Global ETD Search

91	Reconstructions de changements environnementaux dans les archives lacustres par imagerie hyperspectrale / Reconstitutions of environmental changes in lacustrine archives by hyperspectral imaging Van Exem, Antonin 11 July 2018 (has links) Les lacs piègent des particules sédimentaires au fil du temps de manière à former des archives sédimentaires. Tracer l’origine des particules archivées avec une résolution stratigraphique particulièrement détaillée conduit à reconstituer une ou des informations paléoenvironnementales permettant d’identifier les changements environnementaux passés. Afin de décrypter ces informations, les techniques d’analyse des carottes sédimentaires nécessitent d’identifier des marqueurs de leur composition à haute résolution. L’imagerie l’hyperspectrale demeure une des rares techniques capables de représenter ces marqueurs en deux dimensions pour caractériser les variations de la composition du sédiment et les structures stratigraphiques les plus fines. Dans ce mémoire, le potentiel de l’imagerie est mis en valeur à travers l’étude de plusieurs cas. L’objectif est de reconstituer des changements environnementaux à partir de l’origine des matières organiques (MO) sédimentaires à hauterésolution rapidement et sans destruction des archives. Plusieurs marqueurs hyperspectraux permettant de comprendre l’origine des MO sont développés sur deux sites d’étude choisis pour leur potentielle signature organique sédimentaire. Dans un environnement méditerranéen, les apports en MO détritique dans les sédiments du lac Bresson tracent les épisodes d'incendie du couvert forestier alors que les variations de carbone organique total (COT) dans une série d’archives sédimentaires reconstruisent les fluctuations de l’érosion glaciaire dans un lac arctique. Dans ces deux cas, la MO d’origine détritique est tracée pour la première fois par une méthode non-destructive et le traçage de la MO issue de la productivitéprimaire aquatique (plus classique) est amélioré par un nouvel indice spectroscopique. Ces marqueurs sont validés par des méthodes utilisées en routine (HPLC, comptage des particules de charbon, pyrolyse Rock-Eval 6) puis calibrés par ces techniques pour reconstruire des concentrations en COT à haute résolution. L’imagerie hyperspectrale permet donc de tracer lacomposition sédimentaire, voire des variations géochimiques, pour quantifier l'origine des apports organiques. Ces résultats apparaissent comme prometteurs et fournissent les bases essentielles pour développer l'utilisation en routine de cette nouvelle technique afin de reconstituer finement les changements environnementaux passés. / Over time, lakes trap sedimentary particles that form sedimentary reserves. Tracing the origin of those particles with a precise stratigraphic resolution, involves reconstituting one or more paleo environmental information thus allowing the identification of past environmental changes. Decrypting that information requires a sedimentary carrot analysis technic to identify their high resolution composition indicators. Hyperspectral imagery remains one of the rare technics capable of showing those indicators in a two dimensional form so as to characterize the variations in the composition of the sediment as well as the finer stratigraphic structures. In comparison to the methods used routinely, hyperspectral imagery is a highresolution (nanometers resolution) technic that does not destroy the core of the sediment and is time efficient (1 hour per meter of sediment). In this thesis, the potential of the high resolution imagery is highlighted through the study of several case studies. The aim is to reconstitute environmental changes based on the origin of high resolution sedimentary organic matter (OM) quickly whilst preserving their history. Several hyperspectral indicators have been developed on two carefully chosen study sites to understand the origins of those OM. Those sites were chosen based on their potential sedimentary organic signature. In a Mediterranean environment, detrital OM inputs in the Bresson lake give a history of the various forest fires whereas the organic carbon variations in a series of reserve sediments, reconstruct the fluctuations of glacier erosion in an artic lake. In both cases, the OM of detrital origin is traced for the first time through a non-destructive method. Tracing OM issued from Primary aquatic production is improved with a new spectroscopic index. These indicators are validated by the methods routinely used (HPLC and RE6) then are calibrated by these technics in order to rebuilt high resolution COT concentrations. Hyperspectral imagery allows to trace the sedimentary composition and to see geo chemical variations in order to quantify the origin of organic inputs. Those results seem promising and bring essential foundations to develop the routine use of this new technic in order to reconstitute accurately past environmental changes. Core-logging Paléolimnologie Imagerie hyperspectrale Matières organiques Source-to-sink Feux de forêt Productivité primaire Anthropocène Stock de carbone Fluctuations glaciaires Geo limnology Sedimentology Hyperspectral imagery High-resolution proxies Core logging Organic matter Past primary productivity Forest-fire Anthropocene Carbon stock Glacial fluctuations 551.7
92	Forest fire dynamics and carbon stocks in different ecological zones of Ghana Nindel, Sandra 30 August 2018 (has links) Fires occur in most forest reserves in Ghana. However, there is a limited understanding of the fires and their behaviour in the different ecological zones. Therefore, this research was to analyze the spatial and temporal distribution of fires, examine the driving factors, direct and underlying causes and impacts of the fires, determine and compare the fuel dynamics to predict fire behaviour and estimate the effects of fire on carbon stocks in different ecological zones of Ghana. The research used different methodologies including questionnaires, fire records, satellite fire data from MODIS (2001 to 2015) (first approach) and field experiment (second approach). A total of 304 respondents was sampled for eight communities, two communities each around the moist and dry semi-deciduous forest, upland evergreen forest and savanna. The spatial distribution of fire showed a trend along the forest boundaries, open vegetation, degraded areas, human settlements, shrubs, farms, rivers and roads. The temporal trend was significant in the dry forest (435 hotspots), followed by the savanna (229 hotspots), moist forest (76 hotspots) and the least in the evergreen forest (5 hotspots). The fires were observed from August, October to May with the dry forest having the longest seasonality. Sunday, Tuesday and Thursday were the peak days of the detected fire hotspots in the dry, moist and savanna respectively. Most of the fires in the different ecological zones peaked from 13 to 14 pm. The results of the research also revealed that the fires were driven primarily by socioeconomic factors which were supported by environmental, type of vegetation and cultural factors. In all the ecological zones, fires were originating from humans. The study pointed out three categories of human-caused fires through activity (farming), non-activity (carelessness or negligence) and others (unknown causes). The major underlying causes of fire mentioned were the inadequate management of the forest and weak compliance and enforcement of forest laws. All these fires have resulted in several impacts in the various ecological zones. Concerning the fuel dynamics, the total downed woody fuel load in the evergreen forest was found to be higher (228 and 208.4 tonnes per hectare). The litter and duff density (112.2 kilogram per cubic meter) in unburned area and loading (6.3 and 13.5 tonnes per hectare) for both burned and unburned area respectively were significantly greater in the moist forest. Also, the dry forest showed 2.4 tonnes per hectare of herbaceous loading in the burned area. However, fires were predicted to be severe in the savanna regarding the surface rate of spread, flame length and fireline intensity, but with low reaction intensity and heat per unit area. The total amount of aboveground tree carbon, aboveground non-tree and belowground root for both burned and the unburned area varied under the different ecological zones. The highest was seen in the moist forest with the emission of 294 tonnes of carbon per hectare accounting for 82% losses. This research has brought out the current situation of fire in the various ecological zones for the implementation of necessary actions for the future. info:eu-repo/classification/ddc/630 ddc:630
93	Assessment and analysis of wildfires with the aid of Remote Sensing and GIS Vorster, Willem Adriaan 12 1900 (has links) Wildfires destroy large tracts of veld and forest land every year in South Africa. These fires can be devastating, resulting in loss of human lives, the destruction of property and the loss of income, for example the forest fire in the Sabie district in Mpumalanga in 2007 which destroyed about 7% of South Africa’s forested areas. There are frequently legal disputes with respect to the origin of wildfires, the extent of the fire and the land cover destroyed by the fires. The forensic capabilities of remote sensing in detecting and analysing post-wildfire characteristics have become an important contribution towards solving such legal disputes and in understanding wildfire characteristics. These post fire products can be used as evidence in court cases. Most of the time those court cases came up a few years after the fire event. By then, little or no evidence can be found on the terrain where the fire was. Remote sensing archives provide a reliable source of data that can be used to analyse these events after these long intervals. The objective of this project is to highlight the methods used to generate these post-wildfire analysis products. / Environmental Sciences / M. Sc. (Environmental Science) Wildfires Post-wildfire Remote Sensing Veld fires Landsat AFIS MODIS National Veld and Forest Fire Act Forensic Disputes Optical sensors 363.3790285
94	Att få en plats på kartan : En etnologisk studie av skogsbranden i Västmanland 2014 / To get a place on the map : An ethnological study of the forest fire in Västmanland 2014 Litborn, Julia January 2017 (has links) The forest fire of Västmanland in 2014 had a significant cultural impact on local communities. Research is warranted to better understand the impact and process of recovery after natural disasters, as well as to discover how underlying political and cultural structures affect rescue and recovery. Thus far, any research in this area has been carried out by government-funded studies and evaluations of crisis management. This study complements that existing body of research by exploring this topic through local experiences and memories of the fire and emergency operations. The analysis builds on four theoretical perspectives: Foucault’s theory of power; phenomenology; memory theory, and theories of identity. Through these, the study examines how locals relate to the burnt landscape as well as explores how political tensions relating to Swedish countryside have gained new relevance as a result of the fire. These research results indicate that memories of the fire are characterized by chaotic rescue operations and crisis management, and that their failure generally is interpreted as a result of current political and cultural discourses defined by urban norms that for decades have disfavored infrastructure and social security in rural parts of Sweden. The research shows that favorable conditions for rural life in general are crucial for successful crisis management. From a societal perspective, the battle for resources between urban and rural areas, combined with inequality between city and countryside, is very problematic. Many crises occur in rural areas, which require security and infrastructure nationwide. The study therefore stresses the importance of active use of local knowledge in governing on local and regional as well as national levels. Diversity is not only a matter of ethnicity, gender and sexual orientation, but also includes perspectives from all generations living all over the country. forest fire Västmanland ethnology Fagersta Norberg Surahammar Sala fenomenology Foucault power memory place space landscape multilocality discourse Virsbo Surahammar rescue operations crisis management infrastructure rural urban resources diversity Skogsbranden i Västmanland Salabranden etnologi skogsbrand Virsbobranden Hälleskogsbrännan Öjesjöbrännan brand Fagersta Norberg Surahammar Sala fenomenologi Foucault makt minne place space plats rum landskap multilokalitet diskurs överlokal Virsbo Surahammar Länsstyrelsen i Västmanlands län bildspråk liknelser urban urbanitet landsbygd glesbygd lokal lokala tillhörighet kultur identitet krishantering räddningsinsats infrastruktur resurser mångfald Ethnology Etnologi
95	Assessment and analysis of wildfires with the aid of Remote Sensing and GIS Vorster, Willem Adriaan 12 1900 (has links) Wildfires destroy large tracts of veld and forest land every year in South Africa. These fires can be devastating, resulting in loss of human lives, the destruction of property and the loss of income, for example the forest fire in the Sabie district in Mpumalanga in 2007 which destroyed about 7% of South Africa’s forested areas. There are frequently legal disputes with respect to the origin of wildfires, the extent of the fire and the land cover destroyed by the fires. The forensic capabilities of remote sensing in detecting and analysing post-wildfire characteristics have become an important contribution towards solving such legal disputes and in understanding wildfire characteristics. These post fire products can be used as evidence in court cases. Most of the time those court cases came up a few years after the fire event. By then, little or no evidence can be found on the terrain where the fire was. Remote sensing archives provide a reliable source of data that can be used to analyse these events after these long intervals. The objective of this project is to highlight the methods used to generate these post-wildfire analysis products. / Environmental Sciences / M. Sc. (Environmental Science) Wildfires Post-wildfire Remote Sensing Veld fires Landsat AFIS MODIS National Veld and Forest Fire Act Forensic Disputes Optical sensors 363.3790285
96	Developing a 2D Forest Fire Spread Simulation for Enhanced Decision-Making During Catastrophes in Sweden Gauffin Dahlin, David January 2024 (has links) This thesis presents the development and evaluation of a 2D simulation model designed to predict the spread and behavior of forest fires, with a specific focus on Swedish forest ecosystems. Despite the model's simplicity and inherent limitations due to assumptions such as homogeneity in fuel distribution and the exclusion of topographical influences, the simulations yield remarkably accurate predictions of fire spread and intensity. The model integrates basic meteorological data (wind speed and direction, temperature) and uses a discretized spatial approach to simulate the dynamics of forest fires. Initial results suggest that even with minimal input variables and broad assumptions, the model offers significant predictive capabilities, highlighting potential areas for future refinement. Key aspects such as the interaction between conduction and advection terms, the role of water vaporization in fire dynamics, and the influence of wind on fire propagation are discussed. The findings encourage further development of the model, aiming at incorporating more complex variables such as topography and more forest fuels, potentially enhancing its utility in real-time fire management and decision-making processes. Forest Fire Simulation 2D Fire Spread Model Heat Transfer in Forest Fires Cellular Automata Wildfire Behavior Meteorological Data in Fire Modeling Fire Dynamics Fire Management Decision-Making Forest Ecosystems Sweden Wildfire Study Computational Fire Models Advection and Conduction in Fires Water Vaporization in Wildfires Fire Induced Weather Patterns Fire Spread Prediction Real-time Fire Management Environmental Impact of Forest Fires Empirical Data for Fire Simulation Firefighter Interventions Stochastic Wind Modeling Mathematics Matematik

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