Tidal effects on groundwater dynamics in unconfined aquifers

The variation of seawater level resulting from tidal fluctuations is usually neglected in regional groundwater flow studies. Although the tidal oscillation is damped near the shoreline, there is a quasi-steady-slate rise in the mean water-table position, which may have an influence on regional groundwater flow. In this paper the effects of tidal fluctuations on groundwater hydraulics are investigated using a variably saturated numerical model that includes the effects of a realistic mild beach slope, seepage face and the unsaturated zone. In particular the impact of these factors on the velocity field in the aquifer is assessed. Simulations show that the tidal fluctuation has substantial consequences for the local velocity field in the vicinity of the exit face, which affects the nearshore migration of contaminant in coastal aquifers. An overheight in the water table as a result of the tidal fluctuation is observed anti this has a significant effect on groundwater discharge to the sea when the landward boundary condition is a constant water level. The effect of beach slope is very significant and simplifying the problem by considering a vertical beach face causes serious errors in predicting the water-table position and the groundwater flux. For media with a high effective capillary fringe, the moisture retained above the water table is important in determining the effects of the tidal fluctuations. Copyright (C) 2001 John Wiley & Sons, Ltd.

The calculation of accident risks in fitness for work assessments: diseases that can cause sudden incapacity

Risk equations have been developed to assist in determining fitness for work of people with diseases that may cause rapid loss of control. The four equations calculate the frequency of fatal injury to the person with the disease, the frequency of fatal injury to colleagues in the workplace, and the cost of fatal injury and property damage to the employer, it is suggested that the additional risk of fatal injury to the person with the disease should not exceed the fatal injury rate in high-risk industries such as forestry, fishing and mining. it is also suggested that the additional risk of fatal injury to each colleague should be no more than one-tenth of the fatal injury rate due to motor vehicle accidents in the community. Two hypothetical case examples are given, demonstrating the use of the equations. The equations highlight the need to examine the risks associated with individuals, their specific jobs and their workplaces. They also highlight significant uncertainties in the determination of fitness, which perhaps have been underestimated in the past. Wherever possible, redundant defences should be utilized to prevent accidents in the event of sudden incapacity.

A low-latitude bloom of the surf-zone diatom, Anaulus australis (Centrales, Bacillariophyta) on the coast of Southern Queensland (Australia)

A novel bloom of the surf diatom Anaulus australis Drebes et Schultz was observed in subtropical waters off Surfers' Paradise, Queensland, Australia (27 degrees 55'S; 153 degrees 23'E) in early May 2000. This is the lowest latitude in which an Anaulus australis surf diatom bloom has been reported. Nitrogen stable isotope analysis of surf diatoms may indicate anthropogenic nutrient inputs in this environment.

Wildlife-based tourism & increased support for nature conservation financially and otherwise: evidence from sea-turtle ecotourism at Mon Repos

The arguments of most conservationists supporting ecotourism have been based on the view that it is environmentally friendly as a resource-use and that receipts from it can counter demands to use the natural resources involved for more extractive economic purposes. But wildlife-based ecotourism can also have positive impacts in itself on the willingness of tourists to pay for wildlife conservation, strengthen the pro-conservation attitudes of tourists, and foster personal actions by them that contribute to wildlife conservation. These aspects are explored in this article on the basis of a survey of tourists visiting Mon Repos Beach near Bundaberg, Queensland, for the purpose of watching marine turtles. The results enable several of the conservation impacts of this experience on tourists to be quantified, and highlight important relationships between specific socio-economic variables and the willingness of tourists to pay for the protection of sea turtles. Furthermore, it is shown that the on-site experiences of ecotourists have positive impacts on the willingness of tourists to pay for the conservation of wildlife, and that willingness to pay is sensitive to whether or not wildlife is seen. It is suggested that in situ ecotourism is likely to be a more powerful force for fostering pro-conservation attitudes and actions among visitors than ex situ wildlife-based tourism in aquaria and zoos.

A risk-based system to penalize and reward line management for occupational safety and health performance

Penalizing line management for the occurrence of lost time injuries has in some cases had unintended negative consequences. These are discussed. An alternative system is suggested that penalizes line management for accidents where the combination of the probability of recurrence and the maximum reasonable consequences such a recurrence may have exceeds an agreed limit. A reward is given for prompt effective control of the risk to below the agreed risk limit. The reward is smaller than the penalty. High-risk accidents require independent investigation by a safety officer using analytical techniques. Two case examples are given to illustrate the system. Continuous safety improvement is driven by a planned reduction in the agreed risk limit over time and reward for proactive risk assessment and control.

Beware the boogie board: blunt abdominal trauma from bodyboarding

Riding waves on a bodyboard (boogie board) at the beach is popular with children. Three teenagers who sustained blunt abdominal trauma during bodyboarding are described. Two suffered lacerated livers, one a lacerated spleen. Serious blunt abdominal injuries from bodyboarding mishaps have not previously been reported. The usual method of riding a bodyboard may place the rider at risk of abdominal trauma.

Numerical modelling of contaminant transport in coastal aquifers

This paper employs a two-dimensional variable density flow and transport model to investigate the transport of a dense contaminant plume in an unconfined coastal aquifer. Experimental results are also presented to show the contaminant plume in a freshwater-seawater flow system. Both the numerical and experimental results suggest that the neglect of the seawater interface does not noticeably affect the horizontal migration rate of the plume before it reaches the interface. However, the contaminant will travel further seaward and part of the solute mass will exit under the sea if the higher seawater density is not included. If the seawater density is included, the contaminant will travel upwards towards the beach along the freshwater-saltwater interface as shown experimentally. Neglect of seawater density, therefore, will result in an underestimate of solute mass rate exiting around the coastline. (C) 2002 IMACS. Published by Elsevier Science B.V. All rights reserved.

Tide-induced water table fluctuations in coastal aquifers bounded by rhythmic shorelines

Previous studies on tidal water table dynamics in unconfined coastal aquifers have focused on the inland propagation of oceanic tides in the cross-shore direction based on the assumption of a straight coastline. Here, two-dimensional analytical solutions are derived to study the effects of rhythmic coastlines on tidal water table fluctuations. The computational results demonstrate that the alongshore variations of the coastline can affect the water table behavior significantly, especially in areas near the centers of the headland and embayment. With the coastline shape effects ignored, traditional analytical solutions may lead to large errors in predicting coastal water table fluctuations or in estimating the aquifer's properties based on these signals. The conditions under which the coastline shape needs to be considered are derived from the new analytical solution.

Effects of seawater components on immature Culicoides molestus (Skuse) (Diptera : Ceratopogonidae)

Following analysis of beach sites and an indication that seawater components might influence larval occurrence, we studied the impact of increasing salinity and seawater concentration on survival of fourth-instar larvae of the canal biting midge, Culicoides molestus . While NaCl had little effect on immature survival, increasing the concentration of seawater increased mortality prior to the adult stage. Seawater at three and four times the normal concentration killed all immatures. Artificial elevation of seawater concentration in the sandy substrate preferred by larvae, therefore, has the potential to reduce immature midge survival. Diet also affected survival, with higher mortality of immatures that were fed fish-food flakes compared with those that were fed live nematodes.

Occurrence of immature Culicoides molestus (Skuse) (Diptera : Ceratopogonidae) in relation to habitat characteristics

Analysis of beach sites on the Gold Coast, Australia, found that 14 physical and chemical habitat characteristics differed significantly between sites where numerous immatures of the canal biting midge, Culicoides molestus (Skuse), were found and sites where no midge immatures occurred. Five of the chemical factors found to reliably distinguish C. molestus habitat are major components of seawater, while another, electrical conductivity, is related to the concentration of seawater components. Calcium was the only one of the six primary components of seawater that was not a statistically significant correlate of C. molestus habitation by sand analysis. It is likely that a causative variable in occurrence of immatures is the concentration of seawater present in canals, because larvae are found where seawater component concentration is low in relation to uninhabited sites of similar appearance.

Do expertise and the degree of perception-action coupling affect natural anticipatory performance?

Two experiments using a temporal occlusion paradigm (the first with expert and novice participants and the second with participants of intermediate skill) were conducted to examine the capability of tennis players to predict the direction of an opponent's service in situ. In both experiments two different response conditions, reflecting differing degrees of perception-action coupling, were employed. In a coupled condition players were required to make a movement-based response identical to that which they would use to hit a return of service in a game situation, whereas in an uncoupled condition a verbal prediction of service direction was required. Experiment 1 provided clear evidence of superior prediction accuracy under the coupled response condition when ball flight was available, plus some limited evidence to suggest that superior prediction accuracy under uncoupled response conditions might hold true if only advance (pre-contact) information was available. Experiment 2 showed the former finding to be a robust one, but was unable to reveal any support for the latter. Experiment 1 also revealed that expert superiority is more apparent for predictions made under natural (coupled) than uncoupled response-mode conditions. Collectively, these findings suggest that different perceptual processes may be in operation in anticipatory tasks which depend on skill level, the type of information presented, and degree of perception-action coupling inherent in the task requirements.

Caracterização morfodinâmica do litoral Norte Fluminense, RJ, Brasil

A morfologia das praias é reflexo da ação hidrodinfunica com o tipo de sedimento disponível. Esta interação se dá a partir da base de ação das ondas, tornando-se mais efetiva na zona de arrebentação onde a energia é dissipada, originando na zona de surfe que se estende em direção à linha de costa até Q limite do espraiamento na face de praia. O objetivo deste trabalho é apresentar as características morfodinâmicas do litoral NE do Estado do Rio de Janeiro, baseando-se na análise da variação espaço Hemporal de perfis de praia, na morfologia da plataforma continental e em fotos aéreas. Os perfis de praia foram levantados durante cinco anos pela PETROBRÁS S/A, em oito estações ao longo do litoral. O comportamento morfodinâmico distinto de setores do litoral estudado é função do padrão de ondas e direção da linha de costa, morfologia da plataforma interna controlando a extensão da zona de surfe e o número de zonas de arrebentação, características dos sedimentos e gradiente da face de praia. Foram reconhecidos quatro compartimentos morfodinâmicos distintos, com base na morfologia dos perfis praiais e plataforma interna, no índice de mobilidade da linha de praia, granulometria x gradiente da face de praia e o parâmetro Q. Os quatro compartimentos são: Atafona/Foz do Rio Paraíba do Sul - estágio morfodinâmico intermediário a dissipativo, com o maior índice de mobilidade e elevada taxa de erosão; Sul de Atafona-Cabo de São Tomé - estágio intermediário a refletivo com baixo índice de mobilidade da praia; Cabo de São Tomé - estágio refletivo a intermediário com alto índice de mobilidade da praia; Cabo de São Tomé-Cabiúnas - estágio refletivo com baixo índice de mobilidade.

Campo térmico e higrométrico da Regional Praia do Canto no município de Vitória (ES)

Nesta pesquisa foi analisado o comportamento térmico e higrométrico em diferentes locais da Regional Praia do Canto no município de Vitória (ES) tanto no período chuvoso quanto no seco por meio da técnica de transecto móvel. A análise confirmou que as mudanças de uso e cobertura da terra associado com as características do relevo influenciam diretamente as variáveis meteorológicas, neste caso a temperatura do ar e umidade relativa do ar. A análise das condições médias de temperatura do ar e umidade relativa do ar permitiu observar dois núcleos aquecidos um ao norte e outro ao sul na área em estudo. Às 15h, tanto no verão como no inverno, a temperatura do ar atingiu o valor máximo e as taxas de umidade relativa, o seu valor mínimo. No verão e inverno, as áreas mais aquecidas ficaram bem definidas, áreas correspondentes aos núcleos aquecidos. As maiores influências do tecido urbano nas variáveis meteorológicas foram verificadas sob atuação da Alta Subtropical do Atlântico Sul. A maritimidade têm um peso importante no comportamento topoclimático urbano, sobre tudo na parte da manhã e da tarde. Na porção centro-leste da área em estudo observou-se até 3ºC a menos nos períodos vespertinos em relação aos pontos localizados na porção norte e sul. Os pontos à centroleste sofrem influência direta dos efeitos da maritimidade e dos arranjos dos prédios que formam sombreamento (Cânions Urbanos), fato que dificulta a formação de núcleos aquecidos durante o dia sobre esta porção. Foram observadas nos dois períodos, tanto no período chuvoso (verão) como também, no período seco (inverno), elevado gradiente térmico, estes localizadas onde há intenso fluxo de veículos, e também nas áreas de construção mais verticalizadas. A intensidade do gradiente térmico é maior sobre a atuação da Alta Subtropical do Atlântico Sul. Às 09 horas, são registrados os maiores gradientes térmicos para os dois períodos analisados. A umidade relativa do ar mantevese elevada durante os dois campos, tanto no verão quanto inverno. Os menores valores de umidade foram registrados em pontos que compõem o núcleo aquecido verificado na parte norte da área em estudo. Em virtude do comportamento das variáveis observadas foram identificadas três unidades Topoclimáticas Urbanas na Regional Praia do Canto.

Identification of tsunami-induced deposits using numerical modeling and rock magnetism techniques: A study case of the 1755 Lisbon tsunami in Algarve, Portugal

Storm- and tsunami-deposits are generated by similar depositional mechanisms making their discrimination hard to establish using classic sedimentologic methods. Here we propose an original approach to identify tsunami-induced deposits by combining numerical simulation and rock magnetism. To test our method, we investigate the tsunami deposit of the Boca do Rio estuary generated by the 1755 earthquake in Lisbon which is well described in the literature. We first test the 1755 tsunami scenario using a numerical inundation model to provide physical parameters for the tsunami wave. Then we use concentration (MS. SIRM) and grain size (chi(ARM), ARM, B1/2, ARM/SIRM) sensitive magnetic proxies coupled with SEM microscopy to unravel the magnetic mineralogy of the tsunami-induced deposit and its associated depositional mechanisms. In order to study the connection between the tsunami deposit and the different sedimentologic units present in the estuary, magnetic data were processed by multivariate statistical analyses. Our numerical simulation show a large inundation of the estuary with flow depths varying from 0.5 to 6 m and run up of similar to 7 m. Magnetic data show a dominance of paramagnetic minerals (quartz) mixed with lesser amount of ferromagnetic minerals, namely titanomagnetite and titanohematite both of a detrital origin and reworked from the underlying units. Multivariate statistical analyses indicate a better connection between the tsunami-induced deposit and a mixture of Units C and D. All these results point to a scenario where the energy released by the tsunami wave was strong enough to overtop and erode important amount of sand from the littoral dune and mixed it with reworked materials from underlying layers at least 1 m in depth. The method tested here represents an original and promising tool to identify tsunami-induced deposits in similar embayed beach environments.

Identification of tsunami-induced deposits using numerical modeling and rock magnetism techniques: A study case of the 1755 Lisbon tsunami in Algarve, Portugal

Storm- and tsunami-deposits are generated by similar depositional mechanisms making their discrimination hard to establish using classic sedimentologic methods. Here we propose an original approach to identify tsunami-induced deposits by combining numerical simulation and rock magnetism. To test our method, we investigate the tsunami deposit of the Boca do Rio estuary generated by the 1755 earthquake in Lisbon which is well described in the literature. We first test the 1755 tsunami scenario using a numerical inundation model to provide physical parameters for the tsunami wave. Then we use concentration (MS. SIRM) and grain size (chi(ARM), ARM, B1/2, ARM/SIRM) sensitive magnetic proxies coupled with SEM microscopy to unravel the magnetic mineralogy of the tsunami-induced deposit and its associated depositional mechanisms. In order to study the connection between the tsunami deposit and the different sedimentologic units present in the estuary, magnetic data were processed by multivariate statistical analyses. Our numerical simulation show a large inundation of the estuary with flow depths varying from 0.5 to 6 m and run up of similar to 7 m. Magnetic data show a dominance of paramagnetic minerals (quartz) mixed with lesser amount of ferromagnetic minerals, namely titanomagnetite and titanohematite both of a detrital origin and reworked from the underlying units. Multivariate statistical analyses indicate a better connection between the tsunami-induced deposit and a mixture of Units C and D. All these results point to a scenario where the energy released by the tsunami wave was strong enough to overtop and erode important amount of sand from the littoral dune and mixed it with reworked materials from underlying layers at least 1 m in depth. The method tested here represents an original and promising tool to identify tsunami-induced deposits in similar embayed beach environments.