorescent indices indicated a strong terrestrial character in the DOM pool likely originated from material sources with a high degree of humification. An EEM-PARAFAC model reveals the dominance of humic-like components of high molecular weights and the occurrence of degraded material, whatever the tidal regime. When the residence time of the groundwater was longer, with higher radon activities, protein-like components with lower molecular weights were microbially produced, probably enhancing the bioavailability of the DOM exported to surrounding seawater. Our results suggest that transgressive coastal systems can be a hot spot for terrigenous DOM transformation which could affect the optical and chemical properties of coastal waters.

Geotechnical performance of fine tailings in an oil sands pit lake

Syncrude Canada Ltd.’s Base Mine Lake (BML), the first commercial-scale demonstration of an oil sands pit lake, was commissioned in December 2012, following in-pit deposition of fine tailings (FT) between 1995 and 2012. The geotechnical design basis for the FT in BML is that it will consolidate and densify over time, contributing to fines sequestration below the water cap. This paper presents the geotechnical performance of the FT in BML within the context of this geotechnical design basis. The FT has settled from 196.0 to 171.6 Mm3 by 2019, with cumulative settlement varying spatially between 0.3 and 6.7 m. FT settlement is consistent with the expected self-weight consolidation as modeled by finite-strain non-linear consolidation theory, and is reflected as temporal increase in the profiles of solids content and effective stress. Sonar surveying, profile sampling, shear strength, and underwater photography show that the transition of geotechnical properties at the mudline becomes increasingly distinct over time. These observations support the geotechnical design basis for BML and indicate the fines continue to be sequestered below the water cap.

Natural and nature based features for environmental enhancement and coastal storm risk management: a case study on Marco Island, Florida, United States

Natural and Nature-Based systems provide an opportunity for adaptive response to Coastal Storm Risk Management and Sea Level Rise. The Tigertail Lagoon/Sand Dollar Island Restoration on Marco Island, Florida, presents a case study designed to maintain and enhance an existing coastal barrier system consisting of a 3-km-long sand spit and tidal lagoon ecosystem that is otherwise evolving toward closure. The case study is part of a nature-based adaptive management plan to restore and stabilize the sandspit and tidal lagoon through cyclic use of sediment within the system. This approach seeks to preserve existing protective habitats and landforms that also serve as natural coastal barriers to protect upland development. Design of the restoration plan considers the functions of a wildlife nature preserve and evolution of complex tidal inlet morphologic features bordered by a heavily developed barrier Island. The design aims to restore and enhance a sandspit degraded by a sequence of storms since Major Hurricane Irma impacted Southwest Florida in 2017 and improve the existing deteriorated habitat by enhancing tidal exchange through restoration of the lagoon flow channel. Total wetland area will be increased by relocating the sand spit seaward of its present location to where it was located in approximately 2017. The reconstructed beach berm will provide enhanced resiliency to high frequency weather events. Sediment will be sourced from the existing sand spit and an innovative sand trap that will maintain the lagoon entrance open while providing beneficial re-use for excess sediment that continues to accumulate at the end of the spit. Components of the project were analyzed using existing engineering models and methods such as the Coastal Modeling System (CMS) and XBeach. Enhancing and preserving this barrier island feature and productive ecosystem provides an example of the enhanced coastal resiliency provided by natural and nature-based systems that are adaptable and responsive to sea level rise and ongoing coastal processes.

The use of soil-biological methods in monitoring the soils of sand pits in the Northern taiga

The article deals with the problem of the applicability of soil-zoological and soil-microbiological methods in monitoring young ecosystems formed in the subzone of the northern taiga of Western Siberia. It is shown that different components of the destructive link of the biological cycle are characterized by different recovery rates after the complete destruction of the taiga ecosystem. During the development of young soils in the northern taiga subzone, there is a gradual increase in the content of C-biomass, and during the first 22 years of soil formation, the content of C-biomass increases 12-fold. The restoration of communities of oribatid mites after their disturbances during the formation of quarries, in the initial period (up to 5 years after the disturbance) is relatively slow. After 22 years since the violation, the process of restorative succession is noticeably accelerated. The results of the study show that indexes of microbial biomass, abundance and species richness of oribatids in soils can be successfully used in the practice of ecological monitoring of young ecosystems forming in the taiga zone.

SATELLITE-BASED LAND/SEA CONTINUUM: AN APPLICATION TO MONITOR THE SAINT LOUIS COAST (SENEGAL, WEST AFRICA)

Abstract. The historical city of Saint Louis in Senegal is situated on the Langue de Barbarie sand spit and is particularly prone to erosion: buildings have collapsed and population relocated due to shoreline retreat. At Saint Louis understanding the beach-morphodynamics is essential, and relies on the monitoring of nearshore topography and bathymetry. Remote sensing techniques relying on very high resolution (sub metric) satellites such as the Pleiades constellation and Planet now offer new perspectives in coastal monitoring and engineering. Digital Elevation Models (DEMs) of the emerged part of the beach, topography, and the submerged nearshore bathymetry can be obtained using respectively (tri-)stereogrammetry, and depth inversion through wave kinematics or/and colour based methods. These methods offered promising results (Almeida et al., 2019, Taveneau et al., 2021, Almar et al., 2019a) in previous studies when applied to Pleiades satellite. This work showcases a DEM derived from a 3-images (dT ≃ 9.5s) Pleiades acquisition in March 2020 and covering the key topography/bathymetry morphological continuum. Root mean squared errors of about 5 m for bathymetry and 0.9 m for topography are obtained. To limit erosion at Saint Louis urban beaches, the construction of a protection structure has begun in late 2020. Here, satellite DEM is used to monitor the efficiency of the structure and its downstream impact along the sand spit.

Monitoring Sand Spit Variability Using Sentinel-2 and Google Earth Engine in a Mediterranean Estuary

Estuarine degradation is a major concern worldwide, and is rapidly increasing due to anthropogenic pressures. The Mediterranean Guadiaro estuary, located in San Roque (Cadiz, Spain), is an example of a highly modified estuary, showing severe negative effects of eutrophication episodes and beach erosion. The migration of its river mouth sand spit causes the closure of the estuary, resulting in serious water quality issues and flora and fauna mortality due to the lack of water renewal. With the aim of studying the Guadiaro estuary throughout a 4-year period (2017–2020), the Sentinel-2 A/B twin satellites of the Copernicus programme were used thanks to their 5-day and 10 m temporal and spatial resolution, respectively. Sea–land mapping was performed using the Normalized Difference Water Index (NDWI) in the Google Earth Engine (GEE) platform, selecting cloud-free Sentinel-2 Level 2A images and computing statistics. Results show a closure trend of the Guadiaro river mouth and no clear sand spit seasonal patterns. The study also reveals the potential of both Sentinel-2 and GEE for estuarine monitoring by means of an optimized processing workflow. This improvement will be useful for coastal management to ensure a continuous and detailed monitoring in the area, contributing to the development of early-warning tools, which can be helpful for supporting an ecosystem-based approach to coastal areas.

Microbially induced sedimentary structures (MISS) generated by episodic storm surges in a temperate coast

This study recognizes the creation of primary sedimentary structures in a modern environment that reports valuable insights into the role of microbiota in sculpting sedimentary structures, and it may explain many previously confusing sedimentary structures in the rock record. The research considered the frequent flooding events on a coastal sedimentary flat colonized by microbial mats and the effect produced by severe storm surge events. Large-scale microbially induced sedimentary structures (MISS) were created; thus, the interaction between meteorologic, oceanographic, and geomorphologic conditions necessary to form them was analysed. The study was developed in Paso Seco, Argentina (40°38′31” S - 62°12′54” W), a sedimentary flat behind a sand spit, coated by thick microbial mats recurrently affected by storm events. Water level measurements were recorded continuously for five years (measurement interval 10 min). The seawater inundations were related to synoptic weather maps and oceanographic parameters (wave height, period, and tides) to analyse the cause of storm surges. Two situations of severe storms were studied in 2018 and 2019. The inundation of the study area occurs when a cold front in association with a low-pressure centre in the Atlantic Ocean, moving in an SW-NE direction, produces strong SW winds higher than 45 km h−1 and wave height higher than 2 m. Strong winds and storm duration (two or three days) in co-occurrence with spring tides create an extreme erosional event that affects the sedimentary microbial flat. In sum, the interaction between storm surge, high tide, wave setups and wave heights in Paso Seco produces coastal hinterland flooding that creates meter-sized MISS such as roll-ups, erosional pockets, and remnants mats structures. The impact of storm surges on the coast is common and catastrophic in modern times but is challenging to identify in the sedimentary record. Therefore, the microbial structures presented here could help interpret high-energy events occurrence, favourable to assessing past environmental conditions.

Time-Lapse Camera Monitoring and Study of Recurrent Breaching Flow Slides in Cap Ferret, France

In this paper, we present a low-cost method designed to monitor recurrent breaching flow slides that impact the security of a beach. This beach, located in France at the inlet of Arcachon Bay, connects a sand spit to a tidal channel while ending at the toe of a coastal defense. Monitoring is based on capturing images and intends to add continuous information to intermittent direct observations so that triggering and influencing factors can be assessed more precisely. The method is based on time-lapse picture collection and processing. The field of view shows successive emerged manifestations of flow slide phenomena, as well as some possibly related environmental elements. On-site application for 576 days provides important indications and details on flow slide event progress and beach recovery. A simple but quantitative analysis of the influence of sand spit topographic changes is proposed as a preliminary approach of the method’s suitability for studies of environmental processes in conjunction with coast protection.