Wave Swash Research Articles

Zonation by size of the pacific mole crab, Hippa pacifica dana (Crustacea:Anomura:Hippidae), in hawaii

The Pacific mole crab, Hippa pacifica Dana, demonstrates zonation by size on Hawaiian beaches, with small (carapace length < 13.5 mm) crabs concentrated in the upper half of wave wash and larger (reproductively mature) ones in the lower half. This zonation appears to result primarily from competitive dominance by large crabs during feeding. Commonly used collecting methods (bait-trapping, sieving) have neglected this zonation and have consequently underestimated small crabs in studies of population structure. A transect-sieving method of sampling is necessary for an adequate analysis.

Ecological Interactions Among Bangia, Cladophora, and Ulothrix Along the Lake Erie Shoreline

Bangia atropurpurea, a recent invader of Lake Erie, has altered the community structure of the littoral zone, which previously had been dominated by Cladophora or Ulothrix. Vertical and horizontal zonation patterns of these algae suggest that competition and differing physical tolerances may be involved. To determine the relative importance of these factors, seasonal changes in littoral algal distribution patterns and environmental conditions were monitored. Additionally, Bangia was examined in culture to relate growth and reproductive mechanisms to distribution patterns and competitive potential. Ulothrix established extensive cover immediately below mean water level (MWL) after thaw in mid-April along moderately exposed shores. By early May, Bangia colonized from +0.5–1.0 m to just below MWL coexisting with Ulothrix near MWL. As water temperature neared l5° C in late May, the distribution of Cladophora expanded from patches at −0.5–1.0 m upward into the Ulothrix band. In early June, Ulothrix sporulated, the remaining empty filaments disintegrated, and the alga was not observed for the remainder of the summer. Cladophora continued upward colonization, eventually dominating the substrate to the +0.5–1.0 m level. Bangia was dominant above the Cladophora zone, up to +2.0 m. During periods of moderate wave wash, Cladophora dominated up to the +1.0 m level. Heavy wave wash resulted in the detachment of Cladophora, allowing domination by Bangia from +0.5 m to 2.0 m. Bangia shares substrate with Ulothrix in the limited areas where their distributions overlap, and perhaps through greater desiccation tolerance can persist in areas where Cladophora does not grow. This partial niche segregation provides Bangia with refugia in time as well as space. Coexistence between Bangia and the competitively dominant Cladophora occurs as a result of partial niche segregation as well as the impact of wave action in initiating the detachment of Cladophora.

Sedimentology of an ordovician fan delta complex, Western Libya

The Ordovician Haouaz Formation in the western-central Gargaf Arch of western Libya provides a well-exposed example of an ancient fan delta system. The Haouaz sequence consists of delta front deposits overlain by subaqueous distributary channels with intervening distributary mouth shoals and swash bars. This delta front complex is abruptly and erosively overlain by braided fluvial and distributary channels of the lower deltaic plain. Lower deltaic plain deposits may show reworking by wave swash processes in the upper portion, indicating marine destructive phases of delta building. This process is attributed to diminished or absent detrital influx allowing wave reworking of the deltaic plain margin. These reworked deposits may in turn be overlain by thin transgressive marine shelf sequences, also formed during periods of minimal detrital influx. The lower deltaic plain may also pass upward into an upper deltaic plain and alluvial plain environment.

Pleistocene marine kettle-fill deposits near Ottawa, Canada

Exposures at several localities in the Ottawa region reveal Champlain Sea deposits filling depressions on what were formerly submerged surfaces of Wisconsin sand and gravel ridges. The deposits, referred to as "kettle fill," constitute materials eroded from the ridges in a marine environment and redeposited in ice-melt depressions or kettle holes. Processes responsible for the deposition of the sediment appear to include debris flows and small turbidity currents initiated by wave washing and slope instability. The dimensions of the depressions, their depth in relation to the falling wave base, and the steepness of the flanks were important factors controlling sedimentation. The kettle-fill facies comprise diamicton (pebbly mud), gravel, sand, and lutite.

Genesis and Significance of Marsh Islands Within Southeastern North Carolina Lagoons

ABSTRACT Fifty-four islands of low relief, varying from 36 m to 1512 m long are present within the narrow, marsh-filled lagoons behind the barrier islands between New River Inlet and Carolina Beach Inlet in Southeastern North Carolina. Information derived from inspection of aerial photographs, historic maps and charts, and field data, indicate that these islands form where sands overtop marshes forming a narrow berm. These features likely form during periods of increased wave swash. The occurrence of these geomorphic features can be used to indicate the migration of a single inlet or several inlets along a zone prone to inlet formation. The islands consistently present a stratigraphic sequence where fine-grained, humic-stained, carbonate-free sands overlie muddy peat. Landward of these islands organic-rich peat sequences are commonly thick (>100 cm) while just seaward, peat sequences are thin (<30 cm). Vegetation composition and species diversity on the islands are dependent upon age and height above mean sea level. Saltmeadow cordgrass (Spartina patens) and sea oxeye (Borrichia frutescens) generally characterize young islands or those islands occasionally flooded by spring tides. On islands with relief greater than 1 meter, tidal flooding is uncommon. A diverse flora, including wax myrtle (Myrica cerifera), red cedar (Juniperus virginiana), yaupon (Ilex vomitoria), and occasional live oak (Quercus virginiana) succeed the colonizers, cordgrass and sea oxeye.

Tidally influenced barrier island and estuarine sedimentation in the upper carboniferous of southern West Virginia

Upper Carboniferous orthoquartzites exposed in the Guyandotte Valley of southern West Virginia are interpreted as barrier island and backbarrier deposits. They overlie fossiliferous marine limestones and shales, and are overlain in turn by fluvio-deltaic subgraywacke sandstones, siltstones and coals. Only the upper one-third of the 180 m thick orthoquartzitic interval is exposed, but these rocks outcrop over a distance of 16 km, and reveal landward transition of the barrier orthoquartzites into backbarrier and alluvial or delta-plain deposits. Within the exposed orthoquartzitic interval are three major orthoquartzite bodies, separated by subordinate siltstones containing smaller sandstone bodies. The major orthoquartzites are 10–25 m thick and are lenticular in transverse section, with a north-south elongation approximately perpendicular to the palaeoslope. These sandstone units are subdivisible into three facies. Facies 1 is most widespread and comprises mainly upward-thinning sets of cross-stratification, with a silty interval occasionally preserved towards the top. Palaeocurrent indicators reflect increasing dispersal from the base of the sequence upward. These deposits are interpreted as originating within laterally migrating tidal inlets, in which ebb currents were dominant. Facies 2 contains low-angle bedding suggestive of wave swash processes, with patterns of minor sedimentary structures similar to those observed in modern ebb tidal deltas. Facies 3 consists of sandstone with a preponderance of landward-directed cross-stratification, and is attributed to a flood tidal delta, flood-channel and washover berm origin. The orthoquartzites merge eastward and southeastward (landward) into inferred estuarine or lagoonal siltstones, but in places they are in lateral contact with fluvio-deltaic subgraywackes. Thus the barrier sediments are thought to have been derived at least in part by the reworking of abandoned delta lobes. Longshore drift created spit extension towards the south and southwest, thereby enclosing lagoons within which accumulated siltstones and sandstones with brackish or marine fossils and a variety of structures suggestive of tidal processes and local subaerial exposure. Washover sands were deposited to landward of the barrier. Both barrier and backbarrier deposits are incised by small tidal channels. Occurrence of washover features in association with small but well-developed tidal deltas suggests moderate to strong wave activity and a mesotidal (2–4 m) range.

An embayment model for tidal and wave swash deposits occurring within a fluvially dominated middle proterozoic sequence in South Africa

The occurrence of tidal and wave swash deposits within the dominantly alluvial middle Proterozoic Waterberg Supergroup in the eastern Transvaal, South Africa, is in response to a shoreline morphology determined by the fluvial system. Tidal flats developed on the inner margin of an embayment (interdistributary) between areas of active detrital influx, whereas wave swash deposits developed as local destructive bars on the margins of alluvial lobes (fan deltas) during periods of little detrital influx.

Le contrôle de l'émergence et des nages nocturnes chez les péracarides des plages de méditerranée. Eurydice affinis Hansen (Isopoda), Gastrosaccus mediterraneus Bacescu, Gastrosaccus spinifer (goës) (Mysidacea)

Along the Mediterranean sandy shores, Eurydice affinis Hansen, Gastrosaccus mediterraneus Bacescu and Gastrosaccus spinifer (Goës) are present during the day in the sand of the beaches, either near the limit of the wave wash or in the superficial fringe of the infralittoral. In the evening there is a general emergence and the animals rejoin the planktonic populations of the open sea. All the three species when kept in aktographs under constant conditions and continuous darkness exhibit a circadian rhythm of emergence and swimming activity of nocturnal frequency. The rhythm is clear and in the two Gastrosaccinae persists for ten days at least; it has been observed over about fifty days in G. spinifer. In E. affinis, the rhythm is only on some occasions clear; one frequently observes a permanent burying in the sediment, in which case the swimming rhythm can be brought to light by a mechanical disturbance or the withdrawal of the sediment. A study of the changes in the photokinetic reactions in a horizontal beam of white light, with intensities varying from 4000 to 10 −6 lux, allow the synchronization of the rhythms to be ascribed to a slight photonegative tendency of the animals at intensities > 1000 lux and a photopositive tendency, often marked, at lower intensities. The variations in the intensity of the reactions in the three species allows an explanation of the autonomous rhythms. A comparison between the photokinetic reactions of these species and those of the infralittoral Peracarida, which migrate in the nocturnal plankton, shows great differences with respect to light intensity. In the latter, the phototaxis is strongly negative and frequently accompanied by a strong photo-inhibition while in the former the phototaxis is still often positive and the kinesis is high. The photopositive reaction allows the animals to rejoin their daytime habitat soon after dawn when the swimming activity decreases.

SAND CIRCULATION PATTERN AT PRICE INLET, SOUTH CAROLINA

A sand circulation pattern has been determined for Price Inlet, South Carolina, using wave refraction diagrams, littoral process measurements, bedform orientations and inlet hydraulic data. The dominant process acting on the ebb-tidal delta is wave swash which impedes the ebb-tidal currents and augments the flood-tidal currents. This produces a net landward transport of sand on the ebb-tidal delta as evidenced by the landward migrating swash bars. Bedform orientations and velocity measurements taken on the swash bars also support this conclusion. Countering the general landward transport direction is the ebb dominance of the main channel. This dominance can be explained by higher inlet efficiency at low water than at high water. Consequently, bay tide phase lag is larger at high than at low water resulting in a longer flood duration. This causes higher mean ebb-tidal currents and a consequent larger potential net ebb transport of sand. This inlet characteristic explains why little sand is transported inside the inlet, why the throat remains scoured and why sand entering the main channel is carried seaward.

FORTNIGHTLY MOLTING AND REPRODUCTIVE CYCLES IN THE SAND-BEACH ISOPOD, EXCIROLANA CHILTONI

1. The isopod, Excirolana chiltoni is found buried in the sand in a narrow zonal band on the high intertidal beach during low tide and emerges only during high tide to swim and forage in the wave wash. The position of the zonal band during low tides bears a consultant relationship to the level of the water line during the preceding high tide. Because of this relationship the isopod zone moves up and down the beach on a fortnightly schedule which corresponds to the semi-monthly variation in tide amplitudes (the spring-neap cycle). 2. Excirolana chiltoni stores considerable quantities of mineral prior to ecdysis in localized concretions of the integument (dermoliths). 3. Molting takes place in two steps. First the posterior portion of the isopod including the abdomen and last 3 thoracic segments is cast which is followed by the casting of the anterior portion of the animal. Isopods which are in the process of molting can be easily recognized since the newly exposed posterior exoskeleton is fully expanded before the anterior cast is made. 4. The development of dermoliths and the relative abundance of half-molted individuals were used to determine the frequence of molting in a field population which was sampled at 2 day intervals for a period of a month. These data indicate that molting is largely if not entirely restricted to the weeks preceding new or full moon when the amplitude of the tides is increasing. 5. Excirolana chiltoni also shows fortnightly periodicities in feeding and the degree to which it is infested with external parasites. 6. Indirect evidence suggests that the release of young also follows a fortnightly schedule and is most intense at the same phase of the spring-neap cycle that the population molts. Females retain their broods internally and might therefore be capable of controlling the timing of birth with considerable precision. 7. Synchronous molting was not as apparent in populations which were held under non-tidal conditions in the laboratory. 8. Synchronization of molting and birth to the ascending series of high tides and the storage of mineral reserves prior to ecdysis are interpreted as adaptations which serve to decrease the probability of an isopod being marooned above the waterline for extended periods of time where it would be subject to a high risk of death by desiccation.

The mechanics of sand transport on beaches

On steep-faced beaches where waves break and swash at an angle to the shoreline the littoral drift of beach material results from the saw-tooth motions of the sediment in the longshore direction. The sand moves forward obliquely to the shore under the incoming wave swash and then moves normal to the shoreline under the return flow. For such transport conditions a rational derivation leads to the relationship Ii=K(ECn)b sin αb cos αb, where Ii is the longshore transport rate of sediment expressed as an immersed weight, (ECn)b is the flux of wave energy at the breaker zone, αb is the angle the breaking wave makes with the shoreline, and K is a dimensionless proportionality coefficient. This often applied relationship, previously only intuitive, is therefore more rigorously established for special saw-tooth transport. It has recently been shown to also apply when the sediment is transported by a longshore current proportional to um sin αb, where um is the orbital velocity under the breaking waves. These are the two most important mechanisms by which sediment is transported along the shore under wave action, and hence the successful application of the above relationship can be expected. Deriving the relationship by two different approaches suggests that the ratio tan β cos αb/cf may be constant, where tan β is the beach slope, and cf is the coefficient of bottom friction. This helps to explain the observation that the longshore current is proportional to um sin αb and to account for the lack of dependence of the sand transport relationships on the beach slope. The profiles of variation of the longshore sand transport as a function of the distance seaward of the swash line are examined theoretically. The results conform with the field observations.

Behavior and Physical Factors Causing Migration and Aggregation of the Sand Crab Emerita Analoga (Stimpson)

Migration and distribution of Emerita on sand beaches can be explained in terms of water flow and a simple behavioral response. Wash zones of sand beaches are bounded burrow out of fluid sand and so are kept within the boundaries of the wave wash. As the position of a wash zone is shifted with the tide, Emerita are carried in it to new locations on the beach. Lateral flow within the wave wash distributes Emerita into clumps along the shore.

Comparison of Quartz and Carbonate Shallow Marine Sandstones, Fredericksburg Cretaceous, Central Texas

The lower Fredericksburg Cretaceous of central Texas contains two shallow marine sandstone deposits of similar shape but of contrasting lithologic character, genesis, and porosity trend. The lower sandstone (Paluxy Formation) is part of the initial clastic phase of the lower Fredericksburg depositional cycle and is composed predominantly of quartz sand and clay. It occurs as a tongue which projects southward from the main body of the formation. The Paluxy tongue was deposited by longshore currents, and modified shoreward by wave swash and tidal action in a coastal nearshore marine environment. The trend of the tongue is controlled by the position of the shoreline and by the configuration of the sea floor. The upper sandstone (Whitestone Limestone Member of the Walnut Formation) is the terminal phase of the lower Fredericksburg cycle and is composed entirely of carbonate grains. The Whitestone is an elongate, mound-shaped body of lime-grainstone trending northwest; it was deposited in an agitated, offshore, shallow marine environment by northwest-southeast-trending marine currents which were modified locally by surge channels normal to this trend. The trend of the mound is controlled by linear shoal areas.

Coastal Sand Dunes of Guerrero Negro, Baja California, Mexico

A dune field of uniform 6-m-high barchan ridges, about 40 square km in area, has blown inland from a barrier beach and has formed a partition of sand across the lagoon. The partition connects the barrier beach with the Baja California mainland. During 3.5 years of observation, the dunes advanced with a mean velocity of 18 m/year. This is equivalent to a discharge of 23 cu m of sand/m width/year. This discharge acting over the 1800-year life of the barrier beach, as dated by Carbon-14, is shown to be compatible with total volume of sand required to extend the dune field across the lagoon to the mainland. Observed travel rate of dunes was about twice that predicted from wind measurements. During high water accompanying spring tides, the floor of the interdune areas is inundated by water from the lagoons; thus, the windward margins of the dunes are subjected to the action of small waves generated by wind. The waves form miniature barrier beaches that are preserved as the dune migrates and serve as fortnightly and monthly time markers in the sediments. Avalanche bedding is the most common small-scale internal structure in the dune field. Gently sloping laminations associated with wind-blown ripples and with wave swash on the miniature barrier beaches are also common.

Comparison of Quartz and Carbonate Shallow-Marine Sandstones, Cretaceous Fredericksburg, Central Texas: ABSTRACT

End_Page 1751------------------------------The lower Fredericksburg Cretaceous of central Texas contains two shallow-marine sandstone deposits of similar shape but of contrasting lithology, genesis, and porosity trend. The lower sandstone (Paluxy) is part of the initial clastic phase of the lower Fredericksburg depositional cycle and is composed predominantly of quartz sand and clay. It occurs as a tongue which projects southward from the main body of the Paluxy Formation. The tongue was deposited by longshore currents, modified shoreward by wave swash and tidal action, in a coastal near-shore marine environment. The trend of the tongue is controlled by the position of the shoreline and by the configuration of the sea floor. The upper sandstone (Whitestone Member of the Walnut Formation) is the terminal phase of the lower Fredericksburg cycle and is composed entirely of carbonate grains. The Whitestone is an elongate, mound-shaped body of calcarenite trending northwest. It was deposited in an agitated, offshore, shallow-marine environment by northwest-southwest-trending marine currents which were modified locally by surge channels normal to this trend. The trend of the mound is controlled by linear shoal areas. End_of_Article - Last_Page 1752------------

Ångermanlands Kustland Undér Isavsmältningsskedet

Abstract Detailed mapping of bedrock hills capped with ground moraine have clearly shown the difficulties of determining the exact elevation of the highest shoreline of the Bothnian Sea in angermanland. Differences up to 10′m in the elevation of the upper limit of wave washing have been observed on several hills located in what was the outermost part of the Finiglacial coastal area. The greatest differences between elevations of the upper limit of wave washing exist in areas that were exposed to more or less open sea, whereas the differences are less in areas that were protected from storm waves. The highest point on the shoreline in the area is on Skuleberget, where it is 285.5 m above sea level. A re-evaluation of the shoreline on “Rosstjarnsberget” shows the elevation there to be 281.3 m above sea level, rather than 295 m as previously believed. Recession of the land ice was evaluated in the area northeast of angermanalven by means of varve studies. A close correlation has been shown to exist between t...

18 建築物の水害に関する研究

While a flood can be defined in a variety of ways, generally the term "flood" is loosely used. A flood sometimes is regarded as a condition when a stream overflows its banks, but the damage from the effects of water is just as real wind-driver tides, tidal wave wash, high water from excessive precipitation in areas far removed from streams or rivers, mud flows and the like. Anyways by a flood buildings receive damages. So that on this stady want to solve these problems.

Protohydra and Kinorhyncha in Africa

ALONG the southern shores of South Africa there are streams which, flowing into sunken valleys, form lagoons only open to the sea at intervals of months or years. Their mouths are closed by wide bars over which the dunes move in their march along the coast. At high tides in stormy weather, waves wash over the bar and in time the waters of the lagoon rise above sea-level. When floods from the land make the river rise rapidly, the bar is breached and the waters of the lagoon pour out into the sea until it becomes a shallow estuary and so remains for a few weeks.

Wave-Wash Control on Mississippi River Levees

Unprotected levees along the lower Mississippi River are subject to serious wave-wash damage where the foreshore is narrow and without protective vegetation. The need for protection works is almost continuous below New Orleans, La., and intermittent as far upstream as Baton Rouge, La. Above New Orleans the situation is less severe because ship traffic is lighter and the river banks are generally high enough to contain the river at ordinary stages, limiting wave-wash attack on the levees to periods of high water. Many types of protection have been suggested, and most of them have been tried, but no single type has met reasonable criteria for economy and effectiveness. Present practice (1953) is to use either of two major types of protection for the levee, and under special conditions, a supplemental structure to keep the wave wash protection work from being undermined.