Showing papers in "Journal of Coastal Research in 2010"

Coastal Vulnerability Assessment for Orissa State, East Coast of India

Abstract: Coastal areas of Orissa State in the northeastern part of the Indian peninsula are potentially vulnerable to accelerated erosion hazard. Along the 480-km coastline, most of the coastal areas, including tourist resorts, hotels, fishing villages, and towns, are already threatened by recurring storm flood events and severe coastal erosion. The coastal habitats, namely the largest rookeries in the world for olive Ridley sea turtles (the extensive sandy beaches of Gahirmatha and Rushikulya), Asia's largest brackish water lagoon (the “Chilika”), extensive mangrove cover of Bhitarkanika (the wildlife sanctuary), the estuarine systems, and deltaic plains are no exception. .The present study therefore is an attempt to develop a coastal vulnerability index (CVI) for the maritime state of Orissa using eight relative risk variables. Most of these parameters are dynamic in nature and require a large amount of data from different sources. In some cases, the base data is from remote sensing satellites; for othe...

Exploring data-related uncertainties in analyses of land area and population in the “Low-Elevation Coastal Zone” (LECZ)

Abstract: Analyses of land area and population distribution in the Low Elevation Coastal Zone (LECZ) and their potential susceptibility to future sea level rise have been used to derive first-order assessments of areas and populations at risk. Variations in results are shown to be highly dependent on the input datasets. In this paper we explore differences in land and population distribution estimates in the LECZ resulting from the use of three digital elevation models and two population datasets at global, continent, and country levels. Results at the global scale show differences of up to 150% in area estimates, depending on the elevation model used. The differences are most extreme below 1 m elevation and diminish at higher elevation increments. On the continent level, the use of different elevation models produced area estimate differences ranging from more than 1200% at an elevation of 1 m to 160% in the LECZ. Country-level differences are even higher. Similarly, substantial differences in population ...

Improving Coastal Vulnerability Assessments to Sea-Level Rise: A New Indicator-Based Methodology for Decision Makers

Abstract: Integration of impacts of sea-level rise to coastal zone management practices are performed through coastal vulnerability assessments. Out of the types of vulnerability assessments, a proposed model demonstrated that relative vulnerability of different coastal environments to sealevel rise may be quantified using basic information that includes coastal geomorphology, rate of sea-level rise, and past shoreline evolution for the National Assessment of Coastal Vulnerability to Sea-Level Rise for U.S. Coasts. The proposed methodology focuses on identifying those regions where the various effects of sea-level rise may be the greatest. However, the vulnerability cannot be directly equated with particular physical effects. Thus, using this concept as a starting point, a coastal vulnerability matrix and a coastal vulnerability index that use indicators of impacts of sea-level rise are developed. The developed model compares and ranks different regions according to their vulnerabilities while prioritizing...

Tracking Oil Slicks and Predicting their Trajectories Using Remote Sensors and Models: Case Studies of the Sea Princess and Deepwater Horizon Oil Spills

Abstract: Oil spills can harm marine life in the oceans, estuaries, and wetlands. To limit the damage by a spill and facilitate cleanup efforts, emergency managers need information on spill location, size and extent, direction and speed of oil movement, and wind, current, and wave information for predicting oil drift and dispersion. The main operational data requirements are fast turn-around time and frequent imaging to monitor the dynamics of the spill. Remote sensors on satellites and aircraft meet most of these requirements by tracking the spilled oil at various resolutions, over wide areas, and at frequent intervals. They also provide key inputs to drift prediction models and facilitate targeting of skimming and booming efforts. Satellite data are frequently supplemented by information provided by aircraft, ships, and remotely-controlled underwater robots. The Sea Princess tanker grounding off the coast of Wales and the explosion on the Deepwater Horizon rig in the Gulf of Mexico provide good examples ...

An Estimate of the U.S. Population Living in 100-Year Coastal Flood Hazard Areas

Abstract: CROWELL, M.; COULTON, K.; JOHNSON, C.; WESTCOTT, J.; BELLOMO, D.; EDELMAN, S., and HIRSCH, E., 2010. An estimate of the U.S. population living in 100-year coastal flood hazard areas. Journal of Coastal Research, 26(2), 201– 211. West Palm Beach (Florida), ISSN 0749-0208. The Federal Emergency Management Agency (FEMA) recently completed a coastal demographics study of the United States and U.S. territories. As part of this study, FEMA estimated the United States population subject to the 1% annual chance (100 y) coastal flood hazard as mapped by FEMA. This determination followed a three-step process: (1) create a national digital flood hazard database by compiling the best available coastal-proximate, digital flood-hazard-area data using FEMA data sets; (2) develop a systematic method to separate coastal and riverine flood hazard areas and incorporate this boundary into the digital flood hazard database; and (3) combine the year 2000 census data with the digital flood hazard database using a geographic information system. This enabled estimates of the U.S. population subject to the 1% annual chance coastal flood. The analysis was conducted at the census block-group level, with census block-group populations (permanent residents) assumed to be uniformly distributed across each block group. The results demonstrate that approximately 3.0% of the U.S. population lives in areas subject to the 1% annual chance coastal flood hazard. It must be emphasized, however, that these numbers are based on the 1% annual chance (100 y) coastal flood. Historical coastal floods less frequent than the 1% chance annual flood have occurred in the U.S. on numerous occasions. If less-frequent coastal flood events were considered in this study, such as the 0.2% annual chance (500 y) coastal flood or, if seasonal (vacations) population were considered, then a much greater percentage of the U.S. population would be determined as subject to coastal flooding.

A Review of Sediment Budget Imbalances along Fire Island, New York: Can Nearshore Geologic Framework and Patterns of Shoreline Change Explain the Deficit?

Abstract: Sediment budget analyses conducted for annual to decadal timescales report variable magnitudes of littoral transport along the south shore of Long Island, New York. It is well documented that the primary transport component is directed alongshore from east to west, but relatively little information has been reported concerning the directions or magnitudes of cross-shore components. Our review of budget calculations for the Fire Island coastal compartment (between Moriches and Fire Island Inlets) indicates an average deficit of 217,700 m3/y. Updrift shoreline erosion, redistribution of nourishment fills, and reworking of inner-shelf deposits have been proposed as the potential sources of additional sediment needed to rectify budget residuals. Each of these sources is probably relevant over various spatial and temporal scales, but previous studies of sediment texture and provenance, inner-shelf geologic mapping, and beach profile comparison indicate that reworking of inner-shelf deposits is the sou...

Importance of Coastal Change Variables in Determining Vulnerability to Sea- and Lake-Level Change

Abstract: In 2001, the U.S. Geological Survey began conducting scientific assessments of coastal vulnerability to potential future sea- and lake-level changes in 22 National Park Service sea- and lakeshore units. Coastal park units chosen for the assessment included a variety of geological and physical settings along the U.S. Atlantic, Pacific, Gulf of Mexico, Gulf of Alaska, Caribbean, and Great Lakes shorelines. This research is motivated by the need to understand and anticipate coastal changes caused by accelerating sea-level rise, as well as lake-level changes caused by climate change, over the next century. The goal of these assessments is to provide information that can be used to make long-term (decade to century) management decisions. Here we analyze the results of coastal vulnerability assessments for several coastal national park units. Index-based assessments quantify the likelihood that physical changes may occur based on analysis of the following variables: tidal range, ice cover, wave height,...

Recent Subsidence-Rate Reductions in the Mississippi Delta and Their Geological Implications

Abstract: The Mississippi Delta has long been characterized as an area of rapid subsidence; however, recent subsidence rates are substantially lower than previously reported. Tide-gauge records indicate that rates of relative sea-level rise were slow from 1947 until the mid-1960s, relatively fast from the mid-1960s until the early 1990s, and then slow since the early 1990s. These trends and rates are independently verified by repeat benchmark surveys and height monitoring at continuously operating geographic positioning system stations. Subsidence rates for the slow periods were a few millimeters per year, comparable to rates averaged over geological time scales that are attributed to natural processes such as shallow sediment compaction and deep crustal loading. The decadal pattern of slow, then rapid, then slow subsidence may be caused by natural deep-basin processes (e.g., gravity gliding and salt migration), but it is more likely related to rates of hydrocarbon production that followed the same tempora...

Barrier Islands: Coupling Anthropogenic Stability with Ecological Sustainability

Abstract: Barrier islands provide a host of critical ecosystem services to heavily populated coastal regions of the world, yet they are quite vulnerable to ongoing sea level rise and a potential increase in the frequency and intensity of oceanic storms. These islands are being degraded at an alarming rate, in part because of anthropogenic attempts at stabilization. In this article, we outline a possible sustainability strategy that incorporates the natural degree of substrate instability on these sedimentary landscapes. We recommend placing the focus for managing barrier islands on maintaining ecosystem function and process development rather than emphasizing barrier islands as structural impediments to wave and storm energy.

Relative Importance of Vessel-Generated and Wind Waves to Salt Marsh Erosion in a Restricted Fetch Environment

Abstract: HOUSER, C., 2010. Relative importance of vessel-generated and wind waves to salt marsh erosion in a restricted fetch environment. Journal of Coastal Research, 26(2), 230–240. West Palm Beach (Florida), ISSN 0749-0208. Erosion of a salt marsh at Fort Pulaski National Monument threatens a pier of historical significance along the North Channel of the Savannah River, the main shipping channel for the Port of Savannah, Georgia. The erosion was initiated by the alongshore and onshore migration of a supratidal oyster shell ridge that exposed a marsh scarp that is susceptible to lateral retreat in response to both wind-generated and vessel-generated waves undercutting the upper-marsh surface. An instrumented field study was completed between October 2007 and February 2008 to examine the relative importance of wind-generated and vessel-generated waves to the retreat of the scarp by 0.21 m along the instrumented transect. On average, there were 14 sailings by container ships per day and up to twice as many sailings by pilot boats ferrying the harbor pilots to container ships offshore, but only those vessels that sailed within 1 m of the high-tide water level had waves capable of reaching the scarp. The vessel-generated waves accounted for 5% of the cumulative wave energy over the study, but because of their larger height and longer period, they accounted for almost 25% of the cumulative wave force. It is the locally generated wind waves that account for most of the wave force acting on the exposed scarp and which are largely responsible for the observed retreat. Waves generated during both frontal and tropical storms tend to be associated with storm tides that maintain water levels at or near the elevation of the scarp for several days. Now that the shell ridge has largely migrated past the site and the areas of greater retreat historically are protected by a wedge of sand, it is argued that an increase in vessel traffic and/or the use of larger, post-Panamax ships will not significantly accelerate the retreat of the marsh.

Sediment Transport around Australia—Sources, Mechanisms, Rates, and Barrier Forms

Abstract: The Australian coast can be subdivided into three broad sedimentary provinces occupying the east, south, west, and northwest coasts. The 11,978-km long eastern province extends from the western Gulf of Carpentaria along the entire east coast to eastern Tasmania. It is characterized by tropical to temperate humid climates, quartz sediments, and overall northerly sediment transport, with significant onshore transport where shoreline orientation and wave and wind energy combine to produce massive coastal dune systems, including the world's largest sand islands. The 9587-km long south and west coast province has an arid to semiarid climate with little terrigenous sediment. Much of the coast faces into the prevailing southerly winds and the high year-round Southern Ocean swell, resulting in massive transfer of shelf and nearshore carbonate-rich sediments to the shore and into extensive coastal barrier-dunes systems, the largest dunes extending 110 km inland. The 9106-km long northwest province has a t...

Expansion Dynamics of Monospecific, Temperate Mangroves and Sedimentation in Two Embayments of a Barrier-Enclosed Lagoon, Tauranga Harbour, New Zealand

Abstract: In recent years, mangrove expansion has become a coastal management issue in the North Island of New Zealand. Little is known about the spatial evolution and forest structure of temperate mangrove forests in New Zealand or about the associated rates of sedimentation. The extent of mangrove colonization in both a large (Waikareao Estuary) and small (Welcome Bay) embayment within Tauranga Harbour were documented. Forest structure and growth rates were described using tree height, stem density, pneumatophore density, and seedling establishment. Surface elevation changes within mangrove habitat were determined from erosion pin measurements and, on bare intertidal flats, using buried baseplates. Sediment texture and availability was also assessed using sediment traps. Results show that in 1943, mangrove vegetation covered <1% of either embayment, with ongoing expansion resulting in mangrove habitat occupying 9% of Welcome Bay and 6% of Waikareao Estuary in 2003. Mean plant heights were all <1.5 m, wit...

Marine Debris in the Island of Santa Catarina, South Brazil: Spatial Patterns, Composition, and Biological Aspects

Abstract: The prevalence of marine debris is a worldwide issue, especially in coastal areas. Half of the Brazilian population live within 200 km of the coast and generate large amounts of garbage, which is not always sent to an appropriate destination. This study aims to assess patterns of spatial variability and composition of marine debris in the beaches of Florianopolis, an important tourist destination in Brazil. Biological aspects were also assessed. Five beaches were sampled twice, and abundances of litter ranging from 12.8 to 498 items/100 m2 were found, depending on location and time of sampling. Plastic items accounted for almost 90% of the material collected. Only 5% of the items collected showed biological encrustations, suggesting that most items had a local origin. A weak negative correlation was found between the number of items and the number of ghost crab (Ocypode quadrata) open burrows. These results can be used for management purposes and to make comparisons with other coastal cities.

Inferring Complex Hydrographic Processes Using Remote-Sensed Images: Turbulent Fluxes in the Patagonian Gulfs and Implications for Scallop Metapopulation Dynamics

Abstract: San Jose Gulf is a small semienclosed bay connected by a narrow mouth to a much larger basin, the San Matias Gulf. Intriguingly, this comparatively small water body, characterized by high biological productivity, has contributed most of the historical shellfish production in the region. A remote sensing approach allowed us to advance a composite conjecture aimed at explaining that phenomenon. A combination of circulation, strong tidal currents, and coastal topography leads to the formation of a frontal system inside San Jose Gulf and to the development of turbulent fluxes that drive the hydrographic regime. The front divides the San Jose Gulf in two domains (west and east). The origin of water flowing into the west domain was tracked to the Valdes Frontal System, on the continental shelf. The west domain is highly turbulent due to the formation of vortexes and dipoles during the tidal cycle. Detachable dipoles formed at the edge of jets outflowing from San Jose Gulf can reach the central part of ...

Analyzing Estuarine Shoreline Change: A Case Study of Cedar Island, North Carolina

Abstract: Continued climate change, sea-level rise, and coastal development have lead to concern about shoreline dynamics beyond oceanfront areas, encompassing more sheltered coastal water bodies such as estuaries Because estuaries are critically important ecosystems, understanding coastline changes in these areas is necessary to evaluating resource risks A transect-based approach is commonly used to quantify shoreline change on linear (ie, ocean) shorelines; however, due to the complex morphology of the study area, a point-based approach was developed and applied in this study Shoreline-change rates and additional parameters (ie, wave energy and shoreline composition) were determined using 1958 and 1998 aerial photography and available datasets From this data, the average shoreline change in the study area is −024 m yr−1, with 88% of the shoreline eroding Of the parameters analyzed, shoreline composition appears to have an important control on shoreline erosion, whereas wave energy is not signif

Effect of Hurricane Ivan on Coastal Dunes of Santa Rosa Barrier Island, Florida: Characterized on the Basis of Pre- and Poststorm LIDAR Surveys

Abstract: Santa Rosa Island, situated along the northwestern Florida coast facing the Gulf of Mexico, is an 85-km-long wave-dominated low-lying barrier island with well-developed incipient and established dunes. In this paper, we examine the regional-scale effect on coastal dunes by a strong category 3 hurricane, Ivan, through comparison of pre- and poststorm airborne LIDAR (light detecting and ranging) surveys. On the basis of pre-Ivan LIDAR survey data, the elevation of the berm and back beach is typically 2.0 m above MSL (mean sea level). Incipient dunes range from 2.5 to 10 m above MSL, or 0.5 to 8.0 m above the surrounding beach. The hummocky dunes that developed over relic washover platforms are typically less than 4.0 m above MSL. The densely vegetated, established dune fields are composed of dunes less than 7.0 m high and intradune wetlands lying at less than 1.0 m above MSL. The entire island was severely affected by Ivan, which made landfall about 45 km to the west in September 2004. The landscap...

Numerical Modeling of Suspended Sediment Transport Affected by Tidal Bore in Qiantang Estuary

Abstract: PAN, C. and HUANG, W., 2010. Numerical modeling of suspended sediment transport in Qiantang River: an estuary affected by tidal bore. Journal of Coastal Research, 26(6), 1123–1132. West Palm Beach (Florida), ISSN 0749-0208. Study of suspended sediment transport in an estuary affected by tidal bore is important for coastal engineering and management because the tidal bore can cause strong sediment resuspension and scour in shallow waters. Numerical modeling of suspended sediment transport in a natural estuary affected by tidal bore is such a challenging research topic that there are few articles on the subject available in the literature. In this study, a two-dimensional, numerical model was developed to investigate suspended sediment transport induced by a tidal bore. The hydrodynamic component of the model employs the Godunov-type scheme with second-order accuracy in space, which effectively describes the rapid supercritical flow and sharp horizontal pressure gradients of the tidal bore. To preserve balance between the source terms and the internal forces, both the water level–bottom topography formulation (WLTF) method and a special technique for triangular mesh have been applied to solve the source term in the model equations to account for the irregular bottom topography. The wet/dry boundary issue was solved by using the improved exact-Riemann solver on the dry bed. The coupled sediment transport model incorporates more reliable equations from recent publications to characterize the rapid increase of sediment resuspension in the water column. The model test against an analytical solution of convection transport shows that the sharp gradient of scalar transport is satisfactorily estimated in the model simulations. The model in the application has been validated to simulate hydrodynamics and suspended sediment transport affected by a tidal bore in the Qiantang River of China. The results compare well with a time series of observations to characterize the rapid increases of surface elevation, currents, and suspended sediment concentration resulting from the tidal bore. Results of spatial distributions of water levels and currents indicate that the model adequately describes the sharp horizontal gradients of the surface elevation and the tidal currents during the passage of the tidal bore and characterizes the suspended concentrations in the estuary.

Salt Marsh Geomorphological Analyses via Integration of Multitemporal Multispectral Remote Sensing with LIDAR and GIS

Abstract: Ecogeomorphological modeling in salt marshes faces distinct challenges due to tidal oscillation and variability, fieldwork logistics, and the inherent dynamic nature of these environments. Recently developed technologies and methods introduce the capability to create fine-scale, system-wide databases to quantitatively characterize salt marsh geomorphology in support of improved understanding of the evolution of intertidal systems. This study combines the use of 20-cm AIMS-1 multispectral imagery flown at spring high and low tides with a LIDAR–derived digital elevation mode (DEM) of a New England estuarine system to quantify relationships among marsh features, their metrics, elevations, and tidal datums. The methods used to quantify features across an intertidal watershed in its entirety represent a significant advance in support of future development of process-driven models to explain these observations. Geomorphological analyses of the distribution of marsh features at the Great Marsh, Massachu...

Wave Overtopping of Levees and Overwash of Dunes

Abstract: Earthen levees are designed for little wave overtopping during a design storm, but excessive overtopping and overflow can occur due to the combined effects of an extreme storm, sea level rise, and land subsidence. The transition from little wave overtopping to excessive wave overtopping and overflow on an impermeable smooth levee is examined in wave-flume experiments consisting of 107 tests. Existing empirical formulas are shown to be applicable to the cases of excessive wave overtopping and overflow in these tests. A numerical model based on time-averaged continuity, momentum, and wave action equations is connected to a new probabilistic model for the wet-and-dry zone, in order to predict the cross-shore variations of the mean and standard deviation of the free surface elevation and depth-averaged fluid velocity from outside the surf zone to the inner slope of the levee. The new model is calibrated to predict the measured overtopping and overflow rates within a factor of about two. The agreement...

Probing the Origins and Stratigraphic Signature of Salt Pools from North-Temperate Marshes in Maine, U.S.A

Abstract: Salt pools (shallow, water-filled depressions) are common landforms in north-temperate salt marshes. Despite their widespread distribution, the origin of pools as primary or secondary features of salt marshes remains uncertain and their description in the geologic record unclear. This study combines analyses of modern sediments and cores to determine pool origin and describe pool deposits. We collected samples from tidal-flat, tidal-creek, salt-pool, low-marsh, and high-marsh environments and 23 Dutch cores through extant and paleopools from salt marshes in Ogunquit, Wells, Brunswick, Gouldsboro, Addison, and Lubec, Maine. Salt-pool sediment is a dark gray, high-water-content mud with intermediate total organic carbon values (2.21–9.08) and typically lower carbon-to-nitrogen ratios than low- and high-marsh sediments. Pool sediment contains a suite of biological macrofossils; most common are drupes of the submerged aquatic plant Ruppia maritima and the gastropod Hydrobia totteni. Microfossil analy...

The Intermittently Exposed, Coarse-Grained Gravel Beaches of Prince William Sound, Alaska: Comparison with Open-Ocean Gravel Beaches

Abstract: Long-term studies (1989–2007) of the gravel beaches in Prince William Sound, Alaska, conducted as part of the Exxon Valdez oil spill monitoring programs, provide the basis for understanding the geomorphology and sediment dynamics of these intermittently exposed, coarse-grained gravel beaches. There are key differences between these beaches and open-ocean gravel beaches, including bermlike ridges that occur at different levels on the beach as a result of the diurnal inequality of the tides. The 1964 earthquake, with up to 3.5 m of uplift, provided information on sediment transport patterns and rates. In less than 25 years, a stable cobble/boulder armor formed on the upper and lower platforms, and the beaches reached a steady-state or graded condition. Eighteen years after the spill, oiled sediments were still present at depths greater than about 25 cm on beaches with a stable armor in the middle and lower intertidal zones. Cleanup efforts to remove the deep oil penetration into the porous gravel o...

Coastal Vulnerability to Oil Spill Pollution: the Case of Noirmoutier Island (France)

Abstract: Over the last 30 years, oil spills have contributed significantly to coastal and marine pollution, causing disturbance of the coastal environment. This recurrent hazard has increasingly been taken into account through prevention plans in Coastal Zones Integrated Management. Numerous studies have attempted to analyse the effects of oil pollution, in particular to identify those areas that are the most vulnerable. Although several studies have considered both environmental and socioeconomic issues, most of them have focused only on environmental vulnerability. The aim of our research is to formalise an alternative approach to map global vulnerability, using both environmental and socioeconomic factors. This article describes and discusses the methodology used to identify the critical variables required to assess coastal vulnerability to oil spills. The first part introduces previous research and identifies the parameters that have been used to map this type of vulnerability. The study area is presented in the second part of the paper. The third part presents the method we used to compute a spatialised vulnerability index that is based on a multicriteria analysis including both environmental and socioeconomic parameters. The final part of this paper describes and discusses the results of the implementation of this method on Noirmoutier Island located off the west coast of France. The resulting synthetic mapping for risk monitoring, carried out using a geographical information system, seems to be a relevant and useful complementary tool to improve the management of oil spill crises.

Investigation of Beachrock Using Microanalyses and OSL Dating: A Case Study from Bozcaada Island, Turkey

Abstract: We investigated the origin and absolute age of beachrock samples on Bozcaada Island, located on the northern Aegean Sea coast of Turkey, using energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) analyses and optically stimulated luminescence (OSL) dating. Various types of cements were identified, such as micritic, meniscus, and biologic cements, revealing that the beachrock could have occurred as a result of the combined effects of marine-phreatic and supratidal cementation conditions. Optical dating results showed that the formation of beachrock ranged in age from 5.41 ± 0.58 ka BP to 0.33 ± 0.05 ka BP. However, much of the beachrock body (about 3 m in thickness) is drowned or submerged today, suggesting that submerged beachrocks extending to −5 m date to earlier times than the start of the cementation period discussed herein.

Capturing Coastal Geomorphological Change within Regional Integrated Assessment: An Outcome-Driven Fuzzy Logic Approach

Abstract: Climate change will have pervasive effects on the world's coasts, but at broad scales these changes have typically proven difficult to analyse in a systematic manner. This paper explores an outcome-driven deductive methodology for geomorphological analysis that recognises the nonlinearity of coastal morphology and organises current knowledge and understanding using fuzzy logic concepts. Building on recent large-scale coastal investigations and with reference to a case study of the East Anglian coast, U.K., the methodology defines the active coastal system using a flexible generic classification and integrates expert opinion, using the notion of possibility, as a basis for the assessment of potential future geomorphological response to changes in sea level and sediment supply. Preliminary results for the East Anglian coast suggest that the constraining of the active coastal system by sea defences is already having, and will continue to be, a significant influence on coastal evolution irrespective ...

Transgressive Ravinement versus Depth of Closure: A Geological Perspective from the Upper Texas Coast

Abstract: The upper Texas coast is one of the most populated areas along the Gulf of Mexico. Three dynamic barriers along this section of coastline (Bolivar Peninsula, Galveston Island, and Follets Island) have a well-documented history of shoreline change. Numerous engineering studies incorporating both sedimentological data and numerical models have been established for this system to understand sediment fluxes. However, rarely have previous studies examined sediment fluxes for the upper Texas coast in light of certain fundamental concepts of coastal geology. Here, we discuss the current theory and understanding of barrier island dynamics from a geologic standpoint as they relate to sediment budgets for the upper Texas coast. From sediment cores, we quantify both shoreface and washover sand fluxes, which previously were not incorporated as sand sinks into sediment budgets for this system. Shoreface sand fluxes represent a sizable portion of the total budget, whereas modern washover sand fluxes are minima...

Spatial Trends in Tidal Flat Shape and Associated Environmental Parameters in South San Francisco Bay

Abstract: Spatial trends in the shape of profiles of South San Francisco Bay (SSFB) tidal flats are examined using bathymetric and lidar data collected in 2004 and 2005. Eigenfunction analysis reveals a dominant mode of morphologic variability related to the degree of convexity or concavity in the cross-shore profile—indicative of (i) depositional, tidally dominant or (ii) erosional, wave impacted conditions. Two contrasting areas of characteristic shape—north or south of a constriction in estuary width located near the Dumbarton Bridge—are recognized. This pattern of increasing or decreasing convexity in the inner or outer estuary is correlated to spatial variability in external and internal environmental parameters, and observational results are found to be largely consistent with theoretical expectations. Tidal flat convexity in SSFB is observed to increase (in decreasing order of significance) in response to increased deposition, increased tidal range, decreased fetch length, decreased sediment grain s...

New approaches to sediment management on the inner continental shelf offshore Coastal Louisiana

Abstract: Coastal restoration in Louisiana requires clean sands for beach and dune restoration, whereas mixed sediments are required to rebuild marshes. The Louisiana coastal erosion problem is especially dire because it occurs on several fronts with the narrowing and overtopping of barrier islands and loss of back barrier bay and interior marshlands. Coastal restoration efforts in Louisiana depend on emplacement of sediment to build up barrier island and deltaic systems. Discovery of usable sediment is thus a vital factor in restoration efforts because up to 80% of some restoration project budgets can be allocated to exploration, exploitation, and emplacement of sediment. Because this cost is directly proportional to the distance of borrow sources from the project area, the cost-effectiveness of barrier island restoration and marsh creation depends on locating sufficient sediment volumes that are suitable for placement on beaches and dunes and for creating marshes. The restoration of Louisiana's barrier i...

Patterns of Sediment Transport Pathways on a Headland Bay Beach—Nanwan Beach, South China: A Case Study

Abstract: Embayed beaches bounded by headlands, headland bay beaches, are a common feature along the coast of southern China. The patterns of sediment transport pathways in these beaches are important for understanding changes in beach and nearshore geomorphology that are a response to different wave energy conditions. Nanwan Beach in southern China is characterized by a large seasonal variation of incident waves. In this study, sediment samples and a series of beach profiles from Nanwan Beach are examined to determine spatial changes in sediment transport pathways. Empirical orthogonal function analysis of the profile data indicates that the variation of sediment transport occurs in two distinct modes. The first mode is related to seasonal changes in cross-shore sediment transport with associated alongshore sediment transport. The trend of sediment transport is seaward in winter and landward in summer. The second mode is onshore-offshore sediment exchange, which occurs in the intertidal zone in summer and...

Predictions of Turbidity Due to Enhanced Sediment Resuspension Resulting from Sea-Level Rise on a Fringing Coral Reef: Evidence from Molokai, Hawaii

Abstract: Accelerating sea-level rise associated with global climate change will affect sedimentary processes on coral reefs and other shoreline environments by increasing energy and sediment resuspension. On reefs, sedimentation is known to increase coral stress and bleaching as particles that settle on coral surfaces interfere with photosynthesis and feeding, and turbidity induced by suspended sediment reduces incident light levels. Using relationships developed from observations of wave orbital velocity, water-surface elevation, and suspended-sediment concentration on a fringing reef flat of Molokai, Hawaii, predictions of the average daily maximum in suspended-sediment concentration increase from ~11 mg/l to ~20 mg/l with 20 cm sea-level rise. The duration of time concentrations exceeds 10 mg/l increases from 9% to 37%. An evaluation of the reduction of wave energy flux through breaking and frictional dissipation across the reef flat shows an increase of ~80% relative to the present will potentially re...

Shoreline Evolution and Management of Hawke's Bay, New Zealand: Tectonics, Coastal Processes, and Human Impacts

Abstract: The evolution of the coast of Hawke's Bay, New Zealand, and its erosion problems have been governed by multiple factors, including its tectonic setting with an earthquake in 1931 that altered land elevations along its shore, ranging from a 2-m uplift at its north end to 1-m subsidence at its south. Human environmental impacts have also been important, including the deforestation of the watersheds of rivers and the mining of gravel and sand from their channels, having decreased the sediment supplies to the beaches. Significant erosion has occurred at the south end of the Hawke's Bay shore, attributed in part to its subsidence in 1931, together with the net northward longshore transport of the beach sediment that is greater than the volumes being supplied by the rivers, the beach-sediment budget being significantly “in the red.” Midway along the Bay's shore, the construction of the Port of Napier's breakwater in 1887–90, extending seaward from the Buff Hill headland within that city, is interpreted...