Monitoring Mangrove forest landcover changes in the coastline of Bangladesh from 1976 to 2015     

Md. Monirul Islam  Helena Borgqvist  Lalit Kumar 《国际地球制图》2013,28(13):1458-1476

Abstract

This study used multi-date Landsat images to quantify mangrove cover changes in the whole of Bangladesh from 1976 to 2015. Images were pre-processed with an atmospheric correction using Dark Object Subtraction (DOS) and Relative Radiometric Normalization (RRN) using Pseudo-Invariant Features (PIFs). Land Use/Land Cover (LU/LC) classification map was generated using Maximum Likelihood (MaxLike) algorithm, indicating the areal extent of mangroves increased by 3.1% between 1976 and 2015, where 1.79% of this increase occurred between 2000 and 2015. Though mangrove areas remained almost constant in the Sundarbans, Chakaria Sundarbans has almost disappeared between 1976 and 1989. The overall accuracy of Landsat MSS, TM, ETM+, and L8 OLI classified images were 80%, 80%, 87%, and 97% respectively. The study also found deforestation, shrimp & salt farm, coastal erosion and sedimentation, and mangrove plantation could be responsible for mangrove changes in Bangladesh.  相似文献   

Recalibrating aeolian sand transport models   总被引：1，自引：0，他引：1  

Douglas J. Sherman  Bailiang Li  Jean T. Ellis  Luis Parente Maia  Helena Granja 《地球表面变化过程与地形》2013,38(2):169-178

A quality‐controlled data set comprising measurements of aeolian sand transport rates obtained at three disparate field sites is used to evaluate six commonly employed transport rate models (those of Bagnold, Kawamura, Zingg, Owen, Hsu, and Lettau and Lettau) and to recalibrate the empirical constants in those models. Shear velocity estimates were obtained using the von Kármán constant and an apparent von Kármán parameter. Models were recalibrated using non‐linear regression and non‐linear regression with least‐squares lines forced through axes origins. Recalibration using the apparent von Kármán parameter and forced regression reduced the empirical constants for all models. The disparity between the predictions from the different models is reduced from about an order of magnitude to about a quarter of an order of magnitude. The recalibrated Lettau and Lettau model provided the greatest statistical agreement between observed and predicted transport rates, with a coefficient of determination of 0·77. Evaluation of the results suggests that our estimations of threshold shear velocity may be too slow, causing errors in predicted transport rates. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Modelling topographic potential for erosion and deposition using GIS     

Helena Mitasova  Jaroslav Hofierka  Maros Zlocha  Louis R. Iverson 《International journal of geographical information science》2013,27(5):629-641

Abstract

Modelling of erosion and deposition in complex terrain within a geographical information system (GIS) requires a high resolution digital elevation model (DEM), reliable estimation of topographic parameters, and formulation of erosion models adequate for digital representation of spatially distributed parameters. Regularized spline with tension was integrated within a GIS for computation of DEMs and topographic parameters from digitized contours or other point elevation data. For construction of flow lines and computation of upslope contributing areas an algorithm based on vector-grid approach was developed. The spatial distribution of areas with topographic potential for erosion or deposition was then modelled using the approach based on the unit stream power and directional derivatives of surface representing the sediment transport capacity. The methods presented are illustrated on study areas in central Illinois and the Yakima Ridge, Washington.  相似文献   

Fragility curves for old masonry building types in Lisbon     

Ana Simões  Jelena Milošević  Helena Meireles  Rita Bento  Serena Cattari  Sergio Lagomarsino 《Bulletin of Earthquake Engineering》2015,13(10):3083-3105

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Combined hydrochemical,isotopic, and multivariate statistics techniques to assess the effects of discharges from a uranium mine on water quality in neighboring streams     

Carlos A. De Carvalho Filho  Rubens M. Moreira  Otavio E. A. Branco  Pedro H. Dutra  Elizângela A. Dos Santos  Igor F. S. Moura  Peter M. Fleming  Helena E. L. Palmieri 《Environmental Earth Sciences》2017,76(24):830

The Caldas Uranium Mine (CUM), located on the Poços de Caldas Plateau in the southeastern region of Brazil, is presently undergoing a decommissioning process. The aim of the present investigation is to identify and characterize the effects of acid mine drainage (AMD) originating from the CUM on surface water quality. To achieve these aims, sampling stations were located at two AMD sources: the retention pond at the foot of waste rock pile#4 (WRP#4) and the settling pond that receives effluents from the tailings dam (TD). Ten additional sampling stations were located along watercourses in the vicinity, both downstream and upstream of the mine. Sampling was performed during the rainy and dry seasons in 2010 and 2011. The water analysis detected significant changes in pH, electrical conductivity, F^?, Cd, U, Zn, Al, Mn, As, Ca, SO₄ ^2?, Pb, ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³²Th, ²²⁸Ra, and Mo in waters downstream of both pond discharge sites. It was demonstrated that the disequilibrium between ²²⁶Ra and ²³⁸U can be used to trace the extent of AMD impacts in nearby streams. Variations in ¹⁸O and ²H enabled the flow of mining-impacted water to be traced from the ponds to nearby streams. Multivariate analysis yielded a three-factor model: Factor 1 was interpreted as being associated with AMD (from WRP#4) and Factor 2 with a Ca–Mo relationship associated with the chemical constitution of the ore and with the treatment of tailings wastes in the area (from TD); Factor 3 was interpreted as being associated with the natural influence of geogenic processes on water quality in the area. The results of this study provide a scientific basis for recommending appropriate remedial actions during mine decommissioning.  相似文献   

Lithosphere conductivity structure using the CAM-1 (Lisbon-Madeira) submarine cable     

Fernando A. Monteiro Santos  António Soares  Rita Nolasco  Helena Rodrigues  Rafael Luzio  Nick Palshin  the ISO-D team 《Geophysical Journal International》2003,155(2):591-600

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July 2006     

Maria Helena Henriques  Rui Pena dos Reis  José Brilha  Teresa Mota 《Environmental Geology》2005,48(2):276-277

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Electron microprobe dating of monazite from high-T shear zones in the São José de Campestre Massif, NE Brazil     

Zorano Srgio de Souza  Jean-Marc Montel  Simone Maria Lima Costa Gioia  Maria Helena Bezerra Maia de Hollanda  Marcos Antonio Leite do Nascimento  Emanuel Ferraz Jardim de S  Venerando Eustquio Amaro  Mrcio Martins Pimentel  Jean-Marc Lardeaux  Michelle Veschambre 《Gondwana Research》2006,9(4):441-455

The easternmost domain of the Borborema Province, northeastern Brazil, presents widespread, extensional-related high-temperature metamorphism during the Brasiliano (=Pan-African) orogeny. This event reached the upper amphibolite to granulite facies and provoked generalized migmatization of Proterozoic metapelitic rocks of the Seridó Group and tonalitic to granodioritic orthogneisses of the Archean to Paleoproterozoic basement. We report new geochronological data based on electron microprobe dating of monazite from metapelitic migmatite and leuconorite within the high-T shear zones that make up the eastern continuation of the huge E–W Patos shear belt. These data were also constrained by using the Sm–Nd isotopic systematic on garnet from a syntectonic alkaline granite and two garnet-bearing leucosomes. The results suggest an age of about 578 to 574 Ma for the peak of the widespread high-T metamorphism. This event is best recorded by Sm–Nd garnet-whole rock ages. The U–Th–Pb isotopes on monazite of the metapelitic migmatite show a younger thermal event at 553 ± 10 Ma. When compared to the Sm–Nd garnet-whole rock ages, the U–Th–Pb electron probe monazite ages seem to record an event of slightly lower temperatures after the peak of the high-T metamorphism. This may reflect the difference in the isotopic behavior of the geochronological methods employed. Otherwise, the U–Th–Pb ages on monazites could indicate an event not yet very well defined. In anyway, this paper reveals the partial or even complete re-opening and resetting of the U–Th–Pb isotopic system produced by the action of low-T Ca-rich fluid.  相似文献   

Researching European 'alternative' food networks: some methodological considerations     

Laura Venn  Moya Kneafsey  Lewis Holloway  Rosie Cox  Elizabeth Dowler  Helena Tuomainen 《Area》2006,38(3):248-258

Recent European literature on 'alternative' food networks (AFNs) draws heavily upon an apparently accessible and diverse body of non-conventional food networks in the agro-food sector and whilst researchers frequently refer to individual examples of farmers markets, box schemes, producer cooperatives and community-supported agriculture projects, less attention is given to the methodological processes that facilitate the identification and examination of these networks. From the preliminary stages of a research project focusing on examples of AFNs, ² this paper examines the process of operationalizing AFNs research and reviews the difficulties associated with identifying, comparing and characterizing AFNs.  相似文献   

Optimized History Matching with Direct Sequential Image Transforming for Non-Stationary Reservoirs     

M. Helena Caeiro  Vasily Demyanov  Amilcar Soares 《Mathematical Geosciences》2015,47(8):975-994

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