KANE, H.H.; FLETCHER, C.H.; ROMINE, B.M.; ANDERSON, T.R.; FRAZER, N.L., and BARBEE, M.M., 2012. Vulnerability assessment of Hawai′i′s cultural assets attributable to erosion using shoreline trend analysis techniques.

Hawai‘i’s beaches are a focal point of modern lifestyle as well as cultural tradition. Yet coastal erosion threatens areas that have served as burial grounds, home sites, and other forms of cultural significance. To improve understanding of the convergence of erosion patterns and cultural uses, we mapped shoreline changes from Kawela Bay to Kahuku Point on the capital island of O‘ahu. Shoreline change rates are calculated from historical photographs using the single-transect (ST) and eigenbeaches (EX) method to define the 50- and 100-year erosion hazard zones. To ensure that shoreline change rates reflect long-term trends, we include uncertainties attributable to natural shoreline fluctuations and mapping errors. A hazard zone overlay was compared to cultural data provided by the Hawaii State Historic Preservation Division (SHPD) and the Office of Hawaiian Affairs (OHA) to identify threats to cultural features. Cultural features identified in the study include iwi kupuna (burials), Hawaiian artifacts, and Punaulua (a freshwater spring). Our analysis indicates that, except for Punaulua, all cultural features identified are vulnerable to coastal erosion at historical rates. The data produced in this study may be used as a proactive management tool to rank the vulnerability to threatened cultural features, as well as to develop protocols to appropriately manage cultural assets.

KLEMAS, V., 2012. Remote sensing of ocean internal waves: an overview.

The oceans are density stratified because of vertical variations in temperature and salinity. Oceanic internal waves can form at the interface (pycnocline) between layers of different water density and propagate long distances along the pycnocline. Internal waves on continental shelves are important because they can attain large amplitudes and affect acoustic wave propagation, submarine navigation, nutrient mixing in the euphotic zone, sediment resuspension, cross-shore pollutant transport, coastal engineering, and oil exploration. Internal waves induce local currents that modulate surface wavelets and slicks, causing patterns of alternating brighter and darker bands to appear on the surface. The surface patterns can be mapped by satellites using synthetic aperture radar (SAR) or visible imagers. The objectives of this article are to discuss methods for remotely studying and mapping ocean internal waves and to present examples illustrating the application of satellite remote sensing.

CARR-BETTS, E.; BECK, T.M., and KRAUS, N.C., 2012. Tidal inlet morphology classification and empirical determination of seaward and down-drift extents of tidal inlets.

The Hayes classification of tidal inlet geomorphic type and the distances from the inlet to the most seaward and down-drift extents of ebb deltas are examined. For this purpose, a database was compiled for 89 tidal inlets along the Atlantic Ocean, Gulf of Mexico, and Pacific Ocean coasts of the United States. The database contains spring or diurnal tidal prism and the average significant wave height and wave period from a 20-year hindcast. The Hayes diagram aims to classify inlet plan-view morphology by tide range and wave height. Based on the work presented here, it is concluded that the inlet classification of Hayes has limited applicability for describing the morphology of typical tidal inlets, and replacement of tide range by inlet tidal prism did not improve the classification. Best correlation for the two ebb delta extents was found for inlets segregated by wave exposure (as mild, moderate, or high) and by tidal prism. There was poor or no correlation for moderately wave-exposed inlets, and moderate to high correlation was found for mildly and highly exposed inlets. The seaward and down-drift extents of inlets tend to remain constant up to a tidal prism less than 10⁸ m³, depending on wave exposure, and then increase linearly with tidal prism. It is postulated that a tidal prism less than approximately 10⁸ m³ is a tipping point required to overcome other factors controlling tidal inlet plan-form morphology.

DAILIDIENĖ, I.; DAVULIENĖ, L.; KELPŠAITEĖ, L., and RAZINKOVAS, A., 2012. Analysis of the climate change in Lithuanian coastal areas of the Baltic Sea.

This paper investigates the changes in the long-term hydroclimatic conditions in the SE Baltic Sea, along the Lithuanian coast, on the basis of the monitoring data obtained within a 45-year period (1961–2005). Furthermore, the paper discusses the processes behind those changes. Time series of relevant data along the Lithuanian coast from previous centuries were used to investigate climatic variability and trends. The study finds an increased period of westerly winds during winter. During recent decades, the impact of global climate change on sea-level rise has drawn wide interest, since the coastline changes have ecological, economic, and social impacts on the coastal areas of the Baltic Sea. The analysis of the trends for the Lithuanian coastal zone found results similar to those obtained from global and regional analyses showing increasing sea levels today and in the future.

PAIS, A.; SERRA, S.; MELONI, G.; SABA, S., and CECCHERELLI, G., 2012. Harvesting effects on Paracentrotus lividus population structure: A case study from northwestern Sardinia, Italy, before and after the fishing season.

The edible sea urchin Paracentrotus lividus is commercially exploited in many European countries. In recent years, however, its stocks have shown a large reduction in several regions because of overfishing. This paper reports the effects of harvesting on P. lividus population structure in shallow rocky reefs from a central-western Mediterranean area where this activity is intensively practiced. Density, size (test diam), and biomass of sea urchin were assessed in October 2004 (just before the fishing season) and in May 2005 (immediately after the fishing season) at two locations where intense P. lividus harvest occurs and at two controls within an adjacent Marine Protected Area (MPA) where P. lividus harvest is prohibited. Density, size, and average biomass of P. lividus were significantly higher at the protected areas than at the exploited ones. In particular, large-sized specimens (test diam >5 cm) were notably less abundant at the fished locations; however, very similar results were detected for both the periods examined (i.e., before and after the fishing season), suggesting that effects of pressing activity of harvest through the past years may have produced effects much more evident than those attributable to the single fishing season. These results reveal the existence of a heavy-fishing impact on P. lividus in northwestern Sardinia and the urgent need of regulating its harvesting to prevent severe direct effects on its populations.

KLEMAS, V., 2012. Remote sensing of coastal and ocean currents: an overview.

Ocean currents influence the global heat transport; weather and climate; larval transport; drift of water pollutants; sediment transport; and marine transportation. As a result, oceanographers, coastal managers, and ships need up-to-date information on ocean and coastal currents. Arrays of current meter moorings can measure currents at local scales. Shore-based high-frequency radars are able to map coastal currents over a range of up to 200 km. Ocean drifters can be tracked to obtain circulation patterns over larger areas, but may take months to accomplish it. Only satellite remote sensors can determine currents synoptically over extensive ocean and coastal regions. Satellite altimetry is one of the essential remote-sensing techniques for monitoring dynamic ocean conditions, including surface currents, local wind speed, and significant wave height. Satellite altimetry measures sea surface heights, providing data on geostrophic circulation, including major ocean currents. Ocean currents can also be determined by satellite synthetic aperture radar (SAR) or tracking the movement of thermal and color features in the ocean. The flow patterns of currents like the Gulf Stream are being mapped with satellite infrared scanners. The objective of this paper is to review practical remote-sensing techniques for measuring and mapping coastal and ocean currents.

BAKKER,M.A.J.; VANHETEREN, S.; VONHÖGEN, L.M.; VAN DER SPEK, A.J.F., and VAN DER VALK, L., 2012. Recent coastal dune development: effects of sand nourishments.

Much of the Dutch coast has been subject to structural erosion. From 1990 onward, sand nourishments have been used under a government policy of dynamic preservation. Annual monitoring and field inspections show that the structural erosion has decreased or even turned into coastal progradation after 1990. The monitoring data concern only morphodynamics and thus supply limited information on system-related geological processes driving the observed changes. Recently acquired ground-penetrating radar (GPR) data help establish the origin of sedimentary elements within the beach-foredune area, determine their decadal-scale preservation potential under the present nourishment policy, and demonstrate temporal and spatial accretion/erosion variability along nourished coasts. GPR images from a nonnourished retrograding barrier section show historical storm surge deposits within the eroding foredune and accumulations of natural eolian sediment farther landward. GPR images from a heavily nourished, prograding site show that the accreted foredune and beach consist of nourishment embankments (20%), wind-blown units derived from nourished sand (70%), and progradational beach deposits (10%). The net volume of accretion at this site is approximately 200 m³/m. Remarkably, almost all sand nourished before 2000 has been washed away, except for embankments constructed in 1990. Analysis of meteorological data suggests that 1999 storm surges are responsible for this erosion. The relative longevity of post-2000 nourishments can be attributed to a combination of shoreface nourishment and favorable meteorological conditions. During a storm surge in 2007, water-lain embankments proved to be more resistant against wave erosion than nourished sand redistributed by wind, indicating the importance of grain size, roundness and packing in the durability of nourishments.

SMITH, S.M.; MEDEIROS, K.C., and TYRRELL, M.C., 2012. Hydrology, herbivory, and the decline of Spartina patens (Aiton) Muhl. in outer Cape Cod salt marshes (Massachusetts, U.S.A.).

Salt marsh dieback in different regions of the United States exhibits considerable variability in symptoms, processes, and theoretical or proven causes. On Cape Cod (Massachusetts), where losses within the low-marsh zone (elevations below mean high tide, dominated by smooth cordgrass [Spartina alterniflora Loisel.]) have been particularly severe, recent studies suggest that intense grazing pressure from increased abundances of a native, herbivorous, purple marsh crab (Sesarma reticulatum) is to blame. Low-marsh dieback is spatially heterogeneous because it is closely related to the distribution of the crabs' preferred substrate (peat vs. sand or mud). However, vegetation losses have also occurred in the high marsh, which is comprised of mainly saltmeadow cordgrass (Spartina patens [Aiton] Muhl). In contrast to the low marsh, high-marsh losses consistently occur along the seaward-most edge of this zone, suggesting a link with hydrology (flooding frequency). In this study, we attempted to determine the relative contribution of environmental factors and crab herbivory to high-marsh dieback. To do this, we (1) characterized tidal regimes in dieback vs. healthy areas, (2) assessed the extent of herbivory on S. patens using crab-exclosure cages, (3) documented the ability of S. patens to recover from simulated grazing (clipping) in different marshes and in different areas of individual marshes, and (4) estimated densities of S. reticulatum in two high-marsh dieback areas. The results indicate that S. patens losses are likely the result of a combination of stressors. Flooding frequency and salinities are higher in dieback areas, which impart a higher level of physiological stress. Plants growing there also seem to have a much-reduced capacity to recover from both simulated and actual grazing by the herbivorous crab, S. reticulatum. Continued losses of high-marsh vegetation could eliminate this community from coastal wetlands on Cape Cod, Massachusetts.

GUILLOU, N. and CHAPALAIN, G., 2012. Modeling the tide-induced modulation of wave height in the outer Seine estuary.

During the last decades, numerous models have been implemented to investigate the effects of tide on wind-generated surface-gravity waves. The present study analyzes the influences of the tide-induced time-varying water depths and currents on the wave height in the outer Seine estuary (France, English Channel). Two modeling systems based on the coupling of circulation and wave propagation modules are applied at the scales of (i) the English Channel and the North Sea and (ii) the Bay of Seine and the harbor of Le Havre, respectively. Numerical results are compared with field data collected with two current meters and two wave buoys in the access channel to Port 2000 (Le Havre). Predictions exhibit a local increase of 30% of the wave height induced by current refraction at slack tide. On the basis of this local comparison of numerical results with measurements, three mappings of the wave height modified by the (i) tide, (ii) water levels alone, and (iii) currents alone are established at the scale of the outer Seine estuary. The currents have a major influence on the wave height modulating at a tidal frequency the direction of incident waves through refraction. This effect is exhibited along the southern breakwater of the harbor of Le Havre and the vicinity of coastal topographic features of the outer Seine estuary.

VIRDIS, S.G.P.; OGGIANO, G., and DISPERATI, L., 2012. A geomatics approach to multitemporal shoreline analysis in Western Mediterranean: the case of Platamona-Maritza Beach (northwest Sardinia, Italy).

This study examines the shoreline change evolution at two spatiotemporal scales over ca. 18 km of Platamona-Maritza beach (northwest Sardinia, Italy). A multitemporal dataset spanning the period 1955–2010 was used and made up of archival aerial photographs, orthophotos, satellite imagery, light detection and ranging data, terrestrial laser scanner, Global Positioning System, and recent and historical topographic maps. We integrated this dataset by implementing a repeatable processing procedure, for which the global sensitivity for shoreline change estimation was evaluated (ca. 10 m as a product of time interval and change rate). The applied methodology indicates that the wet/dry boundary can be used as a good shoreline proxy. It is also demonstrated how reliable shoreline positional uncertainty (from 1.9 to 8.6 m) can be estimated whenever a large set of multitemporal data is available and geomatic tools are properly integrated.

Results showed how shoreline evolutionary trends affected the entire coastal zone and roughly migrated from east to west, with the largest rates between 1970 and 2000. Where long-term analysis provided higher erosion rates, a sediment volumetric change was estimated, although only for a 2-year window and for a 300-m-wide stretch of beach. An analysis of geomorphic features along the coast also indicates variable longshore drift direction as a consequence of changes in a combination of wind, wave, and current regimes. A direct relationship between the evolutionary trend of hydrometric and pluviometric data recorded at the study site highlight that, although rainfall regime is nearly constant, average discharge of main rivers underwent a dramatic decrease since 1965 in conjunction with land use change and upstream dam construction for agriculture and urban development. Therefore, it has been argued that river sediment supply also was reduced; hence, besides other natural and anthropogenic causes, it likely influenced erosion and accretion events in the southern sector of the Gulf of Asinara.

CHOI, K.H.; SEONG, Y.B.; JUNG, P.M., and LEE, S.Y., 2012. Using cosmogenic ¹⁰Be dating to unravel the antiquity of a rocky shore platform on the west coast of Korea.

Shore platforms commonly occur at the base of coastal cliffs on rocky shores. It is generally accepted that they form by the retreat of such cliffs through wave action and weathering processes. Although a handful of previous studies have sought to directly constrain the rate of shore platform development over annual–decadal scales, there remains little consensus on the rate of their long-term (>millennial) evolution, as a result of the complex nature of shielding processes that operate in parallel with variable sea levels. Some platforms show contemporary features; however, the possibility that some features were inherited from the last interglacial or earlier stages always exists. The occurrence of wide shore platforms in resistant rocks is often regarded as evidence of such inheritance because the short stillstands of the Holocene offered insufficient time for the sculpting of extensive platforms on resistant rocky coasts. This study focuses on dating the wide shore platforms, which are common on headlands along the west coast of the Korean Peninsula, based on the abundance of cosmogenic ¹⁰Be. This macrotidal coast is dominated by tidal processes with tidal ranges of up to 6 m. The very gently sloping (<2°) shore platform of the study site is up to 150 m wide at low tide and composed mainly of metamorphosed sandstones. Samples for cosmogenic ¹⁰Be surface exposure dating were collected along two transects oriented perpendicular to the cliff line. The apparent surface exposure ages of the samples ranged from the Holocene (ca. 4 ka) to the Pleistocene (ca. 148 ka) and increased with increasing distance from the sea cliff along both transects. Given the apparent antiquity and range of the surface exposure ages, it seems likely that this shore platform originated in the Pleistocene, when sea levels were similar to those of today, and that the present shore platform is cutting into its interglacial predecessor.

PENG, W.; LEE, KWANG-HO, and MIZUTANI, N., 2012. Application of direct-forcing IB-VOF method to the simulation of wave deformation by submerged structures.

In this work, direct numerical simulation is employed to estimate the deformations of free-surface waves by submerged fixed structures using the immersed boundary method and volume of fluid method. The direct-forcing immersed boundary method is applied to handle solid object boundaries that are replaced with a proper force in the Navier–Stokes equations imposed on the body surface. The volume of fluid method is employed to track the free surface. Submerged obstacles of different shapes, including rectangles, trapezoids, and semicircles, are investigated to validate the ability of the numerical model to simulate fluid structure problems involving geometrically complex solid boundaries. The comparisons between the results of the developed numerical model, available experimental data, and previous numerical estimations reveal a favorable agreement between the water particle velocity fields as well as the free-surface profiles. The fully nonlinear phenomenon such as the flow separation and vortex generation can be reproduced and captured accurately using the proposed model.

SHAND, T.D.; BAILEY, D.G., and SHAND, R.D., 2012. Automated detection of breaking wave height using an optical technique.

Obtaining accurate information of nearshore wave characteristics including the position and height of individual breaking waves is essential to understanding the drivers of coastal processes, for engineering design and hazard prediction. Demand for such information in real time for recreational planning and hazard assessment is also high. Remote optical techniques would offer considerable economic and spatial coverage advantages over conventional in situ instrumentation. However, optical methods for obtaining wave height information have been slow to develop and those available remain computationally expensive and require “favourable” environmental conditions. This paper presents a relatively simple yet robust approach to detecting and quantifying breaking wave position and height across a wide surf zone using a twin video camera configuration coupled with an image time-stack analysis approach. A numerical algorithm, HbSTACK, is developed and successfully tested under the environmental conditions experienced during field trials. Errors and uncertainties may arise in both the photogrammetric transformation from pixels to real-world coordinates and in the detection of wave crest and trough positions. These errors have been assessed using both field verification of the transformation model and manually detected crest and trough locations by experienced practitioners. Errors in output wave heights were thus estimated to be less than 7%.

FERNÁNDEZ LUQUE, I.; AGUILAR TORRES, F.J.; AGUILAR TORRES, M.A.; PÉREZ GARCÍA, J.L., and LÓPEZ ARENAS, A., 2012. A new, robust, and accurate method to extract tide-coordinated shorelines from coastal elevation models.

The extraction of highly accurate shoreline data is fundamental to carrying out accurate and reliable studies to enhance our understanding of coastal evolution and coastal vulnerability. In our case, shoreline extraction was needed to develop a method based on an extrapolation process because the most suitable height for datum-coordinated shoreline extraction along Spanish coastal areas turned out to be the orthometric datum origin, i.e., the origin of the vertical reference system in Spain. Because of the microtidal nature of the Mediterranean Sea, using this vertical datum is rather troublesome for remotely extracting ground points to apply to traditional shoreline-extraction methods based on interpolation procedures. Because of these difficulties, a new method for shoreline extraction, based on extrapolation from an iterative digital-elevation model, is presented in this article. The Elevation Gradient Trend Propagation method employs the local elevation gradient to estimate the shoreline position by extrapolating the slope until the zero-elevation contour, representing the modeled intersection of the vertical datum and the beach profile, is reached.

The proposed methodology was tested on a Light Detection and Ranging (LIDAR)–derived digital-elevation model, which comprised a coastal area of Almería (Mediterranean Sea, south Spain). The results obtained from the new approach were compared with those provided by the widely known Cross-Shore Profile (CSP) method.

A validation process was conducted for both methods to highlight their advantages and shortcomings. An alternative contour level of 0.4 m was employed as a ground truth because the zero-elevation contour was not available because LIDAR returns under the water surface were unavailable. The validation process showed that the proposed method was more robust and more suitable than CSP method was for microtidal coasts and for data that need to be extrapolated to reach the desired contour level. In addition, the influence of the starting point in applying the elevation extrapolation process was also proven.

COTT, G.M.; JANSEN, M.A.K., and CHAPMAN, D.V., 2012. Salt-marshes on peat substrate: where blanket bogs encounter the marine environment.

Salt marshes typically develop on low-energy coasts under the influence of the tide. However, there are peat salt-marshes along the west coast of Ireland that formed in an inherently different way. This paper examines the ontogeny of these salt-marshes and highlights their uniqueness both in an Irish and global context. The peat of these marshes formed in postglacial times when climatic conditions were such that ombrogenic blanket bogs formed along the western Atlantic coast of Ireland. A subsequent marine transgression caused a shift from freshwater to saline conditions, and these bogs now support salt-marsh vegetation. These systems have been termed “Fringe” marshes in the Irish salt-marsh inventory. Unlike other organogenic salt-marshes in Europe, they formed under predominantly freshwater conditions, thus making them unique in geological foundation. This paper examines the complexity of natural controls on salt-marsh systems and relates this to the ecological character of fringe marshes. It emphasises that their position on the western Atlantic seaboard, coupled with peat substrate and its inherent properties, could drive a unique ecological character. Ongoing and future threats to these habitats are discussed. The term “Fringe” is used internationally in many other contexts and therefore does not specifically describe these peat substrate marshes. In order to distinguish the peat salt-marshes of the west coast of Ireland from those formed under different conditions, the term “Ombrogenic Atlantic Salt-Marsh” is proposed.

THEUERKAUF, E.J. and RODRIGUEZ, A.B., 2012. Impacts of transect location and variations in along-beach morphology on measuring volume change.

Real Time Kinematic–GPS profile surveys are currently the most common method used by engineers and researchers for monitoring beach erosion. This study assesses the accuracy of volumetric-change measurements based on profile surveys at various beach morphologies along Onslow Beach, North Carolina. High-resolution digital elevation models (DEMs) were created from topographic data collected using a three-dimensional terrestrial laser scanner at six ∼150-m-long focus sites at annual, seasonal, and storm time intervals. Profiles were extracted from the DEMs every 0.5 m along the beach, a distance equal to the grid size, and each profile was independently used to measure volumetric change at each site. Along-beach variability in the measurements of volumetric change was analyzed to test the assumption that one transect can be used to determine volumetric change for a ∼150-m stretch of beach. Results show that the accuracy of profile-based volumetric change decreases as along-beach morphologic variability increases. At sites with beach cusps, beach nourishment, and pockets of anomalous erosion and/or accretion, less than 5% of the ∼300 transects accurately measure volumetric change to within ±10% of the true volumetric change. At the site with the lowest along-beach morphologic variability, that number only increased to 35% of the ∼300 transects. Three-dimensional surveys or closely spaced beach profiles should be employed at morphologically variable, and/or recently nourished or engineered, beaches to accurately quantify erosion and accretion over short timescales.

LONARD, R.I.; JUDD, F.W., and STALTER, R., 2012. The biological flora of coastal dunes and wetlands: Salicornia bigelovii J. Torrey.

Salicornia bigelovii J. Torrey is a New World tropical-, subtropical-, and temperate-zone annual, succulent halophyte that is an important pioneer species in hypersaline coastal landscapes. Also known as annual glasswort, it ranks as one of the world's most salt-tolerant land vascular plants. It tolerates salinities as high as 120 ppt. Optimal growth of S. bigelovii occurs where competing cover of perennials is low. Salicornia bigelovii has potential as a crop plant in arid coastal sites.

FURUKAWA, Y. and WATKINS, J.L., 2012. Effect of organic matter on the flocculation of colloidal montmorillonite: A modeling approach.

The effect of organic matter (OM) on the flocculation of colloidal montmorillonite was investigated through a complementary use of laboratory experiments and computational flocculation modeling. The model, based on Smoluchowski's coagulation model and population balance equation (PBE), was established with two key flocculation parameters: sticking efficiency and breakup parameter. The laboratory flocculation experiments tracked the temporal evolution of the mean floc sizes for aqueous systems with colloidal bare montmorillonite as well as those with montmorillonite and OM (humic acid, chitin, or xanthan gum). The key flocculation parameters were derived and calibrated through the interactive optimization of the model results by juxtaposing against the laboratory results.

The calibrated flocculation parameter values revealed that OM has a complex influence on the flocculation behavior of montmorillonite. They also showed that the effect of OM on flocculation depends on the types of OM. For example, xanthan gum does not significantly modify the flocculation behavior of montmorillonite that is primarily determined by the electrical double-layer repulsion (i.e., ζ-potential) and van der Waals attraction [i.e., Derjaguin and Laudau, Verwey and Overbeek (DLVO) interaction energies], whereas chitin modifies both the sticking efficiency and breakup parameter.

This study illustrates that there is no universally predictive correlation between DLVO energies or ζ-potential and flocculation parameters, as some OM has little effect on the DLVO interaction of montmorillonite colloids whereas other types of OM exert significant non-DLVO interactions such as repulsive hydration, steric repulsion, and polymer bridging. Further understanding of the physical-chemical properties of OM is needed in order to predict the flocculation behaviors of estuarine and coastal suspended colloids.