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Characterization of plant-water interaction in Kilombero River Catchment in Tanzania using Normalized Difference Vegetation Index (NDVI)Minas, Michael Getachew January 2014 (has links)
Remote-sensing based indices such as Normalized Difference Vegetation Index have yielded valuable information about plant health. As the availability of water is one of the factors that controls plant's response to their environment, it is possible to indirectly studythe hydrology of an area via vegetation indices. Hence the thesis work used this tool to characterize the potential shifts in vegetation cover within and between years in Kilombero river catchment in Tanzania and make connection to the hydrology in the area. Separate time series analyses conducted on data pertaining to NDVI values and the areal coverage variability of arbitrarily defined NDVI-classes. The former data was extracted from a naturally vegetated wetland in the middle of the catchment while the latter from the topographically defined areas of the catchment. Results from the analyses showed that bothdatasets are sensitive to the seasonal rainfall while at inter-annual scale the areal coverage variability displayed significant correlations with past precipitation. Meanwhile the relatively higher sensitivity of the lowland area‟s NDVI to precipitation conforms to the initial assumption which emphasizes the importance of the wetland sub-catchment codenamed 1KB17 in describing Kilombero‟s hydrology. But the datasets show weak trends and it was not possible to make accurate future predictions on the hydrological conditions in the area. Meteorological distortions like clouds and environmental processes such as climate patterns or disturbances might have caused the problem in trend detection. Further studies needed to shed more light on the connection between land cover and hydrologic response in Kilombero.
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Tillämpning av oskarp logik i GIS-baserad skredanalys : Cuenca del Arga i Navarra, SpanienPalmkron, Katarina January 2014 (has links)
Målet med denna studie är att framställa en modell för sannolikheten för skred i Cuenca del Arga i Navarra, Spanien, med hjälp av GIS och oskarp logik. Utifrån denna modell framställs en karta som visar områden där det finns sannolikhet för skred. Övergripande har metoden skett i fyra steg. Först har en skredindexkarta framställts, sedan har medlemsfunktioner skapats utifrån dessa med hjälp av skredriskparametrar. De ingående parametrarna har varit sluttningsvinkel, topografisk fuktighetsindex, avstånd till vattendrag, jordmån och markanvändning. Sedan har medlemsfunktionerna applicerats på parametrarna, som sedan slutligen kombinerats genom WLC (weighted linear combination). Detta resulterade i en sannolikhetskarta för skred med fem klasser. / The aim of this study is to construct a model in GIS (geographical information system) for landslide susceptibility mapping for Cuenca del Arga in Navarre, Spain, to identify potential areas for landslides. The model is based on fuzzy logic approach and the parameters are overlaid with WLC (weighted linear combination).
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External Conditions Effects on the Self-Organised Criticality of the Calving Glacier Front of Tunabreen, Svalbard / Externa faktorers effekt på den själv-organiserade kritikaliteten av Tunabreens kalvningsfront, SvalbardWestrin, Pontus January 2015 (has links)
Mass balance processes in glaciers are important for determining the growth or retreat of ice. Calving, the mechanical breakage of ice bergs from a glacier front, is a poorly understood phenomenon. This process has great importance to the mass balance of many glaciers, for example on Antarctica and in the Arctic. A recent paper by Åström et al. (2014) compare calving fronts to Self-Organized Critical (SOC) systems, especially the Abelian sand pile model, meaning that the calving front will stay at a critical state at all times. Fluctuations in external conditions will cause the glacier front to either retreat or advance. The calving frequency and size distribution of Tunabreen, a tidewater glacier in Svalbard, was studied during August and September, 2014, with the use of a time-lapse camera set up in front of the calving front. An 11-day period is studied in detail and compared to certain external factors, i.e. tide, air temperature, humidity, atmospheric pressure, wind speed and wind direction. The results are also compared to the relationships found by Åström et al. (2014). The results vary: tide relationships are found as the amplitude reaches above 1 meter, but seize to correlate as the tide falls off. Temperature trends are found for certain periods, but are of low credibility. Humidity, atmospheric pressure, wind speed and wind direction show low to no correlation with the calving size distribution. Fragment size distribution and calving rates show good correlation with the results from Åström et al. (2014). This helps to confirm the theory of SOC applied to calving fronts. Time-lapse photography is deemed as a good way to observe calving fronts, but have certain problems which are mostly related to the weather. Longer time periods would be needed to find better long term relationships between external conditions and calving frequencies, but data is hard to acquire and time consuming to process. The theory of SOC applied to calving fronts is promising and opens up new discussions for the research community. / Massbalansprocesser för glaciärer är viktiga för att bestämma om isen drar sig tillbaka eller avancerar. Den mekaniska brytningen av isberg från glaciärer kallas kalvning. Kalvning är väldigt viktig för ett flertal glaciärers massbalans, exempelvis för landisen på Antarktis och glaciärer i Arktis. Ny forskning visar att kalvande glaciärfronter alltid försöker befinna sig i ett kritiskt läge, liknande ett så kallat Self-Organized Critical (SOC) system. Detta kan liknas vid hur en sandhög försöker befinna sig vid sin kritiska sluttningsvinkel när ett konstant flöde av sandkorn adderas. Adderandet av sandkorn kan jämföras med hur externa förhållanden, så som temperatur och tidvatten, ändras. När dessa värden ändras med tid så kommer fronten kalva, mycket likt hur sandhögen rasar när sandkorn tillförs. Externa förhållanden kommer alltså styra om glaciären kalvar eller inte, och när.En time-lapse-kamera installerades framför Tunabreen, en tidvatten glaciär på Svalbard, under Augusti-September, 2014. Bilderna över Tunabreens kalvningsfront, som varade över en 11-dagars period, användes för att ta ut varje enskild kalvingshändelse. Denna data jämfördes sedan med tidvatten, temperatur, luftfuktighet, atmosfäriskt tryck, vindhastighet och vindriktning. Resultaten jämfördes även med de förhållanden som visades i den nya studien som beskrevs tidigare.Resultaten är blandade. När tidvattnets amplitud var större än 1 meter så följer kalvningen tidvattnets mönster, men detta avtar när amplituden är mindre. Temperaturen visar viss korrelation, men endast för kortare perioder. Då temperaturens förhållande till kalvningen inte följer under de högsta och lägsta värden som fanns så bedöms temperaturen ha låg trovärdighet som kontrollerande faktor. Luftfuktighet, atmosfäriskt tryck, vindhastighet och vindriktning visar låg, till ingen, korrelation med kalvning. Storleksfördelningen av fragment och kalvningshastigheten har god korrelation med forskningen kring SOC, resultaten hjälper till att bekräfta denna teori. Time-lapse-fotografi bedöms som en bra metod för att observera kalvningsfronter, men har ett flertal problem som relaterar till det lokala vädret.Längre tidsperioder behövs för att bedöma om förhållanden stämmer på lång sikt. Data är svår att förvärva och tidskrävande att behandla. SOC stämmer bra in på kalvningsfronter vilket öppnar upp nya diskussioner inom forskningsvärlden.
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Water scarcity-induced change in vegetation cover along Teesta River catchments in Bangladesh : NDVI, Tasseled Cap and System dynamics analysisRahman, Md. Azizur January 2013 (has links)
Water scarcity is both natural and man-made phenomenon. Water control and uneven distribution of upstream TeestaRiver water makes artificial scarcity in downstream areas which can be minimized at least to the water stress level by balancing distribution and sustainable water use. Tasseled Cap transformation and NDVI methods were used in this study in order to find the magnitude of water scarcity in the downstream areas. NDVI and Tasseled Cap Greenness methods were applied to get proxy for soil moisture values in the form of biomass content and Tasseled Cap Wetness method were used to detect change in soil moisture content from Landsat TM and ETM+ data (1989-2010). System dynamic analysis method was applied to identify temporal and spatial differences between supply and demand of water in the TeestaRiver catchments area in the northwestern part of Bangladesh. It was found that, the vegetation cover and soil moisture content changed and shifted over time. Overall vegetation declined between 1989 and 2010 and soil moisture content also turned down. Moreover, TeestaRiver water is playing an important role for maintaining the balance between water supply and water scarcity in this region. There is a correlation between water scarcity in the downstream and availability of water in the TeestaRiver during dry seasons. / Master's Thesis
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Åsars bildning och modellering av isälvar under äldre och yngre Dryas i Svealand / Eskers Formation and Modelling of Channel Ice Streams During Older and Younger Dryas in SvealandÅström, Emilie January 2020 (has links)
Sveriges geomorfologi har till största del bildats under den senaste glaciationens erosion och depositions processer. Vid denna glaciations avsmältning rann smältvattnet bort från glaciären i isälvarna genom tunnlar under inlandsisen. Från dessa isälvar bildas åsar när materialet som transporterats med glaciären förs med i det turbulenta flödet i isälven innan det avsätts och bygger upp dessa långsträckta terrängformer. Isälvarnas position under inlandsisen bestäms av hydrauliska potentialen vilken bestämmer rörelseriktningen för vatten under glaciären. I vissa områden kommer den ha en lägre potential och andra en högre potential beroende på isens tjocklek och formen av den underliggande terrängen. Där den hydrauliska potentialen konvergerar kommer isälvar bildas av de stora mängder smältvatten som transporteras bort. Syftet med detta projekt var att bekräfta åsbildningen i Svealand genom att göra en modellering av den hydrauliska potentialen under inlandsisen i ArcGIS. Två modelleringsalgoritmer för flödesriktning kallade D8 och D-infinity, jämfördes också för att avföra vilken av dessa som bäst modellerar smältvattnets flödesvägar under inlandsisen. Tidsintervallen 11 000, 12 000 och 13 000 år sedan valdes för denna undersökning då inlandsisen då gick från att ligga strax söder om Svealand till mellersta Svealand. Mellan 11 000 och 10 000 år sedan avsmälte glaciären väldigt hastigt och retirerade till Kaledoniderna i norra Sverige och används därför ej i denna undersökning. I ArcGIS beräknades hydropotentialen för de olika tidpunkterna varefter sänkor i rastret fylldes upp. Flödesriktningen och flödesackumulationen beräknades för både D8 och D-infinity. Från flödesackumulationen togs isälvarna fram genom en omklassning av rastret. För att avgöra vilken flödesriktningsalgoritm som modellerade smältvattnets flödesvägar under inlandsisen bäst användes ett verktyg som summerade antalet pixlar av isälvar som låg under polygoner över nutida åsar i Svealand. Från detta beräknades en procentskillnad mellan D8 och D-infinity för att avgöra vilken av dem som stämde bäst överens med de nutida åsarna. En karta för varje tidsintervall som undersöktes samanställdes med de modellerade isälvarna och de nutida åsarna i Svealand för att visuellt avgöra om det gick urskilja en kronologisk bildningsföljd av åsarna. D-infinity beräknades modellera isälvarna upp till 2,5 procentenheter bättre än D8. Skillnaden mellan modelleringsalgoritmerna minskade i takt med att glaciärtäckningen av Svealand minskade. I kartorna som sammanställdes gick en viss kronologisk trend att se. Vissa åsar som när de låg långt från inlandsisens kant blev inte modellerade som isälvar förrän inlandsisens kant kom närmare dem. Vissa modellerade isälvar låg inte direkt på de nutida åsarna utan lite till sidan av dem vilket skulle kunna bero på att den rumsliga upplösningen som modelleringen gjordes i var för grov eller att fler faktorer behöver tas med i modelleringen. Till exempel skulle snävare tidsintervall kunnat användas i modelleringen för att bekräfta den kronologiska bildningsföljden av åsar. Transmissivitetens koppling till den hydrauliska potentialen och avståndet mellan isälvar hade möjligtvis också förbättrat modelleringen av isälvarnas rumsliga position. / Sweden's geomorphology has largely been formed during the recent glaciation erosion deposition processes of recent glaciation. During the deglaciation, the meltwater ran away from the glacier in the channel ice streams through tunnels under the ice sheet from which eskers were formed. The position of the glaciers in the ice sheet is determined by the hydraulic potential, which determines the direction of movement of water below the glacier. In some areas, it will have a lower potential and others a higher potential depending on the thickness of the ice and the shape of the underlying terrain. In places where the hydraulic potential converges, ice rivers will be formed by the large amounts of melt water transported away. The purpose of this project was to confirm the esker formation in Svealand by modelling the hydraulic potential during the glaciation in ArcGIS. Two flow direction modelling algorithms, D8 and D-infinity, were also compared to determine which of these best models the meltwater flow paths under the ice sheet. The years 11,000, 12,000 and 13,000 years ago were chosen for this study as the ice sheet then went from lying just south of Svealand to central Svealand. Between 11,000 and 10,000 years ago, the glacier melted very rapidly and retreated to the Caledonids in northern Sweden and is therefore not used in this study. In ArcGIS, the hydraulic potential for the different time intervals was calculated, after which sinks in the grid were filled up, the flow direction and the flow accumulation were calculated for both D8 and D-infinity. From the flow accumulation, the channel ice streams were generated by a reclassification of the grid. To determine which flow direction algorithm best modelled the meltwater flow paths under the ice sheet, a tool was used that summed the number of pixels of channel ice stream that were below polygons over current eskers in Svealand. From this, a percentage between D8 and D-infinity was calculated to determine which of them best matched the current eskers. A map for each assessed year was compiled with the modelled channel ice streams, ice sheet edge and the current eskers in Svealand to visually determine whether a chronological sequence of the eskers could be discerned. D-infinity was estimated to model the channel ice streams up to 2.5 percentage points better than D8. The difference between the modelling algorithms decreased as the glacier coverage of Svealand decreased. In the maps that were compiled, a chronological trend could be inferred to a certain point. Some eskers that, when they were far from the edge of the ice sheet, were not modelled as channel ice streams until the edge of the ice sheet were much closer to them. The modelling could be improved by increasing the resolution in which the modelling was made as it might have been too coarse or that more factors need to be included in the modelling. For example, narrower time intervals could be used in the modelling to confirm the chronological sequence of ridges. The connection between the transmissivity and the hydraulic potential and the distance between ice rivers may have also improved the modelling of the spatial position of the ice rivers.
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Methods for Coastal Flooding Risk Assessments : An Application in Iceland / Metoder för bedömning av översvämningsrisk från havet : En tillämpning på IslandJóhannsdóttir, Guðrún Elín January 2019 (has links)
Flood risk increases with rising sea levels and coastal settlements need to adapt to this increasing risk. For that, hazard and risk assessments are an important step. Coastal floods have caused problems in Iceland in the past and are thought to do so in the future as well. Therefore, a coastal flooding risk as- sessment needs to be made for Iceland. A risk assessment is currently in the early steps of preparation and a fitting method needs to be developed. To facilitate the process, an overview of the methods used in neighbouring countries is provided here and the suitability of the methods for Iceland is discussed. Building on these methods, a coastal flood scenario is produced for both present and future conditions as a preliminary hazard assessment for the country. The scenario produced is an upper bound scenario, highly unlikely but still possible. As a result, flooded areas are mapped and areas that need to be studied further in regard to flood hazard and risk are identified. It is shown that hazard estimation can be per- formed for Iceland through scenario production and that scenario results can be used in risk assessments. / De nuvarande klimatförändringar i världen kommer påverka människor på många olika sätt. En av de många saker som förändras är havsnivån. Havsnivån har stigit allt snabbare sedan i början av 1900 talet och kommer nästan säkert att fortsätta stiga i flera århudraden. Förhöjda havsnivåer föl- jer ökad översvämningsrisk som vi måste anpassa oss efter (Church, Clark, et al., 2013). Därför är riskbedömningar, alltså systematiska förfarande för att värdera risk, viktiga så att passande förebyggande åtgärder kan användas för att minska negativa påverkan från havsöversvämningar. En bedömning av översvämningsrisk från havet fattas för Island men för närvarande förbereder Is- ländska Meteorologiska Byrån att genomföra en. En tillämplig method behövs hittas och för att un- derlätta arbetet beskrivas i denna rapport metoder för preliminära bedömningar av översvämningsrisk från några av Islands grannländer; Danmark, Norge, Sverige och Storbrittanien. I huvudsak använder alla dessa länder liknande metoder, även om de har olika fysiska förutsättningar. De använder statis- tiska återkomsttider från mareograf data och informationer om historiska översvämningar för att bedöma faran. Sårbarhet identifieras inom fyra sårbarhets klasser, ofta genom ett index. Till slut sammanställs faro- och sårbarhetskartor för att bedöma risken och utpeka områden med översvämningsrisk. Eftersom Island har inte tillräckligt mycket data för att använda samma metoder som grannländerna, produceras i den här rapporten ett scenario för att värdera översvämningsfaran. Scenariot bygger på idéer från grannländerna och ska vara osannolikt men möjligt. Det är beräknad för både nuvarande och framtida förhållanden. Genom att subtrahera landhöjden från scenario havsnivån är översvämningsdju- pet beräknat. Några områden vart vattnet sannolikt skulle flöda och måste vara grundligt forskade är identiferade. Många påverkande faktorer är inte inkluderade i scenariot och därför anger resultatet inte noggranna översvämningskartor utan grovt överblick över översvämningsfaran. Resultaten ger alltså en idé om vart faran från havsöversvämningar är som störst och i vilka områden framtidiga havsnivåförän- dringar kommer bli som största. De visar också att ett scenario kan användas för farobedömning på Island, som sen kan kombineras med sårbarhetsbedömning via en index för att bedöma översvämn- ingsrisken på samma sätt som i grannländerna.
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Modelling the effects of climate change on ice dynamics at Kangerlussuaq Glacier, GreenlandBarnett, Jamie January 2021 (has links)
A consequence of climate change is rising global sea levels, predicted to bring increased socio-economic and environmental impacts to coastal communities. The Greenland Ice Sheet has become a prominent contributor to rising sea levels, a consequence of the Arctic warming at twice the rate of the global average. Mass loss from the ice sheet is separated between changes in surface mass balance and ice discharge at marine terminating outlet glaciers, with the later dominating mass loss over the past fifty years. While advances in ice sheet modelling have provided greater clarity on Greenland’s future mass loss, there remains inefficiencies in modelling the response of outlet glaciers in Greenland’s fjords. This thesis aims to provide greater insight into behaviour of Kangerlussuaq Glacier, SE Greenland, by employing a 2D flowline model to understand the processes governing ice dynamics and to explore how the glacier may respond to a warming climate. Results indicate that the presence of a winter ice mélange is the principle dictator of Kangerlussuaq Glacier’s behaviour and likely protects against further retreat towards a reverse sloped section of bedrock. However, if such a retreat does materialise, then large overdeepenings in Kangerlussuaq Fjord raise the spectre of uncontrollable retreat and excessive mass loss.
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Relative vegetation height variation and reflectance of herbaceous-dominated patches in Central SwedenSantiago, Jo January 2020 (has links)
Semi-natural landscapes are recognized as suitable habitats for different plant species and provide ecosystem services that contribute to increased plant biodiversity. At the stand level, plant biodiversity is influenced by vegetation structure, of which vegetation height is an important parameter. Photogrammetry from drone captured images has the potential to provide a quick and cost-effective analysis of vegetation height. In addition, the relation between spectral signatures and species distribution can indicate where higher plant biodiversity can be found, as species can be identified based on their spectral signature. Spectral signatures are thus used in the current study in conjunction with vegetation height as a proxy for plant biodiversity in herbaceous-dominated patches. Two field surveys were conducted to collect drone data and reflectance data in July and August 2019. Twelve plots of ten metres diametre were delimited in the drone-derived orthophotos around the reflectance readings coordinates. In order to assess vegetation height, the difference between the digital surface model derived from the orthophotos and the national digital elevation model was determined. Two statistical indices were calculated: the modified soil-adjusted vegetation index (MSAVI) and the coefficient of variation of heights (CV). The relationship between the two indices was evaluated as a proxy for plant biodiversity. Drone-derived point clouds can be used to measure vegetation height in herbaceous-dominated environments due to the very fine scale of drone imagery. A possible negative correlation was found between MSAVI and CV on both surveyed months (July r2 = 0.675; August r2 = 0.401) if the outlier plots were removed from the analysis. There is not enough evidence to clearly explain the anomalous behaviour of the outlier plots. Further research is needed to confirm the use of the relationship between vegetation height variability and reflectance as a proxy for plant biodiversity assessment in herbaceous-dominated environments.
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Metal mobility and transport from an oil-shale mine, Lake Nõmmejärv, EstoniaEkelund, Åsa January 2020 (has links)
Mining activities have a large impact on the environment, for example by the release of heavy metals from acid mine drainage and erosion of mine waste. North-eastern Estonia has the largest commercially exploited oil-shale deposit in the world. Waste from the mining processes have led to contamination of groundwater and streams polluted by phenols, oil products, sulphates and heavy metals. This thesis concerns the metal mobility from oil-shale mines in north-eastern Estonia, through water flow in the drainage system directed into Lake Nõmmejärv, which acts as a sedimentation basin for the mining water. A sediment core along with lake bottom surface samples were retrieved and analysed for heavy metals associated with mining. Water samples were collected and analysed for TOC. The sedimentary records show distinctively the change with the high inflow of water. The analysis of heavy metal content does not suggest a high impact on the environment, possibly because of a buffering effect by the limestone bedrock. The contents of heavy metals are somewhat elevated compared to background contents in Swedish lake sediments, but only cadmium and nickel levels are in the range that can be hazardous for the survival of organisms.
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Det finns inget dåligt väder, bara dåliga bostäder : Kartläggning av bebyggelse med risk för höga temperaturer i Kalmar läns största tätorter / There’s no bad weather, only lousy residences : Mapping of buildingswith risk of high temperatures in Kalmar County's largest citiesJohansson, Victor January 2021 (has links)
Global warming risks overthrowing the Earth's climate system, which would mean thatmany communities need to be reshaped and adapted to a new climate. The PublicHealth Agency of Sweden has run a project during the years 2017-2019 that aims toincrease society's ability to identify, prevent and manage harmful heat in existingbuildings. The project focuses on covering the occurrence and developing measures toprevent heat stress in both urban outdoor- and indoor environments. The agency has commissioned a GIS method which, based on the buildings' groundcover, aims to identify areas that are at risk of developing harmful temperatures. Themethod is based on first calculating the total land area of the cities in order to be able tocalculate the proportion of the area covered by high vegetation, hardened surfaces,building bodies and low vegetation. Based on this calculation, areas with a highproportion of paved surfaces and building bodies as well as a low proportion of highvegetation have been identified as areas with a higher risk of developing harmfultemperatures. In this essay, the method has been used to identify risk areas in KalmarCounty's largest cities; Kalmar, Västervik and Oskarshamn. High temperatures can be dangerous for all people, but elderly people are highlighted asa particularly vulnerable group as they have a reduced ability to regulate bodytemperature. Therefore the survey of the thesis has been supplemented with data onwhere people over the age of 65 live in relation to the risk areas in order to make furtherpriorities in where the measures are needed the most. The conclusion is that the need for cooling measures in the mapped cities is greatest inthe urban centers, as the high density of urban areas there provides good conditions fordeveloping high temperatures while a large part of the old population live in thesecentral areas. Several industrial areas have been identified as risk areas in all mappedcities, but there the need for cooling measures is less as they are usually located on theoutskirts of the cities and lack residents over 65 years. The exception is the OldIndustrial Area in Kalmar, whose central location and the circular design of Kalmarindicate that high temperatures develop here at night, which can drive the urban heatisland in the city.
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