Hazard assessment in rock cliffs at Central Algarve (Portugal): A tool for coastal management

Coastal hazards are in the interface of human activities with natural coastal processes. The conflicts arising from this relationship require new approaches suitable for coastal management that consider the dynamic of coastal areas. A method to assess hazard in rock cliffs is presented, combining cliff evolution forcing mechanisms along with protection factors, according to a weighted factors system. This method provides a rapid evaluation of vulnerability for cliffed areas, supporting coastal management and hazard mitigation. The method was applied to the rocky cliffs of the densely populated coastal zone between Galé and Olhos de Água (Southern Portugal), where high and very high hazard values were found to be dominant. A method validation was made using the vulnerability areas and the recorded mass movements over a 45 year period in the same area.     

Numerical prediction of an intense convective system associated with the July 1987 montreal flood. part II: A trailing stratiform rainband

Abstract

In this study, the internal circulation structures of the 14 July 1987 intense mesoscale convective system (MCS) are investigated using an improved high‐resolution version of the Canadian regional finite‐element model. It is found that although the MCS is characterized by a leading convective line followed by a trailing stratiform rainband, the associated circulation structures differ substantially from those in the classical midlatitude squall system. These include the rapid propagation and separation of the leading convection from the trailing rainband, the development of a surface‐based instead of an elevated rear‐to‐front descending flow and a shallow front‐to‐rear ascending flow associated with the stratiform precipitation, the generation of low‐ and mid‐level rather than mid‐ to upper‐level stratiform cloudiness and the development of a strong anticyclonic vorticity band at the back edge of the stratiform region. It is shown that the trailing stratiform rainband is dynamically forced by frontogenetical processes, and aided by the release of conditional symmetric instability and local orographical lifting. The intense leading and trailing circulations result from latent heat released by the convective and explicit cloud schemes, respectively. Sensitivity experiments reveal that the proper coupling of these two cloud schemes is instrumental in obtaining a realistic prediction of the above‐mentioned various mesoscale components. Vorticity budget calculations show that tilting of horizontal vorticity contributes the most to the amplification of the anticyclonic vorticity band, particularly during the squall's incipient stage. The sensitivity of the simulated squall system to other model physical parameters is also examined.     

Long‐term final void salinity prediction for a post‐mining landscape in the Hunter Valley,New South Wales,Australia

Opencast mining alters surface and subsurface hydrology of a landscape both during and post‐mining. At mine closure, following opencast mining in mines with low overburden to coal ratios, a void is left in the final landform. This final void is the location of the active mine pit at closure. Voids are generally not infilled within the mines' lifetime, because of the prohibitive cost of earthwork operations, and they become post‐mining water bodies or pit lakes. Water quality is a significant issue for pit lakes. Groundwater within coal seams and associated rocks can be saline, depending on the nature of the strata and groundwater circulation patterns. This groundwater may be preferentially drawn to and collected in the final void. Surface runoff to the void will not only collect salts from rainfall and atmospheric fallout, but also from the ground surface and the weathering of fresh rock. As the void water level rises, its evaporative surface area increases, concentrating salts that are held in solution. This paper presents a study of the long term, water quality trends in a post‐mining final void in the Hunter Valley, New South Wales, Australia. This process is complex and occurs long term, and modelling offers the only method of evaluating water quality. Using available geochemical, climate and hydrogeological data as inputs into a mass‐balance model, water quality in the final void was found to increase rapidly in salinity through time (2452 to 8909 mg l⁻¹ over 500 years) as evaporation concentrates the salt in the void and regional groundwater containing high loads of salt continues to flow into the void. Copyright © 2004 John Wiley & Sons, Ltd.     

The role of shoshonitic and calc-alkaline suites in the tectonic evolution of the Carajás District, Brazil

In the Carajás District, the Bahia Prospect and Grão Pará volcanosedimentary sequences, both of Archean age, have been the object of extensive petrochemical studies for major, trace, and rare earth elements. In spite of the widespread spilitization that affected the volcanic mafic rocks, the petrochemical nature of the mafic volcanism may still be assessed on the basis of the less mobile elements like P, Cr, Zr, Nb, Ti, and REE. The Bahia Prospect basalts have a petrochemical affinity with Phanerozoic island-arc calc-alkaline basalts. The Grão Pará basalts and basaltic andesites, on the other hand, have a petrochemical affinity with Phanerozoic basalts of a mature island arc environment. The petrochemical data presented here lead to a new geotectonic interpretation of the area, where the volcanic sequences are genetically linked to Archean subduction processes.     

Biogeochemistry of the Madeira river basin

A biogeochemical characterization of the Madeira river basin has been made to evaluate the local and global effects of possible alterations in the ecosystem caused by recent intensive occupation in Rondonia state. During the period April 1983—January 1986, sampling was made both by land and river along the tributaries and main channel of the Madeira river. The parameters analysed lead to a detailed study of the physicochemical quality of the waters of the basin and their relationship with the local geology, associated with the transport of solid material and the hydrological behavior of the ecosystem.Penman's method adapted to tropical rainforest conditions was used to evaluate the potential evapotranspiration for the basin. Estimated potential evapotranspiration was 1420 mm/y, 77% due to the energy balance. Real evapotranspiration was 94% of the estimated potential and the main residence time of the rain water in the basin was 2 months. The isotopic behavior of Hydrogen and Oxygen in the river waters of the region was typical of great rivers, the values being more positive during the dry season and more negative during the rainy season. An isotopic gradient of ¹⁸O 0.038 ()/100 km, was established from Porto Velho station to the estuary, which was considered low when compared with the value of 0.063 ()/100 km, obtained for the Amazon river.In general, the waters of the tributaries were poor in dissolved ion species when compared with the main channel of the Madeira river. Seasonal variation in the transport of suspended sediment kept the same pattern, greater transport being observed on rising water than during high water. A transport of 2.85 million tons per day was observed in the Madeira river near the mouth.     

Observations of mine seismicity in the eastern Wasatch Plateau,Utah, U.S.A.: A possible case of implosional failure

In the summer of 1984, a three-dimensional, high-resolution microearthquake network was operated in the vicinity of two coal mines beneath Gentry Mountain in the eastern Wasatch Plateau, Utah. During a six-week period, approximately 3,000 seismic events were observed of which the majority were impulsive, higher frequency (>10 Hz), short duration (<2–3 sec) events probably associated with the caving of the roof from a longwall operation. In contrast, 234 of the largest located events appeared to occur predominantlybeneath the mines to a depth of 2 to 3 km consistent with previous studies. The magnitudes of these events ranged from less thanM _c 0 to 1.6. In addition to the unusual depths of these latter events, an anomalous aspect displayed by the events was an apparent dilatational focal mechanism suggesting a non-double-couple, possibly implosional source. Implosional events have been observed in other studies of mine seismicity; however, the generally inadequate instrumental coverage of the focal sphere has cast some doubt on the validity of such mechanisms. Previously suggested source mechanisms for such implosional events have included tensional failure through strata collapse, and a shear-implosional displacement mechanism. Shear failure must be involved in the failure process of the Gentry Mountain implosional events as evidenced by well-defined shear waves in the observed seismograms. Simultaneous monitoring in the East Mountain coal mining area to the south by the University of Utah revealed typical shear failure events mixed with implosional events. The observed double-couple, reverse focal mechanisms at East Mountain were similar to mechanisms determined in previous studies and a composite focal mechanism determined in this study for a sequence outside the mining areas. This suggested that the shear events within the mining areas are being influenced by the regional tectonic stress field. Thus in addition to the seismic events associated with caving of the roof from the longwall operation, there appear to be at least two other types of mining-induced seismic events occurring in the eastern Wasatch Plateau, both submine in origin: (1) events characterized by apparent non-double-couple possibly implosional focal mechanisms and well-defined shear waves; and (2) shear events, which are indistinguishable from tectonic earthquakes and may be considered mining triggered earthquakes. The small mining-induced stress changes that occur beyond a few hundred meters from the mine workings suggest both types of seismic events are occurring on critically stressed, pre-existing zones of weakness. Topography, overburden, method of mining, and mine configuration also appear to be significant factors influencing the occurrence of the implosional submine events.     

The rank evaluation of South Brazilian Gondwana coals on the basis of different chemical and physical parameters

Rank evaluation of South Brazilian Gondwana coals according to the American (American Society for Testing and Materials, ASTM) and German (Deutsche Industrie Normen, DIN) standard specifications or on the basis of Alpern's Universal Classification has too often led to conflicting results.When any attempt is made to determine the rank of Brazilian coals by using methods established for the Northern Hemisphere coals, two sorts of difficulties arise: namely, (1) the reflectence measurements do not indicate the real degree of coalification of the organic matter because of the liptinitic impregnations of the vitrinites, and (2) random reflectance values (R_ran, moisture, volatile-matter and carbon contents as well as the calorific value do not correlate when plotted on the ASTM and DIN classification schemes.In addition, when rank determinations are carried out by using fluorescence measurements and geochemical analyses the results are at variance in relation to those determined by the conventional chemical and physical parameters.It is suggested that the rank evaluation of South Brazilian coals is far more meaningful if carried out by reflectance measurements on vitrinites along with fluorescence measurements on sporinites, alginites and coal extracts.     

Seasonal soil water storage changes beneath central Amazonian rainforest and pasture

Evaporation and infiltration were compared for tropical rainforest and pasture, near to Manaus, Brazil from October 1990 to February 1992 using measurements of soil water storage over a depth of 2 m. The soil is a clayey oxisol of low water available capacity. In both of the dry seasons studied, the maximum change in soil water storage in the forest was 154 mm and in the pasture it was 131 and 112 mm. Similar behaviour of the soil water reservoir below forest and pasture in the wet season implied that differences in evaporation and drainage were small. In the dry season, soil water storage behaviour in the upper metre of the soil was similar but there were marked differences in the second metre. The pasture took up little water from below 1.5 m but the forest appeared to utilise all of the available water in the 2 m profile in both seasons.

The water balance of the 2 m profile showed that the pasture evaporation rate was equal to that of the forest until storage had decreased 80 mm from the maximum. There was then a decline in pasture evaporation rate to 1.2 mm day⁻¹ as the storage decreased by a further 50 mm. In contrast, the forest uptake rate remained above 3.5 mm day⁻¹ until storage had decreased 140 mm from the maximum (within 15 mm of the extraction limit), before declining abruptly to less than 1.5 mm day⁻¹. There was strong evidence that the forest was able to abstract water from depths greater than 3.6 m.

Spatial variability of soil water storage was significantly greater beneath the pasture than beneath the forest, particularly following rainfall events in the dry season. This was largely the result of redistribution of rainfall as local surface runoff. There was no evidence of redistribution or runoff in the forest.     

North Atlantic Oscillation sensitivity to the El Niño/Southern Oscillation polarity in a large-ensemble simulation

A large ensemble modeling experiment with the Melbourne University General Circulation Model is presented. Thirty 17-year-long independent simulations were performed. All integrations were forced by the same observed sea surface temperatures, obtained from the Atmospheric Model Intercomparison Project II. The simulations were analyzed to assess the sensitivity of the North Atlantic Oscillation (NAO) to the El Niño/Southern Oscillation (ENSO) polarity. The results show signals of the ENSO phases both in the mean strength of the NAO as well as in its internal variability. During the cold ENSO phase, the probability density function of the NAO index presents a small but positive mean value, whereas it is negative during the warm ENSO phase. Also, the NAO variability associated with each ENSO phase shows a different behavior: during the warm phase the probability density function of the NAO index presents a larger variance and suggests a bimodality, whereas no bimodality is suggested in the cold phase.     

Aquifer development planning to supply a seaside resort: a case study in Goa,India

Using the hydrogeological and socio-economic data derived from a European Commission research project on the measurement, monitoring and sustainability of the coastal environment, two optimization models have been applied to satisfy the future water resources needs of the coastal zone of Bardez in Goa, India. The number of tourists visiting Goa since the 1970s has risen considerably, and roughly a third of them go to Bardez taluka, prompting growth in the tourist-related infrastructure in the region. The optimization models are non-linear mixed integer models that have been solved using GAMS/DICOPT++ commercial software. Optimization models were used, firstly, to indicate the most suitable zones for building seaside resorts and wells to supply the tourist industry with an adequate amount of water, and secondly, to indicate the best location for wells to adequately supply pre-existing hotels. The models presented will help to define the optimal locations for the wells and the hydraulic infrastructures needed to satisfy demand at minimum cost, taking into account environmental constraints such as the risk of saline intrusion.

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Résumé A l’aide de données hydrogéologiques et socio-économiques, dérivées d’un projet de recherche de la Commission Européenne sur l’étude, la surveillance et la durabilité de l’environnement c?tier, deux modèles d’optimisation ont été appliqués en vue de satisfaire les besoins futurs en ressources en eau de la zone c?tière de Bardez au Goa en Inde. Le nombre de touristes qui visitent le Goa depuis les années 70 a considérablement augmenté et environ un tiers d’entre eux se rend à Bardez taluka, ce qui encourage la croissance des infrastructures liées au tourisme dans la région. Les modèles d’optimisation sont des modèles non linéaires mixtes en nombres entiers qui ont été résolus en utilisant le logiciel commercial GAMS/DICOPT++. Les modèles d’optimisation ont été utilisés pour indiquer premièrement les zones les plus appropriées pour construire des stations balnéaires et des puits pour approvisionner en quantité d’eau suffisante l’industrie touristique, et deuxièmement pour indiquer la meilleure localisation de puits pour l’alimentation des h?tels préexistants. Les modèles présentés aideront à définir les localisations optimales des puits et des infrastructures hydrauliques nécessaires à la satisfaction de la demande à un co?t minimum, tout en prenant en compte les contraintes environnementales, tel que le risque d’intrusion saline.

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Resumen Se han aplicado dos modelos de optimización en base a datos socio-económicos e hidrogeológicos derivados de un proyecto de investigación de la Comisión Europea sobre medición, monitoreo y sostenibilidad del ambiente costero para satisfacer las necesidades futuras de recursos hídricos de la zona costera de Bardez en Goa, India. El número de turistas que visita Goa desde la década de 1970′s ha subido considerablemente y cerca de un tercio de ellos van a Bardez taluka impulsando el crecimiento en la infraestructura turística de la región. Los modelos de optimización son modelos de números enteros mixtos no-lineales que se han resuelto usando el programa comercial GAMS/DICOPT++. Los modelos de optimización se usaron, primero para indicar las zonas más adecuadas para la construcción de centros de diversión en las márgenes del océano y pozos para abastecer la industria turística con una adecuada cantidad de agua, y segundo, para indicar la mejor localización de pozos para el abastecimiento de hoteles pre-existentes. Los modelos que se presentan ayudarán a definir las localizaciones óptimas para los pozos y las infraestructuras hidráulicas necesarias para satisfacer la demanda al mínimo costo, tomando en consideración restricciones ambientales tal como el riesgo de intrusión salina.