Meters Of Sand Research Articles

Middle Palaeolithic occupation of the southern North Sea Basin: evidence from the Sandscaping sediments emplaced on the beach between Bacton and Walcott, Norfolk, UK

ABSTRACTDuring the summer of 2019, the Bacton to Walcott Coastal Management Scheme involved the emplacement on to the foreshore of 1.8 million cubic metres of sand and gravel dredged from the submerged sediments of the Palaeo‐Yare in the southern North Sea 11 km off Great Yarmouth. During the following 2‐year period, an active group of collectors identified Palaeolithic artefacts eroding from these sediments, including Levallois cores and flakes, and cordiform handaxes. In this paper, we present an analysis of the lithic artefacts, and consider the relationships between the different elements of the assemblage. We discuss its significance in the context of the Middle Palaeolithic record of northwest Europe and the light it shines on the human occupation of the submerged landscape of the southern North Sea during the later Middle Pleistocene. Interrogation of beach survey data shows the reworking of these sediments to the southeast towards Happisburgh where archaeologically significant exposures of the Cromer Forest‐bed Formation are located. The implications of the introduction of a Middle Palaeolithic assemblage to this stretch of the North Norfolk Coast are considered, highlighting the importance of continuing dialogue between researchers, local authorities and local communities for capturing information and monitoring this critical Palaeolithic resource.

Locating submerged prehistoric settlements: A new underwater survey method using water-jet coring and micro-geoarchaeological techniques

In the past few decades the field of submerged prehistory has produced important data highlighting ancient coastal habitation across the globe. Most prehistoric underwater sites are discovered by chance (e.g., by industry, fishermen or recreational divers). New methods for detecting submerged prehistoric settlements have been developed using sophisticated remote sensing devices, yet with limited success. Simple, practical, and inexpensive methods for locating submerged settlements remain rare. Over 60 years of underwater archaeology and submerged prehistory in Israel, specifically along the Carmel coast, has led to a model for locating and studying submerged settlements, based on sand removal by storms. This study aimed to take this model a step further by developing a new, inexpensive method to identify, locate and characterize submerged sites. We collected undisturbed paleosol cores from exposed areas as well as under a few meters of sand, using a newly developed water-jet core sampling system. The cores were analyzed using micro-geoarchaeological techniques initially developed on terrestrial sites. The rationale behind this methodology is based on established knowledge that where human settlements occur, sediments are enriched by specific mineralogical signatures (e.g., heated clay minerals) and anthropogenic micro-remain assemblages (e.g., phytoliths, ash pseudomorphs and dung spherulites). Additionally, micromorphology can assist in identifying micro-stratigraphic patterns typical of human settlements. We tested sediment cores in three underwater contexts: a) exposed prehistoric surfaces within two known Neolithic sites (Atlit-Yam and Neve Yam), b) exposed paleosols without visible archaeological remains (serving as a control), and c) as a blind test, a buried paleosol currently covered by 1–3 m of sand, where the existence of a site is unknown. In the cores taken from the exposed Neolithic settlements, the micro-geoarchaeological characterization showed clear anthropogenic signals (typical mineralogy, elevated micro-remain concentrations, micro-stratigraphy). In the paleosol control cores, there was an absence (or negligible presence) of anthropogenic signals. The ‘blind test’ at the sand-covered locality revealed sediments without anthropogenic enrichments (similar to the control paleosols), thus suggesting the absence of a submerged settlement in this specific location. The new method is time- and cost-effective and can easily be applied worldwide along the shallow continental shelf as well as in deep water. The new method will facilitate discovery of new underwater sites and provide selection criteria (e.g., where the highest anthropogenic signal exists) for investment in underwater excavations. Additionally, it can be used to check for anthropogenic signals in buried locations detected by remote sensing, and to understand the spatial organization of submerged sites.

Mathematical Modeling and Forecast 11 Years in Advance of the Dumping of Sand in Varadero Beach, Cuba, Using the Regressive Objective Regression (Ror) Methodology

The specialists estimate that the most important challenge on the beaches is the dumping of sand. Sustainable tourism in our time must be conceived towards the future to ensure that resources are managed with due protection of ecological processes, biological diversity and the environment in general, hence our objective is to know the amount of the following sand dumps on the beach of Varadero mathematically modeling according to the data we have. A database of the dumping of cubic meters of sand in Varadero was used from 1987 to 2012, the methodology used was the Regressive Objective Regression (ROR). We can conclude that the model explains 100% of the variance with an error that cannot be determined, over time, all the variables are significant, the model depends on the shedding twelve times ago (Lag12Vert). In the long term, resources can be saved and the resilience of coastal communities to climate change and rising sea levels can be improved, maintaining the quality indicators required of the sand strip for the enjoyment of bathers and protection of the dunes. The forecast obtained for the next discharges has a maximum of 2,225,140.6 m3, in t50 discharge, a value this May that the discharge occurred before 2012.

Economic viability of implementing an infrastructure for recycling bedding sand from a free-stall facility for dairy cows

This study proposes to examine the economic viability of implementing the necessary infrastructure for the recycling of bedding sand from a free-stall facility in a milk production system in southern Minas Gerais, Brazil. In specific terms, the total production cost (TC), total operating cost (TOC) and effective operating cost (EOC) of a cubic meter of recycled sand were estimated in order to estimate the total sand consumption for the free-stall system and per bed year-1 as well as the equilibrium point of the amount of recycled sand, in cubic meters. The experiment was carried out on a farm located in the south of Minas Gerais from January 2016 to December 2017. Three scenarios were analyzed by the tree-point estimation method (MOP - most likely, optimistic, and pessimistic). Utilization of 85%, 95% and 75% of the recycled sand was considered for scenarios 1, 2 and 3, respectively. In all of them, the value charged per cubic meter of sand by a supplier close to the farm was considered. Monte Carlo simulation was also carried out with hurdle rates (HR) of up to 90%. Under the studied conditions, sand recycling showed to be economically viable in all scenarios, with positive net present values (NPV), internal rates of return above the HR, simple and discounted payback below the 10-year horizon, and satisfactory cost benefit-1 ratios (greater than 1). The EOC of one cubic meter of recycled sand was estimated at R$5.04, R$4.51 and R$5.72 for scenarios 1, 2 and 3, respectively, whereas the average TC, considering all scenarios, was R$6.84 (+0.81), which is less than the acquisition price of R$28.57 at the sand extraction site. The TC was R$37,219.51 and R$34,637.74 for the scenarios with HR of 8.50 and 6.99%, respectively, whereas TOC was R$22,572.08 in all analyzed scenarios. The estimated total annual sand consumption by the free-stall system was 526.44 m³, with an estimated average of 1.23 m³ (+0.28) bed-1 year-1. All Monte Carlo simulation models showed positive NPV as well as HR of up to 90%, which reflect a high probability of positive NPV.

Geotechnical Hazards and Environmental Changes Threatening the Sphinx Avenue and the Project of Luxor: Open Museum

The simulation of the ceremonies of the Pharaonic celebrations in the Sphinx’s Avenue is one of the most important Millennium Goals for Luxor Governorate, which is supported by UNESCO until 2022. All sections of the road were constructed during the eighteenth to thirty dynasty period. Some attachments have been added to the road in different periods, such as wine presses used in major ceremonies that were held on the road such as ophthalmic feasts and beautiful valley feasts, etc. The road has been neglected across different periods, and more than 4 meters of sand, silt and Nile clay were accumulated in different sites. Excavations began on the road in the late 1940s, until work was halted after the January Revolution due to lack of funds. The aim of these study is examination of the geotechnical properties of the project to Facing challenges that led to bury and deterioration of the road and also to develop sustainable geotechnical solutions to resist threats and risks. Scanning Electron Microscope was used to investigate the six samples of soil under the six sections of the road to study the hazards due to the impaction of clay minerals which threaten the Sphinx Avenue and The Project of Luxor, Open Museum. Basic properties test of the foundation soils illustrated the expansive properties which often were classified moderate. Expansive properties are one of the factors of the evaluation of the hazard besides the relevance of the construction to environmental changes and sustainability agents.

Sand spit dynamics in a large tidal‐range environment: Insight from multiple LiDAR, UAV and hydrodynamic measurements on multiple spit hook development, breaching, reconstruction, and shoreline changes

AbstractSand spits with distal hooks have been well documented from coasts with low to moderate tidal ranges, unlike high tidal‐range environments. Datasets from 15 LiDAR and 3 UAV surveys between 2009 and 2019 on the Agon spit in Normandy (France), a setting with one of the largest tidal ranges in the world (mean spring tidal range: 11 m), combined with in‐situ hydrodynamic records between 2013 and 2017, highlight a three‐stage pattern of spit hook evolution. Stage 1 (2009–2013) commenced with the onshore migration and attachment of a swash bar, followed by persistent spit accretion updrift of the bar and erosion downdrift because of the slow speed of bar migration in this large tidal‐range environment. In stage 2 (2013–2016), three overwash events and a 220 m‐wide breach culminating in the total destruction of the spit during winter 2015–2016 involved the landward mobilization of thousands of cubic metres of sand. These events occurred during short durations (a few hours) when spring high tides coincided with relatively energetic waves, underscoring the importance of storms in rapid spit morphological change. Strong spring tidal currents maintained the breach. Stage 3 (2016–2019) has involved new hook construction through welding of a swash bar and spit longshore extension, highlighting the resilience of the spit over the 10‐year period, and involving a positive sediment balance of 244 000 m3. The three stages bring out, by virtue of the temporal density of LiDAR and UAV data used, a high detail of spit evolution relative to earlier studies in this macrotidal setting. The large tidal range strongly modulates the role of waves and wave‐generated longshore currents, the main process drivers of spit evolution, by favouring long periods of inertia in the course of the spring–neap tidal cycle, but also brief episodes of significant morphological change when storm waves coincide with spring high tides. © 2020 John Wiley & Sons, Ltd.

The beach as a strategic element of governance for Spanish coastal towns

ABSTRACTGovernance models and future strategic visions for Spain's beach social–ecological systems are assessed using an online questionnaire. Beaches continue to represent the most valuable attraction for Spanish coastal towns, but their strategic vision regarding the beach consists more of it being a profitable attraction and of maintaining the traditional “sun and sand” model, rather than of planning strategically. There are three trends looking to 2020. First, beach resorts are becoming linked with culture and heritage, gastronomy, events and ecotourism to enhance their attraction capacity and competitiveness. Second, the coastal towns plan to reduce the strain on beaches by increasing the number of square metres of sand per user. Third, they plan to reduce the strain of the seasonal population compared to the year-round population. Two indices (Beach Quality and Governance Quality) and two factors (Beach Management Proximity and Tourist Resource Expectations) were developed to assess municipal beach governance frameworks, enabling us to construct a typology of four municipal governance models. The country follows a classical public hierarchical model of beach management. Other than at the local scale, beaches are not strategically managed. There is a lack of implementation of adaptive measures, collective actions, integrated management, or policy learning.

Natural and Human-Induced Dynamics on Big Hickory Island, Florida

Big Hickory Island, located in Lee County along the mixed-energy west Florida coast, experiences high long-term rates of shoreline recession, with much of the erosion concentrated along the central and southern portions of the island. In 2013, approximately 86,300 cubic meters of sand from an adjacent tidal inlet to the north were placed along 457 m to restore the beach and dune system. In an effort to combat erosion, seven concrete king-pile groins with adjustable panels were constructed subsequent to the completion of the beach nourishment. Natural and human-induced dynamics of Big Hickory Island are discussed through analysis of shoreline and morphologic change using historic aerial photographs and topographic and bathymetric field surveys of the recent beach erosion mitigation project. Although much of the long-term anomalously high rates of erosion for the area are related to natural interchanges between the sand resources of the barrier islands and adjacent ebb tidal shoals, additional reduction in sand supply is a result of human-interventions updrift of Big Hickory over the last several decades. The coupled natural and anthropogenic influences are driving the coastal processes toward a different morphodynamic state than would have occurred under natural processes alone.

OPTIMIZATION OF THE CLOSURE OF A BREACHED BARRIER ISLAND IN THE GULF OF MEXICO

A chain of barrier islands in the Gulf of Mexico reduces storm and hurricane impacts along the Mississippi coast. Ship Island, one of the largest islands of this chain, was breached by hurricanes Camille and Katrina creating a 5.5 kilometer wide gap. US Army Corps of Engineers plans to restore the island nourishing 15 million cubic meters of sand. Extensive modeling studies were carried out to support the environmental impact assessment and to optimize design. The main objective of these studies was to determine the impact of the restored island on the environment. The possible increase of sedimentation rates in the adjacent navigation channel connecting a major port to the Gulf of Mexico was of particular interest. The Delft3D models, calibrated on measurements of waves, tidal levels and currents, were used to estimate the annual sediment transport rates. These models were subsequently applied to optimize the design of the closure of Camille Cut. The optimum construction sequence was established. Sediment losses from the fill, and the impact of turbidity plumes on the nearby sea grass fields were determined.

Manmade Vulnerability of the Cancun Beach System: The Case of Hurricane Wilma

AbstractClimate change and resultant coastal erosion and flooding have been the focus of many recent analyses. Often these studies overlook the effects of manmade modifications to the coastline which have reduced its resilience to storm events. In this investigation, we integrate previous reports, historical photo analysis, field work, and the application of numerical models to better understand the effects of Wilma, the most destructive hurricane to affect Cancun, Mexico. Huge waves (of significant height, >12 m), long mean wave periods (>12 s), devastating winds (>250 km/h), and powerful currents (>2 m/s) removed >7 million cubic meters of sand from the Cancun beach system, leaving 68% of the sub‐aerial beach as bedrock, and the rest considerably eroded. Numerical simulations show that the modifications to the barrier island imposed by tourist infrastructure have considerably increased the rigidity of the system, increasing the potential erosion of the beach under extreme conditions. If there were no structural barriers, a series of breaches could occur along the beach, allowing exchange of water and alleviating storm surge on other sections of the beach. If the effects caused by anthropogenic changes to Cancun are ignored, the analysis is inaccurate and misleading.

Field instrumentation case study at a pilot site in the Changi land reclamation project

Since the early 1990's till early 2000s, the Changi East Reclamation Project in the Republic of Singapore involved the filling of approximately 200 million cubic meters of sand for the reclamation of a total land area of about 2500 hectares. The land reclamation works were carried out in 5 phases. The edges of the newly reclaimed land in the project were either retained by vertical retaining structure or coastal shore protection rock bund with suitable slopes and stability berms. Land reclamation was carried out using fill materials derived from dredging granular material from the seabed at the borrow source. Prefabricated vertical drains with surcharge were used extensively in the project to accelerate the consolidation process. In addition, the hydraulically placed sandfill was densified by using various deep compaction methods. Geotechnical instruments were required to monitor the settlement and pore pressure during the consolidation of soft soil. During the implementation of the 5 phases of land reclamation and soil improvement projects, geotechnical instruments of various types were installed. In order to monitor the performance of ground improvement and to validate the efficiency of the prefabricated vertical drain system several geotechnical instruments were installed in a Pilot Test site within one of the phases of work. This paper provides a case study of the performance of a Pilot Test Site carried out in the Changi East Reclamation Project (Phase 1B).

Stratigraphy, sedimentology, age and palaeoenvironment of marine varved clay in the Middle Swedish end‐moraine zone

Johnson, M. D. & Ståhl, Y. 2009: Stratigraphy, sedimentology, age and palaeoenvironment of marine varved clay in the Middle Swedish end‐moraine zone. Boreas, 10.1111/j.1502‐3885.2009.00124.x. ISSN 0300‐9483Deglaciation of the Middle Swedish end‐moraine zone and age of the sediment in and between the moraines have been discussed for about a hundred years. The goal of this project was to determine the stratigraphy and age of the sediment in and between the moraines. Inter‐moraine flats are underlain by clay, 10–25 m thick, overlying thin sand and gravel or till on bedrock. The clay is overlain by a few metres of sand and gravel. Much of the clay beneath the flats consists of rhythmites that grade from grey to red and are 2–74 cm thick. Our interpretation of these rhythmites as being varves is supported by grain size and mineralogical and elemental variations. Foraminifera and ostracods show that the clay was deposited in an arctic marine environment, while radiocarbon dating of the microfossils indicates that the clay was deposited 12 150 cal. 14C years ago, during the Younger Dryas chronozone (YD). Most of the optical stimulated luminescence dates on the clay are much older, containing quartz sand that was insufficiently bleached. The stratigraphy indicates that the moraines are composed of YD clay pushed into ridge forms during ice‐front oscillations. It is not possible to determine how far north the Scandinavian Ice Sheet retreated prior to the YD advance. We neither support nor reject the suggestion that the ice margin retreated to the northern edge of Mt. Billingen during the Allerød, causing the Baltic Ice Lake to drain.

Mining Sand on the Continental Shelf of the Atlantic and Gulf Coasts of the U.S.

Essentially all marine mining along the East and Gulf coasts of the U.S. is for sand used in beach nourishment projects. The current minimal commercial production of sand and aggregate may increase as conventional, on-shore sources become exhausted or are lost to competing land use. Studies published in the late 1990s document a history of nearly 900 individual episodes of beach nourishment having a total cost in excess of $2 × 109 with several hundred million cubic meters of sand placed along over 645 km (400 mi) of shoreline. As exemplified by studies in Florida, prospecting for sand for use in beach nourishment can begin before site specific needs are identified. A full prospecting starts with assimilation of pertinent literature, local knowledge, and an understanding of the geologic and geomorphic settings in which suitable deposits of sand or aggregate occur. High-resolution seismic profiling follows to outline the three dimensional extent of the sand bodies. Finally, vibratory cores are collected to verify the interpretation of the seismic data and to provide samples for geotechnical, especially granulometric, analyses. The actual method of production often is determined by the local availability of different dredge types. Because the mining of marine sands disturbs meaningful areas of the sea floor, environmental concerns must be considered. While it generally is assumed that dredged areas will be left barren, it is possible to assess the likely rate of recolonization. The disruption of bottom habitat also can affect feeding and spawning areas for fishes and other organisms. Alteration in local currents and wave transformation processes need to be modeled and their consequences assessed.

Assessment of ground improvement work using radioisotope cone penetrometers

The effectiveness of radioisotope cone penetrometers (RIcones) under various soil conditions is now well established. This paper briefly describes the design of RI-cones, and the advantages associated with their use. Two case histories are presented in which these cone penetrometers were utilised to investigate their effectiveness in ground improvement works. Both case histories involve land reclamation work. In one, reclamation was effected by hydraulically placing the fly ash obtained from a nearby coal-fired power plant, and in the other, the reclamation of land from sea was effected by pluviating sand by a conveyor belt system. It has been shown that RI-cones can detect any small changes in the density profile, which can result in large savings in a project involving millions of cubic metres of sand. L'efficacité des pénétrateurs cônes radio-isotopes (cônes RI) est désormais bien établie, et ce dans des conditions de sol variées. Cet article décrit brièvement la conception des cônes RI et les avantages associés à leur utilisation. Il présente deux études de cas dans lesquelles ces pénétromètres cônes ont é té utilisés pour évaluer leur efficacité dans des travaux d'amélioration de terrain. Ces deux é tudes comportaient des travaux de réhabilitation de terrain. Dans le premier scénario, la réhabilitation est réalisée par la déposition hydraulique de cendres volantes issues d'une centrale électrique au charbon à proximité. Dans le second, elle est effectuée par pluviation de sable par un système de courroie transporteuse. Il est ici démontré que les cônes RI peuvent détecter même de faibles changements dans le profil de densité, ce qui peut permettre de réaliser d'importantes économies dans un projet impliquant des millions de mètres cubes de sable.

Response of a river sediment budget after historical gravel mining (the lower Tordera, NE Spain)

AbstractThe channel of the lower Tordera River (Catalan Coastal Ranges) was intensively mined between 1956 and 1987, at an extraction rate 14 times higher than the replenishment rates. Mining caused incision of up to 2 m over the whole reach, leading to damage of infrastructures and affecting the groundwater system. In this paper we analyse the response of the river sediment budget by means of sediment transport measurements (both in suspension and as bedload) and topographic surveys. Historical data on mining activities was used to verify current values of sediment transport and to locate the main extraction areas in the long profile of the river. This has led to an integrated methodology that can be useful for assessing and managing current and future sediment deficits in heavily mined rivers. In the lower Tordera, a minimum of 3 million cubic metres of sand and gravel were extracted, especially from two gravel pits still visible as concavities in the river's longitudinal profile. Nowadays, 15 yr after mining ceased, the river shows during dry periods a general tendency towards aggradation (3.6 mm yr−1 on average and up to 12 mm yr−1 in central sections where mining took place), but a slight long‐term tendency to erode the riverbed. Sediment yield at the entrance of the study reach attains 552 000 t yr−1, while net sediment deposition reaches 16 400 t yr−1 (78% as bedload), mostly during small floods in dry periods. Estimated time for the river to recover pre‐extraction bed‐level is of the order of 420 yr. Copyright © 2005 John Wiley & Sons, Ltd.

Post-settlement emigration affects mortality estimates for two Bahamian wrasses

Understanding the dynamics of open marine populations is inherently complex, and this complexity has led to decades of debate regarding the relative importance of pre- versus post-settlement processes in structuring these populations. Movement between patches may be an important modifier of patterns established at settlement, yet local immigration and emigration have received less attention than other demographic rates. I examined loss rates from tagged populations of juvenile wrasses (yellowhead wrasse Halichoeres garnoti and bluehead wrasse Thalassoma bifasciatum) at two sites in the Bahamas. Assuming that all losses were due solely to mortality would have significantly underestimated survivorship of yellowhead wrasse by 29% and bluehead wrasse by 14%. On average, per capita mortality and emigration rates were higher for yellowhead than bluehead wrasse, but neither demographic rate differed between sites for either species. With respect to within-species density, bluehead wrasse mortality was density-dependent at the patch reef site, but mortality rates of yellowhead wrasse were consistently density-independent. Evaluating the effects of between-species density, yellowhead wrasse mortality increased with a decrease in bluehead wrasse density, but this effect was limited to the patch reef site. Emigration rates were not a function of either within-species or between-species density, but instead varied inversely with isolation distance. Numerous previous studies of coral-reef fish, conducted on patch reefs separated by only a few meters of sand and often using untagged fish, may have confounded losses due to emigration with those due to mortality. A better understanding of the factors affecting emigration in marine fishes is important to their effective management using spatial tools such as marine protected areas.

Archaeological geophysics: 3D imaging of the Muweilah archaeological site, United Arab Emirates

The sand-covered Muweilah archaeological site in the United Arab Emirates (UAE) is a unique Iron Age site, and has been subject to intensive investigations. However, excavations are time consuming and may require twenty years to complete. Thus geophysical surveys were undertaken with the objective of characterising the site more expeditiously. This paper presents preliminary results of these surveys.Ground penetrating radar (GPR) was tested as a primary imaging tool, with an ancillary shallow time domain EM (MetalMapper) system. Dense 3D GPR datasets were migrated to produce horizontal (plan view) depth slices at 10 cm intervals, which is conceptually similar to the archaeologists’ excavation methodology. The objective was to map all features associated with anthropogenic activity. This required delineating extensive linear and planar features, which could represent infrastructure. The correlation between these and isolated point reflectors, which could indicate anthropogenic activity, was then assessed. Finally, MetalMapper images were used to discriminate between metallic and non-metallic scatterers.The moderately resistive sand cover allowed GPR depth penetration of up to 5 m with a 500 MHz system. GPR successfully mapped floor levels, walls, and isolated anthropogenic activity, but crumbling walls were difficult to track in some cases. From this study, two possible courtyard areas were recognised. The MetalMapper was less successful because of its limited depth penetration of 50 cm. Despite this, the system was still useful in detecting modern-day ferruginous waste and bronze artefacts.The results (subject to ongoing ground-truthing) indicated that GPR was optimal for sites like Muweilah, which are buried under a few metres of sand. The 3D survey methodology proved essential to achieve line-to-line correlation for tracking walls. In performing the surveys, a significant improvement in data quality ensued when survey areas were flattened and de-vegetated. Although MetalMapper surveys were not as useful, they certainly indicated the value of including other geophysical data to constrain interpretation of complex GPR features.

Potential Impacts of Sand Mining Offshore of Maryland and Delaware: Part 2—Biological Considerations

The mining of sand resources from the inner continental shelf for beach nourishment may lead to impacts or increase stress on commercial and noncommercial living resources that utilize these areas. The objective of our work was to characterize benthos present in areas likely to be mined and to predict impacts of sand mining. In 1998 and 1999 we used a combination of methods (grab samples, sediment profile cameras, video sled, and trawl) to collect data on the benthos, both fishes and invertebrates, which utilized several potential sand mining areas. We found benthic communities and fish assemblages to be typical of middle Atlantic sandy inner continental shelf habitats. A sand mining scenario that removed the top meter of sand from Fenwick Shoal would disturb approximately 7.7 km2 with the potential acute impact on noncommercial sessile species being the loss of about 150 × 106 individuals representing 300 kg of wet weight biomass that could have functioned as trophic support to fishes. In addition, mobile species would be displaced and have to search for replacement habitat. To minimize impacts and promote recolonization of mined areas the total removal of substrate should be avoided. Small areas with a project area should be left to serve as refuge patches that would promote recolonization and serve as habitat for mobile species. Predicted impacts on demersal fishes would be lessened by a rapid recolonization, particularly the recovery of mobile epifaunal crustacean that serve as the primary trophic support species. Project timing and engineering could also be used to lessen impacts on fishes by reducing stress on crustaceans. For example, mining activities that ended in time for Spring/Summer recruitment would favor crustaceans while a Fall/Winter end would favor annelids.

Laboratory and field measurements of the modification of radar backscatter by sand

Over the last two decades, the use of synthetic aperture radar (SAR) to address geologic problems has expanded as new applications for radar have been developed. One of the earliest and perhaps most surprising results from orbital SAR images of the Sahara was that, under certain conditions, radar signals penetrated up to several meters of sand to reveal subsurface features such as ancient river channels. Subsequent studies of radar penetration of arid sand deposits have dealt with factors that govern the ability of radar to penetrate a sand cover. This paper presents results from a laboratory experiment in which radar backscatter from a surface of rocks was measured under controlled conditions as a function of frequency, polarization, incidence angle, and sand cover thickness. The sand used in the experiment had a moisture content of 0.28 vol.% and caused calculated average attenuations of 4.2±1 dB/m for C-band and ∼11±2 dB/m for X-band. Results from the experiment were compared to field measurements of sand thickness during acquisition of airborne radar images. In AIRSAR images, the extent of dry sand in a dune field appears best in C-band because longer wavelength L- and P-band signals penetrate thinner sand deposits. Images of wet sand (4.9 vol.%) suggest that L-band was able to penetrate thin sand even though that sand was wet. Together, these laboratory and field measurements contribute towards a better understanding of how a sand cover modifies the radar backscatter of a surface.

Archaeological geophysics: 3D imaging studies at Muweilah, United Arab Emirates (UAE)

The sand covered Muweilah archaeological site in the United Arab Emirates (UAE) is a unique Iron Age site, and subject to intensive excavation. However, this time consuming process would require up to 20 years to complete. This paper presents preliminary results of geophysical surveys with the ultimate objective of characterising the site far more quickly.Ground penetrating radar (GPR) was trialed as a primary imaging tool with a very shallow time domain EM (MetalMapper) system in a supporting role. Dense 3D GPR datasets were migrated at 10 cm intervals to produce horizontal (plan view) slices which are conceptually similar to the excavation methodology used by archaeologists. The objective here was to delineate extensive linear and planar features. In addition, isolated scatterers were classified. Finally, MetalMapper images were used to discriminate between metallic and non metallic scatterers.The highly resistive sand cover provided GPR depth penetration of up to 5 m. GPR successfully mapped floor levels, walls and isolated anthropogenic activity, although in some cases crumbling walls were difficult to track. From this study two possible courtyard areas were recognised. The MetalMapper was less successful due to the limited depth penetration of 50 cm. Despite this, the system was still useful in detecting modern day ferruginous waste and bronze artefacts.The results (subject to ongoing ground-truthing) indicated that GPR was optimal for sites like Muweilah, which are buried under a few metres of sand. The 3D survey methodology proved essential to achieve line to line correlation for tracking walls. Although MetalMapper surveys were not as useful as hoped, they certainly indicated the value of including other geophysical data to constrain interpretation of complex GPR features. Practically, a significant improvement in data quality accrued when survey areas were flattened and de-vegetated.