Showing papers on "Shore published in 1977"

Beach processes and sedimentation.

Abstract: 1. An Introduction to the Study of Beaches. 2. The Geomorphology of Eroding and Accreting Coasts. 3. Beach Morphology and Sediments. 4. The Changing Level of the Sea. 5. The Generation of Waves and their Movement Across the Sea. 6. Wave Breaking and Surf-Zone Processes. 7. Beach Profiles and Cross-Shore Sediment Transport. 8. Wave-Generated Currents in the Nearshore. 9. The Longshore Transport of Sediments on Beaches. 10. Shoreline Planforms and Models to Simulate Their Evolution. 11. Nearshore Morphodynamics. 12. The Protection of Our Coasts. Index.

Ocean Surface Currents Mapped by Radar

Abstract: A high-frequency radar remote-sensing system for measuring and mapping near-surface ocean currents in coastal waters has been analyzed and described. A transportable prototype version of the system was designed, constructed, and tested. With two units operating tens of kilometers apart, the currents were mapped in near real time at a grid of points 3 by 3 km covering areas exceeding 2000 kM2, out to a distance of about 70 km from the shore. Preliminary estimates of the precision of current velocity measurements show it to be better than 30 cm/sec.

Rates and forms of erosion on intertidal platforms at Kaikoura Peninsula, South Island, New Zealand

Abstract: Shore platform development and processes are examined for Kaikoura Peninsula on the north-east coast of the South Island, New Zealand. The environment is exposed to high energy storm and swell waves, is mesotidal (mean range 1.36 m, maximum 2.57 m) and has a temperate climate with moderate rainfall (average 865 mm yr-1). Shore platforms range from 40 m to over 200 m wide and are cut in Tertiary mudstones and limestones. Most of the profiles display a prominent low water cliff, an outer rampart and channels developed along lines of structural weakness. The inner margins are extensively mantled in beach, hillslope, and lagoonal sediments which are being rapidly eroded except for three locations where there is an active marine cliff. Net tectonic uplift of the peninsula is thought to be of the order of 108 m during the Quaternary and 2 m during the last 1000 years. The shore platforms are thus clearly polycyclic and contain “inherited” morphological features but are being actively rejuvenated by rem...

Seasonal variation in temperature, salinity, and density over the continental shelf off Oregon1

Abstract: Seasonal variations in the hydrography of the waters over the continental shelf off Oregon were observed in a set of hydrographic data collected along 44”39’N at intervals of a few weeks to a few months from 1961 through 1970. The temperature is determined only partly by the local heating and cooling cycle: at -the surface it is low (9°C) in winter, increasing in spring, lowest in summer, highest in early fall, and decreasing in winter; near the bottom, it is highest in winter and lowest in summer. The summer minimum is associated with coastal upwelling and a strong southward geostrophic current. Variations in salinity are governed by runoff, both locally and through the Columbia River effluent, as well as by coastal upwelling and advection. Neither temperature nor salinity is negligible in determining sigma-t. In summer, sigma-t decreases with distance offshore, and isopycnals slope downward from shore; in winter, sigma-t increases with distance offshore, and isopycnals slope upward from shore. Steric sea level also slopes downward from the coast in winter, and upward in summer. Alongshore geostrophic flow is southward in summer and northward in winter. The variations in temperature, salinity, and sigma-t are caused by seasonal cycles in the surface heat balance, precipitation and runoff, the local wind, and the alongshore flow.

Climate, plant response and development of dunes on barrier beaches along the U.S. east coast

Abstract: In recent years, the U.S. National Park Service has taken responsibility for eight National Seashores along the East and Gulf Coasts and has been supporting research aimed at an understanding of natural processes, human effects, and management techniques that will accomplish various goals related to public use. The importance of developing management approaches, including dune stabilization, consistent with goals of individual Seashores and in keeping with natural dune dynamics, has become increasingly clear. Current studies underway deal with variations in dune ecology along the coast and in the response of dune species to environmental variables. While certain basic processes (such as dune building or migration, inlet formation, littoral transport, and overwash) occur all along the coast, they do not do so with the same importance or frequency. The relative significance of such processes depends on the general climatic and oceanic conditions of any given area. Prevailing winds, shoreline orientation, average wave energies, sea level change, storm frequency, off shore profiles, shore configuration, and tidal range are important environmental factors which determine the relative importance of dune building, overwash, or various combinations of the two. Added to the climatic factors are the response of dune strand species to environmental forces and the distribution of adapted species along the coast. The behavior of plants adapted to dune building, overwash, or both, can be a significant factor in the development of shoreline morphology.

History of heavy metal pollution in Southern California coastal zone - reprise

Abstract: The anthropogenic fluxes of lead, vanadium, and zinc to sediments of an outer basin off the coast of Southern California, 100 km from shore, are substantially less than those to deposits 30 km from shore. The values fall off as the square of the distance from shore. Atmospheric transport, as opposed to fluvial or sewer outfall inputs, appears to be in accord with these measurements. Anthropogenic Cr, Cu, Ag, and Cd are undetectable in the outer basin.

Geomorphic Cycles in Ebb Deltas and Related Patterns of Shore Erosion and Accretion

Abstract: The interrelationship between inlet flow and delta morphology has an important effect upon the bypassing of sediment across inlets. Along the Sea Island Section of the Coastal Plain Physiographic Province the nature of inlet drainage and sediment bypassing profoundly influences patterns of beach erosion and accretion. Small coastal plain inlets generally have arcuate ebb deltas transected by a radially distributed pattern of channels. This arrangement permits an efficient flow of sediment across the inlet with little disturbance to the sediment budget of the adjacent shorelines. Several small inlets also have spits parallel to the shore that divert the flow of river water into the downdrift shore causing erosion. Accretion at the distal ends of these spits takes place at the expense of the proximal end of the spit where the shoreline erodes. Erosion eventually reopens a new channel across the proximal end of the spit and produces a second drainage reentrant. The major inlets along the coastal plain shoreline exhibit shoals with pronounced shore-normal orientations. The proximal ends of these spits may be attached or separated from the shore. When spits are attached to the shore, erosion is observed along the inlet margin and deposition is apparent at the distal end of the spit. When spits are separated from the shore, accretion is observed at shores adjacent to the inlet.

An objective method for sampling the macrophyte vegetation in lakes

Abstract: Methods are described how to select a representative sample of lakes from a certain region and how to objectively sample the macrophyte vegetation in the selected lakes in order to classify the lakes on the basis of their macrophyte composition. The vegetation has been sampled along profiles (1 profile = 2 belt transects). The variation of the vegetation in lakes is considered a function of the lake area and lake-shore development. The method calculates the number of profiles needed for a representative description of the vegetation in lakes with different areas and lake-shore development. The lakes have been grouped into geometric size classes, where the basic number of profiles increases with one from one class to another. The profiles are arranged at right angles along the longest line in each lake. The longest line also describes the main extension of the lake. The method has been tested ‘dry’ in three intensively investigated lakes where the distribution of the different communities have been mapped. Longest line and calculated profiles have been constructed on the maps. Actual and estimated distributions (along the lake-shore) and vegetation areas of distinguished plant communities have been compared in the lake as a whole as well as in parts of the lake. Actual and estimated values concerning community distribution along the shore correspond very well. A few differences have been noticed for plant communities concentrated to lake-ends or with a limited distribution. The areas for different communities can be satisfactory estimated for a lake as a whole, but they are not yet reliable when large differences between parts of a lake occur.

Cyclic erosion–instability relationships: Lake Erie north shore bluffs

Abstract: The 27–45 m high bluffs along the north shore of Lake Erie in Ontario are retreating inland at a 150 year average rate of 0.5 to 3.0 m/year. The retreat mechanisms and rates are cyclic and consist ...

Hurricane-Generated Waves and Coastal Boulder Rampart Formation.

Abstract: : Coral boulder ramparts along the south coast of Grand Cayman Island have no source area near the shoreline. Coral communities acting as a source of rampart rubble are found 0.3 km from shore and at a depth of 10-12 m. Theoretical calculations of wave-induced forces from wave refraction analyses of hurricane-generated waves indicate that the probable hurricane dynamic force spectrum is sufficient to break and transport coral rubble from depths of up to 12 m. In situ breaking force tests accomplished in Puerto Rico on Acropora palmata coral colonies support the theoretical calculations.

Sediments and sedimentary structures of a beach-ridge complex, southwestern shore of Lake Michigan

Abstract: Seven different sedimentary environments occur in the beach-ridge complex along the southwestern shore of Lake Michigan. Poorly sorted gravel and sandy mud form colluvium along the base of slopes. Cross-bedded sands occur as channel deposits, and interbedded sand, silt, and clay occur as overbank deposits in valleys cutting through the clay-till bluff to the west and in channels on the beach-ridge plain. Organic muds and peat are deposited in the marsh, and well-sorted sand in low-angle accretionary cross-sets is found both in dunes and on eolian sand plains. Beach-ridge sediments consist of sand in convex-upward cross beds dipping landward, and sand and gravel in low-angle accretionary cross beds dipping lakeward. Upper shoreface sands consist of trough crossbedded sand formed in lon shore troughs and low-angle planar laminae formed on longshore bars. Very fine-grained sands in wavy horizontal laminae are characteristic of the lower shoreface. These sediments have variable potentials of preservation and inclusion in the vertical sequence. Lower shoreface sands are well represented in both transgressive and regressive sequences, while subaerial facies would tend to be destroyed during periods of transgression. Erosion by migrating troughs apparently occurs during both transgression and regression, resulting in upper shoreface sequences consisting mainly of sediments deposited in longshore troughs.

Diversity of Shallow-Water Gastropod Communities on Temperate and Tropical Beaches

Abstract: Prosobranch gastropod assemblages on a tropical (Costa Rica) and a temperate (Washington) rocky shore were compared to evaluate how composition changes when there is a five-fold difference in regional species lists. Typical tropical beach quadrats (1-4 m2) contained no more species than did ones from the temperate beach; therefore, on the whole, tropical species are distributed more patchily than temperate ones. However, some shore habitats are more diverse than others at each latitude and temperate species are distributed as patchily as tropical ones when equally diverse habitats are compared. Locally, diversity varies with habitat structure (shore height and substrate). However, structure-diversity relationships are different at the two latitudes: High-shore habitats support more species in the temperate community, low-shore cobble habitats support many more in the tropical community, and low-shore rock habitats are equally diverse at both latitudes. Individuals are probably distributed among these habi...

The East Coast, Madagascar and the Indian Ocean

Abstract: The eastern coast of Africa looks out over the Indian Ocean, which, though vast, is comparatively easily navigated. Consequently there has been much contact over the past two thousand years among the peoples who inhabit its shores. This, coupled with similar climatic and ecological conditions in most of the surrounding coastal lands, has resulted in a considerable degree of cultural homogeneity, particularly marked in the western part of the ocean. Communication between the African coast and the interior was, on the other hand, difficult. Voyages in this part of the Indian Ocean would have been facilitated by the pattern of the monsoon regime, the winds blowing from a north-easterly direction towards East Africa for half the year, and from the south-west for the other half. This renders voyages by sailing ship from the Persian Gulf and north-western India particularly easy; those from Aden and the Yemen are rather more difficult. To the south, the South Equatorial Current facilitates voyages from the Far East to Africa, and the return is assisted by the monsoonal drift setting to the east between that current and India, together with predominantly westerly winds in this region. The main motive for voyages to East Africa was trade, but the pressure of population in the arid lands bordering the northern margin of the Indian Ocean provided a stimulus to migration. In the traditions of the coast, religious persecution figures as the reason for migrants leaving their homelands in the Persian Gulf, but it is probable that the attractions of well-watered lands, coupled with the prospect of wealth and a comfortable life in an agreeable environment, played at least as great a part.

A Three-Dimensional Model of Lake Ontario's Summer Circulation I. Comparison with Observations

Abstract: Observations of Lake Ontario during the International Field Year for the Great Lakes are used to develop a. three-dimensional numerical model for calculating temperature and current. The model has a variable grid resolution and a horizontal smoothing which filters out small-scale vertical motion caused by truncation error but has little effect on the strong currents of the coastal boundary layer. Resolution of the shore zones and reduced horizontal smoothing improve simulation of both long-term mean flow and current reversals due to low-frequency waves.

Distribution of opal and quartz on the ocean floor of the subtropical southeastern Pacific

Abstract: The distribution patterns of opal and quartz on the ocean floor of the subtropical southeastern Pacific have been defined by analyzing 59 surface-sediment samples. The opal distribution resembles that of primary productivity in the surface waters, except along the Peruvian and northern Chilean coasts, where dilution reduces opal values. The distribution pattern of quartz represents both eolian and fluvial transport. Quartz distribution extends out as a tongue in the same direction and position as the prevailing southeast trade winds. Along the South American coast, high quartz concentrations are found in patches near shore and decrease rapidly seaward.

The Levantine Countries: The Israeli Coastal Region

Abstract: The shore of Israel forms a rather smooth, concave arc which trends east in the south (northern Sinai), and then farther north gradually turns to the north-northeast. In some areas the coastline formed depositionally, in some erosionally, but for the most part it is structurally controlled. This paper describes for the coastal plain, the continental shelf, and the continental slope: (1) the basic geological results obtained in the last few years, (2) the structure, and (3) the tectonic setting in relation to the structural elements known on land and in the sea.

History of Shoreline Changes Determined by Archaeological Dating: Georgia Coast, U.S.A.

Abstract: Rates of deposition for features associated with progradational shorelines are normally estimated on the basis of direct observation or by the radiocarbon dating of shell or wood fragments recovered from the shoreline depositional features. Archaeological dating provides an alternative to these techniques. Progradation and erosion of Holocene shorelines on the Georgia coast can be grouped into four basic types: --Rapid progradation at the mouth of major rivers --Seaward and southward accretion of recurving beaches at the south ends of barrier islands --Cycles of alternating cuspate progradation and recurving truncations typical of the northern ends of barrier islands --Parallel progradation of straight beachlines typical of the central parts of barrier islands. The temporal significance of each of these types can be determined by archaeological dating. During much of the past 4500 years. Indians inhabiting the Georgia coastal area subsisted in large part on littoral mulluscs, as evidenced by large shell middens which mark former habitation sites. Aboriginal ceramic styles changed rapidly during this time period and recent work by archaeologists has defined 15 cultural phases based on the ceramic changes. These 15 phases have been calibrated by 14C dating. A specific example of how archaeological dating can be applied to the interpretation of shoreline changes is seen in the intertidal coastal zone lying immediately south of Savannah River. Examination of 33 habitation sites on beach ridge remnants in this area shows the presence of six cultural phases, which become progressively younger in a seaward direction. This sequence defines a dramatic progradation of nearly 10 km in the past 4500 years.

Historical Shoreline Changes and Their Causes, Texas Gulf Coast (1)

Abstract: Sequential shoreline monitoring, using vintage charts and aerial photographs, documents temporal and spatial variations in historical Gulf shoreline changes. The regional distribution of shoreline erosion and accretion largely reflects changes in littoral drift cells, decreases in sediment supply, and continuing relative sea-level rise including compactional subsidence. A Late Quaternary (circa 3500 BP) shoreline is postulated with promontories at the Holocene Brazos-Colorado and Rio Grande deltas; a third promontory along the upper coast was probably related to a Pleistocene delta system and the Sabine Arch. The interheadland areas or bights were the locations of littoral drift cells and the sites of accretionary shoreline topography primarily on barrier islands and peninsulas. Historical records (past 125 years) indicate that the deltaic headlands have experienced long-term erosion at relatively high rates. With changes in littoral drift cells, natural net shoreline accretion, supplied primarily by updrift erosion, has been generally restricted to Matagorda Island and central Padre Island in the extant zone of convergence. Short-term (past 5 to 10 years) changes are predominantly erosional with more than 70 percent of the shoreline experiencing land losses totaling about 400 acres annually. Shoreline erosion is caused by the complex interaction of climate, sediment budget, coastal processes, relative sea-level conditions, and human activities. Jettied inlets and navigation channels serve as the greatest sediment sink, and in certain areas major shoreline changes are clearly the result of human alterations. Rates of erosion and the total length of eroding shoreline have increased during historical time. Present data indicate that most of the Texas Coast will continue to retreat landward as part of a long-term erosional trend.

Do Rotifers show "avoidance of the shore"?

Abstract: The term "avoidance of shore" was used in literature to describe the observation that pelagic crustacea are in general absent near the shore. Experiments in the field show, that Rotifers-which form, together with crustaceans, the main mass of zooplankton-can also be divided not only by morphological criteria but also as a result of their horizontal distribution into inhabitants of either the littoral or the pelagic zone of a lake.These differences of horizontal distribution can be explained by a typical behavioral difference between the littoral rotifer Euchlanis dilatata and the pelagic Asplanchna priodonta: when exposed in the shore zone, Asplanchna wanders in the direction of the pelagic zone, while Euchlanis on the contrary does not prefer any particular direction under the same conditions. Experiments at different lakes with other pelagic rotifers confirm that the "avoidance of shore" shown by Asplanchna is a general phenomenon.The influence of the analyzed behavior on the horizontal distribution patterns of rotifers and the factors which cause and determine the direction of the migration are discussed.

Sediment management for Southern California mountains, coastal plains and shoreline

Abstract: The Environmental Quality Laboratory at Caltech and the Shore Processes Laboratory at Scripps Institution of Oceanography have jointly undertaken a study of regional sediment balance problems in coastal southern California (see map in Figure 1). The overall objective in this study is to define specific alternatives in sediment management that may be implemented to alleviate a) existing sediment imbalance problems (e.g. inland debris disposal, local shoreline erosion) and b) probable future problems that have not yet manifested themselves. These alternatives will be identified through a consideration of economic, legal, and institutional issues as well as an analysis of governing physical processes and engineering constraints. The first part of this study (Phase I), which is currently under way, involves a compilation and analysis of all available data in an effort to obtain an accurate definition of the inland/coastal regional sediment balance under natural conditions, and specific quantitative effects man-made controls have on the overall natural process. During FY77, substantial progress was made at EQL and SPL in achieving the objectives of the initial Planning and Assessment Phase of the CIT/SIO Sediment Management Project. Financial support came from Los Angeles County, U.S. Geological Survey, Orange County, U.S. Army Corps of Engineers, and discretionary funding provided by a grant from the Ford Foundation. The current timetable for completion of this phase is Fall 1978. This report briefly describes the project status, including general administration, special activities, and research work as of January 1978.

Marisat -- a maritime satellite communications system

Abstract: This paper describes the communications technique and facilities used in the MARISAT system to provide services to commercial users The commercial portion of the system has been designed to meet performance requirements for high-quality voice and data communications between shore-based subscribers and sea-going vessels as well as other maritime installations The commercial system configuration is described, including the C-band shore stations, the C- and L-band repeaters in the satellites, and the L-band ship terminals which operate automatically Modulation, access, and signaling techniques are discussed to explain how network control, centralized at the shore stations, provides rapid and automatic circuit connections Signal characteristics, frequency plans, link budgets, and system communication capacity are also presented

Researches on the coast of somalia. the shore and the dune of sar uanle: 13. physical environment: geomorphological notes, climate and tides: pubblicazioni del centro di studio per la faunistica ed ecologia tropicali del c.n.r.: cxxxii

Abstract: Geomorphologically, the Sar Uanle coast (0°29′48''S-42°25′30''E, 20 km South of Chisimaio) is successively composed of the reef edge (visible only at lowest syzygyal tides), a back-reef channel abo...