Influence of rainfall spatial variability on flood prediction   总被引：9，自引：0，他引：9  

Patrick Arnaud  Christophe Bouvier  Leonardo Cisneros  Ramon Dominguez 《Journal of Hydrology》2002,260(1-4):216-230

This paper deals with the sensitivity of distributed hydrological models to different patterns that account for the spatial distribution of rainfall: spatially averaged rainfall or rainfall field. The rainfall data come from a dense network of recording rain gauges that cover approximately 2000 km² around Mexico City. The reference rain sample accounts for the 50 most significant events, whose mean duration is about 10 h and maximal point depth 170 mm. Three models were tested using different runoff production models: storm-runoff coefficient, complete or partial interception. These models were then applied to four fictitious homogeneous basins, whose sizes range from 20 to 1500 km². For each test, the sensitivity of the model is expressed as the relative differences between the empirical distribution of the peak flows (and runoff volumes), calculated according to the two patterns of rainfall input: uniform or non-uniform. Differences in flows range from 10 to 80%, depending on the type of runoff production model used, the size of the basin and the return period of the event. The differences are generally moderate for extreme events. In the local context, this means that uniform design rainfall combining point rainfall distribution and the probabilistic concept of the areal reduction factor could be sufficient to estimate major flood probability. Differences are more significant for more frequent events. This can generate problems in calibrating the hydrological model when spatial rainfall localization is not taken into account: a bias in the estimation of parameters makes their physical interpretation difficult and leads to overestimation of extreme flows.  相似文献   

Reflection–refraction seismics in the Gulf of Corinth: hints at deep structure and control of the deep marine basin     

Christophe Clment  Maria Sachpazi  Philippe Charvis  David Graindorge  Mireille Laigle  Alfred Hirn  Giorgios Zafiropoulos 《Tectonophysics》2004,391(1-4):97

The Gulf of Corinth is a natural laboratory for the study of seismicity and crustal deformation during continental extension. Seismic profiling along its axis provides a 24-fold normal-incidence seismic reflection profile and wide-angle reflection–refraction profiles recorded by sea-bottom seismometers (OBS) and land seismometers. At wide-angle incidence, the land receivers document the Moho at 40-km depth under the western end of the Gulf north of Aigion, rising to 32-km depth under the northern coast in the east of the Gulf. Both refraction and normal-incidence reflection sections image the basement under the deep marine basin that has formed by recent extension. The depth to the base of the sedimentary basin beneath the Gulf, constrained by both methods, is no more than 2.7 km, with 1 km of water underlain by no more than 1.7 km of sediment, less than what was expected from past modeling of uplift of the south coast in the East of the Gulf. Unlike the flat sea-bottom, the basement and sedimentary interfaces show topography along this axial line. Several deeps are identified as depocenters, which suggest that this axial line is not a strike line to the basin. It appears instead to be controlled by several faults, oblique to the S60°E overall trend of the south coast of the Gulf, their more easterly strikes being consistent with the instantaneous direction of extension measured by earthquake slip vectors and by GPS.  相似文献   

Erosion and flexural uplift along transform faults   总被引：1，自引：0，他引：1  

Christophe Basile  Pascal Allemand 《Geophysical Journal International》2002,151(2):646-653

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Process and signature of initiation on a finite fault system: a spectral approach     

Christophe Voisin  Michel Campillo  Ioan Ionescu  Riad Hassani  Quoc&#;Lan Nguyen 《Geophysical Journal International》2002,148(1):120-131

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Microbially induced cementation of carbonate sands: are micritic meniscus cements good indicators of vadose diagenesis?   总被引：4，自引：0，他引：4  

Heiko Hillgärtner  Christophe Dupraz  & Wolfgang Hug 《Sedimentology》2001,48(1):117-131

Characteristic fabrics such as micrite envelopes, calcified filaments and micritic grain-to-grain bridges are observed in a modern subtidal firmground (Wood Cay, Bahamas) and in a variety of firm- and hardgrounds of Lower Cretaceous and Upper Jurassic platform carbonates (Swiss and French Jura Mountains). Their similarity to microbial fabrics described in grapestones and in intertidal to continental vadose environments suggests that microbial activity played an important role in the initial stabilization and cementation of carbonate sands. 'Meniscus-type cements' (to distinguish them from vadose meniscus cements), which clearly formed in subtidal environments, are related to filament calcification, trapping of percolating micrite and microbially induced carbonate formation. Such meniscus-type cements are commonly micritic, but meniscus-shaped precipitation of fibrous aragonite or sparitic calcite around organic filaments is also observed. Therefore, an interpretation of vadose early diagenesis should not be based on meniscus cements alone. Similarly, subtidally formed filamentous structures can strongly resemble alveolar septal structures and be interpreted incorrectly as related to subaerial exposure.  相似文献   

Airborne microphysical measurements and radar reflectivity observations near a cold frontal rainband observed during the FRONTS 87 experiment     

Virginie Marcal  Danile Hauser  Christophe Duroure 《Atmospheric Research》1993,29(3-4)

Airborne microphysical measurements and ground-based radar-reflectivity observations, collected at the near of a narrow cold frontal rainband during the FRONTS 87 experiment, are used to infer some characteristics of the precipitation: size-distribution, liquid or ice-water content, mass-weighted fallspeed, radar-reflectivity and relationships between pairs of these quantities. In the ice phase region, two different methods are proposed to calculate the radar reflectivity from the aircraft data. The influence of the choice of the ice particle type on the calculated quantities is discussed from the results of the first method. The second method is new: it is based upon the use of a roughness parameter estimated from the analysis of the two-dimensional particle images of ice precipitation. Although this method is tentative, it gives conclusive results for the two different flight levels studied here.  相似文献   

The Acapulco meteorite: Chemistry,mineralogy and irradiation effects     

H Palme  L Schultz  B Spettel  H.W Weber  H Wänke  M.Christophe Michel-Levy  J.C Lorin 《Geochimica et cosmochimica acta》1981,45(5):727-752

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Present-day deformation of the Dauphine Alpine and Subalpine massifs (SE France)     

Joseph Martinod  Francois Jouanne  Xavier Darmendrail  Jean-Cyrille Notter  Christophe Basile  Joel Taverna  Gilles Mhard  Jean-Francois Gamond 《Geophysical Journal International》1996,127(1):189-200

The positions of 20 geodetic points surveyed in 1946-1952 by the Institut Géographique National in the Grenoble area (western Alps) were remeasured in 1993-1994 using GPS. We evaluate the displacements of the common points of the networks between the two surveys, and calculate the strain-rate tensors for different sets of three adjacent points. The significant N70° shortening direction observed at the boundary of the Belledonne and Taillefer massifs suggests that the dextral strike-slip motion between the External Crystalline Massifs (ECM) and the Subalpine domain is still active. Geological evidence suggests that this deformation, which is compatible with the few focal mechanisms available for the area, occurred throughout the late Neogene. Our data also suggest a roughly 3-5 mm yr⁻¹ active shortening concentrated at the external front of the Subalpine chains. This thrust motion results in a principal axis of compression orientated N130°, oblique to the direction of shortening observed in the ECM. This change in direction is also seen in in situ stress measurements. This motion may mark the southward continuation of the active fault observed in the Jura mountains by Jouanne, Ménard & Darmendrail (1995).  相似文献   

Cation exchanged Fe(II) and Sr compared to other divalent cations (Ca, Mg) in the bure Callovian–Oxfordian formation: Implications for porewater composition modelling     

Christophe Tournassat  Catherine Lerouge  Philippe Blanc  Jocelyne Brendlé  Jean-Marc Greneche  Stéphane Touzelet  Eric C. Gaucher 《Applied Geochemistry》2008

Iron and Sr bearing phases were thoroughly investigated by means of spectrometric and microscopic techniques in Callovian–Oxfordian (COX) samples originating from the ANDRA Underground Research Laboratory (URL) in Bure (France). Strontium was found to be essentially associated with celestite, whereas Fe was found to be distributed over a wide range of mineral phases. Iron was mainly present as Fe(II) in the studied samples (∼93% from Mössbauer results). Most of the Fe(II) was found to be in pyrite, sideroplesite/ankerite and clay minerals. Iron(III), if present, was associated with clay minerals (probably illite, illite-smectite mixed layer minerals and chlorite). No Fe(III) oxy(hydro)xide could be detected in the samples. Strontianite was not observed either. Based on these observations, it is likely that the COX porewater is in equilibrium with the following carbonate minerals, calcite, dolomite and ankerite/sideroplesite, but not with strontianite. It is shown that this equilibrium information can be combined with clay cation exchange composition information in order to give direct estimates or constraints on the solubility products of the carbonate minerals dolomite, siderite and strontianite. As a consequence, an experimental method was developed to retrieve the cation exchanged Fe(II) in very well preserved COX samples.  相似文献   

Numerical modeling of the flow and transport of radionuclides in heterogeneous porous media     

Brahim Amaziane  Mustapha El Ossmani  Christophe Serres 《Computational Geosciences》2008,12(4):437-449

This paper is concerned with numerical methods for the modeling of flow and transport of contaminant in porous media. The numerical methods feature the mixed finite element method over triangles as a solver to the Darcy flow equation and a conservative finite volume scheme for the concentration equation. The convective term is approximated with a Godunov scheme over the dual finite volume mesh, whereas the diffusion–dispersion term is discretized by piecewise linear conforming triangular finite elements. It is shown that the scheme satisfies a discrete maximum principle. Numerical examples demonstrate the effectiveness of the methodology for a coupled system that includes an elliptic equation and a diffusion–convection–reaction equation arising when modeling flow and transport in heterogeneous porous media. The proposed scheme is robust, conservative, efficient, and stable, as confirmed by numerical simulations.   相似文献