Coastal Features Research Articles

Sea-Level Rise Effects on Storm Surge and Nearshore Waves on the Texas Coast: Influence of Landscape and Storm Characteristics

AbstractSea-level rise (SLR) estimates vary broadly, but most estimates predict significant increases in sea levels within the next century. Through the use of validated, coupled wave and hydrodynamic models, this study investigates SLR effects on storm surge and nearshore waves, including variation with coastal landscape type and storm characteristics. Both the wave and hydrodynamic models account for bottom friction based on land-use type, so the modeling procedure accounted for SLR-related changes to land cover, in addition to higher mean sea levels. Simulation of storms with similar meteorological characteristics and track but with landfall in the northeastern and southwestern coastal areas allowed examination of how the coastal features influenced the storm surge and wave response to increased sea levels. The simulation results analyzed here demonstrate that the relationship between storm surge and relative SLR (RSLR) varies between geographic region and storm scenario. The increase in an inundated a...

Influence of large scale oscillations on upwelling‐favorable coastal wind off central Chile

Along the central coast of Chile is typically equatorward, upwelling‐favorable wind associated with the southeast Pacific anticyclone. A coastal low‐level jet often develops, and its wind speed is mostly controlled by the meridional pressure gradient. While the low‐level jet is a mesoscale feature forced by an interaction between synoptic conditions and coastal topography, regional sea level pressure anomalies are associated with changes of the Antarctic, Madden Julian, and El Niño–Southern Oscillation. The connection between the alongshore wind and changes to the large‐scale circulation is examined and quantified using 31 years of the Climate Forecast System Reanalysis, which resolves coastal features better than previous, coarser analyses. Composites based on each index reveal the modulation of the sea level pressure and significant alongshore wind anomalies of ±0.5–1.5 m s−1 that correlate well to meridional surface pressure gradient changes and are centered near 35°S. Constructive and destructive interference exists between the three indices that either enhance or cancel the alongshore wind anomaly. During favorable upwelling conditions the distribution of meridional wind is generally clustered around positive anomalies with a tail toward negative values, representing a stronger and persistent anticyclone. During unfavorable upwelling conditions the anomalies are generally more normally distributed, representing a weaker anticyclone and the passage of more cyclones.

Relation between the Structure of Mangrove Forests and Geomorphic Types of Lagoons of the Baja California Peninsula

González, P.; Lluch-Cota, S.E., and Nava-Sánchez, E.H., 2013. Relation between the structure of mangrove forests and geomorphic types of lagoons of the Baja California Peninsula. There are limited studies involving geomorphic factors and ecological patterns on a landscape scale of coastal features. This study examines the hypothesis that the structure of mangroves varies with habitat type. Using geomorphic criteria, we identified and classified 51 lagoons that contain mangroves on the Baja California Peninsula. Four lagoon types were analyzed: open drowned valley (I-A), barred drowned valley (I-C), Gilbert de Beaumont barrier lagoon (III-A), and cuspate lagoon (III-B). Structure patterns of mangrove forests growing at the edge of the lagoons were identified through photo interpretation and field observations, using landscape indices related to (1) area, density, and variability of the patches; (2) ecotone; and (3) form. Multivariate and univariate analyses were performed to determine the effects of habitat types on mangrove structure. Cluster analysis based on structural similarity showed two groups: (A) forests with limited structural development that grow mostly at the shore of lagoons I-A and I-C, and (B) larger forests with numerous patches, larger average size, average perimeters, and simpler forms than those in the first group, which grow mostly in lagoon type III-A. Similarity analysis showed no differences between the forests of lagoon types I-A and I-C, but there were differences between these two types and type III-A. Variance analysis showed differences in area, perimeter, and the shape of patches with respect to habitat type. Tukey's Honestly Significant Difference post hoc tests confirmed previously identified groups and showed that forest patches in lagoon type III-B are of intermediate structure. Lagoon type III-A appear to be more important in distribution and development of mangrove forests. Finally, we found that the spatial scale analyses and use of geomorphologically defined habitats were effective approaches for a first-order differentiation of mangrove forests.

Optical Remote Sensing of Pristine and Coastal Aerosol Features over the Arabian Sea

This paper purports the results of a co mparative study conducted to investigate aerosol optical, microphysical and radiative characteristics over an Exclusive Econo mic Zone (EEZ) associated with pristine environment, and coastal regions influenced by human activities, during 2009-2011. The measurements over the EEZ of the Arabian Sea (AS) were carried out fro m Sagar Kanya (SK-226) ship while over the coastal locations (Mumbai and Goa); employing Sun-photometers. The aerosol optical thickness (AOT) at 500 n m was found to be in the range of 0.3-0.45 in the EEZ wh ile it was 0.45-0.75 in the coastal regions. The AOTs at all the three sites showed a good association with concurrent meteorological parameters. Angstrom parameters (alpha and beta, representative of aerosol size d istribution and loading, respectively) indicated opposite behavior in the pristine (EEZ) but similar trend in the polluted coastal regions. This feature reveals that the aerosol loading over the EEZ is contributed by coarse-mode particles while the fine-mode particles contribute to the loading over coastal regions. Abundance of fine-mode part icles over the coastal regions is also evidenced from the second order polynomial fit coefficients (a1 and a2) of alpha. This aspect corroborates the long-range transport of air-mass over the experimental sites fro m the western coast India.

Validation of a thirty year wave hindcast using the Climate Forecast System Reanalysis winds

A thirty one year wave hindcast (1979–2009) using NCEP’s latest high resolution Climate Forecast System Reanalysis (CFSR) wind and ice database has been developed and is presented here. The hindcast has been generated using the third generation wind wave model WAVEWATCH III® with a mosaic of 16 two-way nested grids. The resolution of the grids ranged from 1/2° to 1/15°. Validation results for bulk significant wave height Hs and 10m (above Mean Sea Level) wind speeds U10 have been presented using both altimeter records and NDBC buoys. In general the database does a good job of representing the wave climate. At most buoys there is excellent agreement between model and data out to the 99.9th percentile. The agreement at coastal buoys is not as good as the offshore buoys due to unresolved coastal features (topographic/bathymetric) as well as issues related to interpolating wind fields at the land-sea margins. There are some concerns about the wave climate in the Southern Hemisphere due to the over prediction of winds (early part of the database) as well as the lack of wave blocking due to icebergs (in the model).

Is the Intensifying Wave Climate of the U.S. Pacific Northwest Increasing Flooding and Erosion Risk Faster Than Sea-Level Rise?

The relative contributions of sea-level rise (SLR) and increasing extratropical storminess to the frequency with which waves attack coastal features is assessed with a simple total water level (TWL) model. For the coast of the U.S. Pacific Northwest over the period of wave- buoy observations (approximately 30 years), wave height (and period) increases have had a more significant role in the increased frequency of coastal flooding and erosion than has the rise in sea level. Where tectonic-induced vertical land motions are significant and coastlines are pres- entlyemergent relativetothemeansealevel,increasingwave heightsresultinthesestretchesofcoastbeingpossiblysubmergentrelativetothe TWL. Although it is uncertain whether wave height increases will continue into the future, it is clear that this process could remain more im- portant than, or at least as important as, SLR for the coming decades, and needs to be taken into account in terms of the increasing exposure of coastal communities and ecosystems to flooding and erosion. DOI: 10.1061/(ASCE)WW.1943-5460.0000172. © 2013 American Society of Civil Engineers.

Dynamics of coastal landform features along the southern Tamil Nadu of India by using remote sensing and Geographic Information System

This article reveals an application of multi-spectral satellite data for analysing the dynamics of different coastal landform features along the southern coastal Tamil Nadu of India. An integrated approach comprising visual image interpretation and maximum-likelihood supervised classification has been employed to classify the coastal landforms by using IRS data (during the period 1999–2006). The quality of image classification has been assessed by performing the accuracy assessments with the existing thematic maps and finally the coastal landforms have been mapped. The study reveals that the dynamics of coastal landforms such as sandy beaches, mud-flats, sand dunes and salt marshes along the study area are mostly influenced by the coastal processes, sediment transport, geomorphology and anthropogenic activities. Major anthropogenic sources for the perturbation of beach sediment budgets and a cause of beach erosion along the study area are excessive sand mining, removal of sand dunes, coastal urbanization, tourism and developmental activities.

A Barotropic Model of the Red Sea Circulation

A linear depth-averaged numerical model of the horizontal barotropic circulation of the Red Sea is developed. The flow considered is incompressible, quasi-steady and free from vertical buoyancy currents and horizontal density currents. The model predicts general water circulation as affected by friction stresses at the irregular Red Sea bottom and coastal features, variable Coriolis force, vertical, and lateral turbulent friction, and seasonal non-uniformity of wind stress at the sea surface. The implicit finite-difference solution of the boundary value problem is verified with previous solutions for a rectangular constant-depth sea and for an elliptical lake with uniformly-sloping bottom topography. The model output is shown as plots of seasonally-averaged mass-transport vectors and circulation streamlines in the Red Sea basin.

Tampa Bay Coastal Wetlands: Nineteenth to Twentieth Century Tidal Marsh-to-Mangrove Conversion

Currently, mangroves dominate the tidal wetlands of Tampa Bay, Florida, but an examination of historic navigation charts revealed dominance of tidal marshes with a mangrove fringe in the 1870s. This study's objective was to conduct a new assessment of wetland change in Tampa Bay by digitizing nineteenth century topographic and public land surveys and comparing these to modern coastal features at four locations. We differentiate between wetland loss, wetland gain through marine transgression, and a wetland conversion from marsh to mangrove. Wetland loss was greatest at study sites to the east and north. Expansion of the intertidal zone through marine transgression, across adjacent low-lying land, was documented primarily near the mouth of the bay. Generally, the bay-wide marsh-to-mangrove ratio reversed from 86:14 to 25:75 in 125 years. Conversion of marsh to mangrove wetlands averaged 72 % at the four sites, ranging from 52 % at Old Tampa Bay to 95 % at Feather Sound. In addition to latitudinal influences, intact wetlands and areas with greater freshwater influence exhibited a lower rate of marsh-to-mangrove conversion. Two sources for nineteenth century coastal landscape were in close agreement, providing an unprecedented view of historic conditions in Tampa Bay.

Tourism Impact Assessment on Coastal Water Environment - A Case Study on HangZhou Bay North Shore in Shanghai

The study on tourism environment impact on coastal area has been a hot spot for coastal ecological environment research in our country. Based on grey recognition mode, this Paper analyzes the water environment quality of Shanghai Hangzhou Bay north shore coastal artificial bathing place in the spatial-temporal perspectives and researches the impacts of coastal tourism activities on water environment. The research results reveal that: (1) Coastal artificial bathing place is beneficial for protecting and improving coastal water environmental quality and different management modes on coastal artificial bathing place present different temporal features on protection of coastal water body; (2) In tourist peak season, environmental management improves the surrounding water environmental quality of artificial bathing place; (3) In the same coastal artificial bathing place, with different water body purification technologies and different influence mechanism, the tourism activities shows different levels of impact on water environment.

Interseismic coupling, segmentation and mechanical behavior of the central Chile subduction zone

Global Positioning System (GPS) measurements carried out in Chile over the last two decades showed that an entire portion of the Nazca‐South America subduction zone (38°S − 24°S) was locked over this period of time. The induced accumulation of elastic deformation in the upper‐plate was not released until the recent Maule earthquake of 27 February 2010 (Mw 8.8) that ruptured the southern part of this section. Locking or coupling between the two plates varies both with depth and along strike. Here we use our own GPS data (an updated solution of our extended network in central Chile), combined with other published data sets, to quantify the spatial variations of the coupling that prevailed before the Maule earthquake. Using a simple elastic model based on the back‐slip assumption, we show that coupling variations on the subduction plane are sufficient to explain the observed surface deformation, with no need of a sliver in central Chile. We identify four segments characterized by higher coupling and separated by narrow areas of lower coupling. This segmentation is in good agreement with historical and recent seismicity in Chile. In particular the narrow zones of lower coupling seem to have stopped most large seismic ruptures, including Maule's. These zones are often associated with irregular bathymetric or coastal features (fracture zones or peninsulas). Finally, coseismic and early post‐seismic slip distribution of the Maule earthquake, occurring either in previously highly or weakly coupled zones, map a complex distribution of velocity‐weakening and velocity‐strengthening patches on the subduction interface.

East Antarctic Landfast Sea Ice Distribution and Variability, 2000–08

Abstract This study presents the first continuous, high spatiotemporal resolution time series of landfast sea ice extent along the East Antarctic coast for the period March 2000–December 2008. The time series was derived from consecutive 20-day cloud-free Moderate Resolution Imaging Spectroradiometer (MODIS) composite images. Fast ice extent across the East Antarctic coast shows a statistically significant (1.43% ±0.30% yr−1) increase. Regionally, there is a strong increase in the Indian Ocean sector (20°–90°E, 4.07% ±0.42% yr−1), and a nonsignificant decrease in the western Pacific Ocean sector (90°–160°E, −0.40% ±0.37% yr−1). An apparent shift from a negative to a positive extent trend is observed in the Indian Ocean sector from 2004. This shift also coincides with a greater amount of interannual variability. No such shift in apparent trend is observed in the western Pacific Ocean sector, where fast ice extent is typically higher and variability lower than the Indian Ocean sector. The limit to the maximum fast ice areal extent imposed by the location of grounded icebergs modulates the shape of the mean annual fast ice extent cycle to give a broad maximum and an abrupt, relatively transient minimum. Ten distinct fast ice regimes are identified, related to variations in bathymetry and coastal configuration. Fast ice is observed to form in bays, on the windward side of large grounded icebergs, between groups of smaller grounded icebergs, between promontories, and upwind of coastal features (e.g., glacier tongues). Analysis of the timing of fast ice maxima and minima is also presented and compared with overall sea ice maxima/minima timing.

Mapping of mangrove forest land cover change along the Kenya coastline using Landsat imagery

Mangroves in Kenya provide a wide range of valuable services to coastal communities despite their relatively small total area. Studies at single sites show reductions in extent and quality caused by extraction for fuel wood and timber and clearance for alternative land use including saltpans, aquaculture, and tourism. Such studies suggest that Kenyan mangroves are likely to conform to the general global trend of declining area but there are no reliable recent estimates of either total mangrove extent or trends in coverage for the country. The total extent of Kenyan mangroves was estimated at four points in time (1985, 1992, 2000 and 2010) using Landsat satellite imagery. Due to its medium resolution, Landsat may underestimate mangrove areas in Kenya where relatively small, linear, coastal features occur. There is also a high frequency of clouds in the coastal areas which can cause data gaps during analysis. However comparison with aerial photographs taken in 1992 showed satisfactory levels of accuracy (87.5%) and Cohen’s Kappa (0.54) validating its use in this context. These 1992 data provided an independently validated baseline from which to detect changes (fore- and hind-casted) in other periods after removing cloud coverage. We estimated total mangrove coverage in 2010 at 45,590 ha representing a loss of 18% (0.7% yr−1) in the 25 years between 1985 and 2010. Rates of mangrove loss for Kenya varied both spatially and temporally with variations possibly due to legislative inadequacies and differences in habitat alteration patterns. Hence freely available Landsat images proved adequate to detect changes in mangroves and revealed that Kenya shows rates of decline similar to (although slower than) global estimates.

Statistical model predicts shoreline erosion rates due to sea level rise

While sea level rise in the face of global warming is a well‐acknowledged threat, providing estimates of the local impact—the information needed by planners to develop effective strategies against the rising waters—has been difficult. Many attempts treat the global ocean as a giant bathtub, where increased water volume simply rises up and floods the land. Understandably, these approaches fall short of accurately estimating the impact of storms, sea level rise, and human influence on coastlines. The next extension toward an accurate longterm prediction of shoreline change necessarily includes a representation of the dynamic interaction between coastal features and the rising water.

Coastal features analysis using GIS tools–stretch Esmoriz-Furadouro

The aim of this study is to identify morphological features and hydrodynamic patterns (e.g. coastal forms, wave breaking zones, rip current patterns, submerged bars), based on aerial photograph datasets. Understanding past patterns may help to increase the ability to predict future ones. To achieve the proposed objectives, a methodology to analyse aerial photograph datasets was developed. The analysis consists of visual identification of coastal features and patterns in a GIS environment. A GIS database was created to store the existing data and the result of the analysis. Several coastal features and patterns were identified, measured and correlated to the wave climate and other parameters. This correlation indicates that the presence and the dimensions of coastal features and patterns are closely related with the wave conditions and tide level, although the latter has less significance.

Simulation of East India Coastal Features and Validation with Satellite Altimetry and Drifter Climatology

The circulation features of western coast of the Bay of Bengal (BOB) have been analyzed using Regional Ocean Modeling System (ROMS) with Comprehensive Ocean-Atmosphere Data Set (COADS) wind and thermal forcing. The model simulation shows that the coastal current is not continuous throughout the year similar to the structure seen from the drifter climatology. The western boundary current (WBC) is formed in February and persists till May. This boundary current is very strong during March and April due to formation of anticyclonic eddies. From July to September, the coastal current is disorganized because of sequential development of anticyclonic and cyclonic eddies. But in October the coastal current starts to flow southward as the East India Coastal Current (EICC) and it prevails till December with the formation of cyclonic eddies along the coast. The simulated sea surface height anomaly (SSHA) is competent to detect the upwelling and downwelling zones in the coastal region as supported by TOPEX/POSEIDON climatology.

Large Boulder Along the NE Maltese Coast: Tsunami or Storm Wave Deposits?

FURLANI, S., BIOLCHI, S., DEVOTO, S., SALIBA, D and SCICCHITANO, G., 2011. Large Boulder Along the NE Maltese Coast: Tsunami or Storm Wave Deposits. In: Micallef, A. (ed.), MCRR3-2010 Conference Proceedings, Journal of Coastal Research, Special Issue, No. 61, pp. 470. Grosseto, Tuscany, Italy, ISSN 0749-0208.The accumulation of large boulders resulting from tsunamis or large waves is a phenomenon that has been observed in different areas along the Mediterranean Sea, mainly along the shoreline of the Messina Straits and the Apulian coasts. It is known through historical records that very few large earthquakes have originated close to the Maltese Islands. The seismicity which affects the Maltese coasts is mainly related to the Pantelleria Rift, a graben system which was active in Late Miocene till recent times. This rift system interrupts the shallow platform connecting Europe to Africa.The Maltese NE coast, mainly the area between Armier Bay and Il-Ponta ta' L-Ahrax is interspersed by large limestone boulders which are scattered on a large terrace which is gently sloping towards the sea. The deposit is about 100m wide and situated at an altitude ranging between 0m and 5m above sea level. This site probably represents the most suitable area for this type of deposition on the island given to the favourable morphological conditions. Most of the NW coast of Malta is characterised by cliffs that prevent the accumulation of wave deposits, while other sectors are characterised by the accumulation of large limestone boulders which have been deposited due to cliff retreat. This work aims to commence a preliminary survey of these deposits.Block sizes range between few and about 4m3, with the largest one being about 2m×2m×1m in size and with an estimate weight of 10 tonnes. Most of the blocks, mainly in the northernmost sector, are scattered individually while at the central parts of the study area one can find groups of few blocks. The largest boulders show typical coastal karst features (karstic pools, etc) similar to the coastal features found in the area. This suggests that the detachment area is close to the identified deposits. Further studies are foreseen, in particular to determine the nature of the deposits, period of detachment of the blocks and the possibility that the accumulation represents more than a single event (seismic or storm).

Shoreline change analysis along the coast between Kanyakumari and Tuticorin of India using remote sensing and GIS

Shoreline is one of the rapidly changing landform in coastal area. So, accurate detection and frequent monitoring of shorelines are very essential to understand the coastal processes and dynamics of various coastal features. The present study is to investigate the shoreline changes along the coast between Kanyakumari and Tuticorin of south India, where hydrodynamic and morphologic changes occur continuously after the December 2004 tsunami. Multi-date satellite data of Indian Remote Sensing (IRS) satellites (1999, 2000, 2003, 2005, and 2006) are used to extract the shorelines. The satellite data is processed by using the ERDAS IMAGINE 9.1 software and analyzed by ArcGIS 9.2 workstation. The different shoreline change maps are developed and the changes are analyzed with the shoreline obtained from the Survey of India Toposheets (1969). The present study indicates that accretion was predominant along the study area during the period 1969–1999. But recently (from 1999 onwards), most of the coastal areas have experienced erosion. The study also indicates the reversal of shoreline modifications in some coastal zones. The coastal areas along the headlands have experienced both erosion and accretion. Though the coastal erosion is due to both natural and anthropogenic activities, the coastal zones where sand is mined have more impacts and relatively more rate of erosion than that of other zones. Improper and in-sustainable sand mining leads to severe erosion problem along this area. So the concept of sustainable management should be interpreted in the management of the near-shore coastal sand mining industry.

On the genesis of some bottom and coastal features in the Eastern Gulf of Finland

An investigation undertaken recently by the Division of Regional Geoecology and Marine Geology of the Karpinsky All-Russian Research Geological Institute in the coastal zones of the Eastern Gulf of Finland allowed finding some specific relief forms of both near-shore bottom topography and shoreline shape. First of all, among the most interesting objects, the sand ridges on the surface of submarine terrace (between Repino locality and Cape Lautaranta) should be mentioned. These ridges are elongated at an angle to the shoreline and are located beyond the limits of wave action. The other interesting morphological type is represented by longshore sand waves up to some hundreds of meters long and some tens of meters wide near the Bol’shaya Izhora locality. Longshore sand waves move along the southern coast of the gulf, this causing alteration of erosion and accretion zones and leading to formation and degradation of the sand spits. Shore-face-connected ridges are believed to develop under the action of drift currents generated during the passage of deep west cyclones. It is shown that the ridge turned toward the current gives rise to a convergence of the cross-shore flows over the crest and provokes a shift of the maximum velocity toward the front side of the structure. Associated changes in sediment discharges result in accumulation and growth of the ridge. The origin of wavelike features in the shoreline contour (longshore sand waves) is due to a very oblique wave approach caused by predominance of the west winds blowing along the axis of the gulf. Under these conditions a small perturbation of the shoreline contour is shown to manifest a trend to increase with time.

Simulation of wave breaking over complex bathymetries by a Boussinesq model

A Boussinesq-type model is applied herein to study wave propagation and wave breaking over complex bathymetries reproducing common coastal features, namely plane and barred beaches, submerged bars and rip channels. A hybrid finite volume–finite difference numerical scheme solves a set of, in the horizontal plane, two-dimensional extended Boussinesq equations where both nonlinear and dispersive effects are relevant and nonlinear shallow water equations where nonlinearity prevails over dispersion. The shock-capturing features of the finite volume method enable an intrinsic representation of spilling wave breaking and runup. Comparisons with experimental data indicate that the numerical model adequately simulates wave transformation over submerged bars, correctly capturing wave breaking onset and termination including the related energy dissipation. The development of breaking-induced currents and their interaction with wave propagation are also well represented within the applicability range of the governing equations.