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Journal articles on the topic 'Bathymetric profile'
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1
Pettus, Alvin M. "Bathymetric Mapping: Making Underwater Profile Charts." Science Activities: Classroom Projects and Curriculum Ideas 35, no. 3 (January 1998): 24–27. http://dx.doi.org/10.1080/00368129809600914.
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Little, Sarah A., Patricia H. Carter, and Deborah K. Smith. "Wavelet analysis of a bathymetric profile reveals anomalous crust." Geophysical Research Letters 20, no. 18 (September 15, 1993): 1915–18. http://dx.doi.org/10.1029/93gl01880.
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Ghorbanidehno, Hojat, Jonghyun Lee, Matthew Farthing, Tyler Hesser, Peter K. Kitanidis, and Eric F. Darve. "Novel Data Assimilation Algorithm for Nearshore Bathymetry." Journal of Atmospheric and Oceanic Technology 36, no. 4 (April 2019): 699–715. http://dx.doi.org/10.1175/jtech-d-18-0067.1.
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AbstractIt can be expensive and difficult to collect direct bathymetry data for nearshore regions, especially in high-energy locations where there are temporally and spatially varying bathymetric features like sandbars. As a result, there has been increasing interest in remote assessment techniques for estimating bathymetry. Recent efforts have combined Kalman filter–based techniques with indirect video-based observations for bathymetry inversion. Here, we estimate nearshore bathymetry by utilizing observed wave celerity and wave height, which are related to bathymetry through phase-averaged wave dynamics. We present a modified compressed-state Kalman filter (CSKF) method, a fast and scalable Kalman filter method for linear and nonlinear problems with large numbers of unknowns and measurements, and apply it to two nearshore bathymetry estimation problems. To illustrate the robustness and accuracy of our method, we compare its performance with that of two ensemble-based approaches on twin bathymetry estimation problems with profiles based on surveys taken by the U.S. Army Corps of Engineer Field Research Facility (FRF) in Duck, North Carolina. We first consider an estimation problem for a temporally constant bathymetry profile. Then we estimate bathymetry as it evolves in time. Our results indicate that the CSKF method is more accurate and robust than the ensemble-based methods with the same computational cost. The superior performance is due to the optimal low-rank representation of the covariance matrices.
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Specht, Mariusz, Cezary Specht, Henryk Lasota, and Piotr Cywiński. "Assessment of the Steering Precision of a Hydrographic Unmanned Surface Vessel (USV) along Sounding Profiles Using a Low-Cost Multi-Global Navigation Satellite System (GNSS) Receiver Supported Autopilot." Sensors 19, no. 18 (September 12, 2019): 3939. http://dx.doi.org/10.3390/s19183939.
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The performance of bathymetric measurements by traditional methods (using manned vessels) in ultra-shallow waters, i.e., lakes, rivers, and sea beaches with a depth of less than 1 m, is often difficult or, in many cases, impossible due to problems related to safe vessel maneuvering. For this reason, the use of shallow draft hydrographic Unmanned Surface Vessels (USV) appears to provide a promising alternative method for performing such bathymetric measurements. This article describes the modernisation of a USV to switch from manual to automatic mode, and presents a preliminary study aimed at assessing the suitability of a popular autopilot commonly used in Unmanned Aerial Vehicles (UAV), and a low-cost multi-Global Navigation Satellite System (GNSS) receiver cooperating with it, for performing bathymetric measurements in automated mode, which involves independent movement along a specified route (hydrographic sounding profiles). The cross track error (XTE) variable, i.e., the distance determined between a USV’s position and the sounding profile, measured transversely to the course, was adopted as the measure of automatic control precision. Moreover, the XTE value was statistically assessed in the publication.
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Ekpa, A. U., and N. I. Eyakndue. "Determination of a Section of Woji Riverbed Depths for Safe Navigation." Nigerian Journal of Environmental Sciences and Technology 1, no. 1 (March 2017): 55–68. http://dx.doi.org/10.36263/nijest.2017.01.0033.
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The depths of the oceans, seas, rivers, etc. and charting the shape and topography of the ocean floor are only determined though bathymetric processes. And mariners primarily depend on water depths beneath their vessels for safe navigation. Bathymetry also goes a long way to enhance the identification of possible features on the seabed such as elevation changes, rock outcrop, wreckages, sunken vessels, pipeline, or any other obstructions that could cause hazard to navigation. This study employs the bathymetric principles to determine river-bed depths of a section of the Woji River for the purpose of creating a two-dimensional view of the underlying sub-surface and a threedimensional model of the river-bed, to enhance safe navigation. Data acquisition was done using satellite imagery from Google Earth, total tide prediction data, sounding depths using Midas echo sounder and GPS data. Data processing performed on observed bathymetric data include spike removal, tidal correction on instantaneous depths. The processed depths were analysed and presented in form of profile view, graphs, and charts. A flow and sedimentation simulation was carried out using ArcGIS 10.3, to show the nature of the river. The tidal data aided in sounding reduction, and river average depth of 6.022m was obtained. The levelling mis-closure was 0.001m and the average variation in echo sounder calibration was 0.08m. Based on the acquired and output data, the produced chart revealed sedimentation effect on the convex coastline, uneven riverbed topography possibly due to sand excavation, which could pose serious danger to the safety of navigation. Based on these results, the use of Sub-Bottom Profiler and a Multi-Beam Echo Sounder (MBES) is therefore recommended in order to improve the quality of data obtained.
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Zwolak, Karolina, Łukasz Marchel, Aileen Bohan, Masanao Sumiyoshi, Jaya Roperez, Artur Grządziel, Rochelle Ann Wigley, and Sattiabaruth Seeboruth. "Automatic Identification of Internal Wave Characteristics Affecting Bathymetric Measurement Based on Multibeam Echosounder Water Column Data Analysis." Energies 14, no. 16 (August 5, 2021): 4774. http://dx.doi.org/10.3390/en14164774.
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The accuracy of multibeam echosounder bathymetric measurement depends on the accuracy of the data of the sound speed layers within the water column. This is necessary for the correct modeling of ray bending. It is assumed that the sound speed layers are horizontal and static, according to the sound speed profile traditionally used in the depth calculation. In fact, the boundaries between varying water masses can be curved and oscillate. It is difficult to assess the parameters of these movements based on the sparse sampling of sound velocity profiles (SVP) collected through a survey; thus, alternative or augmented methods are needed to obtain information about water mass stratification for the time of a particular ping or a series of pings. The process of water column data collection and analysis is presented in this paper. The proposed method updates the sound speed profile by the automated detection of varying water mass boundaries, giving the option to adjust the SVP for each beam separately. This can increase the overall accuracy of a bathymetric survey and provide additional oceanographic data about the study area.
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Brisbourne, A. M., A. M. Smith, E. C. King, K. W. Nicholls, P. R. Holland, and K. Makinson. "Seabed topography beneath Larsen C Ice Shelf from seismic soundings." Cryosphere Discussions 7, no. 4 (August 15, 2013): 4177–206. http://dx.doi.org/10.5194/tcd-7-4177-2013.
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Abstract. Seismic reflection soundings of ice thickness and seabed depth were acquired on the Larsen C Ice Shelf in order to test a sub-shelf bathymetry model derived from the inversion of IceBridge gravity data. A series of lines were collected, from the Churchill Peninsula in the north to the Joerg Peninsula in the south, and also towards the ice front. Sites were selected using the bathymetry model derived from the inversion of free-air gravity data to indicate key regions where sub-shelf oceanic circulation may be affected by ice draft and sub-shelf cavity thickness. The seismic velocity profile in the upper 100 m of firn and ice was derived from shallow refraction surveys at a number of locations. Measured temperatures within the ice column and at the ice base were used to define the velocity profile through the remainder of the ice column. Seismic velocities in the water column were derived from previous in situ measurements. Uncertainties in ice and water cavity thickness are in general <10 m. Compared with the seismic measurements, the root-mean-square error in the gravimetrically derived bathymetry at the seismic sites is 162 m. The seismic profiles prove the non-existence of several bathymetric features that are indicated in the gravity inversion model, significantly modifying the expected oceanic circulation beneath the ice shelf. Similar features have previously been shown to be highly significant in affecting basal melt rates predicted by ocean models. The discrepancies between the gravity inversion results and the seismic bathymetry are attributed to the assumption of uniform geology inherent in the gravity inversion process and also the sparsity of IceBridge flight lines. Results indicate that care must be taken when using bathymetry models derived by the inversion of free-air gravity anomalies. The bathymetry results presented here will be used to improve existing sub-shelf ocean circulation models.
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Innocenti, C., L. Battaglini, S. D'Angelo, and A. Fiorentino. "Submarine landslides: mapping the susceptibility in European seas." Quarterly Journal of Engineering Geology and Hydrogeology 54, no. 1 (September 16, 2020): qjegh2020–027. http://dx.doi.org/10.1144/qjegh2020-027.
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A map of susceptibility to submarine landslides in European seas has been developed using the maximum entropy model (MaxEnt) and landslide cartography acquired from European Marine Observation and Data Network (EMODnet) Geology (https://www.emodnet-geology.eu/). A total of 15% landslide points were set aside and used as test data, while the remaining 85% were used for model training. Based on EMODnet bathymetry, 33 environmental maps including bathymetric position index (BPI), slope, features, flat curvature and profile curvature, all calculated at different spatial scales, were processed. In an iterative process, all the variables that were highly collinear and those that did not contribute significantly to the model were eliminated. In the end, the model was constructed using only bathymetry and the slope of the seabed. The elaborated model has an area under the ROC (receiver operating characteristic) curve (AUC) of 0.910 calculated on the training set and 0.911 on the test set, and the ROC curves are coincident. The slope is the variable that gives the greatest contribution to the model (82%), but without the contribution of depth (18%) the results degrade significantly. The susceptibility map correctly identifies all the main structures where the presence of landslides is known. The model shows a certain sensitivity to bathymetric acquisition noise.Thematic collection: This article is part of the Mapping the Geology and Topography of the European Seas (EMODnet) collection available at: https://www.lyellcollection.org/cc/EMODnet
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Brisbourne, A. M., A. M. Smith, E. C. King, K. W. Nicholls, P. R. Holland, and K. Makinson. "Seabed topography beneath Larsen C Ice Shelf from seismic soundings." Cryosphere 8, no. 1 (January 2, 2014): 1–13. http://dx.doi.org/10.5194/tc-8-1-2014.
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Abstract. Seismic reflection soundings of ice thickness and seabed depth were acquired on the Larsen C Ice Shelf in order to test a sub-ice shelf bathymetry model derived from the inversion of IceBridge gravity data. A series of lines was collected, from the Churchill Peninsula in the north to the Joerg Peninsula in the south, and also towards the ice front. Sites were selected using the bathymetry model derived from the inversion of free-air gravity data to indicate key regions where sub-ice shelf oceanic circulation may be affected by ice draft and seabed depth. The seismic velocity profile in the upper 100 m of firn and ice was derived from shallow refraction surveys at a number of locations. Measured temperatures within the ice column and at the ice base were used to define the velocity profile through the remainder of the ice column. Seismic velocities in the water column were derived from previous in situ measurements. Uncertainties in ice and water cavity thickness are in general < 10 m. Compared with the seismic measurements, the root-mean-square error in the gravimetrically derived bathymetry at the seismic sites is 162 m. The seismic profiles prove the non-existence of several bathymetric features that are indicated in the gravity inversion model, significantly modifying the expected oceanic circulation beneath the ice shelf. Similar features have previously been shown to be highly significant in affecting basal melt rates predicted by ocean models. The discrepancies between the gravity inversion results and the seismic bathymetry are attributed to the assumption of uniform geology inherent in the gravity inversion process and also the sparsity of IceBridge flight lines. Results indicate that care must be taken when using bathymetry models derived by the inversion of free-air gravity anomalies. The bathymetry results presented here will be used to improve existing sub-ice shelf ocean circulation models.
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Sentchev, Alexei, Thinh Duc Nguyen, Lucille Furgerot, and Pascal Bailly du Bois. "Underway velocity measurements in the Alderney Race: towards a three-dimensional representation of tidal motions." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 378, no. 2178 (July 27, 2020): 20190491. http://dx.doi.org/10.1098/rsta.2019.0491.
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The Alderney Race, located northwest of the Cotentin Peninsula (France), is a site with high tidal-stream energy potential. Circulation through the Alderney Race is complex, with current speed exceeding 3 m s −1 at neap tide. Towed acoustic Doppler current profiler (ADCP) measurements and static point velocity measurements were performed in July 2018 focusing on assessment of circulation and vertical structure of tidal currents. Transect surveys revealed peculiar features of local dynamics such as change in location of the tidal jet on ebb and flood flow. The spatial expanse of the tidal jet was quantified and regions with largely sheared or nearly homogeneous velocity distributions were identified on the cross-sections. Velocity profiles acquired along the cross-sections were accurately characterized using a power law. The spatial variability of the power-law exponent α was found to be large and correlated with the tidal conditions. The largest variation in profile shape was observed in the northern sector and assumed to be generated by the current interaction with a bathymetric constriction. The velocity profiles were found to vary from highly sheared on flood flow to nearly homogeneous on ebb flow, with corresponding range of power-law exponent α variation from 6 to 14. In the southern sector, over a relatively smooth bathymetry, the velocity profile shape was accurately approximated using the 1/7 power law with a range of variation of α from 6.5 to 8, with respect to the tidal conditions. To our knowledge, this is the largest field survey done using towed ADCP and the results could represent a significant advance in tidal site characterization and provide advanced information to turbine developers. This article is part of the theme issue ‘New insights on tidal dynamics and tidal energy harvesting in the Alderney Race'.
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Raju, R. P., P. Anand, Dominic Ricky Fernandez, and A. Raghunadha Rao. "Effect of Azimuthal Asymmetry Caused by Upwelling on 3D Ocean Acoustic Propagation." Defence Science Journal 69, no. 2 (March 6, 2019): 136–41. http://dx.doi.org/10.14429/dsj.69.14220.
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3-D underwater parabolic equation model based on implicit finite difference method has been implemented for South Eastern Arabian Sea (SEAS). The bathymetric and geo-acoustic features have been integrated in the model for a 50 km circular region in SEAS. The model can simulate the effects of azimuthal variation in oceanographic features and compute azimuthally coupled pressure due to an omni-directional source. The azimuthal variation in oceanographic conditions can be observed during an upwelling event. In the first case study, the effect of upwelling event on three-dimensional acoustic propagation has been studied by using sound speed profile data derived from INS Sagardhwani observations. The difference in Transmission loss mosaic for upslope and downslope propagation is due to bathymetry as well as upwelling. In the second case study, the effect of upwelling only, is studied by running a model corresponding to range independent sound speed profile field and range dependent bathymetry. It was observed that during this upwelling event, the transmission loss is higher at longer ranges during upslope propagation than downslope propagation. This is due to the increase in the thickness of sonic layer duct as acoustic wave propagates from shallow to deep water. The effect of azimuthal variation i
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Postacchini, M., L. Soldini, C. Lorenzoni, and A. Mancinelli. "Technical Note: Medium-term morphodynamics in an unprotected sandy beach of the Adriatic Sea." Ocean Science Discussions 12, no. 4 (August 10, 2015): 1711–28. http://dx.doi.org/10.5194/osd-12-1711-2015.
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Abstract. In the recent years attention has been paid to the beach protection by means of soft and hard defenses. Along the Italian coasts of the Adriatic Sea, sandy beaches are the most common landscapes and around 70 % of the Marche-Region coasts (central Adriatic), is protected by defense structures. The longest free-from-obstacle nearshore area in the Region includes the beach of Senigallia, characterized by a multiple barred beach, frequently monitored during the last decades. The bathymetries surveyed in 2006, 2010, 2011, 2012 and 2013 show a good adaptation of the beach to the Dean-type equilibrium profile, though a strong short-/medium-term variability of the wave climate has been observed during the monitored periods. This suggests a slight influence of wave forcing on the long-term profiles, which seems to only depend on the sediment size. Further, the medium-term dynamics of the submerged bars and their geometric features have been related to the wave climate collected by a wave buoy located 40 km off Senigallia during the analyzed temporal windows. An overall interpretation of the complete dynamics, i.e. hydrodynamics (buoy data), sediment characteristics (equilibrium-profile A parameter) and morphodynamics (bathymetric surveys), suggests that the wave climate is fundamental for the morphodynamic changes of the beach in the medium term: waves coming from NNE/ESE are characterized by a larger/smaller steepness and induce seaward/shoreward bar migration, as well as bar smoothing/steepening. Moving southward, the bar dimension increases, while the equilibrium profile suggests a decrease of the sediment size in the submerged beach, this probably due to the presence of both harbor jetty and river mouth North of the investigated area.
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Weitemeyer, Karen, Guozhong Gao, Steven Constable, and David Alumbaugh. "The practical application of 2D inversion to marine controlled-source electromagnetic data." GEOPHYSICS 75, no. 6 (November 2010): F199—F211. http://dx.doi.org/10.1190/1.3506004.
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An algorithm is presented for the inversion of marine controlled-source electromagnetic (CSEM) data that uses a 2D finite difference (FD) forward driver. This code is demonstrated by inverting a CSEM data set collected at Hydrate Ridge, Oregon, consisting of 25 seafloor sites recording a [Formula: see text] transmission frequency. The sites are located across a bathymetric high, with variations in water depth of [Formula: see text] along the [Formula: see text] profile. To model this complex seafloor bathymetry accurately, the FD grid was designed by careful benchmarking using a different 2D finite element (FE) forward code. A comparison of the FE and FD forward model solutions verifies that no features in the inversion are due to inaccuracies of the FD grid. The inversion includes the local seawater conductivity–depth profile as recorded by the transmitter’s conductivity–temperature-depth gauge, because seawater conductivity is known to have a significant effect on the CSEM responses. An apparent resistivity pseudosection of the CSEM data resembles the 2D inversion in general appearance. However, the inversion provides depth and geometric control of features that cannot be provided by the pseudosection and eliminates artifacts generated from the pseudosection projection.
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Ioualalen, M., E. Pelinovsky, J. Asavanant, R. Lipikorn, and A. Deschamps. "On the weak impact of the 26 December Indian Ocean tsunami on the Bangladesh coast." Natural Hazards and Earth System Sciences 7, no. 1 (January 26, 2007): 141–47. http://dx.doi.org/10.5194/nhess-7-141-2007.
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Abstract. The 26 December 2004 Indian Ocean tsunami damaged severely most of the Gulf of Bengal's coastal areas, but the coast of Bangladesh which stands at the edge of an extraordinarily extended continental shelf. This latter feature has been built through huge discharges of river sediments along the Brahmaputra and Ganges rivers. As a result of this enormous discharge, another interesting feature of the area is the deep underwater Canyon, connected with the estuaries, running NE-SW from 25 km off the coast towards the continental slope. We investigate here how these two geological features may have modified/perturbed the Indian ocean tsunami propagation and impact on the Coast of Bangladesh. For that purpose we have realized an ensemble of numerical simulations based on Funwave Boussinesq numerical model and a validated coseismic source. It is found, at first order, that the extended shallow bathymetric profile of the continental shelf plays a key role in flattening the waveform through a defocussing process while the Canyon delays the process. The wave evolution seems to be related at first order to the bathymetric profile rather than to dynamical processes like nonlinearity, dispersion or bottom friction.
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Williams, Christopher N., Stephen L. Cornford, Thomas M. Jordan, Julian A. Dowdeswell, Martin J. Siegert, Christopher D. Clark, Darrel A. Swift, Andrew Sole, Ian Fenty, and Jonathan L. Bamber. "Generating synthetic fjord bathymetry for coastal Greenland." Cryosphere 11, no. 1 (February 1, 2017): 363–80. http://dx.doi.org/10.5194/tc-11-363-2017.
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Abstract. Bed topography is a critical boundary for the numerical modelling of ice sheets and ice–ocean interactions. A persistent issue with existing topography products for the bed of the Greenland Ice Sheet and surrounding sea floor is the poor representation of coastal bathymetry, especially in regions of floating ice and near the grounding line. Sparse data coverage, and the resultant coarse resolution at the ice–ocean boundary, poses issues in our ability to model ice flow advance and retreat from the present position. In addition, as fjord bathymetry is known to exert strong control on ocean circulation and ice–ocean forcing, the lack of bed data leads to an inability to model these processes adequately. Since the release of the last complete Greenland bed topography–bathymetry product, new observational bathymetry data have become available. These data can be used to constrain bathymetry, but many fjords remain completely unsampled and therefore poorly resolved. Here, as part of the development of the next generation of Greenland bed topography products, we present a new method for constraining the bathymetry of fjord systems in regions where data coverage is sparse. For these cases, we generate synthetic fjord geometries using a method conditioned by surveys of terrestrial glacial valleys as well as existing sinuous feature interpolation schemes. Our approach enables the capture of the general bathymetry profile of a fjord in north-west Greenland close to Cape York, when compared to observational data. We validate our synthetic approach by demonstrating reduced overestimation of depths compared to past attempts to constrain fjord bathymetry. We also present an analysis of the spectral characteristics of fjord centrelines using recently acquired bathymetric observations, demonstrating how a stochastic model of fjord bathymetry could be parameterised and used to create different realisations.
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Różyński, Grzegorz. "Local Wave Energy Dissipation and Morphological Beach Characteristics along a Northernmost Segment of the Polish Coast." Archives of Hydro-Engineering and Environmental Mechanics 65, no. 2 (December 1, 2018): 91–108. http://dx.doi.org/10.1515/heem-2018-0007.
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AbstractThis paper analyses cross-shore bathymetric profiles between Władysławowo (km 125 of the Polish coastal chainage) and Lake Sarbsko (km 174) done in 2005 and 2011. Spaced every 500 m, they cover beach topography from dune/cliff crests to a seabed depth of about 15 m. They were decomposed by signal processing techniques to extract the monotonic component of beach topography and to perform a straightforward assessment of wave energy dissipation rates. Three characteristic dissipation patterns were identified: one associated with large nearshore bars and 2–3 zones of wave breaking; a second, to which the equilibrium beach profile concept can be applied; and a third, characterized by mixed behaviour. An attempt was then made to interpret these types of wave energy dissipation in terms of local coastal morphological features and the underlying sedimentary characteristics.
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Lockhart, Doug, Edward Saade, and Jerry Wilson. "New Developments in Multibeam Backscatter Data Collection and Processing." Marine Technology Society Journal 35, no. 4 (December 1, 2001): 46–50. http://dx.doi.org/10.4031/002533201788057973.
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Recognition of the superior data and coverage from multibeam echosounders (MBES) has been widespread and is increasing rapidly. In addition to the significant value of ensonification of a swath as compared to a profile of bathymetric data, the acoustic data have been frequently presented as "psuedo-sidescan-sonar". Field programs conducted during 2001 using Reson MBES systems and TritonElics software gave us the opportunity to develop enhanced acoustic imagery by manipulation of the backscatter information within each MBES beam. This work has resulted in improved MBES data products using new acquisition and processing techniques.
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Mather, Andrew Alan, Derek Stretch, and Gerald Garland. "WAVE RUN UP ON NATURAL BEACHES." Coastal Engineering Proceedings 1, no. 32 (January 31, 2011): 45. http://dx.doi.org/10.9753/icce.v32.currents.45.
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Wave run up is important for quantifying risks to infrastructure in the coastal zone. The performance of global wave run up models are assessed by applying them to two significant storms along the South African coastline in 2007 and 2008. The models produced mixed results and therefore the development of a new wave run up model was undertaken. This model uses the distance offshore to a point on the bathymetric profile, located approximately at the cut off depth, as a proxy for the underwater beach profile. This new wave run up model has been calibrated for open coastlines as well as large and small embayments. The new model outperforms most of the current wave run up models and gives a good first order approximation of wave run up on natural beaches.
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Marchel, Łukasz, Cezary Specht, and Mariusz Specht. "Assessment of the Steering Precision of a Hydrographic USV along Sounding Profiles Using a High-Precision GNSS RTK Receiver Supported Autopilot." Energies 13, no. 21 (October 28, 2020): 5637. http://dx.doi.org/10.3390/en13215637.
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Unmanned Surface Vehicles (USV) are increasingly used to perform numerous tasks connected with measurements in inland waters and seas. One of such target applications is hydrography, where traditional (manned) bathymetric measurements are increasingly often realized by unmanned surface vehicles. This pertains especially to restricted or hardly navigable waters, in which execution of hydrographic surveys with the use of USVs requires precise maneuvering. Bathymetric measurements should be realized in a way that makes it possible to determine the waterbody’s depth as precisely as possible, and this requires high-precision in navigating along planned sounding profiles. This paper presents research that aimed to determine the accuracy of unmanned surface vehicle steering in autonomous mode (with a Proportional-Integral-Derivative (PID) controller) along planned hydrographic profiles. During the measurements, a high-precision Global Navigation Satellite System (GNSS) Real Time Kinematic (RTK) positioning system based on a GNSS reference station network (positioning accuracy: 1–2 cm, p = 0.95) and a magnetic compass with the stability of course maintenance of 1°–3° Root Mean Square (RMS) were used. For the purpose of evaluating the accuracy of the vessel’s path following along sounding profiles, the cross track error (XTE) measure, i.e., the distance between an USV’s position and the hydrographic profile, calculated transversely to the course, was proposed. The tests were compared with earlier measurements taken by other unmanned surface vehicles, which followed the exact same profiles with the use of much simpler and low-cost multi-GNSS receiver (positioning accuracy: 2–2.5 m or better, p = 0.50), supported with a Fluxgate magnetic compass with a high course measurement accuracy of 0.3° (p = 0.50 at 30 m/s). The research has shown that despite the considerable difference in the positioning accuracy of both devices and incomparably different costs of both solutions, the authors proved that the use of the GNSS RTK positioning system, as opposed to a multi-GNSS system supported with a Fluxgate magnetic compass, influences the precision of USV following sounding profiles to an insignificant extent.
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Lahay, Abdulrahman, Rignolda Rignolda Djamaluddin, Hermanto W. K. Manengkey, and Brama Djabar. "PEMETAAN BATIMETRI PANTAI MALALAYANG DUA, KOTA MANADO." JURNAL PESISIR DAN LAUT TROPIS 8, no. 3 (September 30, 2020): 1. http://dx.doi.org/10.35800/jplt.8.3.2020.30445.
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As with other coastal areas, Malalayang Dua Coast has been used for various activities and is predicted to continue to grow along with the development of Manado City. To support efforts to manage and utilize coastal space in an effective and sustainable manner, data and information are needed related to oceanographic factors, one of which is the bathymetry condition of the coastal waters. This research was carried out with the aim of describing the bathymetric conditions and analyzing the slope of the bottom of the waters. The depth measurement by acoustic method was carried out along 15 survey lines and 750 fixed measurement points, and the bathymetry map was drawn with reference to Mean Seawater Level (MSL). The results obtained indicate that the bathymetry of Malalayang Dua Coast in the west has shallow waters that are wider than the eastern one. Meanwhile, parts of the waters deeper up to a depth of 50 m appear to be steeper in the West than on the East side. In the middle part of the observed waters, there is a part that is relatively deep and protrudes towards the land with a steeper side towards the east. The slope of the bottom of the water in the west (Profile 1) is indicated by flat slopes (2.6%) to a depth of 7 m, and slopes (13%) at a depth of 7 m to 50 m. In the middle section (Profile 2) the slope is categorized as gentle (3%) to a depth of 4 m, and inclined slopes (10%) at a depth of 4 m to 50 m. In the eastern part (Profile 3) the slopes are categorized as sloping slopes (10.28) to a depth of 35 m, and gentle slopes (3.42%) at a depth of 35 m to 50 m. Keywords: bathymetry, acoustics, slope, Malalayang Dua CoastAbstrakSebagaimana wilayah pantai pada umumnya, Pantai Malalayang Dua telah dimanfaatkan untuk berbagai aktivitas dan diprediksi akan terus berkembang seiring perkembangan Kota Manado. Untuk menunjang upaya pengelolaan dan pemanfaatan ruang pantai secara efektif dan berkelanjutan, diperlukan data dan informasi terkait faktor oseanografi dimana salah satu yang penting yaitu kondisi batimetri perairan pantai tersebut. Penelitian ini dilaksanakan dengan tujuan untuk menggambarkan kondisi batimetri dan menganalisis kemiringan lereng dasar perairan. Pengukuran kedalaman dengan metode akustik dilakukan sepanjang 15 lajur perum dan 750 titik fix perum, dan peta batimetri digambarkan dengan referensi Muka Laut Rata-rata (Mean Seawater Level - MSL). Hasil yang diperoleh menunjukkan bahwa batimetri Pantai Malalayang Dua sebelah Barat memiliki perairan dangkal yang lebih lebar dibandingkan sebelah Timur. Sementara itu, untuk bagian perairan yang lebih dalam hingga kedalaman 50 m nampak lebih terjal di bagian Barat dibandingkan sisi sebelah Timur. Pada bagian tengah perairan yang diamati, terdapat bagian yang relatif dalam dan menjorok ke arah darat dengan sisi yang lebih terjal ke arah sebelah Timur. Kemiringan lereng dasar perairan di sebelah Barat (Profil 1) terindikasi lereng datar (2,6%) hingga kedalaman 7 m, dan lereng miring (13%) pada kedalaman 7 m hingga 50 m. Pada bagian tengah (Profil 2) kemiringan lereng terkategori landai (3%) hingga kedalaman 4 m, dan lereng miring (10%) pada kedalaman 4 m hingga 50 m. Pada bagian Timur (Profil 3) kemiringan lereng terkategori lereng miring (10,28) hingga kedalaman 35 m, dan lereng landai (3,42%) pada kedalaman 35 m hingga 50 m. Kata kunci: batimetri, akustik, kemiringan lereng, Pantai Malalayang Dua
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Jiménez-Robles, Alfonso Miguel, Stefano Lanzoni, and Miguel Ortega-Sánchez. "IMPLICATIONS OF PLUME DISCHARGE FOR TIDAL CHANNELS MORPHODYNAMICS: A COUPLED ONSHORE AND OFFSHORE SYSTEM." Coastal Engineering Proceedings, no. 35 (June 23, 2017): 12. http://dx.doi.org/10.9753/icce.v35.sediment.12.
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This contribution investigates the morphodynamic equilibrium of a funnel-shaped, well-mixed tidal channel taking into account the existing dynamical coupling between the tidal channel itself and the related offshore sediment-laden plume. We use a quasi two-dimensional numerical model that resolves the fully nonlinear unsteady shallow water, sediment bed load transport and suspended sediment advection-diffusion equations along with the Exner equation for the bathymetric changes. We close this model by including a dynamic boundary condition at the channel mouth that transfers the offshore plume sediment concentration to the channel dynamics. This model reveals that the offshore plume reduces the timescales to reach equilibrium of the channel and plays a crucial role on shaping it. At equilibrium, the non-plume influence case attains a quasi-linear profile of constant slope in the seaward part. However, the bottom profile in the case that includes the offshore plume tends to increase the concavity of the bottom profile, reducing the final channel mouth depth. Finally, numerical results suggest that the plume characteristics are altered as a consequence of tidal channel evolution.
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Rivera-Rosario, Gustavo, Peter J. Diamessis, Ren-Chieh Lien, Kevin G. Lamb, and Greg N. Thomsen. "Formation of Recirculating Cores in Convectively Breaking Internal Solitary Waves of Depression Shoaling over Gentle Slopes in the South China Sea." Journal of Physical Oceanography 50, no. 5 (May 2020): 1137–57. http://dx.doi.org/10.1175/jpo-d-19-0036.1.
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AbstractThe formation of a recirculating subsurface core in an internal solitary wave (ISW) of depression, shoaling over realistic bathymetry, is explored through fully nonlinear and nonhydrostatic two-dimensional simulations. The computational approach is based on a high-resolution/accuracy deformed spectral multidomain penalty-method flow solver, which employs the recorded bathymetry, background current, and stratification profile in the South China Sea. The flow solver is initialized using a solution of the fully nonlinear Dubreil–Jacotin–Long equation. During shoaling, convective breaking precedes core formation as the rear steepens and the trough decelerates, allowing heavier fluid to plunge forward, forming a trapped core. This core-formation mechanism is attributed to a stretching of a near-surface background vorticity layer. Since the sign of the vorticity is opposite to that generated by the propagating wave, only subsurface recirculating cores can form. The onset of convective breaking is visualized, and the sensitivity of the core properties to changes in the initial wave, near-surface background shear, and bottom slope is quantified. The magnitude of the near-surface vorticity determines the size of the convective-breaking region, and the rapid increase of local bathymetric slope accelerates core formation. If the amplitude of the initial wave is increased, the subsequent convective-breaking region increases in size. The simulations are guided by field data and capture the development of the recirculating subsurface core. The analyzed parameter space constitutes a baseline for future three-dimensional simulations focused on characterizing the turbulent flow engulfed within the convectively unstable ISW.
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Melo, Rafael Roney Camara de, and José Roberto Gonçalves de Azevedo. "Dynamics of sedimentary Capibaribe River bed after deepening dredging." RBRH 21, no. 4 (October 24, 2016): 871–81. http://dx.doi.org/10.1590/2318-0331.01161603.
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ABSTRACT The growth of urban centers in the country are increasingly dependent on the adoption of new mobility options, and before this need was developed and initiated a project to build a river corridor passenger in a part of the Capibaribe River in the city of Recife-PE. For the implementation of a navigation channel deepening are needed dredging to define a geometry of the bed of the river compatible with the needs of ships that will traverse the channel. The monitoring of dredging is done with the constant bathymetric surveys where the information volumes of dredged sediments are removed, aiming to also check the temporal behavior of deposition and erosion processes. In this context, the work aimed to evaluate the geometry of the Capibaribe river bed after the deepening dredging, using data from bathymetric surveys at different times for making longitudinal and transverse profiles, and create digital models of depth to extract information about the deposition/aggradation or erosion/removing sediments and their respective volumes. Early Profile Capibaribe river showed mild slope and heterogeneity in the bottom of the form, especially after kilometer five, with trends of deposition/aggradation downstream of the confluence region with tax arising from the weir Apipucos and upstream of the winding sections in local enlargement of the cross section, and the amount of the fork located at kilometer nine. The scenarios after the dredging to deepen indicate places with predominance of erosion and other sedimentation processes. They compared the longitudinal and transverse profiles of two areas located in western shipping channel, one with 350 meters and over 1000 meters, where it was found that the area 1 to erosion/sediment removal exceeded sedimentation/aggradation, indicating the occurrence of dredging the interval between the two surveys linked to the natural processes. In the study area 2 the sedimentation/aggradation exceeded the removal/erosion, with a volume equivalent to 1 cm thickness. The aggradation occur homogeneously in the navigation channel, while erosion was located on the banks, more intensely on the right bank of the river.
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Barbosa Gentil, Wanderlubio, Fernanda Luisa Ramalho, Celso De Carvalho Braga, Assunção Andrade de Barcelos, and João Batista Pereira Cabral. "Diagnóstico Batimétrico do Reservatório da Usina Hidrelétrica de Caçu-GO." Revista Brasileira de Geografia Física 14, no. 3 (July 20, 2021): 1541. http://dx.doi.org/10.26848/rbgf.v14.3.p1541-1558.
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O presente trabalho teve como objetivo avaliar as mudanças e os níveis de sedimentação ocorridos no reservatório da Usina Hidrelétrica (UHE) Caçu, entre janeiro de 2014 e março de 2015. Os procedimentos empregados para avaliar o processo de sedimentação do reservatório envolveram o diagnóstico dos locais assoreados por meio de levantamento batimétrico e análise da velocidade de escoamento da água com o uso do acoustic doppler current profiler (ADCP). Os resultados obtidos permitiram identificar alterações no perfil topográfico do reservatório, sendo a perda de volume inferior a 0,5% ao ano. O local de maior acúmulo de sedimentos encontra-se no trecho inicial do reservatório (primeiros 6km), ocorrendo a formação de bancos de areia. Os valores máximos de velocidade de escoamento da água nos períodos avaliados variaram entre 0,858m/s a 1,979 m/s. Os valores mínimos da velocidade de escoamento foram detectados nas áreas entre o córrego do Caju e a barragem da usina hidrelétrica de Caçu. The Bathymetric Diagnosis of the Hydroelectric Power Station from Caçu – GO. A B S T R A C TThis research job has as its goal to evaluate the changes and the sedimentation levels occurred in the reservoir of Hydroelectric Power Station (UHE) Caçu, between January 2014 and March 2015. The procedures employed to evaluate the sedimentation process of the reservoir involved the diagnosis of the locals silted through the bathymetric survey and analysis of the water drainage speed with the use of the acoustic doppler current profiler (ADCP). The results obtained permitted to identify changings on the topographic profile of the reservoir, being the loss of the volume under 0,5% per year. The local of the largest sediment accumulation is located in the initial excerpt (first 6 kilometers) occurring the formation of sandbanks. The maximum speed values of water drainage in the evaluated periods varied between 0,858m/s to 1,979 m/s. The minimum values of drainage speed were detected in the areas between the Caju water stream and the dam of the Hydroelectric Power Station of Caçu.Keywords: Sedimentation. Water Speed. ADCP.
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Chazel, Florent, Michel Benoit, and Alexandre Ern. "VALIDATION OF A DOUBLE-LAYER BOUSSINESQ-TYPE MODEL FOR HIGHLY NONLINEAR AND DISPERSIVE WAVES." Coastal Engineering Proceedings 1, no. 32 (February 2, 2011): 14. http://dx.doi.org/10.9753/icce.v32.waves.14.
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A two-layer Boussinesq-type mathematical model has been recently introduced by the authors with the goal of modeling highly nonlinear and dispersive waves (Chazel et al. 2009). The analysis of this model has previously shown that it possesses excellent linear properties, up to kh = 10 at least, for dispersion, shoaling coefficient and vertical profile of orbital velocities. In the present work a numerical one-dimensional (1DH) version of model is developed based on a finite difference technique for meshing the spatial domain. It is then applied and verified against a set of three one-dimensional (1DH) test-cases for which either numerical or experimental reference results are available: i. nonlinear and dispersive regular waves of permanent form; ii. propagation of regular waves on a trapezoidal bar (laboratory experiments by Dingemans (1994)); iii. shoaling and propagation of irregular waves on a barred beach profile (laboratory experiments by Becq-Girard et al. (1999)). The test-cases considered in this study confirm the very good capabilities of the model to reproduce either exact solutions, high-precision numerical simulations and experimental measurements in a variety of non-breaking wave conditions and types of bottom profiles. Nonlinearity, dispersion and bathymetric effects are well accounted for by the model, which appears to possess a rather wide domain of validity while maintaining a reasonable level of complexity.
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Huisman, Bastiaan, Dirk-Jan Walstra, Max Radermacher, Matthieu de Schipper, and Gerben Ruessink. "Observations and Modelling of Shoreface Nourishment Behaviour." Journal of Marine Science and Engineering 7, no. 3 (March 4, 2019): 59. http://dx.doi.org/10.3390/jmse7030059.
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Shoreface nourishments are commonly applied for coastal maintenance, but their behaviour is not well understood. Bathymetric data of 19 shoreface nourishments located at alongshore uniform sections of the Dutch coast were therefore analyzed and used to validate an efficient method for predicting the erosion of shoreface nourishments. Data shows that considerable cross-shore profile change takes place at a shoreface nourishment, while an impact at the adjacent coast is hard to distinguish. The considered shoreface nourishments provide a long-term (3 to ∼30 years) cross-shore supply of sediment to the beach, but with small impact on the local shoreline shape. An efficient modelling approach is presented using a lookup table filled with computed initial erosion–sedimentation rates for a range of potential environmental conditions at a single post-construction bathymetry. Cross-shore transport contributed the majority of the losses from the initial nourishment region. This transport was driven partly by water-level setup driven currents (e.g., rip currents) and increased velocity asymmetry of the waves due to the geometrical change at the shoreface nourishment. Most erosion of the nourishment takes place during energetic wave conditions ( H m 0 ≥ 3 m) as milder waves are propagated over the nourishment without breaking. A data-model comparison shows that this approach can be used to accurately assess the erosion rates of shoreface nourishments in the first years after construction.
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Shaeri, S., R. B. Tomlinson, A. Etemad-Shahidi, D. Strauss, and L. P. Hughes. "Hydrodynamics of a small trained tidal inlet (Currumbin Creek, Australia)." Advances in Geosciences 39 (April 1, 2014): 45–53. http://dx.doi.org/10.5194/adgeo-39-45-2014.
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Abstract. Small tidal inlets are important features of coastal areas, in terms of provision of access from a back barrier water-body to the ocean as well as periodic circulation of fresh nutrients for the local ecology. Usually, dimensional and geometrical characteristics contribute significantly to morphological stability or instability of a particular inlet and necessitate an individual investigation of any desired location. In other words, generalized usage of previous empirical and experimental research of a different position can hardly be used for other places. In this regard, one of the powerful tools to understand the physical processes of a particular region is to collect as much field data as possible. Such a dataset is used to further analyse and explore the governing processes and can also be used for building a numerical computer model for supplementary studies. In this research, the results of a comprehensive field measurement at Currumbin Creek, Queensland, Australia are presented. This study is part of broader research to investigate the long term evolution of the Currumbin entrance and its adjacent beaches. Currently, an annual dredging campaign is needed to reduce the risk of flooding due to excess rainfall inundations and to maintain water quality. The majority of data were collected over a three month period consistent with the time of the 2012 dredging operation. However, due to the loss of some instrumentation, data collection for some of the parameters was repeated till the middle of May 2013. All collected data included: (1) nearshore waves and tide; (2) creek tidal variation; (3) creek flow discharge and velocity; (4) bathymetric survey of the creek; (5) beach profile evolution survey; and (6) sediment sampling. The measurement showed that the creek entrance is tidally dominated, with flood events having a major role in sediment transport into the creek. The nearshore stations' wave data illustrated the marginal effect of the beach curvature between updrift and downdrift stations. Thus, the historical dataset available from the updrift wave rider buoy will be selected to be used for future numerical modelling. Although changes of some beach profiles were comparatively insignificant, the dramatic changes of the profile lines nearby the inlet channel and also rapid bathymetric change of the flood shoal following the dredging completion are valuable information to better calibrate and interpret a local sediment modelling study for the next phase. Essentially, this evaluation needs to be considered for proposing any alternative maintenance activities.
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Falahat, Saeed, Jonas Nycander, Fabien Roquet, and Moundheur Zarroug. "Global Calculation of Tidal Energy Conversion into Vertical Normal Modes." Journal of Physical Oceanography 44, no. 12 (November 26, 2014): 3225–44. http://dx.doi.org/10.1175/jpo-d-14-0002.1.
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Abstract A direct calculation of the tidal generation of internal waves over the global ocean is presented. The calculation is based on a semianalytical model, assuming that the internal tide characteristic slope exceeds the bathymetric slope (subcritical slope) and the bathymetric height is small relative to the vertical scale of the wave, as well as that the horizontal tidal excursion is smaller than the horizontal topographic scale. The calculation is performed for the M2 tidal constituent. In contrast to previous similar computations, the internal tide is projected onto vertical eigenmodes, which gives two advantages. First, the vertical density profile and the finite ocean depth are taken into account in a fully consistent way, in contrast to earlier work based on the WKB approximation. Nevertheless, the WKB-based total global conversion follows closely that obtained using the eigenmode decomposition in each of the latitudinal and vertical distributions. Second, the information about the distribution of the conversion energy over different vertical modes is valuable, since the lowest modes can propagate over long distances, while high modes are more likely to dissipate locally, near the generation site. It is found that the difference between the vertical distributions of the tidal conversion into the vertical modes is smaller for the case of very deep ocean than the shallow-ocean depth. The results of the present work pave the way for future work on the vertical and horizontal distribution of the mixing caused by internal tides.
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Fuiman, Lee A., John D. Gage, and Peter A. Lamont. "Shell morphometry of the deep sea protobranch bivalve Ledella pustulosa in the Rockall Trough, north-east Atlantic." Journal of the Marine Biological Association of the United Kingdom 79, no. 4 (August 1999): 661–71. http://dx.doi.org/10.1017/s0025315498000824.
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The deep sea protobranch bivalve species Ledella pustulosa recently has been described as comprised of four subspecies, differentiated on subtle and qualitative differences in shell morphology. Two of these, L. p. pustulosa and L. p. marshalli, possess overlapping geographic distributions, L. p. pustulosa occurring on the continental slope, and L. p. marshalli occurring on the continental rise and at upper abyssal depths. Principal components analysis was applied to six samples of Ledella pustulosa from the Rockall Trough in order to explore patterns of variation in shell shape and to test whether the variability follows a depth-related cline which might be under environmental control. Two of these samples had previously been identified as L. p. pustulosa and L. p. marshalli, respectively. The distributions of shapes at every depth overlapped broadly with the distributions from other depths and none of the depths had uniformly distinct shells. However, the mean shapes of the six samples divided into two clusters: a shallow cluster characterized by a lower dorsal profile (smaller ‘shoulders’) and a deep cluster with larger ‘shoulders’. No bathymetric cline in shape was found within these clusters. A discriminant function based on training samples of L. p. pustulosa and L. p. marshalli correctly identified 84% of the shells in the training samples and was applicable over a wide range in shell size. It showed that the subspecies differed primarily in the dorsal profile. The discriminant function was applied to 598 shells from depths of 1632–2900 m in the Rockall Trough in order to test the hypothesis of depth-related segregation of the subspecies. Although individual variability was high, the results indicated a gradual transition from L. p. pustulosa dominance at ∼2000 m to L. p. marshalli dominance at 3000 m depth, but not marked segregation. A sample from 1632 m depth with large proportions of both subspecies disrupted the bathymetric trend and suggested a latitudinal gradient in distribution. Possible environmental factors, including bottom currents, acting on a common genotype to cause the observed pattern of differentiation, are also discussed.
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Moskalik, Mateusz, Piotr Grabowiecki, Jarosław Tęgowski, and Monika Żulichowska. "Bathymetry and geographical regionalization of Brepollen (Hornsund, Spitsbergen) based on bathymetric profiles interpolations." Polish Polar Research 34, no. 1 (March 1, 2013): 1–22. http://dx.doi.org/10.2478/popore-2013-0001.
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Abstract Determination of High Arctic regions bathymetry is strictly dependent from weather and ice mass quantity. Due to safety, it is often necessary to use a small boat to study fjords area, especially close to glaciers with unknown bathymetry. This precludes the use of modern multi−beam echosounders, and so traditional single−beam echosounders have been used for bathymetry profiling. Adequate interpolation techniques were determined for the most probable morphological formations in−between bathymetric profiles. Choosing the most accurate interpolation method allows for the determination of geographical regionalisation of submarine elevations of the Brepollen area (inner part of Hornsund, Spitsbergen). It has also been found that bathymetric interpolations should be performed on averaged grid values, rather than individual records. The Ordinary Kriging Method was identified as the most adequate for interpolations and was compared with multi beam scan− ning, which was possible to make due to a previously modelled single beam interpolation map. In total, eight geographical units were separated in Brepollen, based on the bathy− metry, slope and aspect maps. Presented results provide a truly new image of the area, which allow for further understanding of past and present processes in the High Arctic.
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Athanasiou, Panagiotis, Ap van Dongeren, Alessio Giardino, Michalis Vousdoukas, Sandra Gaytan-Aguilar, and Roshanka Ranasinghe. "Global distribution of nearshore slopes with implications for coastal retreat." Earth System Science Data 11, no. 4 (October 2, 2019): 1515–29. http://dx.doi.org/10.5194/essd-11-1515-2019.
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Abstract. Nearshore slope, defined as the cross-shore gradient of the subaqueous profile, is an important input parameter which affects hydrodynamic and morphological coastal processes. It is used in both local and large-scale coastal investigations. However, due to unavailability of data, most studies, especially those that focus on continental or global scales, have historically adopted a uniform nearshore slope. This simplifying assumption could however have far-reaching implications for predictions/projections thus obtained. Here, we present the first global dataset of nearshore slopes with a resolution of 1 km at almost 620 000 points along the global coastline. To this end, coastal profiles were constructed using global topo-bathymetric datasets. The results show that the nearshore slopes vary substantially around the world. An assessment of coastline recession driven by sea level rise (SLR) (for an arbitrary 0.5 m SLR) with a globally uniform coastal slope of 1 : 100, as carried out in previous studies, and with the spatially variable coastal slopes computed herein shows that, on average, the former approach would underestimate coastline recession by about 40 %, albeit with significant spatial variation. The final dataset has been made publicly available at https://doi.org/10.4121/uuid:a8297dcd-c34e-4e6d-bf66-9fb8913d983d (Athanasiou, 2019).
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Skilbrei, Jan Reidar, and Ola Kihle. "Display of residual profiles versus gridded image data in aeromagnetic study of sedimentary basins: A case history." GEOPHYSICS 64, no. 6 (November 1999): 1740–47. http://dx.doi.org/10.1190/1.1444679.
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High‐pass filtered aeromagnetic profiles from the Mid‐Norwegian continental shelf, displayed as shaded relief versions of color stripes, provide a lucid picture of sedimentary layering and structure not easily displayed by proper application of modern enhancement techniques to images of the gridded aeromagnetic data. We show that when the aim is to analyze anomalies related to sedimentary features, it is more useful to study shaded relief versions of the profile data than to study digitally enhanced images of high‐pass filtered or calculated gradient data; a reason for this is probably the loss of high‐wavenumber, very low amplitude, information in the gridding process. The reprocessed data sets reveal anomaly patterns that are interpreted to originate from the following magnetic sources: (1) Quaternary overburden and bathymetric features, (2) magnetic sedimentary rocks, the subcropping sedimentary rock units, (3) magnetic basement in the structural highs and in the coastal zone, and (4) igneous intrusives at relatively deep levels within sedimentary basins. West of the basement rocks along the coast, the subcropping wedge of Mesozoic to Tertiary sediments is characterized by a distinct set of subparallel anomalies. Also, sedimentary layering within the Tertiary can be resolved. Short to intermediate wavelength anomalies correlate with the Late Jurassic faults of the Halten Terrace.
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Erbe, Christine, David Peel, Joshua N. Smith, and Renee P. Schoeman. "Marine Acoustic Zones of Australia." Journal of Marine Science and Engineering 9, no. 3 (March 19, 2021): 340. http://dx.doi.org/10.3390/jmse9030340.
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Underwater sound is modelled and mapped for purposes ranging from localised environmental impact assessments of individual offshore developments to large-scale marine spatial planning. As the area to be modelled increases, so does the computational effort. The effort is more easily handled if broken down into smaller regions that could be modelled separately and their results merged. The goal of our study was to split the Australian maritime Exclusive Economic Zone (EEZ) into a set of smaller acoustic zones, whereby each zone is characterised by a set of environmental parameters that vary more across than within zones. The environmental parameters chosen reflect the hydroacoustic (e.g., water column sound speed profile), geoacoustic (e.g., sound speeds and absorption coefficients for compressional and shear waves), and bathymetric (i.e., seafloor depth and slope) parameters that directly affect the way in which sound propagates. We present a multivariate Gaussian mixture model, modified to handle input vectors (sound speed profiles) of variable length, and fitted by an expectation-maximization algorithm, that clustered the environmental parameters into 20 maritime acoustic zones corresponding to 28 geographically separated locations. Mean zone parameters and shape files are available for download. The zones may be used to map, for example, underwater sound from commercial shipping within the entire Australian EEZ.
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Lemenkova, Polina. "Applying Automatic Mapping Processing By GMT to Bathymetric and Geophysical Data: Cascadia Subduction Zone, Pacific Ocean." Journal of Environmental Geography 13, no. 3-4 (November 1, 2020): 15–26. http://dx.doi.org/10.2478/jengeo-2020-0008.
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Abstract The Cascadia Trench is stretching along the convergent plate boundaries of Pacific Plate, North America Plate and Juan De Fuca Plate. It is an important geomorphological structural feature in the north-east Pacific Ocean. The aim of the paper is to analyse the geomorphology of the Cascadia Trench west of Vancouver Island (Canada and USA) using the GMT cartographic scripting toolset. The unique geomorphological feature of the Cascadia Trench is that the thick sediment layer completely obscures the subduction zone and abyssal hills. This results in the asymmetric profile in the cross-section of the trench. Bathymetric data were extracted from the GEBCO 2019 dataset (15 arc-second grid), sediment thickness by the GlobSed dataset. Due to the dominance of high sedimentary rate and complexity of the tectonic processes and geologic settings, Cascadia Trench develops very specific asymmetric geomorphic shape comparing to the typical V-form. The results of the geomorphic modelling show that eastern side of the trench has a gentle curvature (slope: 35.12°), partially stepped, due to the tectonic movements and faults. The opposite, oceanward side is almost completely leveled. The trench is narrow with maximal depth at the selected segment -3489 m and for the whole dataset -6201 m. The most repetitive depth is in a range -2500 to -2400 m (267 samples) and -2500 to -2600 m (261 samples). The bottom is mostly flat due to the high sedimentation rates indicating the accumulative leveling processes. Marine free-air gravity anomalies along the Cascadia Subduction Zone are characterized by weakly positive values (20 mGal) increasing rapidly in the zone of the continental slope (>200 mGal), which is associated with a decrease in thickness of the Earth’s crust.
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Sakellariou, D., and K. Tsampouraki-Kraounaki. "OFFSHORE FAULTING IN THE AEGEAN SEA: A SYNTHESIS BASED ON BATHYMETRIC AND SEISMIC PROFILING DATA." Bulletin of the Geological Society of Greece 50, no. 1 (July 27, 2017): 134. http://dx.doi.org/10.12681/bgsg.11712.
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Twenty five years after a first attempt by Mascle and Martin (1990), this paper aims at delivering an updated and considerably richer, map of the offshore faults in the Aegean Sea. Reinterpretation of vintage analogue seismic profiles, interpretation of new profiles and records of swath bathymetry data made available in the last two decades, as well as relocation of published faults originally interpreted on lowresolution bathymetric maps, on the new, more accurate bathymetric background have enabled the preparation of a more precise and complete map of active faults occurring in the Aegean Sea. This attempt is a first step towards the creation of an offshore faults database.
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Yunus, Ali P., Jie Dou, Xuan Song, and Ram Avtar. "Improved Bathymetric Mapping of Coastal and Lake Environments Using Sentinel-2 and Landsat-8 Images." Sensors 19, no. 12 (June 21, 2019): 2788. http://dx.doi.org/10.3390/s19122788.
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The bathymetry of nearshore coastal environments and lakes is constantly reworking because of the change in the patterns of energy dispersal and related sediment transport pathways. Therefore, updated and accurate bathymetric models are a crucial component in providing necessary information for scientific, managerial, and geographical studies. Recent advances in satellite technology revolutionized the acquisition of bathymetric profiles, offering new vistas in mapping. This contribution analyzed the suitability of Sentinel-2 and Landsat-8 images for bathymetric mapping of coastal and lake environments. The bathymetric algorithm was developed using an empirical approach and a random forest (RF) model based on the available high-resolution LiDAR bathymetric data for Mobile Bay, Tampa Bay, and Lake Huron regions obtained from the National Oceanic and Atmospheric Administration (NOAA) National Geophysical Data Center (NGDC). Our results demonstrate that the satellite-derived bathymetry is efficient for retrieving depths up to 10 m for coastal regions and up to 30 m for the lake environment. While using the empirical approach, the root-mean-square error (RMSE) varied between 1.99 m and 4.74 m for the three regions. The RF model, on the other hand, provided an improved bathymetric model with RMSE between 1.13 m and 1.95 m. The comparative assessment suggests that Sentinel-2 has a slight edge over Landsat-8 images while employing the empirical approach. On the other hand, the RF model shows that Landsat-8 retrieves a better bathymetric model than Sentinel-2. Our work demonstrated that the freely available Sentinel-2 and Landsat-8 imageries proved to be reliable data for acquiring updated bathymetric information for large areas in a short period.
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Wathen, Gus, Jacob E. Allgeier, Nicolaas Bouwes, Michael M. Pollock, Daniel E. Schindler, and Chris E. Jordan. "Beaver activity increases habitat complexity and spatial partitioning by steelhead trout." Canadian Journal of Fisheries and Aquatic Sciences 76, no. 7 (July 2019): 1086–95. http://dx.doi.org/10.1139/cjfas-2018-0171.
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Freshwater habitat restoration is a major conservation objective, motivating efforts to restore habitat complexity and quality for fishes. Restoration based on the engineering activities of beavers (Castor canadensis) increases fish habitat complexity, but how this affects fish habitat use and movement behaviours is not well known. We used a network of passive integrated transponder antennas to quantify small-scale movement and microhabitat use of 175 individual juvenile steelhead (Oncorhynchus mykiss) in a stream channel with a complex bathymetric profile resulting from a beaver impoundment and in a simplified channel devoid of beaver activity. Our results show that juvenile steelhead exploit microhabitat heterogeneity by employing a range of behaviours that maximizes available habitat via spatial and temporal partitioning among individuals. These results suggest spatial resource partitioning as a potential mechanism for the previously established positive correlations among steelhead density, survival, and production with beaver-based restoration within the study watershed. More broadly, our findings provide insight as to how populations can exploit habitat complexity through spatial partitioning that can be informative for planning restoration and management actions.
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Peirce, C., A. H. Robinson, A. M. Campbell, M. J. Funnell, I. Grevemeyer, N. W. Hayman, H. J. A. Van Avendonk, and G. Castiello. "Seismic investigation of an active ocean–continent transform margin: the interaction between the Swan Islands Fault Zone and the ultraslow-spreading Mid-Cayman Spreading Centre." Geophysical Journal International 219, no. 1 (June 20, 2019): 159–84. http://dx.doi.org/10.1093/gji/ggz283.
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SUMMARY The Swan Islands Transform Fault (SITF) marks the southern boundary of the Cayman Trough and the ocean–continent transition of the North American–Caribbean Plate boundary offshore Honduras. The CAYSEIS experiment acquired a 180-km-long seismic refraction and gravity profile across this transform margin, ∼70 km to the west of the Mid-Cayman Spreading Centre (MCSC). This profile shows the crustal structure across a transform fault system that juxtaposes Mesozoic-age continental crust to the south against the ∼10-Myr-old ultraslow spread oceanic crust to the north. Ocean-bottom seismographs were deployed along-profile, and inverse and forward traveltime modelling, supported by gravity analysis, reveals ∼23-km-thick continental crust that has been thinned over a distance of ∼70 km to ∼10 km-thick at the SITF, juxtaposed against ∼4-km-thick oceanic crust. This thinning is primarily accommodated within the lower crust. Since Moho reflections are not widely observed, the 7.0 km s−1 velocity contour is used to define the Moho along-profile. The apparent lack of reflections to the north of the SITF suggests that the Moho is more likely a transition zone between crust and mantle. Where the profile traverses bathymetric highs in the off-axis oceanic crust, higher P-wave velocity is observed at shallow crustal depths. S-wave arrival modelling also reveals elevated velocities at shallow depths, except for crust adjacent to the SITF that would have occupied the inside corner high of the ridge-transform intersection when on axis. We use a Vp/Vs ratio of 1.9 to mark where lithologies of the lower crust and uppermost mantle may be exhumed, and also to locate the upper-to-lower crustal transition, identify relict oceanic core complexes and regions of magmatically formed crust. An elevated Vp/Vs ratio suggests not only that serpentinized peridotite may be exposed at the seafloor in places, but also that seawater has been able to flow deep into the crust and upper mantle over 20–30-km-wide regions which may explain the lack of a distinct Moho. The SITF has higher velocities at shallower depths than observed in the oceanic crust to the north and, at the seabed, it is a relatively wide feature. However, the velocity–depth model subseabed suggests a fault zone no wider than ∼5–10 km, that is mirrored by a narrow seabed depression ∼7500 m deep. Gravity modelling shows that the SITF is also underlain, at >2 km subseabed, by a ∼20-km-wide region of density >3000 kg m−3 that may reflect a broad region of metamorphism. The residual mantle Bouguer anomaly across the survey region, when compared with the bathymetry, suggests that the transform may also have a component of left-lateral trans-tensional displacement that accounts for its apparently broad seabed appearance, and that the focus of magma supply may currently be displaced to the north of the MCSC segment centre. Our results suggest that Swan Islands margin development caused thinning of the adjacent continental crust, and that the adjacent oceanic crust formed in a cool ridge setting, either as a result of reduced mantle upwelling and/or due to fracture enhanced fluid flow.
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Robertson, Clare M., Douglas I. Benn, Martin S. Brook, lan C. Fuller, and Kat A. Holt. "Subaqueous calving margin morphology at Mueller, Hooker and Tasman glaciers in Aoraki/Mount Cook National Park, New Zealand." Journal of Glaciology 58, no. 212 (2012): 1037–46. http://dx.doi.org/10.3189/2012jog12j048.
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AbstractThe subaqueous margins of calving glaciers have the potential to make significant contributions to glacier mass loss. However, to date, very little is known about the morphology and development of subaqueous margins. A unique combination of sub-bottom profile and bathymetric data collected between 2008 and 2010 in proglacial lakes at Mueller, Hooker and Tasman glaciers in New Zealand’s Southern Alps reveal subaqueous ice ramps extending up to 510 m from the terminus of each glacier. Ice ramp surfaces are undulating and covered with a thick layer (up to 10 m) of unsorted sediment derived from supraglacial and englacial debris, lateral moraines and deltaic deposits. A cyclic calving pattern, relatively stable lake level and the debris cover appear to control the development and maintenance of these ice ramps. High subaerial retreat rates generally correspond to high subaqueous calving rates, although the highest subaerial retreat rates are not associated with the largest ice ramp. Debris mantling the subaqueous ice ramp surfaces insulates the ice from melting and also reduces buoyant forces acting on the terminus. Comparisons with previous studies show that the ice ramps evolve over time with changes in glacier dynamics and water-body properties.
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Terres de Lima, Lucas, Sandra Fernández-Fernández, João Francisco Gonçalves, Luiz Magalhães Filho, and Cristina Bernardes. "Development of Tools for Coastal Management in Google Earth Engine: Uncertainty Bathtub Model and Bruun Rule." Remote Sensing 13, no. 8 (April 7, 2021): 1424. http://dx.doi.org/10.3390/rs13081424.
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Sea-level rise is a problem increasingly affecting coastal areas worldwide. The existence of free and open-source models to estimate the sea-level impact can contribute to improve coastal management. This study aims to develop and validate two different models to predict the sea-level rise impact supported by Google Earth Engine (GEE)—a cloud-based platform for planetary-scale environmental data analysis. The first model is a Bathtub Model based on the uncertainty of projections of the sea-level rise impact module of TerrSet—Geospatial Monitoring and Modeling System software. The validation process performed in the Rio Grande do Sul coastal plain (S Brazil) resulted in correlations from 0.75 to 1.00. The second model uses the Bruun rule formula implemented in GEE and can determine the coastline retreat of a profile by creatting a simple vector line from topo-bathymetric data. The model shows a very high correlation (0.97) with a classical Bruun rule study performed in the Aveiro coast (NW Portugal). Therefore, the achieved results disclose that the GEE platform is suitable to perform these analysis. The models developed have been openly shared, enabling the continuous improvement of the code by the scientific community.
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Matheen, Nashwan, Mitchell D. Harley, Ian L.Turner, Joshua A. Simmons, and Mandi Thran. "DO WE NEED PRE-STORM SURVEYED BATHYMETRY FOR OPERATIONAL EROSION FORECASTING? EVALUATION OF REPRESENTATIVE AND SYNTHETIC BATHYMETRY ALTERNATIVES." Coastal Engineering Proceedings, no. 36v (December 28, 2020): 13. http://dx.doi.org/10.9753/icce.v36v.sediment.13.
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Immediate pre-storm bathymetry is a key input required for numerical models used in coastal hazard Early Warning Systems. However, the expense and challenging nature of hydrographic surveying means that the availability of high-quality data is extremely rare. This study evaluates the extent to which synthetic and representative bathymetry alternatives can be used to obtain reliable predictions of storm induced sub-aerial erosion using the XBeach coastal erosion numerical model. Multiple storm events at 2 contrasting sites are modelled using 6 bathymetry scenarios including pre-storm surveyed bathymetries, an average bathymetry, and Dean profiles. The output is analysed to evaluate the skill of XBeach erosion predictions as a function of the bathymetry used.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/bE3aXVXxZqQ
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Bermúdez-Romero, Anahí, Vanesa Magar, Markus S. Gross, Victor M. Godínez, Manuel López-Mariscal, and Julio Candela. "In-Stream Tidal Energy Resources in Macrotidal Non-Cohesive Sediment Environments: Effect of Morphodynamic Changes at Two Bays in the Upper Gulf of California." Journal of Marine Science and Engineering 9, no. 4 (April 12, 2021): 411. http://dx.doi.org/10.3390/jmse9040411.
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Because of the need to diversify the renewable energy matrix and because hydrokinetic tidal energy technologies are mature, many in-stream tidal energy resource studies are available globally. Still, there are many questions regarding the effect of seabed changes on tidal energy resources. For coastal regions in particular, where the seabed is generally more mobile than in deep waters, bathymetric evolution could significantly affect tidal energy production. Here, two models are used to analyse the potential effect of natural morphodynamic change on tidal energy resources at two macro-tidal sandy bays, Adaír Bay and San Jorge Bay, in the Upper Gulf of California, Mexico. One of the models is (purely) hydrodynamic, and the other is a morphodynamic model (with hydrodynamic–morphodynamic coupling). The models are validated against tidal current observations obtained with acoustic Doppler current profilers in the region of interest, using three different error statistics, which showed good agreement between models and observations. The results also showed that the most significant bed changes and the largest renewable energy resources are located near the shore. Moreover, there was a good correlation between (a) regions with the most significant depth changes and (b) the areas where the difference in annual energy production with and without depth change was largest. Finally, a two-year simulation with the morphodynamic model permitted to analyse the seabed evolution of a zonal profile off Punta Choya, the headland between the two bays. This profile evolved towards a featureless equilibrium, as expected from the morphological classification for macro-tidal sandy environments under a dominant tidal forcing. However, most importantly, this natural evolution would not be detrimental to tidal energy exploitation at the site.
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Szumińska, Danuta, Sebastian Czapiewski, and Jacek Goszczyński. "Changes in Hydromorphological Conditions in an Endorheic Lake Influenced by Climate and Increasing Water Consumption, and Potential Effects on Water Quality." Water 12, no. 5 (May 9, 2020): 1348. http://dx.doi.org/10.3390/w12051348.
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The study aims to analyse changes in the morphological conditions of the endorheic Lake Borówno (39.06 ha) that occurred in the 20th century and early 21st century. The analysis was based on bathymetric measurements carried out in 2018 and cartographic materials, and performed using QGIS 3.10 and SAGA GIS 6.4 software. Moreover, changes in physical (temperature, transparency), chemical (dissolved oxygen, phosphorus, and nitrogen content) and biological (chlorophyll a, phytoplankton) parameters were analysed based on the results of measurements conducted by the Voivodeship Inspectorate of Environment Protection (VIEP) in Bydgoszcz in the period 1984–2017. It was found that Lake Borówno is subject to a constant reduction in surface area and volume, the rate of which increased in the second decade of the 21st century. The lake’s progressive disappearance results from the co-occurrence of hydrological drought over the last several years and an increase in the use of groundwater resources. A decrease in the maximum depth of the lake entails a change in temperature distribution in the vertical profile, which contributes to the tendency toward the lake transforming into an unstratified reservoir. The increase in water temperature affects oxygen content in the bottom water, improves water transparency, and influences the maximum occurrence of chlorophyll a in spring.
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Johnson, M. R., and A. M. Smith. "Seabed topography under the southern and western Ronne Ice Shelf, derived from seismic surveys." Antarctic Science 9, no. 2 (June 1997): 201–8. http://dx.doi.org/10.1017/s0954102097000254.
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Seismic reflection measurements of ice thickness and water-column thickness have been made over the southern and western Ronne Ice Shelf, from which, the seabed elevation has been determined. A 2300 km traverse, covering an area over which little bathymetric data previously existed and at a station interval of 15 km, resulted in 152 new measurements of the seabed elevation. The seismic velocity in the ice shelf was determined using shallow refraction surveys for the snow and firn in the upper 100 m of the ice shelf, and by applying a model assuming a simple temperature profile for the deeper ice. Surface elevations were calculated assuming the ice to be in hydrostatic equilibrium. The estimated error in the seabed elevations is ±15 m. With the addition of the new data there is now complete coverage of the seabed elevation and water-column thickness for Ronne Ice Shelf at a spatial resolution of between 10–100 km. The seabed in the area to the south of Korff and Henry ice rises and the Doake Ice Rumples is about 100 m shallower than had previously been speculated, which will affect the validity of previous assumptions of water circulation and ice-ocean interaction in this area.
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Akselsen, Andreas H., and Simen Å. Ellingsen. "Sheared free-surface flow over three-dimensional obstructions of finite amplitude." Journal of Fluid Mechanics 878 (September 18, 2019): 740–67. http://dx.doi.org/10.1017/jfm.2019.657.
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When shallow water flows over uneven bathymetry, the water surface is modulated. This type of problem has been revisited numerous times since it was first studied by Lord Kelvin in 1886. Our study analytically examines currents whose unperturbed velocity profile $U(z)$ follows a power law $z^{q}$, flowing over a three-dimensional uneven bed. This particular form of $U$, which can model a miscellany of realistic flows, allows explicit analytical solutions. Arbitrary bed shapes can readily be imposed via Fourier’s theorem provided their steepness is moderate. Three-dimensional vorticity–bathymetry interaction effects are evident when the flow makes an oblique angle with a sinusoidally corrugated bed. Streamlines are found to twist and the fluid particle drift is redirected away from the direction of the unperturbed current. Furthermore, a perturbation technique is developed which satisfies the bottom boundary condition to arbitrary order also for large-amplitude obstructions which penetrate well into the current profile. This introduces higher-order harmonics of the bathymetry amplitude. States of resonance for first- and higher-order harmonics are readily calculated. Although the method is theoretically restricted to bathymetries of moderate inclination, a wide variety of steeper obstructions are satisfactorily represented by the method, even provoking occurrences of recirculation. All expressions are analytically explicit and sequential fast Fourier transformations ensure quick and easy computation for arbitrary three-dimensional bathymetries. A method for separating near and far fields ensures computational convergence under the appropriate radiation condition.
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Yepez, Santiago Paul, Alain Laraque, Carlo Gualtieri, Frédéric Christophoul, Claudio Marchan, Bartolo Castellanos, Jose Manuel Azocar, Jose Luis Lopez, and Juan Alfonso. "Morphodynamic change analysis of bedforms in the Lower Orinoco River, Venezuela." Proceedings of the International Association of Hydrological Sciences 377 (April 16, 2018): 41–50. http://dx.doi.org/10.5194/piahs-377-41-2018.
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Abstract. The Orinoco River has the third largest discharge in the world, with an annual mean flow of 37 600 m3 s−1 at its outlet to the Atlantic Ocean. Due to the presence of the Guiana Shield on the right bank, the lower reach of the Orinoco has a plan form characterized by contraction and expansion zones. Typical 1–1.5 km wide narrow reaches are followed by 7–8 km wide reaches. A complex pattern of bed aggradation and degradation processes takes place during the annual hydrological regime. A series of Acoustic Doppler Current Profiler (ADCP) transects were collected on an expansion channel in the Orinoco River, specifically over a fluvial island, representative of the lower Orinoco. In this study, temporal series of bathymetric cartography obtained by ADCP profiles combined with Differential Global Position System (DGPS) measurements (with dual-frequency), were used to recover the local displacement of bed forms in this island. The principal aims of this analysis were: (1) to understand the dynamics and evolution of sand waves and bars at this section and (2) to quantify the volume (erosion vs. accretion) of a mid-channel bar with dunes by applying DEM of Difference (DoD) maps on time series of bathymetric data. This required sampling with ADCP transects during the months of: May 2016; November 2016 and April 2017. Each bathymetric transect was measured twice, 1 day apart and on the same trajectory obtained by a GPS receptor. The spatial analysis of these ADCP transects is presented as a novel tool in the acquisition of time series of bathymetry for a relatively deep section (∼20 m) and under variable flow conditions.
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Jansen, Luis, Lariyah Mohd Sidek, and Pierre Y. Julien. "Preliminary Investigation and Design Considerations for the Rehabilitation of Trash Screen at Jor Reservoir Low Level Outlet." Applied Mechanics and Materials 567 (June 2014): 128–32. http://dx.doi.org/10.4028/www.scientific.net/amm.567.128.
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Jor reservoir was constructed to assure flow regulation for the Woh hydroelectric power station, as well as to provide storage for flood control. The reservoir outlet is frequently operated once every three months to flush the deposited sediments accumulated within the reservoir. Preliminary testing and inspection on the reservoir outlet revealed that the trash screen located at upstream of reservoir outlet had been damaged and dislodged creating a large opening at the trash screen thus permitting entry of larger logs which blocks the passage of water through the reservoir outlet. Bathymetric survey showed the total height of sediment deposition above the reservoir outlet covering the trash screen was estimated at approximately 13 m. The sediment volume estimated to be cleared from above the reservoir outlet area is 15,000 m3. Soil investigation conducted shows that the sediments deposited within the reservoir exhibits various different profile and characteristics. The average sediment distribution at deeper depths closer to the trash screen was found to be of 27% clay, 26% silt, 43% sand and 4% gravel. The rehabilitation works on structure as the low level outlet serves as an important feature for reservoir sedimentation management as well as for safe flood discharge release as designed for the dam. It is important that the function of the reservoir outlet structure is maintained in accordance to the International Dam Safety Standards.
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Mackas, D. L., R. Kieser, M. Saunders, D. R. Yelland, R. M. Brown, and D. F. Moore. "Aggregation of euphausiids and Pacific hake (Merluccius productus) along the outer continental shelf off Vancouver Island." Canadian Journal of Fisheries and Aquatic Sciences 54, no. 9 (September 1, 1997): 2080–96. http://dx.doi.org/10.1139/f97-113.
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From spring through autumn, euphausiids and Pacific hake (Merluccius productus) form dense aggregations off the outer coast of British Columbia along regions of steeply sloping bathymetry such as the continental shelf break. Their spatial overlap is ecologically significant because of their very strong prey-predator interaction. We analyze high-resolution measurements of shelf-edge spatial distributions of euphausiid and Pacific hake biomass (by echo integration), water properties (from surface measurements and conductivity-temperature-depth (CTD)/Rosette profiles), and current patterns (from acoustic Doppler current profiler, CTD profiles, and nearby current meter moorings). Both euphausiids and hake share similar horizontal distributions, although separated vertically by tens of meters during daylight hours. Bathymetric and water property patterns provide good coarse-scale prediction of aggregation location. However, details of patch location are better explained by flow-field indices such as cross-shore position of the shelf break current, intensity of cross-isobath flow and upwelling at the depth of the euphausiid scattering layer, and doming of isopycnals. Under prevailing summer oceanographic conditions along the British Columbia coast, likely ecological consequences of aggregation in and beneath upwelling water include access to high food density in the overlying surface layer, reduced alongshore transport, and horizontal segregation between adult and larval euphausiids.
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Mera, Mas, and Hendra Yuldi. "Prediction of a design flood-discharge that caused sedimentation in the river mouth of Batang Anai." E3S Web of Conferences 156 (2020): 01008. http://dx.doi.org/10.1051/e3sconf/202015601008.
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Batang Anai is a river that crosses through four administrative regions in the West Sumatra Province with a catchment area of about 498 km2. The upstream is a steep topography because it is located in west part of the Marapi mount. While the middle and lower reaches are mild since in the lowlands. The flow empties into the Indian Ocean. These conditions make this river meandering in the middle and lower reaches. The river mouth is influenced by the tide in which resists sedimentation toward the ocean. As a result, the capacity of the river cross-section decreases which eventually causes flooding. In 2013, the lower reach was dredged. In 2015, however, the river mouth was covered back by sedimentation by two-meter height in some points. Bathymetry was measured before and after dredging. This study is conducted to determine a design flood-discharge that caused sedimentation based on the 2015 bathymetry data by simulation using the SMS software, i.e. the RMA2 module for modelling hydrodynamics and the SED2D module for modelling sedimentation. The attention is paid to see both flow patterns and sedimentation profiles. The model scenarios consider by either including or excluding the Batang Kandis flow. Batang Kandis is a tributary of Batang Anai which empties into near its river mouth. The design flood-discharges for simulation are varied according to the return periods of 2, 5, 10, 25 and 50 years. The bathymetry data used for simulation are the 2013 one after dredging. All the simulation results are then compared to the 2015 bathymetry data. The hydrodynamic model in which the Batang Kandis flow included gives velocities close to those from the field for all return periods. The results of the sediment model using the flood flow with a 5-year return period, that’s Batang Anai is 1060 m3/s and Batang Kandis is 268.5 m3/s, show that the sedimentation profiles are closed to the 2015 bathymetric measurement data.
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Mieras, Ryan S., Jack A. Puleo, Dylan Anderson, Daniel T. Cox, Tian-Jian Hsu, and Joe Calantoni. "OBSERVATIONS OF HORIZONTAL AND VERTICAL SEDIMENT FLUXES ON A SANDBAR IN THE SUSPENDED AND SHEET FLOW LAYERS." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 30. http://dx.doi.org/10.9753/icce.v36.sediment.30.
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The majority of prior sandbar migration studies have been conducted from the morphological standpoint, whereby, (i) bathymetric profiles are recorded over periods of time ranging from days to decades, at frequencies ranging from hourly to yearly (Ruessink et al., 2003), and (ii) hydrodynamic observations typically consist of far-field wave and environmental conditions. Subsequent modeling efforts have generally focused on tuning parameters in the sediment transport formulations (suspended load and bed load) to maximize model skill in predicting observed beach profiles over time (Fernández-Mora et al., 2015; Hoefel and Elgar, 2003). However, little emphasis at the operational level has been placed on tuning coastal morphology models to the true relative contributions of the physical processes (e.g. suspended load, bed load and/or sheet flow) that drive the changing bathymetry. This is due, in part, to the lack of detailed sediment transport observations (field and lab) under realistic wave forcing conditions and spatially variable bathymetry. Such a modeling approach leads to the improper quantification (magnitude and/or direction) of each modeled sediment transport component under skewed-asymmetric and/or breaking waves, often observed in the surf zone. The present study aims to better understand the physical mechanisms responsible for driving cross-shore sediment transport over a sandbar by quantifying (a) the vertical exchange of sediment at the near-bed interface (i.e. pick-up layer), and (b) intra-wave horizontal sediment fluxes in the suspended load and sheet layers.