Time Of High Water Research Articles

Hydrochemical characterization of the coastal springs of the Sierra de Irta. Maestrazgo Aquifer (Castellón)

El Maestrazgo aquifer has an approximate surface area of 2400 km2 and occupies the northern half of the province of Castellón, from the coast to Morella. This system is characterized by the absence of important springs in its interior and permanent water courses, in such a way that its fundamental discharge is carried out directly into the sea through springs located along the Sierra de Irta, between Alcossebre and Peñíscola. Several of these discharge points are permanent (springs at Playa de Las Fuentes, Torre Badum, Font de Dins and Prat de Peñíscola) and drain an important volume of water resources that is difficult to quantify. In addition to these well-known springs, in times of high water and mainly after episodes of intense rainfall, occasional springs appear whose precise location and chemical characteristics have not been defined to date. These are the springs of Playa del Carregador, Playa de Las Fuentes Sur and Norte, Playa del Russo and Playa del Pebret. In this article, the waters of all these springs are chemically characterized based on their majority ion content and are classified into five different types. The chosen samples are taken in periods of high water in which all the springs are running, but in a temporary stage relatively far from the torrential events that activated them so that the characterization corresponds to a hydrodynamic context as little altered as possible by the effect of the weather.

The effects of hydraulic works and wetlands function in the Salado-River basin (Buenos Aires, Argentina).

Man-made activities exert great influences on fluvial ecosystems, with lowland rivers being substantially modified through agricultural land use and populations. The recent construction of drainage canals in the upper stretch of the Salado-River basin caused the mobilization of huge amounts of salts formerly stored in the groundwater. The main aim of this work was to analyze the effect of the discharges of those canals into the Salado-River water, under different hydrologic conditions, and the role of the wetlands and shallow lakes placed along the canals' system. Physicochemical variables were measured and water samples were taken during times of high water, mean flows, drought, and extreme drought. The environmental variables and the plankton development were related to the hydrologic regime and reached minimum values during floods because of low temperatures and dilution. Local effects on the water's ionic composition became pronounced during droughts because of groundwater input. Nutrient concentrations were mainly associated with point wastewater discharges. Conductivity, ion concentrations, total plankton biomass, and species richness increased in the Salado-River downstream site, after the canals' discharges. The artificial-drainage system definitely promotes the incorporation of salts into the Salado-River basin. In this scenario, a careful hydraulic management is needed to take into account this issue of secondary salinization that threatens the economic exploitation of the region. The wetlands present in this study acted as service environments not only helping to reduce salt, nutrient, and suspended-solid concentrations downstream but also contributing a plethora of species and plankton biomass into the Salado-River main course.

Serpoleskea minutissima comb. nov., a micro-rheophyte in the Pylaisiadelphaceae

A recent collection of Platydictya minutissima from Kentucky, U.S.A., prompted a re-examination of the species. Based on rhizoid placement and pseudoparaphyllium form, the taxon is transferred to Serpoleskea as S. minutissima (Sull. & Lesq.) W.R.Buck & B.H.Allen. The species is restricted to eastern North America. Ecologically the taxon grows on moist rocks in or along streams, becoming submerged at times of high water.

Flood-tide interaction numerical simulation at Min River tidal reach

Flood and tide features atMin River tidal reach are analyzed anda high-resolution flood-tide coupled model which useshigh-resolution GIS data for Minjiang Estuary with the highest grid resolution of 50-100m at key areas isestablished in this paper. Unstructured triangular mesh that can realize the grid resolution of 50-100m at key areas is employed in the model. Zhuqi section is chosen for flood boundary, and three numerical experimentsare conducted for June 6 2006 flood process. The experimental results indicate that, when coupled with tide and flood, the simulation of each tide gauge agrees very well with measured data compared withmodelresults only with flood or tide, and the original tidal features are changedat the different sections in Min River tidal reachedby the flood signals. Obvious flood characteristics are shown in Wenshanli and Jiefang Bridge station and flood-tidal mixed characteristics are shown in Xianan, Baiyantan and Guantou station.The strong interaction between tide and floodoccursin the watercourse (from Xiannan in South Channel to Guantou) because the current velocity is reduced during high water time but increasedduringlow water time.

On the formation of tide-produced seiches and double high waters in coastal seas

We describe a mechanism by which the tide, forcing a coastal water body, produces an oscillation at the natural period of the water body – a seiche – around the time of high water. The seiche appears as a distortion in the tidal curve which can, under certain conditions, produce a double high water. The formation of the seiche is explored with a numerical simulation of a sea strait, forced by the tide at its open ends. A seiche, of wavelength equal to twice the length of the strait, is formed when the mean depth of the strait is similar to the tidal range: the rapid reduction of friction as high water is approached appears to be an important part of the formation process. Observations of water level in the centre of a shallow sea strait in north Wales confirm that there is a residual oscillation around high water with the form of a damped seiche. The crest of the seiche occurs just before, and the trough just after, the maximum in the fitted tidal curve. The seiche slows the fall of the tide after high water and on one occasion, at neap tides, the fall is reversed and a double high water is formed. It is possible that this mechanism, hitherto unidentified, contributes to the formation of double high waters in other shallow coastal locations.

The tide predictions for D-Day

Based on the physics of Newton and Laplace, the big brass tide-predicting machine designed by Lord Kelvin was crucial for the success of the Normandy invasion in World War II.

Integration Potential of INFOMAR Airborne LIDAR Bathymetry with External Onshore LIDAR Data Sets

Light detection and ranging (LIDAR) data are used for a wide array of purposes in the coastal zone. This can result in LIDAR data being collected multiple times in order to meet the specific needs of different agencies. This paper assesses the potential for airborne LIDAR bathymetry (ALB) and topographic LIDAR to be integrated for use in coastal research. Two topographic LIDAR data sets and an ALB data set are examined in three coastal test areas. Consideration of the potential for data integration focuses upon external validation of each data set using global positioning system (GPS) points, comparison of subareas and onshore-offshore cross-sections, horizontal feature matching onshore, and data set datum conversion. Data accuracy and datum integration potential confirm that all three data sets can be integrated onshore to facilitate extended LIDAR coverage and possibly also to minimise survey duplication in the coastal zone. Integration potential offshore is assessed by comparing the littoral component of an onshore topographic LIDAR digital surface model (DSM) data set with ALB data. Water-surface returns in the topographic LIDAR data collected during times of high water are found to constitute a barrier to data integration offshore, but topographic LIDAR data captured at low tide in one of the three coastal test areas suggest an opportunity to minimise duplicate surveying in the coastal zone.

Mapeamento e avaliação do risco a inundação do Rio Cachoeira em trecho da área urbana do Município de Itabuna/BA

Os mapas de inundação se configuram em um instrumento importante na prevenção, controle e gestão das inundações, pois através deles é possível definir as áreas de risco. Itabuna município localizado ao sul da Bahia, com cerca de 97,20% (IBGE, 2000) de sua população vivendo na zona urbana , vem sofrendo com as constantes cheias do rio Cachoeira. Em geral, ocorrem cheias anuais que inundam, principalmente, trechos de ocupação subnormal ao longo do rio. Dessa forma, o objetivo dessa pesquisa foi reconhecer e mapear os aspectos físico-ambientais de trecho do rio Cachoeira que engloba os aglomerados subnormais do Bananeira, Rua Beira Rio e Jaçanã, tendo em vista a sua avaliação frente ao fenômeno de inundação e enfatizando a definição das áreas potenciais de risco. Assim, com a utilização do programa ArcView foi possível elaborar um mapa de risco com manchas de inundação para vários períodos de retorno. As áreas de risco com maiores problemas em relação ás inundações são as áreas subnormais, principalmente, em função da vulnerabilidade habitacional e da ocupação desordenada, onde a maioria das habitações é constituída por barracos.

Underwater sunlight maxima in the Menai Strait

In a tidal sea, the time variation of underwater daylight depends on the rise and fall of the tide as well as the motion of the sun across the sky. If conditions are right, more than one maximum in underwater daylight can occur in a single day. In this paper we apply a simple analytical solution for the number of maxima and their timing to observations in the Menai Strait in Europe. The number of maxima depends on the value of the parameter γ = kRω2q2 where k is the diffuse attenuation coefficient, R is the tidal range, ω the angular frequency of the tide and q is a factor proportional to the day length. If the value of γ is greater than a critical value, and the day is long enough, then a double maximum in underwater sunlight is formed. The maxima lie between noon and low water, and their time relative to noon is given by tL = γ/(γ+4) where tL is the time of low water relative to noon. The critical value of γ varies from 4 to about 18, depending on the time of high water. The necessary length of day to produce the double maximum depends on the time of low water relative to noon, the required condition being |tL|<3q/2+6q/γ, where tL is the time of low water in hours relative to noon. The observations reported here are in agreement with these predictions. In the high tidal ranges of the Menai Strait, γ exceeds the critical value for about half the spring–neap cycles in summer, and the daily pattern of illumination switches from a double peaked to a single peaked curve. Maxima occur as early as 6 am and as late as 7 pm. Over this complete range, the times of the observed maxima are close to those predicted, the rms difference between times of observed and predicted maxima is about 45 min and the mean difference is less than 10 min. We conclude that the analytical theory presented here is a useful practical tool for predicting maxima in underwater sunlight in a tidal sea.

Geolocation of free-ranging fish on the European continental shelf as determined from environmental variables II. Reconstruction of plaice ground tracks

Between December 1993 and February 1997, 302 electronic data storage tags (DSTs), programmed to record depth at 10-min intervals and temperature daily, were attached to mature female plaice, Pleuronectes platessa, and released in the southern North Sea. Fifty tags were returned, 38 of which functioned fully and recorded 2,955 days of data. Twenty-seven tags recorded data over the full period at liberty, and 34 geographical ground tracks were reconstructed. Reconstruction was performed using a two-dimensional tidal stream simulation model that translated vertical movement of fish, recorded by DSTs, into horizontal movement assuming an initial down-tide swimming speed of 0.6 body lengths s−1. Geographical accuracy of reconstructed tracks was assessed based on closeness of fit between (1) reconstruction endpoint and reported recapture position; (2) reconstructed locations and corresponding locations based on tidal data recorded by DSTs using the tidal location method (TLM; location of areas with similar tidal range and time of high water); and (3) DST temperature records and corresponding averaged sea surface temperature data records for corresponding locations. The results demonstrate that the assumptions of the tidal stream simulation model were sufficient to reconstruct geographically accurate representations of the migrations of individual plaice, which have in turn provided new information on the extent, duration, and directionality of movement. Our study demonstrates how DSTs can provide fishery-independent data with direct management applications in behaviourally driven, individual-based predictive models of fish migration.

Geolocation of free-ranging fish on the European continental shelf as determined from environmental variables

Demersal fish cannot readily be tracked using satellite-based or light-based geolocation techniques. As an alternative, we describe the tidal location method, which uses tidal data recorded by electronic data storage tags (DSTs), to determine geoposition. Times of high water (H) and tidal ranges (R) recorded by DSTs moored at known locations, and from free-swimming tagged plaice, Pleuronectes platessa, were compared with a North Sea tidal database to identify all positions with matching values of H and R. Within the recording precision of the tag (±0.2 m, ±10 min) and the predicted accuracy of the model generated tidal data (±0.15 m, ±20 min), geolocations over much of the North Sea and eastern English Channel were predicted to be accurate to within 40 km, sometimes to within 10 km. Positional estimates of the moored tags were within 15.7±3.5 km of the actual locations. Geolocations made from tagged plaice within 5 days of release and 5 days pre-recapture were within 35±24 km and 37±23 km of release and recapture positions respectively. Our results demonstrate the ability of this method to accurately describe the migrations of North Sea plaice throughout their geographical range with a level of accuracy unattainable using light-based geolocation. The method could equally be applied to any shelf-dwelling demersal fish that periodically rests on the sea-bed for the duration of a tidal cycle. In fisheries management, the method has clear potential application in defining the movements and migrations of other commercial species.

Tidal current asymmetry in shallow estuaries and tidal creeks

We examine tidal asymmetry in a 100-km long coastal plain estuary, a 15-km long tidal creek closed at the end, and a small side channel of a coastal plain estuary closed at low water. Current meter and water depth data were harmonically analyzed for M2 and the M4 and M6 overtide. The results are displayed in a plot of tidal current versus water level and the effects of the M2, M2+M4, and M2+M4+M6 are compared in order to show how overtides affect tidal asymmetry in the different systems.The long estuary showed a gradual increase in tidal current asymmetry. The current takes on a more progressive nature as it goes into the estuary, as indicated by increasing lags between high or low water and the corresponding slack water. On the other hand, the tidal creek has its reflection point at the head, a relatively short distance from the observations, which reflects the incident tidal wave more efficiently.The tidal creek has a high salt marsh which is covered only an hour or so before high water. Since its intertidal areas flood and drain near the time of high water, maximum flood and ebb currents occur a short time before and after high water slack throughout the tidal creek. Most of the tidal energy is dissipated at the end of the creek where M6/M2 of the tidal current almost doubles.The small side channel has tidal flats that become covered soon after the time of low water. The relative time of maximum flood and ebb currents occurs much closer to the time of low-water-slack, which contrasts significantly to the timing in the tidal creek channel surrounded by high salt marsh.

Peculiar Appearance of Nearly Symmetrical Tidal Flooding Time Along the Western Coast of Taiwan

ABSTRACTDuring the past several decades, nearly symmetrical tidal appearances, both the time of high water elevation and the tidal range, were noted along the western coast of Taiwan. Research corresponding to anomalous amplifications of tidal range have been well studied by Lin, et al. [1,2], but the particular symmetrical tidal appearance of high water time has not yet been clarified. In this paper, we firstly apply a harmonic analysis to tidal data compiling. Based on the results, the important symmetric appearances of high water time and tidal range can be located. Emphasis is given on the investigation of symmetrical distribution of high water time by superposing two progressive waves that interfere on a topographic shelf with specific width. A conceptual configuration of co-oscillating standing tides is proposed to demonstrate the symmetrical tidal range distributing in the space domain and oscillating in the time domain.

Changes in Beach Water Table Elevation during Neap and Spring Tides on a Sandy Estuarine Beach, Delaware Bay, New Jersey

A field investigation of temporal and spatial changes in wind and wave characteristics, runup and beach water table elevation was conducted on the foreshore of an estuarine beach in Delaware Bay during neap (April 9, 1995) and spring (April 16, 1995) tides under low wave-energy conditions. The beach has a relatively steep, sandy foreshore and semi-diurnal tides with a mean range of 1.6 m and a mean spring range of 1.9 m. Data from a pressure transducer placed on the low tide terrace reveal a rate of rise and fall of the water level on April 16 of 0.09 mm s−1 resulting in a steeper tidal curve than the neap tide on April 9. Data from three pressure transducers placed in wells in the intertidal foreshore reveal that the landward slope of the water table during the rising neap tide was lower than the slope during spring tide, and there was a slower rate of fall of the beach water table relative to the fall of the tide. Wave heights were lower on April 9 (significant height from 17.1 min records <0.16 m). The water table elevation was 0.08 m higher than the water in the bay at the time of high water, when maximum runup elevation was 0.29 m above high water and maximum runup width was 2.0 m. The elevation of the water table was 0.13 m higher than the maximum elevation of water level in the bay 74 min after high water, when wave height was 0.12 m and wave period was 2.7 s. The use of mean bay water level at high tide will underpredict the elevation of the water table in the beach, and demarcation of biological sampling stations across the intertidal profile based on mean tide conditions will not accurately reflect the water content of the sandy beach matrix.

Numerical modeling of tides in the Gulf of Suez, Egypt

A vertically integrated two‐dimensional (2‐D) and a five‐layer three‐dimensional (3‐D) numerical models were developed to compute the tides in the Gulf of Suez, Egypt. The computational grid used to schematize the Gulf has a horizontal resolution of 3 × 3 km and consists of a lattice of 23 × 100 points in the 2‐D model and five such lattices in the 3‐D model. Both 2‐D and 3‐D simulations clearly revealed the Kelvin wave nature of the tide with partial reflection. The M2 simulations also showed a strong tidal signature in the southern sector as compared to the northern part. For the 3‐D simulations, the horizontal and vertical eddy viscosity coefficients and the coefficient of bottom friction were respectively set to 3 × 106 cm2/s, 200 cm2/s, and 0.001. The tidal range decreases from the entrance of the Gulf of Suez toward the Bank of Tor where it reaches a small value and then increases again to about 1.5 m at Suez. A difference of six hours exists between the times of high water at the southern and north...

Similarity in food source and timing of feeding in deposit- and suspension-feeding bivalves

Although adapted to different methods of feeding, depositand suspension-feeding bivalves in the Wadden Sea (The Netherlands) appear to rely partly on the same limiting food sources. Two conditions for food competition, viz. use of the same food source and simultaneous feeding (in relation to season and tidal cycle), were studied in the field. The algal species composition in the stomachs of 3 suspension feeders (Cerastoderma edule, Mya arenaria and Mytilus edulis) and 2 deposit feeders (Macoma balth~ca and Scrobicularia plana) showed high correlations with the species composition of the water column, but lower correlations with the species composition of the sedment surface. During the phytoplankton spring-bloom penods in April and May, the stomachs of the suspension feeders C. edule, M. arenaria and M. edulis, and the deposit feeder M. balthica contained maximum amounts of algae. During the tidal cycle, the stomachs of the suspension feeders generally contained minimum amounts of algae when the tidal flat was drained and maximum amounts around times of high water. The stomachs of the deposit feeder M. balthica, however, contained relatively high amounts of algae during the entire tidal cycle. These results indicate that, although some difference in feeding behaviour was observed between deposit and suspension feeders, both groups rely on the same food source at the same time, irrespective of type of feeding

Experimental analysis of the diurnal and tidal spawning rhythm in the chiton Acanthopleura japonica (Lischke) by manipulating conditions of light and tide

The environmental time cues entraining the diurnal and tidal spawning periodicity of the chiton Acanthopleura japonica (Lischke) were analysed experimentally by providing artificial tidal and lighting conditions. The timing mechanism of synchronous spawning is entrained by a diurnal light-dark cycle and a semidiurnal tidal immersion cycle, sensed at both the beginning and the end of immersion. Consequently, gametes are released principally before the peak of morning high water on spring tides. The timing mechanism guarantees that chiton gametes are released at the time of high water, when they are immersed and that release is concentrated within a short period, independent of the height of the shore inhabited by the chitons.

Entrainment of Tidal and Semilunar Rhythms by Artificial Moonlight Cycles

A marked feature of the larval release activity of the terrestrial crab Sesarma haematocheir is its synchronization with the time of high water. This activity occurs only at night, so that the pattern of the tidal rhythm recurs at semi-monthly intervals. When adult specimens from Seto (Okayama Prefecture) and Shima (Mie Prefecture) populations were brought from the field into 24-h light-dark conditions in spring, the larval release occurred at night, but the overall activity pattern gave no indication of a tidal component. On the contrary, under simulated moonlight cycles the timing of release was strongly coordinated and exhibited a well-defined tidal component arranged at semi-monthly intervals. The phase difference between the evoked tidal rhythms of the two populations of 4-5 h was about equal to the phase difference of the tidal cycles in their natural habitats. Synchronization of larval release with the artificial moonlight cycle required more than 40 days of exposure. In addition to entraining the tidal rhythm, artificial moonlight induced a semilunar rhythm in both populations. Entrainment could be achieved with exposure to moonlight for just a few days around the time of the full moon. In this paper, underlying mechanisms of the Sesarma larval release rhythm, which involves both tidal and semilunar components, are explained in terms of circadian oscillatory systems.

Internal waves and intense mixing periods in a partially stratified estuary

The results of an echo-sounding survey of the Tees estuary are presented. Intense mixing periods, characterized by a surface layer of increasing salinity and thickness, were observed on the ebb tide and were preceded by periods of internal wave activity. Previously, it had been conjectured that similar mixing periods were caused by the breaking of upstream-travelling internal waves. The present survey, however, reveals that the observed waves were travelling down-stream and indicates that the mixing was principally due to a series of bridges. The times of the onset of mixed water at various stations in the estuary were consistent with the production of mixing from about the time of high water, with subsequent advection downstream. The mixing produced in this way, and by similar structures in other estuaries, clearly needs to be quantified.

Seasonal and semi‐lunar modulation of the endogenous swimming rhythm in the estuarine amphipodcorophium volutator(pallas)

The endogenous circa‐tidal rhythm of swimming activity shown by Corophium volutator varies seasonally, and also over the spring to neap tide cycle. Semi‐lunar modulation is evident in both phase and amplitude and analysis of the free‐swimming period using a modified correlogram technique indicates that the rhythm also undergoes slight (<0.1 phase) changes in period which are correlated with similar variations in the period of the tide. Activity maxima are greatest at or just after the time of spring tides, and these peaks show a greater phase delay relative to the predicted time of high water than those recorded during the neap tide period. This semi‐lunar variation in phase is not significant during the winter when the rhythm is generally less distinct. It is suggested that the results are best interpreted in terms of two interactive oscillators, one of circadian, the other of circa‐tidal period, and the biological significance of these variations in the swimming pattern is considered.