Spatial distribution,variation and trend of five-day antecedent rainfall in Singapore

ABSTRACT

This paper presents the spatial distribution, variation and trend of 5-day antecedent rainfall in Singapore based on rainfall data from 22 meteorological stations. The effect of climate was analyzed by dividing the study period into three decades i.e. Decade 1: 1982–1991, Decade 2: 1992–2001 and Decade 3: 2002–2011. Kriging interpolation was used for rainfall mapping. The results show that spatial distribution of 5-day antecedent rainfall does not coincide with that of the annual rainfall. The maximum annual rainfall occurred in the northwestern side of Singapore. On the other hand, the maximum 5-day antecedent rainfall occurred in the north and northeastern sides. The results of this study suggest that the climate change has increased the amount of 5-day antecedent rainfall quite significantly, i.e. from 420.5 (1987) to 592.9 mm (2006), thus affecting the vulnerability of the area with respect to rainfall-induced slope failure. The analyses also showed that most of slope failures were located in the north and northeast of Singapore between December and earlier March. More slope failures were observed in Decade 3 as compared to Decades 1 and 2. In other words, the analysis confirmed that 5-day antecedent rainfall had affected the slope stability in Singapore.     

Landslide phenomena in the area of Pomarico (Basilicata–Italy): methods for modelling and monitoring

This paper takes into consideration landslide phenomena in the clayey slopes facing the built-up area of Pomarico which is situated in the southern part of the “Fossa Bradanica”, in Basilicata (Italy). Based on the great number of geologic, geomorphologic and historic informations a geotechnical model of the slope was built. Particular attention has been paid to define the geotechnical parameters of the soil and which mechanical models are to be used. The studies point out a correlation between the water level in the detritus cover and the stability condition of the slope showing that phenomena at first located at the foot of the slope spread quickly towards its summit as the piezometric height increases.     

Les rhyolites hyperalcalines (pantellérites) du lac Tchad. Composition et signification tectonomagmatiqueThe peralkaline rhyolites (pantellerites) of the Lake Chad. Composition and tectonomagmatic significance

Remnants of rhyolite lava-dome and of alkaline microgranite extrusions emerge, as inselbergs, in the alluvial plain, south of Lake Chad. The peralkaline, arfvedsonite- and acmite-bearing rhyolites are determined as pantellerites. They can be related to a tectonomagmatic stage, dated of the Late Cretaceous, of the western central Africa rift system. They may constitute the NNE extension of a N50° to 30° elongated succession of small alkaline complexes, from the Gulf of Guinea to the North-Cameroon, which initiated the magmatic activity of the Cameroon Line. To cite this article: J.-P. Vicat et al., C. R. Geoscience 334 (2002) 885–891.     

La vague de chaleur de l'été 2003 et sa prévision saisonnière

The main features of the heat wave that has affected western Europe during the summer 2003 are first recalled, with particular concern to analogies and differences with previous warm-summer episodes. The skills of the various operational and pre-operational seasonal forecasting models in use at that time are evaluated. None of them has been able to consistently forecast the heat wave three month in advance. The meteorological and climatic situation prevailing during spring 2003 is then analysed. A strong sea-surface-temperature (SST) anomaly is found to have developed over North Atlantic a few months before the heat wave. The particular mechanism at work to explain the occurrence of the heat wave is not a ‘simple downwind influence’ of the SST anomaly. It very likely involves complex ocean–atmosphere interaction phenomena of a kind that is not properly taken into account in today's seasonal forecasting models. To cite this article: J.-C. André et al., C. R. Geoscience 336 (2004).     

Diachronisme des bassins turbiditiques d'avant-pays méso/néocrétacés du pays de Sault (Aude,Pyrénées françaises)

The cartographic, sedimentological and micropalaeontological analysis of remnants of Middle–Upper Cretaceous turbiditic basins from the ‘Pays de Sault’ (Aude, French Pyrenees) shows their diachronism (interpreted on a wider scale) and their sequence diversity. The ‘Gesse breccias’ are regarded as the proximal deposits of a Turonian narrow foreland basin, principally supplied by the erosion of the Jurassic–Lower Cretaceous cover of the High Primary Range to the south, induced by a strike-slip and overthrusting faulting within the en-échelon North-Pyrenean Fault Zone. More to the north, the North-Pyrenean ‘Axat Basin’ consists of two successive backstepping turbiditic wedges, respectively corresponding to an Upper Albian distal flysch and to a Middle–Upper Cenomanian more proximal flysch, all the series unconformably overlying structures that were folded then eroded before the Upper Albian. The previous concept of carbonate olistoliths included within the Axat Cenomanian flysch is also refuted: these large-size blocks are now interpreted as belonging to a tectonic slice destroyed and partly collapsed on the southern slope of the Rebenty Valley during the Quaternary. To cite this article: M.-J. Fondecave-Wallez, B. Peybernès, C. R. Geoscience 336 (2004).     

Failles normales Paléocène à Lutétien en zone sud-pyrénéenne (Aragon,Espagne) et flexuration de la plaque ibérique

Close to the South Pyrenean thrust front, synsedimentary normal faults develop in the ‘Garumnian’ continental deposits (Maastrichtian to Palaeocene) and in the carbonate platform during the Lutetian. During the Lutetian, this deformation is accompanied by a change in the sedimentation characterized by the deposit of two series of laminated limestones associated to monogenetic breccias. These normal faults would have formed at the bending of the Iberian plate subducting under Europe. They may also be considered as the starting point for the megaturbidites that deposited further north in the Eocene turbiditic basin. To cite this article: Y. Hervouët et al., C. R. Geoscience 337 (2005).     

Effets de la vitesse d'écoulement sur le transport et la cinétique de dépôt de particules en suspension en milieu poreux saturé

We study in this paper the transport and deposition of suspended particles in saturated porous media. Some chromatographic short-pulse tests were performed in a laboratory column with a tracer and two types of suspended particles. A mathematical model was used to determine the hydrodispersive parameters and deposition rates from the breakthrough curves. The results show that the fitted parameters obtained vary with the flow rate and the characteristics of the suspended particles. We also observe, at high flow rates, that particles have a migration velocity higher than that of the conservative tracer. To cite this article: A. Benamar et al., C. R. Geoscience 337 (2005).     

Relation entre évolution de la matière organique et caractéristiques géostructurales : exemple du bassin yprésien en Tunisie centro-septentrionale

The geochemical analysis of the organic-rich facies from the Ypresian basin in central–northern Tunisia shows that the organic matter is marine originated (type II) and displays a low thermal maturity level in outcropping samples. This study proves that the distribution, conservation and, therefore, the composition of the organic matter have been controlled by the dynamic of the Ypresian basin. The Ypresian period corresponds to an anoxic event, which led to the accumulation and preservation of good quantities of organic matter derived from a high primary production. To cite this article: A. Arfaoui, M. Montacer, C. R. Geoscience 338 (2006).     

Delineation and classification of rural–urban fringe using geospatial technique and onboard DMSP–Operational Linescan System

This study aims to analyse the processes and patterns of peri-urbanization using diurnal earth observation data-sets from onboard DMSP–Operational Linescan System. In this study, multiple correlation, simple and conditional linear regression are used to find out the degree of relationship and spatial behavioural pattern of the factors responsible for the urbanization. All the factors are standardized using the Analytical Hierarchy Process (AHP) coupled fuzzy membership functions. AHP is used to derive the weighting of the factors to produce the urbanity index. In total three functional zones – urban, rural and urban shadow are generated based on factor standardization and spatial contiguity index. Urban fringe is sharing ≥ 60% of Urbanity Index followed by rural fringe (39.50–60% of urbanity index) and urban shadow <39.50% of urbanity index. Shape index indicates that the city is going through unplanned development following cross to star shape growth.     

Platinum-group mineral assemblage of the Prizhimny Creek (Koryak Highland)

In the alluvial deposits of the Prizhlimny Creek (southern part of the Koryak Highland), grains of platinum-group minerals are found along with gold. We have established that the grains are native platinum (Pt, Fe) containing Cu (up to 5 wt.%), Os (up to 8 wt.%), and Rh (up to 2 wt.%). Inclusions in the platinum are native osmium (the content of Ir impurity reaches 12 wt.%, the average content being 0.2–4 wt.%), an unnamed intermetallic compound of composition PtRh, sulfides and arsenides of PGE (cooperite, laurite, malanite, cuproiridsite, cuprorhodsite, sperrylite, hollingworthite, unnamed compounds PdS, (Ir,Ru)S₂, (Ir,Pt)S₂, Cu, and Fe (bornite, chalcopyrite), chromite, and Cr-magnetite. Replacement of native-osmium crystals by compound IrO₂ is described. It has been established that this compound formed during oxidation accompanied by the replacement of isoferroplatinum by native platinum. The data obtained agree with the results of study of platinum-group mineral assemblages from placers localized in weakly eroded Ural–Alaskan-type massifs whose apical parts formed under high oxygen activity conditions. Clinopyroxenites of the Prizhimny massif are considered to be the potential source of PGE.