SciCombinator

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Concept: Beach nourishment

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It is predicted that the coastal zone will be among the environments worst affected by projected climate change. Projected losses in beach area will negatively impact on coastal infrastructure and continued recreational use of beaches. Beach nourishment practices such as artificial nourishment, replenishment and scraping are increasingly used to combat beach erosion but the extent and scale of projects is poorly documented in large areas of the world. Through a survey of beach managers of Local Government Areas and a comprehensive search of peer reviewed and grey literature, we assessed the extent of nourishment practices in Australia. The study identified 130 beaches in Australia that were subject to nourishment practices between 2001 and 2011. Compared to projects elsewhere, most Australian projects were small in scale but frequent. Exceptions were nine bypass projects which utilised large volumes of sediment. Most artificial nourishment, replenishment and beach scraping occurred in highly urbanised areas and were most frequently initiated in spring during periods favourable to accretion and outside of the summer season of peak beach use. Projects were generally a response to extreme weather events, and utilised sand from the same coastal compartment as the site of erosion. Management was planned on a regional scale by Local Government Authorities, with little monitoring of efficacy or biological impact. As rising sea levels and growing coastal populations continue to put pressure on beaches a more integrated approach to management is required, that documents the extent of projects in a central repository, and mandates physical and biological monitoring to help ensure the engineering is sustainable and effective at meeting goals.

Concepts: Sediment, Weather, Coast, Beach, Sand, Coastal geography, Extreme weather, Beach nourishment

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The erosion of the world’s coasts and the shortage of sand to mitigate beach erosion are leading to the increasingly common use of gravel for coastal protection and beach nourishment. Therefore, in order to determine the amount of gravel required for such actions, it is important to know perfectly the equilibrium profile of gravel beaches. However, at present, this profile is obtained from formulas obtained mainly after channel tests, and therefore most of them do not adapt to the real profiles formed by gravel beaches in nature. In this article, 31 variables related to sedimentology, waves, morphology and marine vegetation present on the beaches are studied to determine which are the most influential in the profile. From the study carried out, it is obtained that these variables are the steepness and probability of occurrence of the wave perpendicular to the coast, the profile starting slope (between MWL and -2m), the energy reduction coefficient due to Posidonia oceanica as well as the width of the meadow. Using these variables, different numerical models were generated to predict accurately the gravel beach profile, which will lead to a saving in the volume of material used in the order of 1300m(3)/ml of beach with respect to current formulations, and a greater certainty that the beach nourishment carried out will have the desired effect.

Concepts: Sediment, Coast, Beach, Sand, Coastal geography, Shore, Coastal management, Beach nourishment

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To enhance protection and maintain wide beaches for recreation, beaches are replenished with sand: so-called beach nourishments. We compared four sites: two traditional beach nourishments, a mega beach nourishment and a reference without beach nourishment. Two sites contain calcareous-rich sand, whereas the other two sites have calcareous-poor sand. We aimed to understand hydrogeochemical processes to indicate factors critical for the mobility of trace elements at nourishments. We therefore analysed the chemical characteristics of sediment and pore water to ascertain the main drivers that mobilise toxic trace elements. With Dutch Quality Standards for soil and groundwater, the characteristics of sediment and pore water were compared to Target Values (the values at which there is a sustainable soil quality) and Intervention Values (the threshold above which the soil’s functions are at risk). The pore water characteristics revealed that Target Values were regularly exceeded, especially for the nourishment sites and mainly for Mo (78%), Ni (24%), Cr (55%), and As (21%); Intervention Values for shallow groundwater were occasionally exceeded for As (2%), Cr (2%) and Zn (2%). The sediment characteristics did not exceed the Target Values and showed that trace elements were mainly present in the fine fraction of <150 μm. The oxidation of sulphide minerals such as pyrite resulted into the elevated concentration for all nourishment sites, especially when an unsaturated zone was present and influence of rainwater was apparent. To prevent trace metal mobility at a mega beach nourishment it is important to retain seawater influences and limit oxidation processes. In this respect, a shoreface nourishment is recommended rather than a mega beach nourishment with a thick unsaturated zone. Consequently, we conclude that whether a site is carbonate-rich or carbonate-poor is unimportant, as the influence of seawater will prevent decalcification, creating a low risk of mobilisation of trace elements.

Concepts: Water, Beach, Sand, Beach nourishment

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Resilient coastal protection requires adaptive management strategies that build with nature to maintain long-term sustainability. With increasing pressures on shorelines from urbanisation, industrial growth, sea-level rise and changing storm climates soft approaches to coastal management are implemented to support natural habitats and maintain healthy coastal ecosystems. The impact of a beach mega-nourishment along a frontage of interactive natural and engineered systems that incorporate soft and hard defences is explored. A coastal evolution model is applied to simulate the impact of different hypothetical mega-nourishment interventions to assess their impacts' over 3 shoreline management planning epochs: present-day (0-20 years), medium-term (20-50 years) and long-term (50-100 years). The impacts of the smaller interventions when appropriately positioned are found to be as effective as larger schemes, thus making them more cost-effective for present-day management. Over time the benefit from larger interventions becomes more noticeable, with multi-location schemes requiring a smaller initial nourishment to achieve at least the same benefit as that of a single-location scheme. While the longer-term impact of larger schemes reduces erosion across a frontage the short-term impact down drift of the scheme can lead to an increase in erosion as the natural sediment drift becomes interrupted. This research presents a transferable modelling tool to assess the impact of nourishment schemes for a variety of sedimentary shorelines and highlights both the positive and negative impact of beach mega-nourishment.

Concepts: Time, Sediment, Coast, Term, Beach, Coastal geography, Shore, Beach nourishment

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Sand beaches are highly dynamic habitats that can experience considerable impacts from oil spills. This review provides a synthesis of the scientific literature on major oil spills and their impacts on sand beaches, with emphasis on studies documenting effects and recoveries of intertidal invertebrate communities. One of the key observations arising from this review is that more attention has generally been given to studying the impacts of oil spills on invertebrates (mostly macrobenthos), and not to documenting their biological recovery. Biological recovery of sand beach invertebrates is highly dynamic, depending on several factors including site-specific physical properties and processes (e.g., sand grain size, beach exposure), the degree of oiling, depth of oil burial, and biological factors (e.g., species-specific life-history traits). Recovery of affected communities ranges from several weeks to several years, with longer recoveries generally associated with physical factors that facilitate oil persistence, or when cleanup activities are absent on heavily oiled beaches. There are considerable challenges in quantifying impacts from spills on sand beach invertebrates because of insufficient baseline information (e.g., distribution, abundance and composition), knowledge gaps in their natural variability (spatial and temporal), and inadequate sampling and replication during and after oil spills. Thus, environment assessments of impacts and recovery require a rigorous experimental design that controls for confounding sources of variability. General recommendations on sampling strategies and toxicity testing, and a preliminary framework for incorporating species-specific life history traits into future assessments are also provided.

Concepts: Petroleum, Paleontology, Beach, Oil, Sand, Shore, Dune, Beach nourishment

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Beach nourishment practices are a key aspect in coastal management plans for stakeholders and communities. Stemming from a concrete case-study (Tuscany), this research analyzes: (i) principal problems of current law regulating dredging, (ii) gaps in technical guidelines, (iii) advantages of integrated approaches to the decision-making process, (iv) possible applicable nourishment options and their costs and benefits. Our results show that sand compatibility is driven mainly by grain-size stability due to the occurrence of lower pollution levels in off-shore deposits than in threatened beaches, thus current laws and guidelines should be improved to fill the evident gap in the evaluation process and to include a more complete approach to data evaluation and an integrated approach to ecotoxicity evaluation, which is relevant in cases of geochemical anomalies. The cost-benefit analysis performed indicates that only dredging intended to manage more than 1millionm(3) of aggregates would represent a real advantage for local communities.

Concepts: Evaluation methods, Decision theory, Cost, Case study, Regulation, Beach, Sand, Beach nourishment

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Beach nourishment is increasingly used to protect public beach amenity and coastal property from erosion and storm damage. Where beach nourishment uses fill sediments that differ in sedimentology from native beach sands, press disturbances to sandy beach invertebrates and their ecosystem services can occur. How long impacts persist is, however, unclear because monitoring after nourishment typically only extends for several months. Here, monitoring was extended for 3-4years following each of two spatially separated, replicate nourishment projects using unnaturally coarse sediments. Following both fill events, the contribution to beach sediments of gravel-sized particles and shell fragments was enhanced, and although diminishing through time, remained elevated as compared to control sites at the end of 3-4years of monitoring, including in the low intertidal and swash zones, where benthic macroinvertebrates concentrate. Consequently, two infaunal invertebrates, haustoriid amphipods and Donax spp., exhibited suppressed densities over the entire post-nourishment period of 3-4years. Emerita talpoida, by contrast, exhibited lower densities on nourished than control beaches only in the early summer of the first and second years and polychaetes exhibited little response to nourishment. The overall impact to invertebrates of nourishment was matched by multi-year reductions in abundances of their predators. Ghost crab abundances were suppressed on nourished beaches with impacts disappearing only by the fourth summer. Counts of foraging shorebirds were depressed for 4years after the first project and 2years after the second project. Our results challenge the view that beach nourishment is environmentally benign by demonstrating that application of unnaturally coarse and shelly sediments can serve as a press disturbance to degrade the beach habitat and its trophic services to shorebirds for 2-4years. Recognizing that recovery following nourishment can be slow, studies that monitor impacts for only several months are inadequate.

Concepts: Nutrition, Arthropod, Sediment, English-language films, Annelid, Beach, Sand, Beach nourishment

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Marine dredging operations are not uncommon in coastal waters since they are necessary for several beneficial uses, such as harbour maintenance, beach nourishment or removal/capping of pollutants, amongst others. They also constitute a significant risk for the environment, changing its physical, chemical and biological characteristics, as evidenced by many authors. In this study, two numerical models are used to simulate the dispersion pattern of fine suspended sediment spilled from a dredge barge, considering different hydrodynamic scenarios, particle sizes and dredging tracks in a mesotidal environment. The results show that, in this particular case, the currents (largely induced by the tide) are the main responsible for the final disposition of the settled particles, being the other variables of secondary importance.

Concepts: Environment, Ecology, Natural environment, Environmentalism, Beach, Beach nourishment, Dredging, Coastal erosion

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Madeira forms a mid-Atlantic volcanic archipelago, whose economy is largely dependent on tourism. There, one can encounter different types of sand beach: natural basaltic, natural calcareous and artificial calcareous. Microbiological and mycological quality of the sand was analyzed in two different years. Bacterial indicators were detected in higher number in 2010 (36.7% of the samples) than in 2011 (9.1%). Mycological indicators were detected in a similar percentage of samples in 2010 (68.3%) and 2011 (75%), even though the total number of colonies detected in 2010 was much higher (827 in 41 samples) than in 2011 (427 in 66 samples). Enterococci and potentially pathogenic and allergenic fungi (particularly Penicillium sp.) were the most common indicators detected in both years. Candida sp. yeast was also commonly detected in the samples. The analysis of the 3rd quartile and maximum numbers of all indicators in samples showed that artificial beaches tend to be more contaminated than the natural ones. However, a significant difference between the variables was lacking. More monitoring data (number of bathers, sea birds, radiation intensity variation, and a greater number of samples) should be collected in order to confirm if these differences are significant. In general, the sand quality in the archipelago’s beaches was good. As the sand may be a vector of diseases, an international common set of indicators and values and a compatible methodologies for assessing sand contamination, should be defined, in order to provide the bather’s with an indication of beach sand quality, rather than only the water.

Concepts: Bacteria, Fungus, Portugal, Difference, PH indicator, Beach, Sand, Beach nourishment

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A beach nourishment with approximately 1/3 fine-grained sediment (fines; particle diameter < 63 µm) by mass was performed at Southern California's Border Fields State Park (BFSP). The nourishment was found to briefly (<1 d) increase concentrations of surfzone fecal indicator bacteria (FIB) above single sample public health standards (104 MPN (100 ml)-1), but had no effect on phytoplankton. Contamination was constrained to the nourishment site: waters 300 m north or south of the nourishment were always below single sample and geometric mean (≤ 33 MPN (100 ml)-1) standards. Nourishment fines were identified as a source of the fecal indicator Enterococcus; correlations between fines and enterococci were significant (p < 0.01), and generalized linear model analysis identified fines as the single best predictor of enterococci. Microcosm experiments and field sampling suggest that the short surfzone residence times observed for enterococci (e-folding time 4 h) resulted from both rapid, post-placement FIB inactivation, and mixing/transport by waves and alongshore currents. Nourishment fines were phosphate-rich / nitrogen-poor, and were not correlated with surfzone phytoplankton concentrations, which may have been nitrogen limited.

Concepts: Regression analysis, Statistics, Water, Water pollution, Beach, Plankton, Generalized mean, Beach nourishment