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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
251

How the regional water cycle responds to recent climate change in northwest aridzone of China ?

Huang, Junyi 14 December 2017 (has links)
Climate change has posed significant challenges for the world's sustainable development, and the water cycle is highly dependent on the climate system. In particular, the arid zone fragile ecosystems in northwest China are highly vulnerable to the sophisticated hydrological variations. While ground-based measurements are less capable for large scale hydrological modelling, remote sensing techniques offer enhanced and effective alternatives for various hydrological states/fluxes. With the advancement of the Gravity Recovery and Climate Experiment (GRACE) satellites, the Terrestrial Water Storage (TWS), an integrative measurement of regional hydro-climatic environment, can now be measured as well for examining the overall hydrological response to recent climate change. TWS is an essential element of the water cycle and a key state variable for land surface-atmosphere interaction. Investigating the TWS change is important for understanding the response of the water cycle to climate change. In this study, the intra-annual and inter-annual spatio-temporal change pattern of TWS in Xinjiang Uyghur Autonomous Region of China during 2003-2015 are characterized from Gravity Recovery and Climate Experiment (GRACE) Tellus data products. Sub-regional re-analysis reveals that the increasing/decreasing rate in sub-regions, namely, Altay Mountains (ATM), Junggar Basin (JGB), Tianshan Mountains (TSM), Tarim Basin (TRB) and Kunlun Mountains (KLM), are - 3.41mm, -5.82mm, -6.76mm, -2.59mm and +3.05mm per year in unit of equivalent water height (EWH), respectively. The results suggest that TWS variation presents certain spatio-temporal patterns with spatial heterogeneity. The uncertainties from different GRACE products are also assessed. In conjunction with gridded meteorological data products and land surface model simulations of hydrological variables, the heterogeneous mechanisms of seasonal TWS change are analyzed. The correlation relationship among various hydrologic states/fluxes variables (e.g. snow water, soil water, snow amount) and climatic variables (e.g. temperature and precipitation) with GRACE-derived TWS variation in different sub-regions are investigated. The findings appear to indicate that 1) temperature month-over-month change and temperature anomaly with 4- month time lag, rather than precipitation, are more capable to explain the intra- annual TWS variation; 2) In most part of the study area, the TWS intra-annual change can be primarily attributed to the snow accumulation in winter and melt in spring. On the other hand, the glacier mass variation, which is particularly sensitive to recent climate change, could be a substantial contributor to inter-annual TWS change. The elevation trends over glaciers are estimated based on ICESat altimetry measurements. Correlation analysis results suggest that, during 2003- 2009, the inter-annual TWS loss in Tianshan Mountains (TSM) was tightly associated with glacier mass variation induced by temperature change, particularly in summer. In contrast, TWS gain in Kunlun Mountains (KLM) can be attributed to glacier mass increase. By utilizing remote sensing observation techniques/products, this study has characterized the spatio-temporal change pattern of TWS in northwest arid zone of China, as well as the underlying mechanism. It suggests that TWS is an effective indicator of regional climate change. This study contributes to a better understanding of the hydrologic and climatic processes in arid zone water cycle, and could be beneficial for regional water resources management and climate change adaptation effort.
252

USE OF UNSTEADY MODELING TO PREDICT FLOODING BY CORRELATING STREAM GAGES: A CASE STUDY

Burke, Michael John 01 August 2011 (has links)
Scientific studies have suggested an increase in the frequency and intensity of flooding. The research presented herein is focused on a small watershed, which has experienced intense flooding of a downstream, urbanized area. For emergency response and preparedness, it is pertinent to have the ability to predict intensity and peak flows of a flood. The Town of Dyer, Indiana has been severely impacted by flooding in the last twenty years. A 37.6 square mile watershed begins in a rural section of Illinois with tributaries draining into Plum Creek. The creek crosses into Indiana and becomes Hart Ditch, a straight, narrow, deep channel through the urbanized Town of Dyer. A HEC-HMS hydrologic model was used and calibrated based on USGS gage data. Storm events ranging from short, high intensity to long, intermittent precipitation provided a vast representation of possible scenarios within the watershed. The hydrologic model was paired with an unsteady HEC-RAS hydraulic model to allow for different lateral inflows to the creek providing variations of flow. A comparison between upstream and downstream stream gage readings was utilized to create a working model that predicts downstream water surface elevations for previous real-time storm and hypothetical storms. These conditions were analyzed by two stream gages and a correlation between the two gages was developed. This correlation was used to predict downstream water surface elevations. The correlation was also used to determine the time to crest based on readings at the upstream gage for many different storm events. The ability to know downstream water surface elevations for real-time storm events allows a window of time to implement emergency response in areas where flooding is imminent. The downstream area of concern has known flood elevations that represent various damage levels.
253

Planejamento do uso do solo em uma bacia hidrográfica para conservação dos recursos hídricos

Silva, Ramon Felipe Bicudo da [UNESP] 18 April 2011 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:26:47Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-04-18Bitstream added on 2014-06-13T19:34:37Z : No. of bitstreams: 1 silva_rfb_me_botfca.pdf: 1032918 bytes, checksum: fee4c4cfa450d8a450079bb3d387d04b (MD5) / Universidade Estadual Paulista (UNESP) / O objetivo deste trabalho foi construir um banco de dados digital do meio físico e desenvolver uma metodologia para a definição das áreas hidrologicamente importantes no ciclo hidrológico em uma sub-bacia hidrográfica, visando à priorização destas áreas em planos de recuperação de áreas degradadas, compensações florestais ou uso sustentado por meio de práticas de manejo conservacionistas. A sub-bacia hidrográfica pesquisada, localizada no interior do estado de São Paulo, estende-se sobre o Reverso da Cuesta, atravessando o Front e com sua foz na Depressão Periférica, no Rio Tietê. A cobertura do solo predominante é a cana-de-açúcar - 38% (10423 ha). O levantamento de solos em nível semidetalhado identificou uma série de comportamentos expressos através de diferentes tipos de solos relacionados com declividade, proximidade ao Front da Cuesta, rede de drenagem ou mesmo à Depressão Periférica onde a rocha originária são os arenitos Botucatu e Pirambóia ou ao Reverso da Cuesta onde a rocha originária é o arenito Marília. O uso do Geoprocessamento permitiu equacionar um volume de informações em velocidade e precisão que a mente humana não seria capaz de processar em igual desempenho. A partir dos resultados da pesquisa, pôde-se concluir que: o desenvolvimento de um mapa semidetalhado de solos foi fundamental para a obtenção de informações sobre os comportamentos das diferentes unidades pedológicas da subbacia frente às respostas na sua interação com a água / The objective of the Project was build a digital data base of the physical environment and develop a methodology to the definition of sensible areas for the hydrological process on a watershed, allocation these areas for environmental restoration planning, forestry practices and sustainable use by conservations practices of the management. The watershed is located at the country of Sao Paulo State and spread out above the Reverse of the Cuesta, crossing the Front reaching your river mouth in the Periferic Depression, at Tietê River. The predominant land cover is sugar cane – 38% (10423 ha). The soil survey at the semidetailed level has been identified a number os behaviors expressed by the different kinds of soil and their relationships with slope, proximity of the Front, water drainage and even Periferic Depression where the original rock is Botucatu sandstone, and in the Reverse is the Marília sandstone. The Geoprocessing approach allowed to equate an amount of geoinformations with a high speed and precision that would be impossible by the human mind in equal performance. In according with the results of the research, could be conclude that: the developing of the semidetailed soil map was fundamental for the informations about the behaviors of the soil units in their interactions with water
254

The Sentinel-Arlington Volcanic Field, Arizona

January 2015 (has links)
abstract: ABSTRACT The Sentinel-Arlington Volcanic Field (SAVF) is the Sentinel Plains lava field and associated volcanic edifices of late Cenozoic alkali olivine basaltic lava flows and minor tephra deposits near the Gila Bend and Painted Rock Mountains, 65 km-100km southwest of Phoenix, Arizona. The SAVF covers ~600 km2 and consists of 21+ volcanic centers, primarily low shield volcanoes ranging from 4-6 km in diameter and 30-200 m in height. The SAVF represents plains-style volcanism, an emplacement style and effusion rate intermediate between flood volcanism and large shield-building volcanism. Because of these characteristics, SAVF is a good analogue to small-volume effusive volcanic centers on Mars, such as those seen the southern flank of Pavonis Mons and in the Tempe Terra region of Mars. The eruptive history of the volcanic field is established through detailed geologic map supplemented by geochemical, paleomagnetic, and geochronological analysis. Paleomagnetic analyses were completed on 473 oriented core samples from 58 sites. Mean inclination and declination directions were calculated from 8-12 samples at each site. Fifty sites revealed well-grouped natural remanent magnetization vectors after applying alternating field demagnetization. Thirty-nine sites had reversed polarity, eleven had normal polarity. Fifteen unique paleosecular variation inclination and declination directions were identified, six were represented by more than one site with resultant vectors that correlated within a 95% confidence interval. Four reversed sites were radiometrically dated to the Matuyama Chron with ages ranging from 1.08 ± 0.15 Ma to 2.37 ± 0.02 Ma; and one normal polarity site was dated to the Olduvai normal excursion at 1.91 ± 0.59 Ma. Paleomagnetic correlations within a 95% confidence interval were used to extrapolate radiogenic dates. Results reveal 3-5 eruptive stages over ~1.5 Ma in the early Pleistocene and that the SAVF dammed and possibly diverted the lower Gila River multiple times. Preliminary modeling of the median clast size of the terrace deposits suggests a maximum discharge of ~11300 cms (~400,000 cfs) was necessary to transport observed sediment load, which is larger than the historically recorded discharge of the modern Gila River. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2015
255

Acumulação de elementos traço em organismos no estuário da Lagoa dos Patos

Garcia, Janice Goris January 2011 (has links)
Dissertação(mestrado) - Universidade Federal do Rio Grande, Programa de Pós–Graduação em Oceanografia Biológica, Instituto de Oceanografia, 2011. / Submitted by Cristiane Gomides (cristiane_gomides@hotmail.com) on 2013-12-15T09:45:05Z No. of bitstreams: 1 Janice Goris Garcia.pdf: 702089 bytes, checksum: 1220229f5c1f2087c00596bdbd146af8 (MD5) / Approved for entry into archive by cristiane soares (krikasoares@live.com) on 2013-12-18T17:44:26Z (GMT) No. of bitstreams: 1 Janice Goris Garcia.pdf: 702089 bytes, checksum: 1220229f5c1f2087c00596bdbd146af8 (MD5) / Made available in DSpace on 2013-12-18T17:44:26Z (GMT). No. of bitstreams: 1 Janice Goris Garcia.pdf: 702089 bytes, checksum: 1220229f5c1f2087c00596bdbd146af8 (MD5) Previous issue date: 2011 / Neste trabalho teores de elementos traço As, Cd, Cu, Cr, Fe, Mn, Pb, Ni e Zn foram determinados no camarão-rosa Farfantepenaeus paulensis, no cirripédio Balanus improvisus e no mexilhão Perna perna, coletados entre os anos de 2006 e 2010 no estuário da Lagoa dos Patos. Os resultados foram avaliados em função das variações hidrológicas interanuais ocorridas neste estuário e da comparação com resultados anteriores de trabalhos desenvolvidos com estas espécies neste estuário. As cracas inteiras analisadas mostraram-se adequadas ao monitoramento de As, Cd, Pb e Mn, cujos teores relacionaram-se positivamente às concentrações da água estuarina e inversamente à salinidade. Da mesma forma, os mexilhões juvenis apresentaram maiores concentrações de As, Cd, Cr, Pb, Mn e Zn quando o estuário apresentava-se sob condições menos salinas, exibindo o mesmo comportamento destes metais na água. Já os teores de cobre nesses organismos estiveram associados de forma direta à salinidade do estuário. As maiores concentrações de alguns metais nos mexilhões e cracas amostrados no Farol da Conceição, local sem aporte antrópico direto, com relação à região portuária, podem estar relacionadas a um maior aporte de água subterrânea na região de praia. Os resultados obtidos na região do Farol podem ser usados na comparação qualitativa das flutuações de concentrações de metais ocorrentes na região portuária. A análise do camarão inteiro refletiu melhor as condições ambientais do que a fração limpa, com teores de As, Mn, Pb relacionados inversamente à salinidade e teores de cobre relacionados de forma direta a essa variável. A avaliação temporal de metais acumulados nos organismos mostrou uma redução das concentrações da maioria dos elementos analisados, sendo observado um aumento somente nas concentrações de Cd e Zn com relação ao estudo realizado, em mexilhões,há 10 anos, o que também foi observado para o Cd e Pb nas cracas. A avaliação sanitária dos teores de metais em mexilhões e camarões indicou teores de As, Cr e Cu acima dos limites máximos permitidos pela legislação, indicando a relevância da continuidade do estudo da acumulação de elementos por esses organismos para a identificação de possíveis fontes de contaminação. Soma-se a isso a necessidade de se obter um conhecimento mais aprofundado da variabilidade das concentrações metálicas associadas a aportes continentais e a variações biogeoquímicas do estuário e, sobretudo discernir as frações naturais das antrópicas. / In this study concentrations of trace elements As, Cd, Cu, Cr, Fe, Mn, Pb, Ni and Zn were analyzed in the pink shrimp, barnacles Balanus improvisus and in the mussel Perna perna, sampled between 2006 and 2010 in the Patos Lagoon estuary. The results were evaluated in terms of interannual hydrological variations occurred in this estuary and by comparison with previous data from studies with these species in this estuary. Barnacles total assessed presented to be suitable for monitoring of As, Cd, Pb and Mn, which levels have been correlated positively with concentrations of estuarine water and inversely related to salinity. Likewise, the juvenile mussels showed higher concentrations of As, Cd, Cr, Pb, Mn and Zn when the estuary is presented under less saline conditions, exhibiting the same behavior of these metals in the water. In contrast, the Cu in these organisms was associated directly with salinity of the estuary. The highest concentrations of some metals in mussels and barnacles sampled in Conceição Lighthouse, place whithout direct anthropogenic contribution, in relation with the port region, it may be related to a major input of groundwater in the coastal area. The data from the region of the Conceição lighthouse can be used in the qualitative comparison of the fluctuations of metal concentrations occurring in the port area. The analysis of whole shrimp reflect better the environmental conditions of the edible part, showed concentrations of As, Mn, Pb inversely related to salinity and concentration of Cu directly related to this variable. Temporal evaluation of metals accumulated in organisms showed a reduction in the concentrations of most elements analyzed. It has been observed an increase only in the concentrations of Cd and Zn in mussels and of Pb in barnacles, compared to the study conducted 10 years ago. The health assessment of the metal levels in mussels and shrimp showed concentrations of As, Cr and Cu exceeded the maximum allowed by law, indicating the relevance of studies related to element accumulation by these organisms in order to identify possible sources of contamination. Furthermore it is necessary to get a deeper understanding of the variability of metal concentrations associated with continental inputs and biogeochemical changes in the estuary and, especially, to discern the nature fraction to the anthropogenic one.
256

Avaliação do potencial de aplicação de técnicas compensatórias em áreas urbanas consolidadas / Assessment of application potential of compensatory techniques in consolidated urban areas

Leandro Guimarães Bais Martins 10 February 2017 (has links)
O desenvolvimento urbano altera significativamente o ciclo natural das bacias hidrográficas. Com o surgimento da drenagem urbana sustentável, o rápido escoamento das águas pluviais deu lugar à restituição das características naturais da bacia hidrográfica através do planejamento do desenvolvimento urbano aliado ao uso de técnicas compensatórias que promovem a infiltração e detenção de águas pluviais. Entretanto, em bacias urbanizadas, o uso das técnicas compensatórias tem alcance limitado, principalmente pelo alto grau de impermeabilização das bacias, pela falta de preocupação com a drenagem durante a expansão urbana, pela baixa disponibilidade de espaço e pelos altos custos de aplicação de medidas estruturais de drenagem urbana. Assim, os princípios de drenagem urbana sustentável são muitas vezes considerados inadequados a ambientes de urbanização consolidada. Desta forma, este trabalho teve por objetivo avaliar o desempenho do uso em conjunto de diversas técnicas compensatórias definidas através do desenvolvimento de mapas de adequabilidade de uma bacia hidrográfica urbana à aplicação das técnicas compensatórias e de simulação hidrológica. Foram avaliadas bacias de detenção, pavimentos permeáveis, jardins de chuva, telhados verdes, trincheiras de infiltração e microreservatórios individuais. O desempenho das técnicas compensatórias foi avaliado individualmente e trabalhando em conjunto. Mapas de adequabilidade foram criados para locação e quantificação das técnicas compensatórias na bacia hidrográfica. Os resultados mostraram que a aplicação extensiva de técnicas compensatórias em ambiente urbano pode provocar melhoras significativas na redução de vazão de pico e controle do volume de hidrogramas de cheia, com melhores desempenhos individuais de até 35,5% de redução de pico e 32,48% de redução de volume de hidrogramas (TR 2 anos) com o uso de trincheiras de infiltração e 12,77% de redução de vazão de pico e 9,57% de redução de volume (TR 100 anos) com o uso de telhados verdes. Simulando as técnicas compensatórias mais eficientes funcionando em conjunto, foram obtidas reduções de 59,00% de vazão de pico e 46,37% de redução de volume para precipitações de tempo de retorno de 2 anos e 25,66% de vazão de pico e 26,45% de redução de volume em precipitações de 100 anos de tempo de retorno. Assim, concluiu-se que a adaptação de regiões urbanizadas aos princípios da drenagem urbana sustentável é possível e eficiente, e bons resultados podem ser obtidos mesmo nos ambientes mais densamente ocupados. Entretanto, a falta de planejamento durante o desenvolvimento urbano e a pouca disponibilidade de espaço impede a otimização do arranjo espacial dos dispositivos e limita a eficiência de algumas técnicas compensatórias, principalmente aquelas de grande porte. / Urban development significantly alters the natural cycle of river basins. With the emergence of sustainable urban drainage, rapid stormwater runoff gave way to recovering the natural characteristics of the river basin through the urban development planning coupled with the use of compensatory techniques that promote the infiltration and detention of stormwater. However, in already urbanized basins, the use of compensatory techniques have limited reach, especially by the high impermeabilization of the basins, the lack of concern with drainage during urban sprawl, low space availability and high implementation costs of structural measures of urban drainage. Thus, the principles of sustainable urban drainage are often considered inadequate to consolidated urban environments. Therefore, this study aimed to evaluate the performance of the conjunction use of several compensatory techniques defined after developing suitability maps for the urban basin and hydrologic simulation. We evaluated detention basins, permeable pavements, rain gardens, green roofs, infiltration trenches and individuals cisterns. We assessed the performance of compensatory techniques working individually and working together. Suitability maps were created for positioning and quantification of compensatory techniques in the watershed. The results showed that extensive application of compensatory techniques in an urban environment could lead to significant improvements in peak flow reduction and control of hydrograms volume, with best individual performance up to 35.5% peak reduction and 32.48% hydrograms volume reduction (TR 2 years) using infiltration trenches and 12.77% peak flow reduction and 9 57% volume reduction (TR 100 years) using green roofs. Simulating the most efficient compensatory techniques working together, the results shown 59.00% of peak flow reductions and 46.37% of volume reduction to 2-years rainfalls and 25.66% peak flow reduction and 26.45% of volume reduction in 100-years rainfalls. Thus, we concluded that the adaptation of urbanized areas to sustainable urban drainage principles is possible and efficient, and good results can be obtained even in the more densely occupied environments. However, the lack of planning for urban development and the limited space availability prevents the optimization of devices spatial arrangement and limits the effectiveness of certain compensatory techniques, especially those large as detention basins.
257

Python Tools to Aid and Improve Rapid Hydrologic and Hydraulic Modeling with the Automated Geospatial Watershed Assessment Tool (AGWA)

Barlow, Jane E., Barlow, Jane E. January 2017 (has links)
Hydrologic and hydraulic modeling are used to assess watershed function at different spatial and temporal scales. Many tools have been developed to make these types of models more accessible to use and model results easier to interpret. One tool that makes hydrologic models more accessible in a geographic information system (GIS) is the Automated Geospatial Watershed Assessment tool (AGWA); the GIS enables the development of spatially variable model inputs and model results for a variety of applications. Two major applications of AGWA are for rangeland watershed assessments and post-wildfire rapid watershed assessments. Each of these applications have primarily utilized the Kinematic Runoff and Erosion model (KINEROS2) which is accessible in AGWA. Two new tools were developed which work within the existing AGWA/KINEROS2 framework in ArcGIS to enhance rangeland and post-wildfire watershed assessments. The Storage Characterization Tool, was developed to work with high-resolution topographic data to characterize existing stock ponds so these features can easily be incorporated into AGWA/KINEROS2 for rangeland hydrologic analysis. The second tool simulates reach scale flood inundation (the Inundation Tool) utilizing AGWA/KINEROS2 outputs and local channel properties for Hydrologic Engineering Center (HEC-2) hydraulic calculations to compute flood inundation in post-wildfire environments. Both tools have been validated using multiple datasets and desired applications were outlined so that the tools are properly used.
258

Evaluating the Sensitivity of Cross Section Positioning when Computing Peak Flow Discharge using the Slope-Area Computation in a Mountain Stream

Forbes, Brandon Tracy, Forbes, Brandon Tracy January 2016 (has links)
The slope-area method is a commonly used and widely accepted technique for estimating peak flood flows in rivers where direct discharge measurements could not be obtained during the flood. The method makes multiple assumptions to simplify calculations which include assuming uniform flow conditions between surveyed cross sections, and that losses of energy in the reach occur only due to bank friction. Even though flows in nature do not always exhibit these simplified conditions, this method has been proven to provide adequate results when compared to direct measurements and thus, has become the go-to approach. To conduct a slope-area computation, the hydrologist needs to make multiple assumptions in the field based on experience, judgment, and published resources as guides. One of these assumptions is determining where to locate cross sections for the slope-area computation such that they sufficiently represent the cross-sectional area and slope of the channel. Traditional methods suggest to place the cross sections at breaks in the water surface slope. This research focuses on the variability of results of computed discharge values when cross sections are located at many different locations in the reach. What has been found is that many combinations of cross sections in the reach, including sections not located at the breaks in water surface slope, produce similar results when compared to the traditional methods. In fact, 121 of these combinations of cross sections produce peak discharge calculations within plus or minus five percent of the traditional methodology. What also was found was that variability in channel geometry goes unnoticed when using the traditional locating method, and losses due to expansion and contraction of flow area at locations which would not have been traditionally surveyed are occurring at multiple cross sections in the reach. The results suggest that reaches be evaluated for changes in geometry and not overlooked, so that the changes in shape, and subsequent losses in energy, be considered in the computation.
259

From Drought Monitoring to Forecasting: a Combined Dynamical-Statistical Modeling Framework

Yan, Hongxiang 21 November 2016 (has links)
Drought is the most costly hazard among all natural disasters. Despite the significant improvements in drought modeling over the last decade, accurate provisions of drought conditions in a timely manner is still one of the major research challenges. In order to improve the current drought monitoring and forecasting skills, this study presents a hybrid system with a combination of remotely sensed data assimilation based on particle filtering and a probabilistic drought forecasting model. Besides the proposed drought monitoring system through land data assimilation, another novel aspect of this dissertation is to seek the use of data assimilation to quantify land initial condition uncertainty rather than relying entirely on the hydrologic model or the land surface model to generate a single deterministic initial condition. Monthly to seasonal drought forecasting products are generated using the updated initial conditions. The computational complexity of the distributed data assimilation system required a modular parallel particle filtering framework which was developed and allowed for a large ensemble size in particle filtering implementation. The application of the proposed system is demonstrated with two case studies at the regional (Columbia River Basin) and the Conterminous United States. Results from both synthetic and real case studies suggest that the land data assimilation system significantly improves drought monitoring and forecasting skills. These results also show how sensitive the seasonal drought forecasting skill is to the initial conditions, which can lead to better facilitation of the state/federal drought preparation and response actions.
260

Flood dynamics, hazard and risks in an active alluvial fan system threatening Ciudad Juàrez Chihuahua Mexico

Zuniga, David January 2012 (has links)
The aim of this research is to assess hazards and risks associated with flooding in the city of Juárez, northern México, where there is a flood threat from active alluvial fans from mountains to the southwest and from the Rio Grande (Bravo River) to the northwest forming the northeast border of the city. Aims of this Ph.D. were addressed processing a digital elevation model (DEM) of the study area in a GIS platform to define the several alluvial fans, and thus to examine their history and palaeohydrology. Three OSL dates in the youngest parts of the fans show ages ranging from 74 - 31 ka. However, the fans were subsequently incised, broadly correlating with later Pleistocene to Holocene processes upstream, published in literature, in New México. These changes are not obviously linked to glacial-interglacial cycles, and there is indication of local controls of interplay of climate and topography, for which this work is a preliminary study. The flood threat to Juárez was addressed by using a classification of the uneven topography of the eroded alluvial fans, plus the Bravo River flood plain, into basins and subbasins. Field and laboratory work was used to define litho-facies of soils and rocks, location of structures such as, topographic and hydrologic apex and drainage system in the fans. The data were then used in association with published information on the parameters of the basins and sub-basins provided in published documents from the Mexican authorities to make flood models of the area, using standard models of HEC-HMS and HEC-RAS methods widely applied in semi-arid regions. The result was estimation of the ability of existing flood defences to resist high-flow floods that may be expected in upcoming decades. The modelling predicts that only a small number of the existing defences will hold in a catastrophic 1:100-year flood, and that substantial parts of the city are in considerable danger. Such results are important in relation to the expanded and dense population in Juárez, which is concentrated mostly on the most active part of the flooding system, the Colorado Fan, which is the subject of a focussed secondary study of vulnerability mapping. The map reveals that areas of the city of low socioeconomic development are under the greatest threat. Therefore there is a need for reconsideration of the city's flood planning, and remediation, plus the application of enforcements of areas which should not be built on, because of the threats.

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