Long term high frequency sediment observatory in an alpine catchment: The Arc-Isère rivers,France     

Fabien Thollet  Christophe Rousseau  Benoit Camenen  Stephane Boubkraoui  Flora Branger  François Lauters  Julien Némery 《水文研究》2021,35(2):e14044

We present a dataset on to the Arc-Isère long-term environmental research observatory, which is part of the Rhône Basin Long Term Environmental Research Observatory. This alpine catchment located in the French Alps is characterized by high Suspended Particulate Matter (SPM) in anthropogenized valleys. Suspended Sediment Concentrations (SSC) naturally observed in the river are very high, ranging from a few tens of milligrams per litre at low flow to tens of grams per litre during major natural hydrological events (floods, debris flows) or river dam hydraulic flushes. One research objective related to this site is to better understanding the SSC dynamics along the river using a system of nested catchments (Arvan, Arc, and Isère) in order to assess both temporal and spatial dynamics. The data allow the quantification of fine sediment yields and also the evaluation of possible morphological changes due to fine sediment deposition or resuspension. Additionally, the observatory database support studies on contaminants (either dissolved or particulate contaminants). Our monitoring includes six stations with high frequency (2–30 min) streamflow, SSC measurement using turbidity sensors, and associated automatic sampling. Discharge is measured via water level measurements and a rating curve. The oldest station (Grenoble-campus) started recording discharge and concentration data from April 2006 while others stations were built between 2009 and 2011. Data are available in an online data website called ‘Base de Données des Observatoires en Hydrologie’ (Hydrological observatory database, https://bdoh.irstea.fr/ARC-ISERE/ ) with a DOI reference for the dataset. The hydrological and sediment transport time series are stored, managed and made available to a wide community with unfettered access in order to be used at their full extent. This database is used as a data exchange tool for both scientists and operational end-users and there is an associated online tool to compute integrated fluxes.  相似文献   

High-spatial-resolution imagery helps map deposits of the large (VEI 4) 2010 Merapi Volcano eruption and their impact     

Akhmad Solikhin  Jean-Claude Thouret  Soo Chin Liew  Avijit Gupta  Dewi Sri Sayudi  Jean-François Oehler  Zeineb Kassouk 《Bulletin of Volcanology》2015,77(3):1-23

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Numerical simulation of the quicksand phenomenon by a 3D coupled Discrete Element ‐ Lattice Boltzmann hydromechanical model          下载免费PDF全文

Mouloud Mansouri  Moulay Said El Youssoufi  François Nicot 《国际地质力学数值与分析法杂志》2017,41(3):338-358

This paper deals with the numerical simulation of the quicksand phenomenon using a coupled Discrete Elements – Lattice Boltzmann hydromechanical model. After the presentation of the developed numerical model, simulations of ascending fluid flow through granular deposits are performed. The simulations show that the quicksand actually triggers for a hydraulic gradient very close to the critical hydraulic gradient calculated from the global analysis of classical soil mechanics, that is, when the resultant of the applied external pressure balances submerged weight of the deposit. Moreover, they point out that the quicksand phenomenon does not occur only for hydraulic gradients above the critical hydraulic gradient, but also in some cases with slightly lower gradients. In such cases, a more permeable zone is first gradually built at the bottom of the deposit through a grain rearrangement, which increases the hydraulic gradient in the upper zones and triggers the phenomenon. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Exploratory analysis of statistical post‐processing methods for hydrological ensemble forecasts          下载免费PDF全文

Marie‐Amelie Boucher  Luc Perreault  Franois Anctil  Anne‐Catherine Favre 《水文研究》2015,29(6):1141-1155

Despite many recent improvements, ensemble forecast systems for streamflow often produce under‐dispersed predictive distributions. This situation is problematic for their operational use in water resources management. Many options exist for post‐processing of raw forecasts. However, most of these have been developed using meteorological variables such as temperature, which displays characteristics very different from streamflow. In addition, streamflow data series are often very short or contain numerous gaps, thus compromising the estimation of post‐processing statistical parameters. For operational use, a post‐processing method has to be effective while remaining as simple as possible. We compared existing post‐processing methods using normally distributed and gamma‐distributed synthetic datasets. To reflect situations encountered with ensemble forecasts of daily streamflow, four normal distribution parameterizations and six gamma distribution parameterizations were used. Three kernel‐based approaches were tested, namely, the ‘best member’ method and two improvements thereof, and one regression‐based approach. Additional tests were performed to assess the ability of post‐processing methods to cope with short calibration series, missing values or small numbers of ensemble members. We thus found that over‐dispersion is best corrected by the regression method, while under‐dispersion is best corrected by kernel‐based methods. This work also shows key limitations associated with short data series, missing values, asymmetry and bias. One of the improved best member methods required longer series for the estimation of post‐processing parameters, but if provided with adequate information, yielded the best improvement of the continuous ranked probability score. These results suggest guidelines for future studies involving real operational datasets. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Thermal stresses in borehole heat exchangers          下载免费PDF全文

Selçuk Erol  Bertrand François 《国际地质力学数值与分析法杂志》2015,39(13):1450-1470

The backfilling materials of borehole heat exchangers (BHE), particularly the grout material, must provide a suitable thermal contact and ensure durability to the induced thermal stresses because of the heat loading. In this paper, the thermal stresses that occurred in BHEs because of heat injection or extraction is investigated with an analytical solution of a hollow cylinder model that is adapted for time‐dependent heat loading, the geometry of a BHE, and the thermo‐mechanical properties of surrounding ground conditions. Firstly, the hollow cylinder model is solved with the considered boundary conditions in 2D plane stress. Secondly, the temperature differences at the inner and outer circles of the cylinder are evaluated with the heat line source models for continuous and discontinuous loading to observe the impact of the heat loading schedule. The developed analytical solution for thermal stress investigation is validated with numerical models. It is demonstrated that the analytical solutions agree well with numerical results for two types of BHE configurations (co‐axial and single U‐shaped pipes). Furthermore, the calculated maximum stresses are compared with the tensile strength of grout materials obtained from Brazilian tests. It is predicted that the thermal contraction of the grout, partially constrained by the surrounding rock, generates tensile stresses that may lead to cracking in the BHE. According to the results, the stiffness of rock has a primary role on the developed tensile stresses, and the relationship between the thermal conductivity of the ground and of the grout induces a proportional impact on the magnitude of thermal stresses. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Paragenesis of magma chamber internal wall discovered in Oman ophiolite gabbros          下载免费PDF全文

Adolphe Nicolas  Françoise Boudier  David Mainprice 《地学学报》2016,28(2):91-100

A detailed study in Wadi Farah reveals a singular point in Jebel Dihm (southern Oman ophiolite). Here, we investigated some primitive features of accretion at a fast‐spreading ridge that has exceptionally been exempt from hydrous alteration while crossing the TBL (thermal boundary layer). The conjunction of two factors has made this possible in the Farah area: its location at the point of sharp foliation rotation from the upper to the transitional gabbros and a locally twisted TBL. These factors may have favoured the intrusion within the TBL of hydrous wedges transverse to the ridge. Deeper into the TBL, near the active ridge, the wedges merge and are covered by veneers of totally fresh gabbros bearing glittering acicular clinopyroxene. These gabbros are interpreted as relics of the crystallizing internal wall of the magma chamber that have interacted with hydrous fluids. This internal TBL has anisotropic thermal properties and acts as a thermal blanket, maintaining high magma‐chamber temperatures.  相似文献   

Photometric calibration of the [α/Fe] element: I. Calibration with UBV photometry     

S. Karaali  E. Yaz Gökçe  S. Bilir 《Astrophysics and Space Science》2016,361(11):354

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What shapes mesoscale wind anomalies in coastal upwelling zones?   总被引：1，自引：1，他引：0  

Julien Bo��  Alex Hall  Fran?ois Colas  James C. McWilliams  Xin Qu  Jaison Kurian  Sarah B. Kapnick 《Climate Dynamics》2011,36(11-12):2037-2049

Observational studies have shown that mesoscale variations in sea surface temperature may induce mesoscale variations in wind. In eastern subtropical upwelling regions such as the California coast, this mechanism could be of great importance for the mean state and variability of the climate system. In coastal regions orography also creates mesoscale variations in wind, and the orographic effect may extend more than 100?km offshore. The respective roles of SST/wind links and coastal orography in shaping mesoscale wind variations in nearshore regions is not clear. We address this question in the context of the California Upwelling System, using a high-resolution regional numerical modeling system coupling the WRF atmospheric model to the ROMS oceanic model, as well as additional uncoupled experiments to quantify and separate the effects of SST/wind links and coastal orography on mesoscale wind variations. After taking into account potential biases in the representation of the strength of SST/wind links by the model, our results suggest that the magnitude of mesoscale wind variations arising from the orographic effects is roughly twice that of wind variations associated with mesoscale SST anomalies. This indicates that even in this region where coastal orography is complex and leaves a strong imprint on coastal winds, the role of SST/winds links in shaping coastal circulation and climate cannot be neglected.  相似文献   

Conflicts over industrial tree plantations in the South: Who, how and why?     

Julien-Franois Gerber 《Global Environmental Change》2011,21(1):165-176

Industrial tree plantations for wood, palm oil and rubber production are among the fastest growing monocultures and are currently being promoted as carbon sinks and energy producers. Such plantations are causing a large number of conflicts between companies and local populations, mostly in the tropics and subtropics. Within a political ecology framework, the present paper investigates the nature of such conflicts as related to the alleged impacts of the plantations, the protesters involved, and the modalities of the conflicts with a special emphasis on their outcomes. Relying on the most comprehensive literature review to date, corresponding to 58 conflict cases, I find that the prominent cause of resistance is related to corporate control over land resulting in displacements and the end of local uses of ecosystems as they are replaced by monocultures. Resistance includes the “weapons of the weak” and ranges from dialogue to direct confrontation and from local to international. It often involves NGOs, especially for legal issues. Demonstrations, lawsuits, road blockades and tree uprooting have been reported in several countries. Authorities have responded by repression in about half of the cases analysed, while popular struggles have been able to stop plantations in about one fifth, mainly through winning lawsuits or massive social unrest. While these movements can be regarded as classical land conflicts, they usually also have an ecological content, corresponding to forms of the “environmentalism of the poor”. The documented large number of such conflicts suggests that policies promoting large-scale tree plantations should be reappraised.  相似文献   

A recent history of metal accumulation in the sediments of Rijeka harbor, Adriatic Sea, Croatia   总被引：2，自引：0，他引：2  

Neven Cukrov  Stanislav Fran?iškovi?-Bilinski 《Marine pollution bulletin》2011,62(1):154-167

We studied metal pollution in the sediments of Rijeka harbor, including anthropogenic influence during recent decades and at the present time. Sediment profiles were collected at ten sampling points. The concentrations of 63 elements in bulk sediment were obtained using ICP-MS, and the concentrations of selected elements were evaluated by statistical factor analyses. We also calculated metal-enrichment factors and geoaccumulation indices and constructed spatial-distribution maps.Mercury (Hg) was the heaviest pollutant, with concentrations exceeding 4 mg/kg. Silver (Ag) was the second most important pollutant, with constantly increasing values. The average concentrations of the most toxic elements were comparable to those found in sediments of other ports throughout the world, and their toxicity ranged from threshold values [chromium (Cr), arsenic (As)] and midrange-effect values [cadmium (Cd), lead (Pb), copper (Cu), zinc (Zn), nickel (Ni)] to extreme-effect values (Hg). Metal pollution has decreased during recent decades, except for Ag and barium (Ba).  相似文献