Beach Characteristics Research Articles

Nest-Site Selection by the Loggerhead Sea Turtle in Florida's Ten Thousand Islands

Loggerhead sea turtles (Caretta caretta) nest in numerous substrate and beach types within the Ten Thousand Islands (TTI) of southwest Florida. Nest-site selection was analyzed on 12 islands within this archipelago. Physical characteristics of beaches were recorded to identify the relatedness of these var- iables and to determine their importance for nest-site selection in C. caretta. These characteristics included ordinal aspect, beach length, height of canopy, beach width, overall slope (beach slope and slope of offshore approach), and sand samples analyzed for pH, water content, organic content, shelliness (% of calcium car- bonate content), and particle size (8 size classes). All physical variables, as well as nesting densities and locations, were included in a tree regression model to examine nest-site selection. In the TTI, loggerheads use wide beaches (>8.5 m) that inherently have less slope and, secondarily, wide beaches that have less shells (low amounts of calcium carbonate; >8.5 m) in the nesting substrate. In addition, C. caretta nest sites were located within or in close proximity to the supra-littoral vegetation zone of beaches in the TTI.

The Lake Lahontan highstand: age, surficial characteristics, soil development, and regional shoreline correlation

The Lake Lahontan basin has been the site of numerous pluvial lakes during the Pleistocene. We address the question of whether or not the highest remnant shoreline features around the perimeter of the lake were produced during the most recent Sehoo highstand (∼13 ka), the penultimate Eetza highstand (∼140–280 ka), or both. To do so, we document surficial characteristics, morphologic preservation, and soil development on multiple Sehoo beach barriers in the Jessup embayment to define the range in characteristics displayed by latest Pleistocene beach features. Sehoo barriers generally exhibit original constructional morphology that has been little modified by erosion. Soils developed on Sehoo barriers are generally thin and weakly developed and are strongly influenced by the introduction of eolian fines into the predominately clast-supported coarse beach gravels. Similar observations from 13 other highstand barriers and from seven older-than-latest Pleistocene paleosols located around the basin form the basis for a regional comparison. Based on similar characteristics, including the degree of morphologic preservation and weak soil development, we conclude that the widespread and nearly continuous high shoreline around the perimeter of Lake Lahontan dates from the most recent major lake cycle in all areas except in the Walker Lake subbasin. In the Walker Lake subbasin, isolated early to middle Pleistocene lacustrine outcrops and landforms are elevated as much as 70 m above the late Pleistocene limit, but are differentiated by their degraded form and lack of continuity around the subbasin. Similar unambiguous landforms were not observed elsewhere and at similar elevations in the northern subbasins of Lake Lahontan.

Laboratory Study of Beach Nourishment Behavior

A study of beach nourishment viability was performed to determine the relationship between selected wave and beach characteristics and project performance. Laboratory tests of idealized beach nourishment projects were conducted, with emphasis on project planform changes that arise due to gradients in longshore sediment transport. Nine test cases were designed with monochromatic, nominally shore-normal waves. The idealized beach nourishment projects were compared with trends predicted by simple analytical and numerical shoreline evolution models. Mathematical and laboratory results are in general agreement regarding beachfill behavior at laboratory scale. The rate of evolution, however, is overpredicted for the model nourishment projects when standard calibration factors are applied. This is expected, based on numerous previous laboratory studies of longshore sediment transport. The effects of breaking wave height, wave period, beach slope, beachfill length, and initial planform on the rate at which sediment diffuses from a beach nourishment project are evaluated based on laboratory results. In summary, beachfill longevity was found to be positively correlated with project length and wave period, and negatively correlated with breaking wave height and beach slope. One test suggests that projects with a trapezoidal planform retain sediment better than equivalent rectangular projects.

Effects of a high rise building on wind flow and beach characteristics at Atlantic City, NJ, USA

This study assesses the effects of a high rise building on the beach and dune at an intensively developed shoreline through field investigation of geomorphological and sedimentological characteristics and wind tunnel investigation of wind speed and direction. Results indicate that wind speed is increased close to the building, where wind is often deflected to a more onshore direction. Obliquely offshore northwesterly winds are the most dramatically altered and cause onshore flows (with pronounced upward flows) in the landward portion of the beach near the building. Onshore deflections in wind direction cause besanding of the boardwalk and create highly localized scour and deposition zones. A dune on the backbeach breaks up zones of sediment transport and scour and diminishes the likelihood that scour areas will cause increased hazard to landward buildings as a result of flooding. Generic large-scale studies are required to develop criteria for communities to use to specify optimum dimensions, locations and shapes of landforms that are modified or created by high rise structures.

Beach characteristics and Sand fill movement of the Kashiwazaki beach

Beach characteristics and Sand fill movement of the Kashiwazaki beach were investigated by using aerial photographs, topographic chart and beach profile chart as well as field observation of the coastline. We proposed the best beach conservation plan for the beach face front of the step-type revetment at the joint of groin A.

Field observation of coastline in Kagawa and Tokushima Prefectures

Field observation of coastline in Kagawa and Tokushima Prefectures was carried out to investigate natural characteristics of river mouth bar, gravel beach and sand spit. Topographic features of river mouth bar formed by successive action of longshore sand transport were studied at the Yoda and Minato rivers. Beach erosion triggered by wave reflection due to the construction of the breakwater of Komatsujima Port was found at the Katsu-ura river mouth.

Seashore Walk Commemorating National Holiday of ‘Sea Day’ and its Perspective

Seashore walk commemorating the national holiday of ‘Sea Day’ was carried out on July 20, 1996 at the Hayama coast in Kanagawa Prefecture. Around 60 participants walked along the shoreline while hearing explanation of physical features of sandy beaches and eroding sea cliff. This paper summarizes these activities and the results of additional field observation conducted on late August in 1996 after the event. Also aerial photograph showing the site is investigated to realize natural condition of the beach. Future perspective of this activity is also discussed.

Edge wave trapping and amplification on barred beaches

Theoretical predictions show that edge waves may be trapped on bars, providing a possible mechanism for bar growth. Simple solutions to the linear shallow water equations reveal that bar trapping is controlled by the depth of the water over the bar hbar and the geometry of the inshore trough relative to the bar. For specific geometries, amplification over the bar approaches an order of magnitude or more as the phase speed approaches , where amplification is defined as the surface displacement over the bar relative to the surface displacement at the shoreline. The amplification increases with the cross‐shore length scales of the profiles. The amplification is somewhat frequency dependent, generating stronger currents at the location of the bar in specific frequency ranges. Previous work showed that particular edge wave modes have the correct length scales to generate beach features such as bars and beach cusps, but field observations, notably shoreline run‐up data, frequently show no evidence of edge wave energy being concentrated at the appropriate frequencies. However, for bar‐trapped modes, edge wave energy is concentrated at the location of the bar; therefore this edge wave energy will not necessarily be evident in shoreline measurements. Strong correlation exists between the energy distribution of the longshore component of the orbital velocity observed in data collected at Superduck, October 11, 1986, and the distribution expected for a white edge wave spectrum at the shoreline. This suggests that bar‐trapped edge waves exist, in particular, at incident wave frequencies.

Parametrization of orbital velocity asymmetries of shoaling and breaking waves using bispectral analysis

A bispectral analysis of electromagnetic flow meter data collected from four nearshore environments was undertaken to investigate the spatial variation of velocity skewness and asymmetry for shoaling and breaking surface gravity waves. The data base provides a wide range of wave conditions and beach characteristics (including planar and barred beaches). A simple parametrization for bispectral evolution (amplitude and phase) due to wave shoaling, which is based on the Ursell parameter, is proposed and tested. The results show that the parametrization provides both a good qualitative and reasonably quantitative prediction of velocity skewness and asymmetry arising from phase-coupling between wind-wave frequencies. Infragravity wave velocity skewness and asymmetry are also examined.

Effects of Beach Nourishment on Sea Turtles: Review and Research Initiatives

AbstractBeach nourishment is an engineering solution to erosion of beaches. As in any restoration project, the goals of beach nourishment are the restoration of habitat to promote survival of plants and animals and to maintain aesthetically pleasing sites for humans. Unfortunately, beach nourishment sometimes alters parameters of the natural beach, decreasing the reproductive success of sea turtles. Engineers have recognized this problem and are working to improve nourishment practices. Biologists must specify problems incurred by sea turtles as a result of beach nourishment so that they may be addressed. A review of the literature on sea turtles and beach nourishment found certain problems repeatedly identified. For nesting females, characteristics induced by nourishment can cause (1) beach compaction, which can decrease nesting success, alter nest‐chamber geometry, and alter nest concealment, and (2) escarpments, which can block turtles from reaching nesting areas. For eggs and hatchlings, nourishment can decrease survivorship and affect development by altering beach characteristics such as sand compaction, gaseous environment, hydric environment, contaminant levels, nutrient availability, and thermal environment. Also, nests can be covered with excess sand if nourishment is implemented in areas with incubating eggs. The extent and implication of each problem are discussed, and future research initiatives are proposed.

BEACH RESTORATION PROCEDURES

ABSTRACT A variety of procedures have been applied to the restoration of sandy beaches impacted by oil spills. These procedures have met with varying degrees of success, depending on factors including the nature of the oil, beach characteristics, and environmental conditions. Based on the assumption that no universal procedure exists for beach restoration, determination of appropriate procedures requires evaluation of incident-specific conditions. A series of decision guides has been developed to assist in this process. These decision guides, suitable for development of spill contingency response plans and during actual emergency responses, have been developed to aid in the selection of the most appropriate techniques.

Site selection by migratory shorebirds in Delaware Bay, and its relationship to beach characteristics and abundance of horseshoe crab (Limulus polyphemus) eggs

-The distribution of migratory shorebirds within Delaware Bay, New Jersey, was examined relative to prey abundance and the physical characteristics of the intertidal beaches. Red Knots (Calidris canutus), Sanderlings (C. alba), Ruddy Turnstones (Arenaria interpres), and peeps comprised nearly 100% of the shorebirds on seven study beaches from mid-May to early June in both 1990 and 1991. The most abundant food item on these beaches was horseshoe crab (Limulus polyphemus) eggs, and there were few other available macroinvertebrates. Beaches preferred by shorebirds had higher numbers of crab eggs; the density of eggs in some surface (0-5 cm) sediments exceeded 1 05 / M2. In general, both horseshoe crab eggs and shorebirds increased along the bay shore from Higbee's Beach (near Cape May Point) to Moore's Beach, 32 km up-bay. However, shorebirds were widely distributed within the bay, possibly because eggs were sufficiently abundant on most beaches to support foraging by at least four birds per meter of shoreline. Shorebirds aggregated near shoreline discontinuities, such as salt-marsh creeks and jetties, that acted as concentrating mechanisms for passively drifting eggs. Sediment grain size and heterogeneity were probably not a primary determinant of shorebird distribution within Delaware Bay. Intertidal sand flats were not extensively used by foraging shorebirds, but the potential importance of nearby salt marshes as foraging sites requires further investigation. Received 20 January 1993, accepted 27 March

CHARACTERISTICS OF SHINGLE BEACHES WITH REFERENCE TO CHRISTCHURCH BAY, S. ENGLAND

The rapid recession of the shingle bank of Hurst Beach (up to 3.5m/yr) makes it an excellent natural laboratory for the study of the factors which influence the stability of shingle beaches. Studies have included: the significance of long period, high energy, swell waves - the classification and quantification of overwash processes - run-up and seepage characteristics - the effect of settlement of the underlying strata - and the implications for practices in shingle nourishment. The studies have revealed the distinctive character of shingle beaches as compared with the more fully researched sand beaches. More detailed research on shingle beaches is justified particularly in relation to (i) the run-up characteristics including its interaction with swash cusps and (ii) the influence of the subsidiary sand fraction on the beach characteristics.

Edge waves near a seawall

The edge-wave dispersion relation is found for the case where the beach and water are bounded by a vertical wall. The length of the edge waves which are resonant with incoming swell is shown to be very sensitive, at times, to the water depth at the wall. This sensitivity could have important implications for the stability of beach features thought to be associated with such waves.

Expert System for Computer Interpretation of Beach and Nearshore Facies: ABSTRACT

A user-friendly, rule-based expert system has been designed for interpretation of lithofacies characteristics of beach and nearshore depositional environments. Recently, similar expert systems have been widely applied in medicine, business, and mineral exploration. The expert system runs on a VAX 780 (trade name). By incorporating knowledge and understanding of an expert, the system can interact with a user the way an expert consultant would. Interaction consists of a series of questions about lithology, sedimentary structures, and bioturbation of the lithofacies observed in outcrop or core. Uncertain responses are allowed and incorporated into the reasoning. Dialogue varies in different consultations because questions asked by the system depend on users' responses to previous questions. The result is an evaluation of the likelihood that the deposit under consideration is actually a beach or nearshore deposit. Significant lithofacies characteristics, the reasoning used in reaching the conclusion, and pertinent references are provided. Expert systems for other depositional environments are being designed. As their availability increases, geologists without easy access to experts on a particular depositional environment will have expert consultants as close as a computer terminal. Also the ability of the system to explain its reasoning and provide references lends the system to instructional uses. End_of_Article - Last_Page 276------------

The Boulder Beach: A Fundamentally Distinct Sedimentary Assemblage

Abstract Five boulder beaches located along the coast of New South Wales, Australia, were examined in order to determine if beaches composed of boulders differ in basic sedimentological structure and behavior from beaches composed of cobbles or pebbles. Each beach is aligned obliquely to the approaching waves and is composed of locally derived sediment. Investigation of beach-particle size, morphology, and roundness, along with foreshore slope, reveals consistent up-beach particle fining, positive size skewness, absence of shape zoning, absence of sphericity grading, and low foreshore slope. These characteristics of the five studied boulder beaches contrast markedly with the known characteristics of beaches composed of finer sediment, which suggests that boulders appear to form fundamentally distinct coastal sedimentary assemblages.

Regional Variability of Beach and Foredune Characteristics Along the Texas Gulf Coast Barrier System

ABSTRACT A regional analysis of adjacent beach and foredune variability was conducted along the Texas barrier system. Evaluated parameters include beach morphology, dune internal structures, and comparative textural and heavy mineral characteristics. The most variable element of beach morphology is backshore width, which reflects both long-term erosional trends and local anthropogenic effects. Foredune-ridge height increases southward and is climatically controlled. Dune cross-bedding is highly variable in terms of both dip angles and azimuth distributions, indicating the presence of polygenetic cross-strata. The azimuth distributions are generally polymodal and do not demonstrate a direct relationship to prevailing wind direction. The azimuth distribution modes indicate the presence of both p ramidal dune structures generated by seasonal wind variations, and storm-related structures resulting from multiple episodes of ridge erosion and rebuilding phases. Regional constraints on foredune-ridge orientation imposed by the coastline have some polarizing influence on the cross-bedding azimuth distributions. Comparative textural characteristics of adjacent beach and foredune sediments show both local variations and regional trends. Beach textures are greatly influenced by shell admixtures and show relatively high local variability. In contrast, dune textures are not significantly influenced by shell admixtures and show a low degree of local variability, thus allowing the detection of regional trends. Foredune deposits show a northward reduction in grain size and improved sorting; these trends result mainly from a regional reduction in energy level and competency range of the eolian regime, but they also may be partly attributed to provenance. Comparative beach and foredune heavy mineral assemblages are variable in terms of total concentrations, grain morphology, and grain density. The foredunes generally contain higher total heavy mineral concentrations and higher proportions of dense opaque minerals than the beach population, whereas no apparent difference occurs in the proportion of elongate minerals. Beach and foredune heavy mineral assemblages show regional trends in total concentrations and opaque mineral content that correlate with similar trends on the adjacent continental shelf, indicating a constancy of provenance and regional dispersal patterns during the Holocene transgression.

A Prehistoric Source of the Nile

concerning the Nile valley has continued unabated up to the present, and the range of disciplines contributing to this knowledge has diversified. Geomorphological investigations of the evidence for environmental changes have often been made in association with archaeological work, for example, studies in Nubia by Butzer and Hansen (1968) and Wendorf and Schild (1976), and work in the Central Sudan and Blue Nile valley by Arkell and Ucko (1965), Adamson et al. (1974), and Williams and Clark (1976). Recent major works concerning the history of the Nile include those by Rzoska (1976) and Williams and Faure (1980). The basin of Lake Turkana, formerly Lake Rudolf, has been the scene of much archaeological and other scientific investigation in recent years. This is the result mainly of the discovery of early hominid remains in the lower Omo valley, particularly by French and American expeditions of the late 1960s, and discoveries on the east shore of the lake by Richard Leakey, the results of which are discussed by Coppens et al. (1976). As a result of their work, we have an unusually detailed record of environmental changes in the Turkana basin over the last two to three million years, especially for the northern and eastern margins of the lake. It is against this background of interest and research in the Turkana basin that the British Institute in Eastern Africa has been conducting archaeological exploration in the adjacent areas of the Southern Sudan since 1978. Early in 1980, as part of the commemoration of its 150th Anniversary, the Royal Geographical Society, jointly with the British Institute, sponsored an expedition to the area north-west of Lake Turkana. As members of this expedition, our project was to investigate evidence for changes in the level of Lake Turkana, which resulted from climatic changes, and to explore an ancient overflow channel which lies in the south-east corner of the Sudan. The results of our work are outlined here. Shortly before the expedition left for Africa, an important paper dealing with the history of Lake Turkana was published by Karl Butzer (1980), outlining fluctuations in the lake level during the Holocene. These fluctuations have been reconstructed on the basis of radiocarbon dates for raised beach features. There are 67 dates available for Turkana from sites in all parts of the basin. Figure 1 shows a lake level fluctuation curve based on radiocarbon and historical dates. Using 21 dates on shells from lacustrine deposits in the lower Omo valley, Butzer (1971) suggested that from its present level of

Sediment Transport Study Along a Delta Shoreline

A sediment transport study was conducted along the east shoreline of the Nisqually River Delta, Southern Puget Sound, Washington, to provide baseline data for an Environmental Impact Statement and preliminary design criteria for a forest products exporting wharf. The study was concerned with determining the characteristics of beach and deltaic sediments, the factors affecting sediment transport along the shoreline and on the delta, and the directions and rates of sediment transport. Sediment transport on the beach was determined by interpretation of beach profiles and sediment textural characteristics and by a beach grain tagging experiment. An estimate of sediment movement on the delta platform was obtained from sediment trap data and an historical chart comparison. The analysis suggested that waves were responsible for the small amount of sediment transported on the beach and that tidal currents were responsible for sediments transported over the Nisqually Delta platform. Sediment transport on the beach was relatively low and was in a northerly direction. Sediment transport rates on the delta platform were on the order of 4 t 10 m5 gm/cm-sec or less, with the transport in the direction of the tidal currents.

BARRIER BEACH FEATURES OF CALIFORNIA

Remarkable near-continuous examples of barrier beach features are found in many coastal areas, worldwide. The most notable North American examples are the margins of North America along the Atlantic and Gulf of Mexico, where barrier islands are found along more than 60 percent of the coastline. There are, in fact, 280 large-scale individual barrier features, 70 of which are highly developed and 100 more are being developed (Hobson, et al, 1980). These barriers have been built out of the enormous volumes of sediment available from the extensive watersheds of eastern and central North America and, through the ages, appear to have migrated long distances across a wide continental shelf in response to the interplay of waves and tidal currents, eustatic sea level fluctuations and sand supply. Barrier features are less in evidence on the west coast of North America though they are by no means absent. For example, along a 60-mile reach of the Oregon-Washington coast adjacent to the Columbia River mouth, impressive barrier spits have straightened the coast by blocking the bays and headlands. These are black-sand beaches, formed from the large sediment supply of the extensive inland basin of the Columbia (Bascom, 1980; Cooper, 1967), which has the 29thlargest discharge of the world's rivers (Inman and Nordstrom, 1971). The longest spit in this reach is about 19 miles long. The North Pacific coast is a high-energy wave environment, and these spits are continually shifting. Indeed, one of the most outstanding examples of continuing shore movement in North America is found at Cape Shoalwater at the north side of Willapa Bay, Washington where the inlet has migrated about 2.5 miles northward in the last 95 years across homesites, a cemetery and a lighthouse (Terich and Schwartz, 1981; US Corps of Engineers, 1971a).