Coastal Features Research Articles

Slip distribution from the 1 April 2007 Solomon Islands earthquake: A unique image of near‐trench rupture

We estimate the slip distribution from the MW 8.1 Solomon Islands earthquake in 2007, from two post‐seismic surveys measuring uplifted coral and submerged coastal features. The occurrence of islands extremely proximal to the trench and nucleation of rupture allowed for the collection of unprecedented coseismic deformation dataset along a large megathrust earthquake. Using data from the two surveys along the southeastern half of the slip zone within five weeks of the event, we model the elastic dislocation to identify the optimal (29°), and alternate (20°), dip and distribution of thrust along the southern rupture. The vertical deformation, which includes both coseismic and early postseismic deformation, has highly variable and large slip within 25 km of the trench and straddling Ranongga Island. The shallow focus of slip in the near‐trench area may explain the locally high tsunami run‐up on portions of Simbo Island, however the aseismic contribution of afterslip remains unknown.

Assessing Spatial Uncertainty of Lidar-derived Building Model

Light Detection and Ranging (lidar) technology enables costeffective rapid production of digital models that capture topography and vertical structures of surface features at a fine spatial resolution. The capability has promoted lidar applications for mapping terrain, buildings, forest stands, and coastal features that cannot be adequately captured by other remote sensing means over a large area. However, in complex terrain, lidar data and lidar-derived products may contain significant uncertainty. This research provides a simple method to assess the spatial uncertainty of lidar-derived building model, using downtown Oklahoma City, Oklahoma as an example. Results indicate that significant uncertainty could be found in urban environment where: (a) building structures are complex, (b) buildings are constructed with reflective materials, and (c) vegetation grows near-by. In addition, cities under rapid development also challenge the accuracy assessment of 3D building models. To conclude, we suggest: (a) careful pre-flight planning before data collection, (b) improve the feature extraction algorithm if possible, (c) use of other remote sensing data, and (d) accuracy assessment on suggested urban environments to reduce the spatial uncertainty of lidar data and lidar-derived products.

Quasi-periodic decadal cycles in levels of lakes Michigan and Huron

While Great Lakes' seasonal water-level variations have been previously researched and well documented, few studies thus far addressed longer-term, decadal cycles contained in the 143-yr lake-level instrumental record. Paleo-reconstructions based on Lake Michigan's coastal features, however, hinted to an approximate 30-yr quasi-periodic lake-level variability. In the present study, spectral analysis of 1865–2007 Lakes Michigan/Huron historic levels revealed 8 and 12-yr period oscillations; these time scales match those of large-scale climatic signals previously found in the North Atlantic. While the existing paleodata are inadequate to the task of asserting significance of the 30-yr signal, it is suggested here that this cycle is due to intermodulation of the two near-decadal signals. Furthermore, water budget analysis argues that the North Atlantic decadal climate modes translate to the lake levels primarily through precipitation and its associated runoff.

Coastal Lagoons and Climate Change: Ecological and Social Ramifications in U.S. Atlantic and Gulf Coast Ecosystems

Anthony, A., J. Atwood, P. August, C. Byron, S. Cobb, C. Foster, C. Fry, A. Gold, K. Hagos, L. Heffner, D. Q. Kellogg, K. Lellis-Dibble, J. J. Opaluch, C. Oviatt, A. Pfeiffer-Herbert, N. Rohr, L. Smith, T. Smythe, J. Swift, and N. Vinhateiro. 2009. Coastal lagoons and climate change: ecological and social ramifications in U.S. Atlantic and Gulf coast ecosystems. Ecology and Society 14(1): 8. https://doi.org/10.5751/ES-02719-140108

Coastal Artificialization and Public Policies: The Example of the Beach of Marennes (Seudre Estuary, France)

This study deals with practical issues induced by public policies that have led to coastal artificialization. Problems of management of artificial coastal features are illustrated with the example of Marennes-Plage (French Atlantic Coast), a sand barrier built in 1997 to protect an artificial saltwater lagoon. This lagoon allows safe bathing at any of the tide cycle and the sand barrier acts as a buffer against storm floods. But from now on, the sustainability of Marennes- Plage becomes questionable and has shown signs of frailty. Present storm damages turn out to be more important than 10 years ago and the maintenance costs have dramatically increased. The main problem is to anticipate storms effects. Which storm is able to damage the sand barrier? When will it happen? To help the local managers we have built a tool for storm damage prediction : it is a locally tuned erosion index. This index is based on historical data, field work before and after storms and on online data (wind speed, waves, tides). It allows to sort out which combination of surge/wind speed and wave is likely to erode the artificial barrier. It also allows to anticipate the amount of lost material. This index has been tested for several storms and has proved its efficiency and its accuracy but in practice, the relevancy of our index will entirely depend of mitigation strategies and financial stakes. It could be efficient if managers get prepared for costly fast interventions on the dune/beach just before each damaging storm. It will not be really useful if replenishment is considered has a one year time event (just before tourists arrival) and low cost solution.

A multigrid methodology for assimilation of measurements into regional tidal models

This paper presents a rigorous, yet practical, method of multigrid data assimilation into regional structured-grid tidal models. The new inverse tidal nesting scheme, with nesting across multiple grids, is designed to provide a fit of the tidal dynamics to data in areas with highly complex bathymetry and coastline geometry. In these areas, computational constraints make it impractical to fully resolve local topographic and coastal features around all of the observation sites in a stand-alone computation. The proposed strategy consists of increasing the model resolution in multiple limited area domains around the observation locations where a representativeness error is detected in order to improve the representation of the measurements with respect to the dynamics. Multiple high-resolution nested domains are set up and data assimilation is carried out using these embedded nested computations. Every nested domain is coupled to the outer domain through the open boundary conditions (OBCs). Data inversion is carried out in a control space of the outer domain model. A level of generality is retained throughout the presentation with respect to the choice of the control space; however, a specific example of using the outer domain OBCs as the control space is provided, with other sensible choices discussed. In the forward scheme, the computations in the nested domains do not affect the solution in the outer domain. The subsequent inverse computations utilize the observation-minus-model residuals of the forward computations across these multiple nested domains in order to obtain the optimal values of parameters in the control space of the outer domain model. The inversion is carried out by propagating the uncertainty from the control space to model tidal fields at observation locations in the outer and in the nested domains using efficient low-rank error covariance representations. Subsequently, an analysis increment in the control space of the outer domain model is computed and the multigrid system is steered optimally towards observations while preserving a perfect dynamical balance. The method is illustrated using a real-world application in the context of the Philippines Strait Dynamics experiment.

Biogeographical patterns of rocky intertidal communities along the Pacific coast of North America

AbstractAim Our aim in this paper is to present the first broad‐scale quantification of species abundance for rocky intertidal communities along the Pacific coast of North America. Here we examine the community‐level marine biogeographical patterns in the context of formerly described biogeographical regions, and we evaluate the combined effects of geographical distance and environmental conditions on patterns of species similarity across this region.Location Pacific coast of North America.Methods Data on the percentage cover of benthic marine organisms were collected at 67 rocky intertidal sites from south‐eastern Alaska, USA, to central Baja California Sur, Mexico. Cluster analysis and non‐metric multidimensional scaling were used to evaluate the spatial patterns of species similarity among sites relative to those of previously defined biogeographical regions. Matrices of similarity in species composition among all sites were computed and analysed with respect to geographical distance and long‐term mean sea surface temperature (SST) as a measure of environmental conditions.Results We found a high degree of spatial structure in the similarity of intertidal communities along the coast. Cluster analysis identified 13 major community structure ‘groups’. Although breaks between clusters of sites generally occurred at major biogeographical boundaries, some of the larger biogeographical regions contained several clusters of sites that did not group according to spatial position or identifiable coastal features. Additionally, there were several outliers – sites that grouped alone or with sites outside their region – for which localized features may play an important role in driving community structure. Patterns of species similarity at the large scale were highly correlated with geographical distance among sites and with SST. Importantly, we found community similarity to be highly correlated with long‐term mean SST while controlling for the effects of geographical distance.Main conclusions These findings reveal a high degree of spatial structure in the similarity of rocky intertidal communities of the north‐east Pacific, and are generally consistent with those of previously described biogeographical regions, with some notable differences. Breaks in similarity among clusters are generally coincident with known biogeographical and oceanographic discontinuities. The strong correlations between species similarity and both geographical position and SST suggest that both geography and oceanographic conditions have a large influence on patterns of intertidal community structure along the Pacific coast of North America.

Chevrons enigmatic sedimentary coastal features

Chevrons enigmatic sedimentary coastal features

Late Quaternary Geomorphic Evolution of the Coastal Zone of Kachchh, Western India

The present study attempts to delineate the late Quaternary morphotectonic evolution of the coastal zone of Kachchh on the basis of detailed field mapping of the various coastal and fluvial landforms and lithostratigraphic studies of the associated sediments. The entire coastline has been divided into five morphologically distinct segments from west to east—Narayan Sarovar–Jakhau, Jakhau–Khuada, Khuada–Bhada, Bhada–Mundra, and Mundra–Surajbari segments. Major geomorphic features of interest are the variable width of the intertidal zone; development of beaches, bars, and spits; width of active and stabilised coastal dunes; raised mudflats; raised beaches; uplifted estuarine tidal terraces; and the development of a coastal alluvial plain in the Jakhau–Khuada and Bhada–Mundra segments. The coastal alluvial plain was formed by deposition of fluvial sediments over the peneplained Tertiary rocks during upper late Pleistocene in two separate tectonically created basins. Deeply incised fluvial valleys were formed in response to tectonic uplift of the coast due to movements along E-W trending faults further north during the early Holocene. The sea level was higher than present during 6–2 ka, which led to the deposition of coastal sediments, fluvial terraces along incised fluvial valleys, and formation of a cliffy coast in the Narayan–Sarovar–Jakhau segment. Emergent coastal features consisting of raised beaches, raised mudflats, abandoned coastal cliffs, uplifted estuarine tidal to fluvial terraces, and stabilised coastal dunes developed because of uplift during the last 2 ka. The various morphotectonic divisions of the coast are attributed to the role played by the inherent structural fabric, the subsurface Median high, and general uplift of the coast due to tectonic activity along the E-W trending faults to the north of the study area during the early Holocene and the last 2 ka.

Cabeza de Vaca and the Introduction of Disease to Texas

IN 1528 THE SHATTERED REMNANTS OF A SPANISH EXPEDITION TO LA Florida were cast ashore on the upper Texas coast. Many survivors landed on Galveston Island (or a nearby coastal feature) and were taken in by local Indians. Not long after the starving Spaniards arrived, many of the locals began to die of a mysterious stomach ailment. Many researchers have taken this episode as evidence that the expedition introduced some form of Old World pathogen into what is now Texas. This paper seeks to test that idea by examining the ethnohistoric, epidemiological, and paleopathological evidence. It will also offer alternatives to the traditional interpretation of events.1 When Pinfilo de Narvaiez left Cuba in 1528, he commanded one of the largest conquering forces seen in the Americas up to that point. More than 300 men made landfall on the Florida coast on April 14, 1528, but ultimately only a handful would survive. Narvaiez blundered his way across Florida, alienating native peoples and losing contact with his supporting fleet. After reaching the area of Apalachee Bay, the remaining Spaniards made improvised barges and attempted to sail to the outpost of Painuco, more than 900 miles away (1400 kilometers). They mistakenly believed the journey would be a short one.2

Linking spatial metrics and fish catch reveals the importance of coastal wetland connectivity to inshore fisheries in Queensland, Australia

Many commercially important fish species use coastal marine environments such as mangroves, tidal flats and seagrass beds as nurseries or breeding grounds. The ecological importance of spatially connected habitats to conservation is well established for terrestrial environments. However, few studies have applied spatial metrics, including measures of structural connectivity to marine environments. We examined the relationship between catch-per-unit-effort for commercially caught species and the spatial patterning of mapped benthic habitat types along the coast of Queensland, Australia in their dominant fisheries (trawl, line, net or pot fisheries). We quantified the composition and spatial configuration of seascapes and calculated coastline length, number of estuaries, river length and geographical latitude using 12 metrics within ninety 30-nautical-mile grid cells, which supported inshore fish catch data from 21 species groups. Multiple regression analysis and non-metric multidimensional scaling plots indicated that ecological linkages may exist between geomorphic coastal features and nearshore fisheries production for a number of species groups. Connectivity indices for mangroves, salt marsh and channels explained the largest proportion (30–70%), suggesting the importance of connected tidal wetlands for fisheries. Barramundi (Lates calcarifer) catch-per-unit-effort was best explained by the number of wetland patches, mangrove connectivity and wetland connectivity (r2=0.38, n=28). Catch-per-unit-effort for the Gulf of Carpentaria was highly correlated with wetland connectivity, the number of estuaries and seagrass patch density (r=0.57, n=29). The findings could guide the spatial design of marine protected area networks to maintain ecosystem services and avoid potential disruption to connectivity caused by habitat removal or modification. Application of the same approach to analyses of finer spatial scales would enable catch information to be related to particular estuarine habitats and provide better understanding of the importance of habitat connectivity for fisheries.

Field observations of recent transgression on northern and eastern Melville Island, western Canadian Arctic Archipelago

After ~ 11,000 years of glacio-isostatically induced forced regression, geomorphological evidence indicates that the coastline of eastern Melville Island, western Canadian Arctic Archipelago, is now being transgressed. Recently developed coastal features associated with this transgression include: drowned gullies and small estuaries, barriers and lagoons, barrier islands, erosional notches, backstepping beaches, and drowned tundra vegetation and vehicle tracks dating from the 1970s. We mainly attribute this relative sea-level rise to the eastward migration of a peripheral crustal forebulge. Furthermore, the reported transgression also includes a component from recent eustatic sea-level rise during the 20th century. Recent earthquakes recorded in the Gustav-Lougheed Arch Seismic Zone located in Byam Martin Channel, 70 km east of Melville Island, suggest that neotectonics could also be involved in local relative sea-level adjustments. Other factors associated with global warming, especially the formation of an earlier shore-ice lead coupled with increased storm activity might also be responsible for some of the coastal changes. Our study indicates that the current zero isobase, separating areas of net transgression from those of net regression, is now located off the east coast of the island. Our field observations support recent glacio-isostatic modelling that shows the island is presently undergoing a transgression.

Ptolemy's map of Ireland: a modern decoding

Abstract Claudius Ptolemy (roughly AD 90–168) presents us the oldest surviving account of Ireland in the form of a set of coordinates showing different geographical features or a ‘virtual map’. While Ptolemy's map looks roughly like today's Ireland there are a number of discrepancies. Likewise, while some locations are obvious, others are disputed or obscure. After reviewing earlier attempts at reconciling Ptolemy's map with modern ones we adjust Ptolemy's coordinates to modern references with two equations. We find Ptolemy's map is consistent with some intimate Mediterranean knowledge of Ireland, its peoples, coastal features and principal places with their respective locations. We correct some of the modern locations attributed to Ptolemy, offer possible explanations for certain disputed or uncertain locations and offer some external validation to the prehistoric division of Ireland passed down from pre-Patrician sources.

Tidal energy extraction: renewable, sustainable and predictable.

The tidal flow of sea water induced by planetary motion is a potential source of energy if suitable systems can be designed and operated in a cost-effective manner This paper examines the physical origins of the tides and how the local currents are influenced by the depth of the seabed and presence of land mass and associated coastal features. The available methods of extracting energy from tidal movement are classified into devices that store and release potential energy and those that capture kinetic energy directly. A survey is made of candidate designs and, for the most promising, the likely efficiency of energy conversion and methods of installing them are considered. Overall, the need to reduce CO2 emissions, a likely continued rise in fossil fuel cost will result in a significantly increased use of tidal energy. What is still required, especially for kinetic energy devices, is a much greater understanding of how they can be designed to withstand long-term immersion in the marine environment.

Alexander the Great's tombolos at Tyre and Alexandria, eastern Mediterranean

Tyre and Alexandria's coastlines are today characterised by wave-dominated tombolos, peculiar sand isthmuses that link former islands to the adjacent continent. Paradoxically, despite a long history of inquiry into spit and barrier formation, understanding of the dynamics and sedimentary history of tombolos over the Holocene timescale is poor. At Tyre and Alexandria we demonstrate that these rare coastal features are the heritage of a long history of natural morphodynamic forcing and human impacts. In 332 BC, following a protracted seven-month siege of the city, Alexander the Great's engineers cleverly exploited a shallow sublittoral sand bank to seize the island fortress; Tyre's causeway served as a prototype for Alexandria's Heptastadium built a few months later. We report stratigraphic and geomorphological data from the two sand spits, proposing a chronostratigraphic model of tombolo evolution.

Inverse barotropic tidal estimation for regional ocean applications

Correct representation of tidal processes in regional ocean models is contingent on the accurate specification of open boundary conditions. This paper describes a new inverse scheme for the assimilation of observational data into a depth-integrated spectral shallow water tidal model and the numerical implementation of this scheme into a stand-alone computational system for regional tidal prediction. A novel aspect is a specific implementation of the inverse which does not require an adjoint model. An optimization is carried out in the open boundary condition space rather than in the observational space or model state space. Our approach reflects the specifics of regional tidal modeling applications in which open boundary conditions (OBCs) typically constitute a significant source of uncertainty. Regional tidal models rely predominantly on global tidal estimates for open boundary conditions. As the resolution of global tidal models is insufficient to fully resolve regional topographic and coastal features, the a priori OBC estimates potentially contain an error. It is, therefore, desirable to correct these OBCs by finding an inverse OBC estimate that is fitted to the regional observations, in accord with the regional dynamics and respective error estimates. The data assimilation strategy presented in this paper provides a consistent and practical estimation scheme for littoral ocean science and applications where tidal effects are significant. Illustrations of our methodological and computational results are presented in the area of Dabob Bay and Hood Canal, WA, which is a region connected to the open Pacific ocean through a series of inland waterways and complex shorelines and bathymetry.

Auto‐extraction technique‐based digital classification of saltpans and aquaculture plots using satellite data

Mapping and classification of coastal features from visible (VIS) and near‐infrared (NIR) bands of remote sensing satellite data is less accurate (∼67 to 70 only) than land features due to confusing spatial and spectral characteristics among several contiguous shallow water features. Our study of spectral responses of most alike coastal features such as aquaculture plots, saltpans, sandy beaches, built‐up areas and fly ash dumpsites show mix‐ups in the VIS and NIR band responses. Albeit, the VIS (green) and short‐wavelength infrared (SWIR) bands show subtle distinctions which help to more accurately and automatically perform digital classification of these features with a reasonable accuracy of >95%.

Inter sensor comparison between RESOURCESAT LISS III, LISS IV and AWiFS with reference to coastal landuse/landcover studies

Coastal zone assumes importance due to high productivity of ecosystems, man-made developmental activities, natural hazards and dynamic nature of the coast. As costal ecosystems are unique and fragile, understanding the impact of developmental activities on the sustainability of the coastal zone is very important. Remote sensing, because of repetitive and synoptic nature is an ideal tool for studying this. Time series data analyses for monitoring coastal zone require different type of sensors. Present study deals with atmospheric correction of satellite data, reflectance, selection of coastal features like, mudflat, mangroves, vegetated dune, coastal water, etc. and their inter-comparison using different sensor data of RESOURCESAT sensors. Reflectance values give better separateability for various coastal features in comparison to DN values. LISS IV can be used in place of LISS III or merged (LISS III+PAN) for long-term coastal zone studies.

Optically stimulated luminescence age controls on late Pleistocene and Holocene coastal lithosomes, North Carolina, USA

Luminescence ages from a variety of coastal features on the North Carolina Coastal Plain provide age control for shoreline formation and relative sea-level position during the late Pleistocene. A series of paleoshoreline ridges, dating to Marine Isotope Stage (MIS) 5a and MIS 3 have been defined. The Kitty Hawk beach ridges, on the modern Outer Banks, yield ages of 3 to 2 ka. Oxygen-isotope data are used to place these deposits in the context of global climate and sea-level change. The occurrence of MIS 5a and MIS 3 shorelines suggests that glacio-isostatic adjustment (GIA) of the study area is large (ca. 22 to 26 m), as suggested and modeled by other workers, and/or MIS 3 sea level was briefly higher than suggested by some coral reef studies. Correcting the shoreline elevations for GIA brings their elevation in line with other sea-level indicators. The age of the Kitty Hawk beach ridges places the Holocene shoreline well west of its present location at ca. 3 to 2 ka. The age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast USA, suggesting some regionally contemporaneous forcing mechanism.

Large-scale coastal features generated by atmospheric pulses and associated edge waves

This article presents a hydrodynamic model that predicts the generation of horns and coves on the inner continental shelf, resulting from turbulent wind vortices blowing over the sea surface on the lee side of geographic obstacles (e.g. capes, islands, skyscrapers etc.). Such vortices generate edge waves whose net bedload sediment transport leads to the formation of such features. The resulting morphology reinforces the standing edge wave pattern, produces positive feedback, and exhibits self-forcing behavior. This model is applied to the horns and embayments found at Carchuna Beach (Spain), and offers a plausible explanation of how they have been generated. The results show that the presence of geographic obstacles or human constructions close to a beach may cause the formation of large-scale features on its coastline, significantly altering the beach width.