Showing papers on "Shore published in 1979"
01 May 1979
TL;DR: In this paper, a two-cell zonal circulation scheme was proposed for the initiation of active upwelling in the coastal waters of the state of Oregon, showing that the circulation of the Ekman layer within 0 to 10 km is less than 5 m deep and the surface layer offshore of the frontal region is not continuously transported offshore.
Abstract: Oregon has one of the smaller and best known coastal upwelling systems. It is about 50 km wide, but upwelling is most intense within 15 km of the shore, and episodes of active upwelling primarily affect the circulation and hydrography of the upper 20 m. It is in this nearshore, surface zone that phytoplankton and zooplankton are most abundant. Phytoplankton biomass is 5 to 20 mg chl- a m −3 , and zooplankton 50 to 200 mg dry weight m −3 . Vertically stratified sampling along transects perpendicular to the shore has produced a new picture of the upwelling process and suggests relationships between circulation and the population biology of planktonic animals. The zooplankton is dominated by five species of copepod. Each is distributed in a different pattern: Acartia clausii is almost completely restricted to the upper 5 to 10 m of the water column and the first 5 km from shore. Pseudocalanus sp. is abundant from 0 to 15 km and between 10 and 20 m depth, but it reproduces only within a few kilometers of the shore. Acartia longiremis lives and reproduces offshore (10 km) in the surface (0 to 10-m) mixed layer. Oithona similis is abundant offshore (10 km) between 10- and 20-m depths. Calanus marshallae lives offshore as older copepodite stages, but the females return shoreward and lay their eggs at about 10 km offshore. The nauplii and younger copepodites develop in the very nearshore zone. The patterns of animal distribution together with data on salinity, temperature, and chlorophyll- a lead to the following conclusions about the circulation in the Oregon upwelling zone: First, during active upwelling, the Ekman layer within 0 to 10 km is less than 5 m deep. Offshore of the frontal region, this layer is 10 to 15 m thick. Second, when upwelling is active, the surface layer offshore of the frontal region is not continuously transported offshore. Instead, this mass is moved offshore some fixed distance, no more than 20 to 40 km. During relaxation, this surface water returns shoreward to its former location. Third, we propose a two-cell zonal circulation scheme during initiation of active upwelling: Looking north in vertical section, a divergence is located 10 km from shore, with a clockwise rotating cell on the landward side and a counterclockwise cell on the seaward side. The population of each zooplankton species appears to be maintained within the upwelling zone by a specific relationship between its distribution and the circulation.
224 citations
TL;DR: In this paper, the authors characterized the vertical sequence produced by the slow progradation of most kinds of barred nearshore systems, but they should not occur in deposits formed by a non-barred nearshore system.
Abstract: Many of the straighter, less rocky parts of the southern Oregon coast are characterized by nearshore bars that extend obliquely out from shore and migrate alongshore. A typical oblique bar is attached to the foreshore at its upcurrent end, nearly parallel to shore through most of its length, and bowed seaward into a rip-channel-mouth bar at its downcurrent end. The main part of an oblique bar is separated from the foreshore by a longshore trough that curves seaward into a rip channel. The net wave-induced currents flow obliquely shoreward over the bar, parallel to shore through the longshore trough, and seaward through the rip channel and over the rip-channel-mouth bar. Medium-scale crossbedding formed by the migration of megaripples in the direction of net water flow is the dominant nternal structure in most of the nearshore. Small-scale crossbedding formed by wave-ripple migration is dominant in the inner offshore, and planar bedding is dominant on the foreshore. Most or all of the bar deposits would be destroyed if the coast prograded slowly but continuously. The vertical sequence produced during progradation should be characterized, in ascending order, by inner offshore deposits, possibly deposits of the lower seaward slope of the bar, a subhorizontal erosion surface corresponding to the deepest part of the rip channel, rip channel deposits, longshore trough deposits, deposits of the foreshore-trough transition, and foreshore deposits, Subhorizontal erosion surfaces probably occur in deposits formed by the slow progradation of most kinds of barred nearshore systems, but they should not occur in deposits formed by the progradation of a non-barred nearshore system. The nature of the deposits produced by the progradation of a barred nearshore system should vary with orientation of the bars relative to the shoreline, number of bars, wave energy, and available grain sizes.
181 citations
TL;DR: Nearly 17 years wave records from deep water and shore‐based stations are used to describe the ocean wave characteristics around New Zealand, and there are no strong seasonal rhythms, only shorter period cycles of wave height associated with similar quasi‐rhythmi...
Abstract: Nearly 17 years wave records from deep water and shore‐based stations are used to describe the ocean wave characteristics around New Zealand. The wave environment is dominated by west and southwest swell and storm waves generated in the temperate latitude belt of westerly winds. As a result, the west and south coasts are exposed, high energy shores, the east coast is a high energy lee shore, and the northern coast from North Cape to East Cape is a low energy lee shore sheltered from these winds and waves. South of New Zealand, wave energies are extremely high; the prevailing deep water wave is 3.5–4.5 m high and has a 10–12 s period, with a slight increase in wave heights in winter. The west coast wave environment is mixed, and consists of locally generated westerly and southerly storm waves, and swell waves generated to the south. The prevailing wave is t.0–3.0 m and 6–8 s period. There are no strong seasonal rhythms, only shorter period cycles of wave height (5 day) associated with similar quasi‐rhythmi...
120 citations
01 Jan 1979
113 citations
TL;DR: The physical effects of a large river (Thompson River) entering a deep, intermontane lake (Kamloops Lake, British Columbia) suggest that, depending upon its temperature relative to that of lake water, river water moves through the lake as a surface overflow, an intermediate depth interflow, or a near bottom underflow.
Abstract: The physical effects of a large river (Thompson River) entering a deep, intermontane lake (Kamloops Lake, British Columbia) suggest that, depending upon its temperature relative to that of lake water, river water moves through the lake as a surface overflow, an intermediate depth interflow, or a near-bottom underflow. Circulation is further influenced by the earth’s rotation so that the incoming river flows preferentially along the right-hand shoreline of the lake. Convective overturn in autumn and spring is influenced by cabbeling, which occurs than 4°C and one colder, combine to form a whenever two parcels of water, one warmer mixture whose temperature is at or near 4”~.
109 citations
TL;DR: In this article, the authors show that both the total length of eroding coast and rates of erosion have substantially increased since 1955-60, and that local trends toward accretion or erosion closely correspond with physiographic provinces, which in Texas are defined by transgressive and regressive beaches and barriers.
Abstract: Shoreline changes from sandy oceanic coasts worldwide show temporal and spatial variations that are similar to, and exemplified by, composite data from the Texas coast for four time periods extending from 1850 to 1975. The quantitative data, which exhibit remarkably similar distributions for the first two and latter two periods, show that both total length of eroding coast and rates of erosion have substantially increased since 1955-60. As a result, some shoreline segments that prograded following sea-level stillstand are presently eroding. Spatial variations in shoreline changes occur on regional and local scales. Regional tendencies toward accretion or erosion closely correspond with physiographic provinces, which in Texas are defined by transgressive and regressive beaches and barriers. Within each province, rates of accretion and erosion display periodicities that are irregular to quasi-sinusoidal in form and are attributed to shoreline rhythms resulting from differential rates of sediment transport. Natural processes, such as decreases in sediment supply and continued relative sea-level rise are largely responsible for long-term shoreline retreat. Short-term (historical) shoreline changes reflect the long-term trends. but they also reflect secular sea-level variations and human activities. The latter, in the form of coastal engineering modifications, are clearly responsible for the highest short-term rates of accretion and erosion. On the Texas coast nearly half of the total beach sand supplied by updrift erosion, presently a major sediment source, has been trapped by jetties at harbor entrances. This impoundment of sand at impermeable barriers together with reduced sediment influx from damming of rivers suggest that anthropogenic augmentation of natural shoreline erosion will likely increase from local to regional effects.
85 citations
TL;DR: In 1970, a major storm surge caused by galeforce westerly winds inundated low-lying tundra plains and deltas as far as 5000 m inland and left a driftwood line as much as 3.4 m above normal sea level along the Beaufort Sea coast of Alaska as mentioned in this paper.
Abstract: In 1970, a major storm surge caused by gale-force westerly winds inundated low-lying tundra plains and deltas as far as 5000 m inland and left a driftwood line as much as 3.4 m above normal sea level along the Beaufort Sea coast of Alaska. The height of the surge followed a predictable pattern and was highest along windward-facing shorelines. Coastal retreat and thermoerosion are greatly accelerated on such west-facing shores with eastward sediment transport opposite to normal littoral drift. Evidence suggests an approximate 100-year recurrence interval for similar surges, with potential for damaging the developing oil fields on the North Slope.
81 citations
TL;DR: In this article, the authors used a numerical model to find the edge wave modes on a typical concave beach and showed that estimates of edge wave wavelength using the plane beach assumption can be wrong by ±100% at a fixed mean sea level with a further error of ±50% introduced by the tides.
Abstract: In order to interpret field data in terms of edge wave modes, investigators usually assume that the beach profile is linear, allowing the use of simple analytical solutions for edge wave structure and wavelength. The validity of this assumption is checked by using a numerical model to find the edge wave modes on a typical concave beach. Results show that estimates of edge wave wavelength using the plane beach assumption can be wrong by ±100% at a fixed mean sea level with a further error of ±50% introduced by the tides. Greatly improved estimates can be made if the value of beach slope is chosen to reflect suitably the offshore extent of the edge wave. A rule of thumb for calculating the effective beach slope βe is , where h is the water depth at distance x′ from shore, L is the edge wave wavelength, and n is the edge wave mode number. The motion of the offshore profile of the edge wave due to a change of tidal elevation is dramatically different on a concave beach than on a plane beach. The tendency for the profile to move offshore for a drop in tide is compensated by the decrease in mean beach slope and hence reduction in wavelength and offshore extent of the wave. For a fixed instrument a drop in tide may lead to a profile shift onshore or offshore or no shift at all. Edge wave damping on a concave beach is shown to change as a function of tide. At low tide the surf zone width is increased while edge wave wavelength is decreased, both factors increasing damping. Thus edge wave spectra taken at low tide may be less energetic than those at high tide, particularly at high frequencies.
69 citations
TL;DR: In this paper, a well-preserved and virtually non-burrowed coastal sequence of Messinian age is described from the Sorbas basin, southeastern Spain, which was formed as an out-building coast under the dominant influence of waves.
58 citations
TL;DR: In this article, a method has been developed and tested for mapping shoreline changes using an orthogonal grid system and historical aerial photography, which includes rates and variances of shoreline change and storm-surge penetration at 100m intervals along the coast for 630 km between New Jersey and North Carolina.
Abstract: A method has been developed and tested for mapping shoreline changes using an orthogonal grid system and historical aerial photography. Our data base now includes rates and variances of shoreline change and storm-surge penetration at 100-m intervals along the coast for 630 km between New Jersey and North Carolina. Analysis of the data shows that the average rate of shoreline recession is 1.5 m/yr; however, variance along the 630-km reach is high, with rates of as much as 10 m/yr for the Virginia barrier islands.
53 citations
Journal Article•
TL;DR: The occupation of the northern sector of the Northwest Coast during the Early Period (circa 10,000-5,000 BP) is represented by a scattering of sites on the mainland and the off shore islands of the Alexander Archipelago.
Abstract: The occupation of the northern sector of the Northwest Coast during the Early Period (circa 10,000-5,000 BP) is represented by a scattering of sites on the mainland and the off shore islands of the Alexander Archipelago. Definition of the cultural phase (s) is thus far limited to lithic inventories. Information, thus far available, indicates a considerable amount of contact among groups on the coast and continuing relations with interior groups on the mainland. Characterization of the coastal adaptations during this time period will be based mainly on data from archaeological and geological investigations, and from radiocarbon dating of sites in the Icy Strait-Lynn Canal region.
TL;DR: In 1989, a rock avalanche into Yanahuin Lake demolished the Chungar mining camp along the lake shore, killing several hundred people as mentioned in this paper, due to a combination of highly fractured rock, oversteepened glaciated slopes, and a rigorous alpine environment characterized by heavy seasonal precipitation.
Abstract: A destructive water wave that was generated by fall of a rock avalanche into Yanahuin Lake demolished the Chungar mining camp along the lake shore, killing several hundred people. About 100,000 m 3 of limestone moved at high speed down a steep talus cone into the head of the lake about 400 m below the avalanche source. Conditions conducive to sliding at this site were a combination of highly fractured rock, oversteepened glaciated slopes, and a rigorous alpine environment characterized by heavy seasonal precipitation. The destructive avalanche was preceded about a year earlier by a moderate-sized rockfall that caused a low-amplitude water wave and by intermittent smaller rockfalls since that time. Large masses of intensely fractured rock that remain on the steep slopes above the lake pose a continuing threat to occupation of the lake shore; partly because of this hazard, operation of the Chungar mine has been indefinitely suspended. The Chungar tragedy is the most recent in a long history of disasters in which landslide-generated waves have inundated shorelines in regions of steep unstable slopes.
01 Jan 1979
TL;DR: Decapod crustaceans are listed from the two main subregions of the Argentinian continental shelf: warm-temperat e, from shore to 40- 60 m and between 23° and 44°S latitude; and cold-temperate, 150-200 km from the continent in the north at a depth of 80 m or more.
Abstract: Decapod crustaceans are listed from the two main subregions of the Argentinian continental shelf: A. warm-temperat e, from shore to 40- 60 m and between 23° and 44°S latitude; and B. cold-temperate, 150-200 km from the continent in the north at a depth of 80 m or more, and extending from 34°-35°S latitude southward to the Patagonian shelf, Magellanic region and the Malvinas Islands. Eighty-one mainly benthonic species are included from the two subregions, 54 from the warm-temperate and 45 from the cold- temperate. Some species are found in part of the two subregions.
TL;DR: It is suggested that at the shore levels studied, the harsh physical environment could suppress competitive interactions between algae, so that no species is capable of exploiting a reduction in grazing pressure.
TL;DR: In this article, the authors examined the dependence of longshore currents generated by waves breaking obliquely to the shoreline and suggested that such a dependence is suggested by the formula presented in the Coastal Engineering Research Center.
Abstract: This paper examines the beach-slope dependence of longshore currents generated by waves breaking obliquely to the shoreline. Such a beach-slope dependence is suggested by the formula presented in the Coastal Engineering Research Center.s Shore Protection Manual .
Book•
01 Jan 1979
TL;DR: Kaufman and Pilkey as discussed by the authors evaluated America's beaches from coast to coast, giving sound advice on how to judge a safe beach development from a dangerous one and how to live at the shore sensibly and safely.
Abstract: Our beaches are eroding, sinking, washing out right under our houses, hotels, bridges; vacation dreamlands become nightmare scenes of futile revetments, fills, groins, what have you—all thrown up in a frantic defense against the natural system. The romantic desire to live on the seashore is in doomed conflict with an age-old pattern of beach migration. Yet it need not be so. Conservationist Wallace Kaufman teams up with marine geologist Orrin H. Pilkey Jr., in an evaluation of America's beaches from coast to coast, giving sound advice on how to judge a safe beach development from a dangerous one and how to live at the shore sensibly and safely.
01 Jul 1979
TL;DR: In this paper, a review of recent progress in model calculations towards understanding electromagnetic induction effects at ocean coasts is presented, where it has been shown that the surface magnetic field can vary appreciably close to the coast, particularly on the ocean side of shore, with the result that the effect of the coast is felt at very large distances over both land and sea.
Abstract: This paper reviews recent progress in model calculations towards understanding electromagnetic induction effects at ocean coasts. Early models consisted of two adjacent quarter-spaces of different conductivity, whereas the newer models simulate the ocean with a very thin sheet of a perfect conductor placed on top of a uniform Earth medium. The inducing field is assumed to arise from a monochromatic plane wave incident vertically from above. With any of these models one succeeds at once in explaining the occurrence of large vertical magnetic fields when the inducing electric field is polarized parallel to the coast (E-polarization), thereby also confirming the highly directional character of the coast effects as discovered a few years before by Parkinson. Another important step was made when, first numerically, then analytically, the behavior of the horizontal component of the magnetic field at the surface was rigorously calculated. For H-polarization (inducing magnetic field parallel to shore) this horizontal surface field is uniform, but is not so for E-polarization. Indeed, it has now been shown that the surface field can vary appreciably close to the coast, particularly on the ocean side of shore. With E-polarization, very large currents flow in the ocean, parallel to shore, with the result that the effect of the coast is felt at very large distances over both land and sea. Under H-polarization induction the range of the coast effect is very much shorter, in fact almost an order of magnitude shorter over the land and even reducing to zero at the surface of the perfectly conducting model ocean. The magnetic fields at the ocean floor have also been calculated, which should be of interest in the rapidly expanding field of marine survey and prospecting.
TL;DR: In the case of tin, sub-economic resources were outlined in submerged river channels at a number of places off northeastern Tasmania, but to locate workable tin deposits in the buried alluvium by drilling alone is likely to be impracticable and successful exploration may depend on the development of other geophysical prospecting techniques as discussed by the authors.
TL;DR: In this paper, four onshore bore-holes provide a cross-section ranging from a hillslope on the south, across a central coastal plain, to delta-beach stratigraphy on the north.
Abstract: The Greek historian Pausanias has reported that the ancient coastal-Peloponnesus city of Helice sank into the Corinthian Gulf during an earthquake in 373 B.C. A deductive approach to the present-day search has been made difficult by changes in the location of such local landmarks as braided-rivers and the shoreline. In order to more closely delineate the city's probable site, a geologic investigation of the region has been undertaken.Four onshore bore-holes provide a cross-section ranging from a hillslope on the south, across a central coastal plain, to delta-beach stratigraphy on the north. Three offshore bore-holes reveal a double sequence of beach gravel each overlain by fossiliferous marine silt. Based on radiocarbon dating of the contained fossils, it is hypothesized that a slump plane lies somewhere between these two groups of holes.While Helice mayor may not be found for some time to come, the present investigation represents an effort to draw quantitative limits upon its hidden location.
TL;DR: In this article, spectral analysis of longshore rate change data spanning 40 years and 122.6 km between Cape Hatteras and Cape Lookout revealed that edge waves played a significant role in determining the intensity of regional-scale processes and geomorphological responses along the Atlantic coast barrier islands.
Abstract: Spectral analysis of shoreline rate change data spanning 40 years and 122.6 km between Cape Hatteras and Cape Lookout reveals a hierarchy of longshore periodicities. The periodicities closely match wavelengths of hypothetical standing waves trapped between the offshore shoals of the two large capes. In addition, active and relic inlets and site-level beach characteristics coincide with the periodicities. We conclude that edge waves may play a significant role in determining the intensity of regional-scale processes and geomorphological responses along the Atlantic coast barrier islands.
TL;DR: The amount of kaolinite and illite in bottom muds of Altamaha River and Sound, a partially-mixed estuary, does not vary appreciably downstream, indicating that the bulk of the clays are river-supplied as discussed by the authors.
Abstract: The amount of kaolinite and illite in bottom muds of Altamaha River and Sound, a partially-mixed estuary, does not vary appreciably downstream, indicating that the bulk of the clays is river-supplied. In contrast, much of the bottom mud of Sapelo Sound, a tidal-water body with minor freshwater discharge, seems to be derived from erosion of coastal outcrops. Our results suggest that the clay flux from ocean sources is minimal in either case, and tends to have been overestimated by previous workers. On the other hand, the clay flux from shore erosion tends to have been underestimated in sediment-budget studies of Georgia estuaries.
TL;DR: In this paper, the authors investigated the role of lake-capture processes in the formation of Teshekpuk Lake and found that the lake's formation was a result of erosion produced by the moat-current phenomenon.
Abstract: Observations on a drained and a partially drained lake basin adjacent to Teshekpuk Lake led to the conclusion that the drainage was a result of erosion produced by the moat-current phenomenon of Teshekpuk Lake. The processes of shoreline erosion and lake-capture seem to be responsible for the growth and configuration of Teshekpuk Lake. Similar phenomena between large lakes and the Beaufort Sea may also have influenced the shoreline configuration of vast coastal areas such as Admiralty Bay, Dease Inlet and Harrison Bay.
TL;DR: In this article, the authors investigated the fertility of the A.A. marina in four intertidal study areas near Roscoff (Brittany, France) from 1975 to 1977 and found that the population consists mainly of small immature worms.
Abstract: Dispersion, abundance dynamics, size-frequency, mortality, growth, biomass, productivity, energy flow, germ-cell development, sex ratio, breeding season, natality and fertility ofArenicola marina were investigated from 1975 to 1977 at four intertidal study areas near Roscoff (Brittany, France). Numerical abundance is highest in the upper shore. Here the population consists chiefly of small immature worms. Towards the lower shore, abundance decreases whereas individual size increases. Annual variations in abundance are greatest in the upper shore. Variation in abundance is essentially influenced by wave movement. There is evidence supporting the view that, in spring, small lugworms migrate from the upper part of the shore all over the tidal flat area. Growth rates vary significantly within the areas examined. Generally they increase with increasing duration of submersion.A. marina is the most important producer among the polychaetes so far examined. Productivity is highest in sheltered flats and decreases with increasing disturbance by water movement. Energy budgets of lugworms are estimated. Energy requirements and energy supply are discussed, particularly the extent to which filtration in the headshaft of the burrow may cover food requirements. A brief description of gametogenesis is given. In 1975 at Penpoul the breeding season began in October and lasted two months. At the other study areas— Le Pouldu, Le Guillec and Le Dossen — spawning began in October and lasted one month. In 1976 spawning began earlier but terminated at the same time as in 1975.
TL;DR: Immature bluegills from Par Pond, a 1,120-hectare impoundment on the United States Department of Energy's Savannah River Plant near Aiken, South Carolina, were collected and tested individually by observing their directional movement from the center of a circular testing facility, indicating that they use their sun compass mechanism in oriented swimming.
Abstract: Immature bluegills, Lepomis macrochirus (N = 389), were collected from Par Pond, a 1,120-hectare impoundment on the United States Department of Energy's Savannah River Plant near Aiken, South Carolina, and tested individually by observing their directional movement from the center of a circular testing facility. Bluegills captured 10–20 m from shore in areas lacking extensive submerged vegetation swam in a direction which would have taken them to shore at the area of their capture, whereas those taken from areas having submerged vegetation offshore swam in the direction opposite from shore. The directional responses of fish that were phase-shifted by 6 hours demonstrated that they were using time-compensated sun orientation. Fish exposed to a predator oriented in the direction of shore in their training facility, but if no predators had been present during training, moved in the direction of deep water. Present evidence indicates that immature bluegills use their sun compass mechanism in oriented...
01 Jan 1979
TL;DR: In this paper, the authors identified nineteen beach cells along the west coast of Barbados and intensive studies of wave and current processes leading to changes in beach planform and profile were made at two (Gibbs and Sandy Lane bays).
Abstract: Concern over loss of shore property and local deterioration of the physical condition of beaches on the west coast of Barbados has led to extended analysis of the coastal subsystems. The main features of the west coast are inherited from events associated with complex sea-level fluctuations and extension of coral terraces in the Quaternary. The contemporary coast was established at the close of the Flandrian transgression along an early Wisconsin rocky shoreline. Introduction of sand into the shore system from cliff erosion (2 to 10 m retreat during the period), reef destruction and terrestrial sources has formed a sand beach that has moved seawards with time leaving a narrow sand terrace between the shore and the earlier coastline. Nineteen beach cells were identified along the west coast and intensive studies of wave and current processes leading to changes in beach planform and profile were made at two (Gibbs and Sandy Lane bays). Whilst the volume-shape mechanism operating through an annual cycle leaves a beach cell in quasi-equilibrium, overall loss of beach sand in the past 13 years has been accompanied by a 45 % linear increase of exposed beach rock.