Thèses sur le sujet « Hydrologic flood risk »

Este trabalho teve por objetivo principal estabelecer e comparar diferentes cenários de ocupação urbana e seus efeitos no ciclo hidrológico. Buscou-se avaliar os riscos de enchentes à jusante, causados pelo crescimento urbano e aumento das áreas de impermeabilização que ocorrerão com a implantação do novo campus da USP – São Carlos – SP e a conseqüente ocupação da bacia devido à especulação imobiliária. Dessa forma, a bacia do córrego do Alto Mineirinho foi dividida em sub-bacias, utilizando a abordagem de bacias embutidas. Foram estudados 4 cenários de ocupação urbana: cenário pré-urbanização (1972); cenário atual (2000), cenário 2025 com plano diretor (CPD) que inclui recuperação ambiental; e cenário 2025 sem plano diretor (SPD). Foram necessárias aerofotografias para demarcação do uso e ocupação do solo. Além disso, esse trabalho iniciou o monitoramento experimental de parâmetros hidrológicos e ambientais. Para avaliação e comparação dos diferentes cenários realizaram-se simulações hidrológicas com uso do modelo hidrológico IPH II. Com as análises hidrológicas foi possível verificar que a bacia, com apenas 18,6 % de urbanização (2000), apresenta qualidade hídrica inferior à recomendada para os corpos d’água classe 2 (CONAMA 357/05). Em relação às simulações hidrológicas, pôde-se observar que no cenário 2025 SPD, a vazão máxima cresceu 388,0 % quando comparada ao cenário 1972 e 319,4 % quando comparada ao cenário 2000. Entre os cenários 2025 CPD e 2025 SPD há diminuição de 22,3 % na vazão máxima e o aumento no tempo de pico é de 50 minutos. Porém, os riscos de enchente, analisados pelo método de curvas de permanência, mostraram-se que mesmo com aplicação de diretrizes do PD os riscos de inundações continuam altos, o que indica a necessidade de integrar medidas estruturais e medidas não-estruturais para amenizar os efeitos de enchentes à jusante
This work aims to establish and to compare different scenarios of urban occupation and its hydrologic effects. It evaluates downstream flood risks caused from upstream urban growth increased due to impervious areas and housing speculation surrounding the implantation of the new campus of University of Sao Paulo in Sao Carlos city, SP. The Mineirinho river basin was studied through nested sub-basin approach. Four scenarios of urban occupation have been depicted: pre-urbanization (year 1972), current situation (year 2000), prospective scenario with master plan (until year 2025; CPD), and expected situation without master plan (until year 2025; SPD). Aerial photos were used to help on the evolution of land occupation between past and current situation. The comparison of different scenarios was outlined with use of hydrologic model IPH II. Moreover, this work set the monitoring and record of hydrologic time series. Through experimental analyses it was verified that with 18,6 % of urban areas the water quality of sub-basins decreased significantly. Hydrologic modeling simulations showed that maximum streamflow discharges of scenario 2025 SPD would rise up to 388,0 % higher than scenario 1972 and 319,4 % higher than scenario 2000 respectively. Maximum stream discharges and peak timing of scenario with master plan of year 2025 (CPD) would have respectively a reduction of 22,3 % and a increase of 50 minutes in comparison to scenario without master plan of year 2025 (SPD). Permanency curves revealed with the application of master plan guidelines flood risks however continue high, thereby pointing the needs of integrate structural and non-structural measures to cope with floods downstream

The changes to catchment scale flood risk following river restoration works, including the addition of large wood logjams to the channel, are poorly quantified in the literature. Key concerns following river restoration for river managers and other stakeholders are changes to flood hydrology at the reach and catchment scale and changes in the mobility of large wood pieces. The effects of accumulations of large wood (logjams) on local flood hydrology have been documented in the literature, showing logjams slow flood wave travel time and increase the duration and extent of local overbank inundation. Modelling studies conducted at a reach scale have shown that these local effects can slow flood wave travel time through a reach and delay the timing of flood peak discharge at the reach outflow. How these local and reach scale effects translate to the catchment scale remains to be illustrated in the literature. In this thesis a combination of field and modelling studies are used to; elucidate the link between logjam form and function, to quantify the mobility of pieces of large wood relative to their physical characteristics, to predict the changes in floodplain forest restoration over time and to provide predictions of changes to catchment scale flood hydrology following river restoration at a range of scales and locations. It is shown that logjams inducing a step in the water profile are most effective at creating diverse geomorphology and habitats. Logjams were found to account for 65% of flow resistance in forested river channels, rising to 75-98% of flow resistance where the logjam was inducing a step in the water profile. Large wood in small forested river channels was found to be highly mobile with 75% of pieces moving, with the longest transport length of 5.6km. Large wood mobility is governed primarily by the length of a piece of wood with wood in excess of 1.5x channel width a threshold for a lower probability of movement. Hydrological modelling using OVERFLOW shows that reach scale river restoration can lead to modest changes in catchment scale flood hydrology. It is concluded that flood risk management can incorporate river restoration, but that results are likely to be unpredictable if engineered logjams are used alone. Substantial benefits in reducing catchment outflow peak discharge (up to 5% reduction) are modelled for floodplain forest restoration at the sub-catchment scale (10-15% of catchment area), rising to up to 10% reductions as the forest matures and becomes more complex.

A model for estimating seasonal flood risks which uses flow readings which are equally spaced in time is presented in this thesis. The model is referred to as the Spectral Model. This model can be used to estimate the probability of at least 1 exceedance of given critical levels. The model is based on the Rice distribution for peaks of a Gaussian stochastic process, whose parameters are associated with the spectral moments of the process. In the simpler form of the model, peaks are assumed independent. Simulation results obtained using realisation of Gaussian AR(1) processes indicated that the estimates of the risks using Spectral Model are less biased than those obtained from the EV1 and the POT Model, especially for higher critical levels. A modification which removes the assumption that peaks are independent using the multi-fold integrals of Gupta and Moran is also considered. Gupta's method assumes that the correlation between peaks at any lag are equal to the first autocorrelation. The Monte Carlo simulation of Moran has no such restriction on the autocorrelations but may not converge. The Model was applied to River Greta, a small catchment in County Durham in the North of England.

Hydrological time series are often asymmetric in time, insomuch as rises are more rapid than recessions, as well as having highly skewed marginal distributions. A two-stage transformation is proposed for deseasonalised daily average flow series. Rises are stretched, and recessions are squashed until the series is symmetric over time. An autoregressive moving average (ARMA) model is then fitted to the natural logarithms of this new series The residuals from the ARMA model are represented by Weibull distributions. Seasonal flood risks, as daily average flows, are estimated by simulation. However, floods are often measured as peak flows rather than daily average flows, although both measures are relevant, and the use of growth factors to allow for this is demonstrated. The method is demonstrated with 24 years of daily flows from River Cherwell in the south of England, a 40-years record from the upper reaches of the Thames and 21-years record from the River Coquet in the north-east of England. Seasonal estimates of flood risk are given, and these can be conditioned on catchment wetness at the time of prediction. Comparisons with other methods which allow for time irreversibility are also made. One is ARMA models with exogenous input, in this case rainfall, which will, because of its intermittent nature, impact a natural time irreversibility to the streamflow series. A disadvantage of these models is that they require rainfall data in addition to the streamflow record. A second is the development of a class of shot noise models, which naturally generate highly time irreversibility series. This is the Neyman-Scott model. But, despite its attractive physical interpretation it is inevitably less flexible than the two stage transformation because it has fewer parameters. Although it was found to provide a good fit to daily data it is less convincing for the extremes. Overall the two stage transformation (TST) compared favourably with both models.

A avaliação do risco de inundação surge como medida de mitigação da vulnerabilidade da comunidade à ocorrência de eventos hidrológicos extremos. Os objectivos principais do presente estudo são a apresentação e âmbito de aplicação de seis modelos hidráulicos, disponíveis no mercado, e a comparação da aplicação dos modelos LISFLOOD-FP e HEC-RAS na avaliação do risco de inundação, num troço de 4 km do Rio Lis, entre a ponte de Miguel e a ponte da Bajanca. Na aplicação ao troço do Rio Lis foi efectuada a caracterização fisiográfica da bacia hidrográfica, com recurso aos sistemas de informação geográfica. No cálculo do caudal centenário aplicou-se o modelo hidrológico HEC-HMS. Após a preparação dos dados de entrada nos modelos escolhidos foram obtidas as zonas inundáveis para o troço em estudo e comparados os resultados. A avaliação do risco de inundação efectuada teve em atenção os termos do Decreto-Lei n.º 115/2010, de 22 de Outubro; ABSTRACT:Flood risk assessment comes up as a mitigation measure of the community vulnerability to the occurrence of extreme hydrological events. The main aims of the current study are the presentation and scope of six hydraulic models available in the market and the comparison of application of the models LISFLOOD-FP and HEC-RAS in a 4 km reach of the River Lis, between bridge of Miguel and bridge of Bajanca. It was made a description of the physiographic features of the River Lis watershed with the support of geographic information systems. To estimate the discharge for a storm event of 100 years it was applied the model HEC-HMS. After preparing the input data of the two models the delineation of the study area was obtained and the results were compared. The flood risk assessment took into account the terms of Portuguese law.

The old water system in Sala, formerly belonging to thesilver mine, is analysed with regard to dam safety focusing onthe hydrological aspects. The hydrological safety of the riskclass I dams in the area, built in the 16th century, is notconsidered adequate according to the Swedish guidelines fordesign flood determination. A review is made of internationalprinciples for design flood determination. The overview showsthat there is no common principle used internationally whendealing with design flood for dams. In some countries there isan ambition to implement risk assessment for evaluation ofhydrological safety. However, at present Australia is the onlycountry that has fully integrated risk assessment in theirdesign flood guidelines. A risk assessment of the water systemin Sala shows that neither increasing the spillway capacity norimplementing flood mitigation measures in the watershed haveany significant effect on dam safety in the area. Nothingindicates that watersheds with a high presence of mires, likein the Sala case, should be particularly well suited forimplementing flood mitigation in the watershed as a dam safetymeasure. In order to safely handle the design flood in Sala andavoid dam failure due to overtopping the flood needs to bediverted from the water system.

Key words:dam safety; design flood; flood mitigation;hydrological; risk assessment

Water contamination during urban flood events can have a negative impact on human health and the environment. Prior flood studies lack investigation into how GIS can map and analyze this at a large scale (cadastral) level. This  thesis  focused on how GIS can  help map and analyze water contamination risk in urban  areas  using  LiDAR  elevation  data,  at  a  large-scale  (cadastral)  level,  and  symbology  and  flood classification  intervals  specifically  selected  for  contamination  risk.  This  was  done  by  first  completing a literature review about past research and studies  of similar scope. Based on  the findings, a method to map and analyze water contamination risk during sea-based flood scenarios was tested in the Näringen district of Gävle, Sweden. This study area was investigated and flood contamination risk maps were produced  for two different  flood scenarios which illustrated  which properties are vulnerable to flooding and at what depth, what their contamination risk is, and if they are hydrologically connected to the ocean.  The findings from this investigation  are that this method of examining water contamination risk could be useful to planning officials who are in charge of policies relating to land-use. These findings could help guide landuse  or  hazardous  material  storage  regulations  or  restrictions.  To  further  research  in  this  topic,  it  is recommended  that  similar  studies  are  performed  that  use  a  more  detailed  land-use  map  which  has information  on  what  type  and  quantity  of  possible  contaminants  are  stored  on  individual  properties. Furthermore, flood modeling should be employed in place of the flood mapping which was conducted in this thesis.

Many regions in Africa are presently faced with an increasing flood risk due to impending climate change and population growth. One useful mitigation strategy to decrease this risk would be to map it, so that urban planning, warnings systems and emergency response subsequently could be designed to reduce societal vulnerability. This is, however, not widely feasible on the African continent, as developing countries often lack access to the topography and discharge data required to produce high- quality flood risk maps. To seek a way around this problem, on-going research is investigating the possibility of obtaining alternative model inputs, by using global datasets of elevation, derived from remote sensing, and methods to estimate flood flows. This thesis presents a case study within this context where the aim was to determine the accuracy of an African catchment-scale flood map, produced with the satellite product SRTM (Shuttle Radar Topography Mission) as topography input, and to explore the potentials and limitations of such a model scheme. Two high-magnitude floods, occurring in year 2000 and 2013 in the Lower Limpopo Basin (Mozambique), were modelled for inundation extent, using a no-channel 2D model built for the LISFLOOD-FP flood modelling software. Flood water levels were also simulated to assess the models vertical performance. Model outcomes were evaluated against satellite imagery and recordings of high watermarks, adjusting the value representing the roughness of the floodplain to optimize flood extent correspondence. Due to different hydrograph dynamics, simulations of the two floods required different values of roughness (0.02 and 0.09 s m-1/3) to reach maximum accuracy (F = 0.59 and 0.64, respectively). However, the results also indicated that a model calibrated with a flood of relatively low return period potentially could be used to map rare flood events. Simulation inaccuracies were mainly attributed to (1) reservoirs and streams, temporarily connecting to the river system during high flow conditions, (2) limitations of the topography data, in terms of recognizing riverbed geometry and floodplain micro-topography, and (3) cloud cover, reducing the accuracy of flood extent reference data. The vertical simulation accuracy, with an average error of ± 2 m, was well within the uncertainty bounds of input data. Errors were in this case ascribed the SRTM’s representation of high slope terrain and possible radar speckles in urban areas. The findings of this study indicate that there is high potential in using SRTM data for mapping of high-magnitude flood risk in Africa, but also that consideration to river system complexity is crucial.
Många  områden  i  Afrika  står  för  närvarande  inför  en  ökad  översvämningsrisk  på  grund  avklimatförändringar och befolkningstillväxt. En användbar strategi att minska denna risk skulle vara att kartlägga den, så att stadsplanering, varningssystem och respons vid nödsituationer därefter skulle kunna utformas till att begränsa samhällets sårbarhet. Detta är dock inte möjligt på bred front över Afrikas kontinent, då utvecklingsländer ofta saknar det data av topografi och vattenflöde som behövs för producera högkvalitativa översvämningsriskkartor. För att försöka hitta ett sätt att kringgå detta problem undersöker pågående forskning möjligheten att generera alternativ modelleringsinput, från globalt tillgängligt höjddata, insamlat av satelliter, och metoder att uppskatta översvämningsflöden. Denna uppsats presenterar en fallstudie inom denna kontext där syftet var att bestämma kvalitén hos en översvämningskarta över ett Afrikanskt avrinningsområde, producerad med satellitprodukten SRTM (Shuttle Radar Topography Mission) som topografiinput, och att utforska möjligheterna och begränsningarna med en sådan karteringsmodell. Två stora översvämningar, vilka inträffade år 2000 och 2013 i Nedre Limpopobassängen (Mocambique), simulerades för utbredning med hjälp av en 2D- model utan flodfåra byggd för modelleringsprogrammet LISFLOOD-FP. Vattennivåer simulerade också för att kunna bedöma modellens vertikala prestation. Resultaten jämfördes med satellitbilder och dokumenterade höga vattenmärken (observerade på t ex. husfasader), samtidigt som flodplanets flödesmotstånd justerades för att optimera överensstämmelsen. Då översvämningarna var av olika karaktär behövdes olika flödesmotstånd (0.02 and 0.09 s m-1/3) för att maximal kvalité på respektive översvämningskarta skulle uppnås. Denna kvalité beräknades till 0.59 och 0.64, på en index-skala (F) där 1.00 motsvarar en perfekt simulering. Trots olika optimala flödesmotstånd antydde resultaten även att en modell kalibrerad med en relativt frekvent återkommande översvämning möjligtvis kan användas till att kartlägga sällsynta översvämningar. Avvikelserna mellan dokumenterad och simulerad översvämningsutbredning tillskrevs i huvudsak: (1) sjöar och vattendrag som temporärt ansluter till flodsystemet under höga flöden, (2) begränsningar i topografidatat gällande att fånga flodens geometri och flodplanets mikro-topografi samt (3) moln som skymmer översvämningarna i referensdatat och minskar dess sanningshalt. Vattennivåer simulerades med ett genomsnittligt fel av±2 m, vilket med marginal ligger inom inputdatats totala osäkerhetsram. Avvikelserna troddes i detta fall bero på SRTM-datats representation av sluttande terräng och möjliga radarfläckar (reflektioner) i urbana områden. Resultaten i denna studie indikerar att det ligger stor potential i att använda SRTM- data för att kartlägga risken för stora översvämningar i Afrika, men belyser också vikten av attuppmärksamhet ges till flodsystems komplexitet.

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.

Cette thèse aide à approfondir les connaissances sur les différentes sources d’incertitude dans l’évaluation économique du risque inondation. Elle explore plusieurs disciplines afin d’analyser l’impact des stratégies utilisées pour modéliser l’aléa inondation et la vulnérabilité d’un territoire, sur l’évaluation des dommages potentiels. On a mesuré la variabilité des estimations en fonction des bases de données, modèles, méthodes et échelles considérés pour : analyser la probabilité des inondations (hydrologie) ; modéliser et cartographier l’aléa inondation (hydraulique) ; caractériser la vulnérabilité des enjeux et leur susceptibilité à subir des dommages (génie civil, géographie et économie de l’environnement). Les analyses et méthodes développées devront appuyer la prise en compte d’incertitudes, la détermination de priorités et l’optimisation de la distribution des ressources entre les différents modules de l’évaluation. Afin d’explorer un degré de complexité supplémentaire d’analyse de risque, nous avons développé une méthode d’analyse de la vulnérabilité systémique des réseaux d’infrastructure en lien avec leur résilience
This thesis aims at exploring different sources of uncertainty related to the economic analysis of the flood risk. It embraces several fields of knowledge in order to determine how the selection of strategies used to model flood hazard and assess the vulnerability of a territory may affect damage potential estimations. We measured the variability of damage estimations as a function of the datasets, methods, models and scales considered to: analyse the probability of floods (hydrology); model and map flood hazard (hydraulics); assess the vulnerability and susceptibility of properties to floods (civil engineering, geography and environmental economics). The methods and analyses developed here should bring support for practitioners in the investigation of uncertainties, determination of evaluation priorities and optimisation of the distribution of resources between the different modules of the evaluation process. In order to explore a second level of complexity of flood risk evaluations, we developed a method for analysing the systemic vulnerability of infrastructure networks, in relation with their resilience

Le tiers de la population mondiale, vit dans des espaces où les risques potentiels sont liés plus ou moins directement à la nature ; Les inondations, sont responsables de plus de la moitié des risques dommageables. À l’instar le risque inondation affecte les villes marocaines et plus particulièrement celles situées sur les piedmonts dir. Les agglomérations de dir de Béni Mellal sont très menacée par les inondations. Ces catastrophes sont le fait de crues-éclair (flash flood) trouvant leur origine dans la structure des précipitations (intensités remarquables) et une topographie propice à la concentration des écoulements sur de petits bassins versants de forte pente.Ce travail est une contribution opérationnelle à la connaissance du phénomène « crue-éclair » affectant les agglomérations du "dir" de Béni-Mellal dont l’objectif est l’amélioration de la résilience du "dir" de l’Atlas de Béni-Mellal face aux inondations et aux "crues-éclair". À cause de l’absence des stations hydro pluviométriques, est vue la spécificité de dire comme une zone de transition, la démarche élaborée repose sur une étude fine des deux facteurs du risque, l’aléa et la vulnérabilité, sur des bassins versants représentatifs du domaine du dir de Béni Mellal. Notre approche, que l’on peut qualifier "hydrologique intégrée" considère l’aléa comme une solidarité hydrologique entre l’amont et l’aval ou plutôt la dépendance de l’aval vis-à-vis de l’amont. La gestion des risques dans le dir de Béni-Mellal, demande donc l’intégration des techniques hydrologiques modélisatrices et l’association des mesures non structurelles telles que, la conscience du risque, la réduction de la vulnérabilité, la maîtrise de l’occupation du sol, surtout la dynamique urbaine. Les solutions adoptées doivent être cohérentes entre elles. A cet égard, notre méthodologie s’articule sur la valorisation de données multi-sources. Elle s’appuie, d’un côté, sur une approche de l’hydrologie classique, qui consiste en l’étude analytique de « l’aléa historique » et l’étude hydrométrique dont les données hydrométriques et pluviométriques produites, seront utilisées pour la caractérisation de « l’aléa » et des crues torrentielles. Une approche hydrologique modélisatrice où les résultats seront utilisés pour la calibration et la validation d’une modélisation hydraulique et pour la production des cartes de risques. D’un autre côté, elle vise à intégrer le contexte socio-économique et cultuel, le degré d’organisation de l’occupation du sol, et les politiques publiques de la gestion des risques…etc
One-third of the world's population lives in areas where potential risks are more or less directly related to nature. Floods are responsible for more than half of the damaging risks. Like other countries, the flood risk affects the Moroccan cities and especially those located on the piedmonts. For instance, the agglomerations of Béni Mellal piedmonts are very threatened by floods. These disasters are the result of flash floods originating principally from a changing rainfall pattern (remarkable intensities) and a favorable topography conductive to the concentration of the flows on small watersheds of steep slope.This study is an operational contribution to the knowledge of the "flood-lightning" phenomenon that is affecting the agglomerations of the "piedmont " of Beni-Mellal. Its objective is to identify the resilience of the Atlas “piedmont” of Beni-Mellal in the face of floods and "flash floods".Because of the absence of hydro-rainfall stations, and the specificity of the study area considered as being a transition zone, the approach developed is based on a detailed study taking into account two risk factors, namely the hazard and the vulnerability..Our approach, which can be described as "an integrated hydrological approach" considers the hazard as a hydrological solidarity between upstream and downstream or rather the dependence of downstream towards the upstream. Therefore, risk management in the piedmonts of Béni-Mellalrequires the integration of modeling hydrological techniques and the association of non-structural measures such as, risk awareness, vulnerability reduction, controlof soil occupation, especially urban dynamics. For this reason, the adopted solutions a must be coherent with each other. In this respect, our methodology is based on the valuation of multi-source data. It relie, on one hand, on a classical hydrology approach, which consists of the analytical study of "historical hazard"and the hydrometric study whose hydrometric and rainfall data will be used for the analysis. Characterization of "hazard" and flashfloods events (The results of this modeling hydrological approach will be used for the calibration and validation of hydraulic modeling and for the elaboration of risk maps. On the other hand, it aims at integrating the socio-economic and cultural context, the degree of organization of the occupation of the ground, and the public policies of the risk management ... etc

Recentes catástrofes provocadas por eventos hidrológicos extremos ocorridos nas cidades brasileiras revelaram a fragilidade das atuais políticas empregadas no tratamento do problema das inundações. Freqüentemente, faltam recursos mesmo para as ações emergenciais, e as ações estruturais aplicadas muitas vezes consistem de medidas pontuais e paliativas que não promovem soluções definitivas no âmbito de bacia hidrográfica. O tratamento do problema de inundações de maneira orientada ao risco, em lugar da tradicional abordagem orientada a evento, é uma alternativa que propicia soluções mais eficientes e sustentáveis. A gestão do risco de desastres naturais compreende três níveis: antes, durante e após o evento extremo, com base em ações que visam à redução do risco por meio de suas três componentes: ameaça, vulnerabilidade e exposição. No contexto do desenvolvimento e fortalecimento econômico do Brasil, os seguros para desastres naturais têm papel importante como agentes de transferência do risco que possibilitam a recuperação econômica das áreas atingidas. Vencido o entrave inicial à implantação de seguros deste tipo no Brasil, que foi a abertura, em 2007, ao mercado ressegurador internacional, o desafio que se apresenta atualmente é o desenvolvimento de metodologias que possibilitem relacionar a magnitude do evento natural extremo com o prejuízo monetário correspondente e o prêmio de seguro que possibilite ressarcir as perdas contabilizadas, considerando cenários de longo prazo. O modelo de seguros proposto neste trabalho é baseado no princípio de seguro indexado, em que o pagamento de indenizações é vinculado a uma variável climática, no caso, a vazão máxima de cheia. Foram utilizadas ferramentas de modelagem e simulação hidráulico-hidrológica para gerar mapas de risco de inundação e quantificar os prejuízos correspondentes às cheias de diferentes probabilidades de ocorrência. Em seguida, foi simulado um modelo econômico de seguros para obter o prêmio ótimo capaz de ressarcir os prejuízos estimados, considerando diferentes cenários de longo prazo. Um estudo de caso ilustra a aplicação do método em uma bacia hidrográfica caracterizada por problemas recorrentes de inundação, dado o processo de expansão urbana que nela vem ocorrendo. Foram avaliadas faixas de cobertura em função dos períodos de retorno das cheias correspondentes. Os resultados mostraram que a metodologia é adequada à análise do comportamento do fundo de seguros. Resseguros podem ser requeridos para o tratamento de eventos de períodos de retorno muito extremos.
Recent disasters caused by extreme hydrological events, occurred in Brazilian cities, have exposed how fragile the current policies are to manage such situation. Often, a lack of resources is observed even for emergency actions, while structural actions commonly consist of palliative and punctual measures that do not promote real solutions considering the watershed sphere. To face the problem based on a risk-oriented approach instead of the traditional event-oriented approach represents an alternative that provides more efficient and sustainable solutions. Disaster risk management comprehends three time-oriented phases: before, during and after the extreme event, each phase focusing on the three risk\'s components: hazard, vulnerability and exposition. As Brazil\'s economy grows stronger and more stable, natural disaster insurance plays an important role as a risk transfer mechanism, promoting economic resilience in damaged areas. After the opening of the reinsurance\'s market in 2007, Brazil\'s challenge is to develop methodologies relating extreme events hazard with its corresponding damage and an insurance premium, in a way that the losses can be refunded in long term sceneries. The insurance model proposed in this work is based on the indexed insurance, where the refunds are linked to a weather variable - the maximum discharge. Hydrologic and hydraulic simulations were developed in order to generate risk maps and to quantify the damage related to floods with different return periods. Afterwards, a flood insurance model was simulated in order to obtain the optimal insurance premium sufficient to refund the expected damage for long term sceneries. A case study illustrates the method in a watershed where flood events are frequent due to urban occupation. The insurance coverage associated to each flood return period was examined and the results have shown that the methodology is suitable for the analysis of the flood insurance\'s behavior. Reinsurance may be required to deal with extreme events with high return periods.

In response to increased greenhouse gases and global temperatures, changes to the hydrologic cycle are projected to occur and new precipitation characteristics are expected to emerge. The study of these characteristics is facilitated by common indices to measure precipitation and temperature developed by the Expert Team on Climate Change Detection and Indices (ETCCDI). These indices can be used to describe the likely consequences of climate change such as increased daily precipitation intensity (SDII) and heavier rainfall events (R95p). This study calculates a subset of these indices from observed and modelled precipitation data in Portland, Oregon. Five rainfall gages from a high resolution rain gage network and projections from three downscaled global climate models including CanESM2, CESM1, CNRM-CM5 are used to calculate precipitation indices. Mann-Kendall's tau is used to detect monotonic trends in indices. The observational record is compared with models for the historic period (1977-2005) and these past trends are compared with projected future trends (2006-2100). The influence of study unit on trend detection is analyzed by computing trends at the annual and monthly scale. Study unit is shown to be important for trend detection. When the annual study unit is used, projected future trends towards increased precipitation intensity and event volumes are not observed in the historic data. However, when analyzed with a monthly study unit, trends towards increased precipitation intensity and event volumes are observed in the historic data. These trends are shown to be important for Portland area flooding, as precipitation indices are shown to significantly correlate with 40 maximum peak flow events that occurred during the period of study.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
As inundações constituem um dos impactos ambientais mais observados nas áreas urbanas. A incidência destes eventos varia conforme as características climáticas e socioambientais das cidades. Esta pesquisa teve como objetivo principal avaliar o risco a enchentes, a alagamentos e ao escoamento superficial concentrado na área urbana de Ituiutaba (MG), a partir de suas condicionantes físicas e de suas características socioespaciais, inerentes ao processo de urbanização. Para isto, realizaram-se análises do geossistema urbano; da variabilidade pluvial com enfoque na recorrência das precipitações extremas; das ocorrências de transtornos associados ao impacto pluvial e da percepção do problema por parte da população atingida e do poder público municipal. Verificou-se que os impactos hidrometeóricos concentram-se durante os meses da primavera e do verão, quando as chuvas são mais abundantes. Em média, treze episódios chuvosos com volume a partir de 30mm/24h acontecem a cada ano, representando, assim, um potencial de danos ao ambiente urbano. De forma mais esporádica, acontecem ainda precipitações mais intensas, por volta de 90mm/24h, com potencial de impacto muito maior. Os arquivos das ocorrências do Corpo de Bombeiros e as reportagens publicadas pela imprensa local constituíram importantes fontes para o mapeamento e análise dos impactos. Como consequência desses eventos, tem-se na área central da cidade e bairros adjacentes, que são mais impermeabilizados, as ocorrências de escoamento superficial concentrado e os alagamentos. Além disso, a rede de galerias pluviais é insuficiente para drenar os locais onde os problemas são mais evidentes, principalmente em quatro áreas, sendo estas as avenidas José João Dib, Minas Gerais, Dezessete e Prof. José Vieira de Mendonça. Na primeira, observam-se alagamentos devido à deficiência na drenagem do escoamento superficial, que não consegue direcionar as águas para dentro da canalização do Córrego São José. Nos demais locais o problema é o escoamento superficial concentrado, que forma um fluxo ao longo das vertentes, suficiente para arrastar pessoas e veículos, além de provocar danos na pavimentação de ruas e calçadas. No tocante à população afetada pelas inundações, a maior parcela é formada por pessoas de baixa renda, cujas residências são mais vulneráveis ao acúmulo/escoamento de água em superfície. Este cenário demanda a atuação efetiva da administração pública no sentido de elaborar planos estratégicos para a gestão das águas pluviais.
Floods are one of the most observed environmental impacts in urban areas. The incidence of these events varies according to the climatic and socio-environmental characteristics of the cities. The main objective of this research was to evaluate the risk to the overflows, the floods and the concentrated surface runoff in the urban area of Ituiutaba (MG), based on its physical conditioning aspects and its socio-spatial characteristic, which are inherent in the urbanization process. For that purpose, some analyzes of the urban geosystem, the rainfall variability with focus on the recurrence of the extreme precipitations, the occurrences of disturbances associated with the rainfall impact and the perception of the problem by the affected population and the municipal public power were carried out. It was found that the hydrometeoric impacts are concentrated in the spring and summer months, when the rains are more abundant. On average, thirteen rainy episodes with a volume from 30mm/24h happen each year, which represents a potential for damages to the urban environment. More sporadically, there are some intense precipitations, around 90mm/24h, with a much greater potential impact. The Fire Department's archives and the news published in the local press were important sources for the mapping and analysis of the impacts. As a consequence of these events, there are in the city centre area and adjacent neighborhoods, which are more waterproofed spaces, the occurrences of concentrated surface runoff and flooding. In addition, the rain gutter network is insufficient to drain the places where the problems are more evident, mainly in four areas, which are the avenues José João Dib, Minas Gerais, Dezessete and Prof. José Vieira de Mendonça. At the José João Dib Avenue, floods are observed due to the deficiency in drainage of the surface runoff, that cannot direct the water into the canalization of the São José stream. In the other avenues, the problem is the concentrated runoff which forms a flow along the slopes that is enough to drag people and vehicles as well as cause damage to the paving of streets and sidewalks. With regard to the population affected by the floods, the majority is made up of low-income people, whose homes are most vulnerable to surface water accumulation / runoff. This scenario demands an effective action from the public administration in an effort to elaborate strategic plans for the management of the rainwater.
CNPq: 134118/2015-4

A presente pesquisa concentra-se no estudo hidrológico utilizando o potencial das geotecnologias na modelagem do escoamento na bacia do rio Bengalas, cujo rio principal de mesmo nome, corta o município de Nova Friburgo, RJ, no sentido Sul-Norte. Esse município, um dos mais importantes da região serrana, sofre frequentemente com inundações e deslizamentos, onde, dados históricos e acontecimentos recentes mostram que a ocupação inadequada de encostas e calhas dos rios são as áreas destacada e negativamente afetadas. A metodologia tem suporte no uso de um SIG, extraindo informações, que por sua vez, serão entrada de dados na fase de modelagem, e reforçando a apresentação dos resultados das simulações através de mapas. Ela está divida basicamente em três etapas: "SIG", "Modelagem" e "Suporte à Tomada de Decisão/Simulação". Esse primeiro estudo permitiu compor um banco de dados geográfico com as características fisiográficas da bacia; a seleção criteriosa de uma modelagem matemática e encadeamento de seus parâmetros com os componentes do ciclo hidrológico; realizar a calibração do modelo de transformação chuva-vazão, Soil Conservation Service (CN); e simular a passagem dos volumes gerados pela precipitação efetiva na calha do rio Bengalas, com o objetivo de identificar e analisar as áreas suscetíveis a inundações na porção central da cidade de Nova Friburgo. Modelagem dessa natureza vem sendo empregada, principalmente, no gerenciamento de recursos hídricos, onde a tomada de decisões embasada nos resultados de simulações computacionais, contribuem para evitar prejuízos materiais e financeiros, e ainda, perdas de vidas humanas em áreas de risco, neste caso, aquelas suscetíveis a inundações. Analisando os resultados encontrados temos que a área suscetível à inundação para uma chuva com tempo de recorrência de 50 anos, o mais crítico estudado, seja de aproximadamente 1,0 km, distribuídos nos seus 8,5km na região central de Nova Friburgo-RJ, sendo está, ora delimitada, prioritariamente edificada.
This research focuses on the hydrological study using the potential of geotechnology into runoff modeling of the Bengalas Basin, whose main river, with same name, crosses the city of Nova Friburgo - RJ, in a south-north orientation. This city, one of the most important in "Região Serrana", suffers often with floods and landslides, which, historical data and recent events show that the inappropriate occupation of hillsides and margins of rivers are the highlighted and negatively affected areas. The methodology has basis in a GIS application, extracting information, which in turn, are input in the modeling phase, and enhancing the presentation of simulation results through maps. It is basically divided into three stages: "SIG", "Modelagem" and "Suporte à Tomada de Decisão/Simulação." This first study allowed to compose a geographic database with the physiographic features of the basin; the careful selection of a chain of mathematical modeling and its parameters with the hydrological cycle components, perform the calibration of the rainfall-runoff transformation model, Soil Conservation Service (CN) and simulate the transition of volumes generated by an effective precipitation in the Bengalas river, in order to identify and analyze the susceptible flooding areas in the central part of Nova Friburgo. A kind of this modeling has been used, mainly, in the water resource management, in which decision-making are based on results of computer simulations, helps to avoid a range of losses, such as material, financial and, especially, humans, that in this case, people who lives in areas susceptible to flooding. Analyzing the results, it was found that an area susceptible to flooding by a rainfall with a recurrence time of 50 years, the most critical studied, results in approximately 1.0 km, distributed in its 8.5km (central part of Nova Friburgo - RJ) which this bounded area has a great part with buildings.

This diploma thesis deals with the basic legal prerequisites to determining the amount of damage done to a real estate (building) in the legal framework of Slovak Republic. Its aim is to determine and quantify the property damage caused by extreme weather. It deals with climate problems as well as its indicators. This is accomplished through two different approaches - the analysis of actual damage done to the property for one, and secondly, the damage dealt to the building during its restoration into previous condition. The thesis aims to establish a methodological procedure for calculating all damages done to the property.

La ville de Toliara qui se trouve à l’exutoire du bassin de Fiherenana (Madagascar) est soumise chaque année aux aléas inondations. Les enjeux sont donc d'une importance majeure dans cette région. Cette étude débute par l’analyse de l’aléa avec les données hydro climatiques existantes. On cherche alors à déterminer les tendances en utilisant des modèles statistiques basés sur les séries temporelles. Une méthode de reconstitution des données manquantes est alors proposée. Ensuite, deux approches sont menées afin d’évaluer la vulnérabilité de la ville de Toliara et des villages alentours : une approche statique, à partir de relevés de terrain et de l’utilisation d’un système d’information géographique (SIG) ; et une autre avec l'utilisation d'un modèle multi-agents (SMA). La première étape est la cartographie d’un indicateur de vulnérabilité qui est l’agencement de plusieurs critères statiques propre à chaque maison comme la hauteur d’eau potentielle ou la typologie architecturale. La deuxième partie mettra en scène des agents afin de simuler un évènement catastrophique (montée des eaux et évacuation en simultanée). On cherche à savoir quelles sont les chances pour que les occupants d’une habitation puissent sortir indemne d’une inondation, en comparant divers paramètres et scénarios afin d’évaluer le degré de vulnérabilité de chaque ménage. Certains scénarios prennent en compte l’effet de certaines prises de décisions (Informations, sensibilisations etc.). Les indicateurs et les simulations permettent alors de mieux appréhender les risques inondations afin d’être une aide à la gestion des crises
Hydrological risks are recurrent on the Fiherenana watershed - Madagascar. The city of Toliara, which is located at the outlet of the river basin, is subject each year to hurricane hazards and floods. The stakes are of major importance in this part of the island. This study begins with the analysis of hazard by collecting all existing hydro-climatic data on the catchment. It then seeks to determine trends, despite the significant lack of data, using statistical models (time series). Then, two approaches are used to assess the vulnerability of the city of Toliara and its surrounding villages. First, a static approach, from surveys of land and the use of GIS are conducted. Then, the second method is based on a multi-agent model. The first step is the mapping of a microscale vulnerability index which is an arrangement of several static criteria. For each House, there are several criteria of vulnerability such as potential water depth or architectural typology. As for the second part, scenes of agents are simulated in order to evaluate the degree of housing vulnerability to flooding. The model aims to estimate the chances of the occupants to escape from a catastrophic flood. For this purpose, we compare various settings and scenarios, some of which are conducted to take into account the effect of various decisions made by the responsible entities (awareness campaign etc.). The simulation consists of two essential parts: the simulation of the rise of water and the simulation of the behaviour of the people facing the occurence of hazard. Indicators and simulations allow to better understand the risks in order to help crisis management. Key Words: Hy

Avec le développement des mesures de pluie à hautes résolutions spatiales et temporelles , l’utilisation de modèles hydrométéorologiques distribués est désormais envisagée pour anticiper les phénomènes de crue soudaine sur les petits bassins versants non jaugés. Toutefois les approches développées jusqu’ici se sont généralement concentrées sur l’évaluation des phénomènes hydrologiques, laissant de côté la question de leurs impacts, qui dépendent fortement de la configuration du terrain et des enjeux qui y sont présents. Ce travail de thèse a permis de développer et tester une méthode d’évaluation directe de ces impacts à partir des sorties d’un modèle pluie-débit sur un territoire limité. La démarche mise en oeuvre repose sur un travail préalable d’analyse du territoire permettant d’une part d’évaluer les emprises submergées dans une large gamme de débits par une approche hydraulique simplifiée, puis de construire des relations univoques débit-enjeux pour chaque bief de cours d’eau. Ces relations permettent de produire des cartes d‘enjeux potentiellement touchés ,pouvant être actualisées régulièrement en cours d’événement. Deux études des cas ont permis de réaliser une première évaluation des performances de cette approche, du point de vue de la qualité d’estimation des emprises inondées, et du point de vue des impacts estimés à l’échelle d’un événement grâce à la comparaison avec des données d’assurance. Finalement, ces travaux ont permis de confirmer le potentiel de la méthode, dont les performances semblent en adéquation avec l’objectif visé : obtenir rapidement une première hiérarchisation des impacts occasionnés par les crues soudaines à l’échelle d’un grand territoire
With the development of rainfall measurements at highspatial and temporal resolutions, the use of distributed hydrometeorological models is now considered to forecast flash floods on small and ungauged catchment areas. Current flashflood monitoring systems generally enable a real-time assessment of the potential flash-flood magnitudes. However they do not assess the potential impacts of flash-flood, which highly depends on the catchment areas configuration and on the importance of potentially affected assets. The purpose of this PhD research work was to develop and test a method which can be used to directly estimate the impacts of flash-floods, based on the outputs of a distributed rainfall-run off model. The approach is based on a prior analysis of the study area in order to assess the potential impact of different discharge levels on the flooded areas and to identify from geography database the associated buildings at risk. The aim is to build impact models on specific river reaches, using discharge versus impact graphs. The use of these impact models combined with a rainfall-run off model, has enabled us to compute maps of potential impacts, based on real time assessment of flood events updated every 15 minutes. This method was evaluated on two case studies looking at the accuracy and relevance of estimated impacts for each event – and comparing the outcomes to insurance losses data. This research work has helped to confirm the efficiency of this new combined method, which may become a useful tool to forecast large-scale effects of local impacts of flash-floods

Le changement climatique dû à l'augmentation des émissions de gaz à effet de serre est considéré comme l'un des principaux défis pour les êtres humains dans 21ème siècle. Il conduira à des changements dans les précipitations, l'humidité atmosphérique, augmentation de l'évaporation et probablement augmenter la fréquence des événements extrêmes. Les conséquences de ces phénomènes auront une influence sur de nombreux aspects de la société humaine. Donc, il y a une nécessité d'avoir une estimation robuste et précise de la variation des facteurs naturels dus au changement climatique, au moins dans les événements de cycle et d'inondation hydrologiques pour fournir une base solide pour atténuer les impacts du changement climatique et s'adapter à ces défis. Le but de cette étude est de présenter une méthodologie pour évaluer les impacts de différents scénarios de changement climatique sur une zone inondable du bassin de la rivière côtière dans la région centrale du Viet Nam - bassin versant de Vu Gia Thu Bon. Les simulations hydrologiques sont basées sur un modèle hydrologique déterministe validé qui intègre la géologie, les sols, la topographie, les systèmes fluviaux et les variables climatiques. Le climat de la journée présente, sur la période de 1991-2010 a été raisonnablement simulée par le modèle hydrologique. Climat futur (2091-2100) information a été obtenue à partir d'une réduction d'échelle dynamique des modèles climatiques mondiaux. L'étude analyse également les changements dans la dynamique des inondations de la région de l'étude, le changement hydrologique et les incertitudes du changement climatique simulation
Climate change due to the increase of greenhouse gas emissions is considered to be one of the major challenges to mankind in the 21st century. It will lead to changes in precipitation, atmospheric moisture, increase in evaporation and probably a higher frequency of extreme events. The consequences of these phenomena will have an influence on many aspects of human society. Particularly at river deltas, coastal regions and developing countries, the impacts of climate change to socio-economic development become more serious. So there is a need for a robust and accurate estimation of the variation of natural factors due to climate change, at least in the hydrological cycle and flooding events to provide a strong basis for mitigating the impacts of climate change and to adapt to these challenges. The aim of this study is to present a methodology to assess the impacts of different climate change scenarios on a flood prone area of a coastal river basin in the central region of Viet Nam – Vu Gia Thu Bon catchment. The hydrological simulations are based on a validated deterministic hydrological model which integrates geology, soil, topography, river systems and climate variables. The present day climate, over the period of 1991-2010 was reasonably simulated by the hydrological model. Future climate (2091-2100) information was obtained from a dynamical downscaling of the global climate models. The study also analyzes the changes in the flood dynamics of the study region, the hydrological shift and the uncertainties of climate change simulation

En Bretagne, les « marées vertes » sont récurrentes depuis le début des années 70 et occupent une place importante dans le débat public en terme sanitaire, politique et économique. Lors de cette thèse, une large revue bibliographique a été réalisée sur l’export d’azote et une méthodologie innovante a été mise en place afin d’étudier la variabilité spatio-temporelle de l’export de nutriments dans 2 bassins versants à algues vertes à une échelle intra-annuelle et pendant des évènements extrêmes (évènements pluvieux, période touristique de basses eaux,…). Les bassins versants sélectionnés pour les expérimentations de terrain sont l’Ic et le Frémur (Côtes d’Armor). 3 types d’expérimentations ont été réalisées sur ces bassins versants : 1) Des campagnes de prélèvements ponctuels par temps sec et par temps de pluie (32 stations, 27 campagnes) ; 2) des prélèvements automatiques en crue (3 stations, 8 crues) ; et 3) la mesure haute fréquence (2 stations, en continu). Les paramètres hydrologiques et physico-chimiques classiques, les matières en suspension, les spectres UV et toutes les formes de macronutriments (carbone, azote, phosphore) ont été analysés lors de ces expérimentations. Les résultats obtenus confirment pour une part un certain nombre de résultats de la littérature. D’autre part, il met en lumière la relation carbone/nitrates, jusqu’à présent peu étudiée à différentes échelles spatio-temporelles et pendant des évènements pluvieux, qui semble pourtant primordiale dans la compréhension des phénomènes d’export de nitrates à l’échelle de l’année. Enfin, l’analyse de toutes les formes de nutriments révèle l’importance des formes particulaires issues de l’érosion des sols. Ces résultats soulèvent de nombreuses questions de recherche qui mériteraient un approfondissement afin d’améliorer la connaissance des transferts de nutriments dans les bassins versants et prioriser les actions de remédiations. Les perspectives de ce travail sont à la fois scientifiques et pratiques. Au niveau scientifique, les efforts de recherche sur la relation carbone/nitrate et l’identification de la fraction de carbone organique assimilable par les organismes dénitrifiants doivent être poursuivis. De même, l’amélioration des connaissances sur l’export de nutriments en crue passe par l’identification précise des sources de nutriments particulaires pendant les crues printanières. Au niveau pratique, il doit contribuer à l’amélioration des pratiques agricoles, à la reconnaissance de l’intérêt des zones humides naturelles et à l’amélioration des types de traitement utilisés par les stations d’épuration. Les résultats obtenus lors de cette étude devraient notamment être mis en relation avec la dynamique des nutriments observée dans l’estran pendant la période de développement des algues vertes. Enfin, un effort d’amélioration de l’accès à certains type de données sur les bassins versants est nécessaire afin d’améliorer la compréhension des transferts de nutriments
In Brittany (Western France), "green tides" are recurrent since the early 70s and have an important place in public debate in health, political and economic terms. In this thesis, a wide bibliographic review was performed on the export of nitrogen, and an innovative methodology has been set up to study the spatial and temporal variability of nutrient export in two coastal watersheds on an intra-annual basis and during extreme events (rainfall events, tourist periods of low water, ...). Watersheds selected for the field experiments are Ic and Frémur (Côtes d'Armor). 3 types of experiments were performed on these watersheds: 1) Campaigns of grab samples by dry and wet weather (32 stations, 27 campaigns); 2) automatic sampling during floods (3 stations, 8 floods); and 3) high frequency measurement (2 stations, continuous). Conventional hydrological and physicochemical parameters, suspended solids, UV spectra and all forms of macronutrients (carbon, nitrogen, phosphorus) were analyzed during these experiments. The results confirm in part a number of results of the literature. Furthermore, it highlights the relationship carbon / nitrates far little studied at different spatial and temporal scales and during rainfall events, which however seems to be crucial in understanding of nitrate export. Finally, the analysis of all forms of nutrients reveals the importance of particulate forms from soil erosion. These results raise many research questions that merit further development in order to improve knowledge on nutrient transfers in watersheds and prioritize remediation actions. The prospects of this work are both scientific and practical. At the scientific level, research efforts on the relationship carbon / nitrate and identification of the assimilable fraction of organic carbon by denitrifying organisms must be continued. Similarly, the knowledge on nutrient export must be improved through the precise identification of particulate nutrient sources during the spring floods. On a practical level, it should contribute to the improvement of agricultural practices, the recognition of the interest of natural wetlands and improvement of the types of treatment used by treatment plants. The results obtained in this study should in particular be linked to the dynamics of nutrients in the foreshore observed during the development of green algae. Finally, an effort to improve access to certain types of data on watersheds is needed to improve understanding of nutrient transfers

The Flood Directive 60/2007/EC requires the European countries to verify the effectiveness of existing flood defence infrastructure to mitigate flood risks. The current practice establishes that the river flood control structures must respect a basic requirement, usually consisting of a certain safe freeboard under a design peak flow rate corresponding to a certain probability of exceedance. This requirement has some critical issues. It is based on a univariate frequency analysis of only flood peak, and therefore it assumes a perfect correspondence between the probability of occurrence of the hydrological variable and the failure of the flood-control structure. The thesis aims to define a methodology to overcome these issues implementing a bivariate hydrological risk analysis for river-related flood risk. The methodology is mainly focused on the overtopping failure for river levees. River levees are the most common river flood-control structure. They are raised, predominantly earth, structures (also called dykes, digues or embankments). The overtopping failure of a river levee caused several flood disasters such as Elbe flood (2002), New Orleans flood (2005), Emilia Romagna Flood (2017) or Arkansan flood (2019). The proposed procedure is carried out through two steps: (i) the evaluation of hydrological failure related to the overtopping risk for a levee; (ii) the estimation of the probability of occurrence of the hydrological failure introducing the concept of the Bivariate Failure Return Period. The hydrological failure is determined considering the mutual interaction between a bivariate hydrological load of peak discharge (Q) and the volume of the hydrograph (V), the river conveyance, and the levee resistance with respect to overtopping. The bivariate hydrological load considers an approximation of the real bivariate distribution of Q and V, functional to determine the hydrological failure. The shape of the hydrographs is classified concerning the overtopping introducing the Overtopping Hydrograph Shape Index (OHSI). The hydrological failure condition is represented by a curve in Q-V space containing all the hydrographs causing the initiation of the damage. This curve demonstrates that not only the peak flow but also the volume of the hydrograph are essential variables to characterise the overtopping failure. The risk of overtopping failure is expressed by the probability of occurrence of the hydrological failure within a new interpretation of the return period. Because of the hydrological failure curve is a function in Q-V space, the return period is estimated in the bivariate framework. Several definitions of the bivariate return period are available, each of which gives a different interpretation of it. This critical issue is overcome introducing the Bivariate Failure Return Period. The Bivariate Failure Return Period assesses the probability of the failure curve of the hydraulic structure generating possible scenarios through a Monte Carlo simulation. Two case studies are presented to demonstrate the applicability of the methodology and the advantages of using it respect to the current practice. In the thesis, the methodology is also applied to the problem of flood damage estimation demonstrating the flexibility and the validity of the proposed procedure. In this case, the hydrological failure consists in equal-euro curve in Q-V space, which includes all the hydrographs causing the same euro flood damages in a site. The procedure proposed needs Q-V data at the target site where the risk is to be assessed but most of the sites are ungauged. This issue is overcome by testing the bivariate regional frequency analysis. It is applied to the case study of the entire Tuscany Region (Italy). By the bivariate regional analysis, the Q-V series can be estimated at ungauged sites, and the uncertainty is reduced at gauged sites.

The purpose of this study is to determine if Low Impact Development (LID) can effectively mitigate flooding under projected climate scenarios. LID relies on runoff management measures that seek to control rainwater volume at the source by reducing imperviousness and retaining, infiltrating and reusing rainwater. An event-driven hydrologic/hydraulic model was developed to simulate how climate change, land use and LID scenarios may affect runoff response in the Bowker Creek watershed, a 10km2 urbanized catchment located in the area of greater Victoria, British Columbia, Canada. The first part of the study examined flood impacts for the 2050s (2040-2069) following the A2 emissions scenario. For the 24-hour, 25-year local design storm, results show that projected changes in rainfall intensity may increase flood extents by 21% to 50%. When combined with continued urbanization flood extents may increase by 50% to 72%. The second part of the study identified potential locations for three LID treatments (green roofs, rain gardens and top soil amendments) and simulated their effect on peak in-stream flow rates and flood volumes. Results indicate that full implementation of modeled LID treatments can alleviate the additional flooding that is associated with the median climate change projection for the 5-year, 10-year and 25-year rainfall events. For the projected 100-year event, the volume of overland flood flows is expected to increase by 1%. This compares favourably to the estimated 29% increase without LID. In term of individual performance, rain gardens had the greatest hydrologic effect during more frequent rainfall events; green roofs had minimal effect on runoff for all modelled events; and top soil amendments had the greatest effect during the heaviest rainfall events. The cumulative performance of LID practices depends on several variables including design specifications, level of implementation, location and site conditions. Antecedent soil moisture has a considerable influence on LID performance. The dynamic nature of soil moisture means that at times LID could meet the mitigation target and at other times it may only partially satisfy it. Future research should run continuous simulations using an appropriately long rainfall record to establish the probabilities of meeting performance requirements. In general, simulations suggest that if future heavy rainfall events follow the median climate change projection, then LID can be used to maintain or reduce flood hazard for rainfall events up to the 25-year return period. This study demonstrates that in a smaller urban watershed, LID can play an important role in reducing the flood impacts associated with climate change.
Graduate

在中国，绝大多数煤矿事故主要是由煤矿瓦斯和煤矿突水造成。统计数据显示，目前煤矿水灾引起的直接经济损失已经排在了所有煤矿灾害之前，煤矿水灾已经日益成为最危险的一种煤矿灾害。现阶段在煤矿完全方面主要目标就是尽量减少发生煤矿瓦斯爆炸和水灾的隐患。因此，对于预防和处理煤矿水灾来说，设计一种快速且准确的煤矿水灾的风险评价方法是非常急需的。传统的风险评价方法需要进行大量的广泛的地质调查来寻找地表裂隙等引起煤矿水灾的分险源。这些裂隙主要是因为地面形变造成，这种地面形变在煤矿区一般是由于地下采矿活动或者煤火造成塌陷引起的，或者两者共同作用引起的。一般情况下，煤矿区地处偏远，高海拔，不宜居住的地方，尤其是有煤火的地方，更加不易进行全面地调查。因此，我们认为使用卫星遥感数据对煤矿区大范围周期性的监测，并及时提取与煤矿水灾相关的信息进行风险分析的方法相对与传统方式来说更为便捷，更为及时。经过对乌达煤矿区的野外调查，我们确定了一些会引起乌达煤矿水灾的致灾因素，例如煤火，剥挖坑，渣堆等特有的因素。
本论文提出一个利用遥感，地理信息技术以及水文模型相结合的煤矿区水灾分险评估模型。在这个模型中，首先根据地质和水文数据确定了14个引起该地区水灾灾害的主要影响因素。通过野外调查，专家组一致认为降雨，特别是大暴雨，剥挖坑和地表裂隙是乌达煤矿区最重要的几个因素。分析野外调查成果，可以发现煤火和沉降与试验区地表裂隙有着正相关性。因此在这个模型中，引入煤火和沉降信息来代替实际地表裂隙情况。煤火和沉降信息可以通过多种遥感数据获得。在获得所有致灾因素的信息后，结合专家组的意见，通过层次分析法（AHP）来建立致灾因素的层次并通过成对比较矩阵计算各个致灾因素的权重。最后，通过模型计算得到最终的煤矿区风险评估图。本文得到的结果与神华（北京）遥感勘查有限责任公司实地调查后形成的风险评估图进行对比，结果显示风险分布基本相同。本文也探讨了可能造成两者差异的原因。最后，针对某一高风险区进行实地的钻孔和地震探测验证，结果显示该地区的致灾因素特征明显，具备高风险特性。
验证结果表明，本文提出的方法是具有可操作性的且准确高效，具有一定的煤矿水灾预测作用。我们希望该方法通过进一步的改进，能够应用到实际的煤矿水灾风险评价预测中去。
In China, coal mine accidents were mainly caused by gas and water inrush. Recently, the direct economic loss caused by coal mine flood has been ranked the first among all kinds of coal mine disasters. Reducing water inrush accidents become the main direction and aiming of coal mine security control. From the statistics of coal mine disasters, we learned that the coal mine flood disasters have become the most dangerous mine disaster. There is, therefore, an urgent need to design and provide a coal mine flood risk assessment timely and accurately for mine companies to prevent and deal with the coal mine flood. Traditional approaches investigate the geological condition and find out the exactly numbers and width of fissures caused by coal mining or coal fires burnt. However, the shortcomings of these methods are time consuming, difficult to repeat, and costly to apply over large areas, especially, for many coal mine area located in isolated region, high up in the mountains, in dense forests, and other inhospitable terrains. Hence the use of GIS technology and remote sensing data, particularly satellite remote sensing with a capability of repeated observation of the earth surface, was considered as a very effective approach to detect, analyze and monitor information of mine flood in coal mine area over a large areas.
In this research a risk assessment model was proposed to assess the mine flood risk in Wuda coal mine area using RS, GIS techniques and basic hydrological model. First of all, we analyzed the major factors causing coal mine flood in Wuda coal field, based on the geological and hydrological data. According to the investigated material and the experiences from geologists and coal mining experts, four main criteria including water sources, surface condition, water conductors and water containers as well as fourteen factors were selected to participate the assessment, among which, rainfall, stripping digging pits and fissures were considered as the three main factors to cause mine flood in Wuda coal mine area. The rainfall and sinks information were easily to derive. However, the fissures information was difficult to obtain. Based on the analysis of investigation, the positive correlation between fissures and coal fires or subsidence was obtained. Therefore, the coal fire factor and ground subsidence factor were imported to indicate the fissures information. Then, a method for deriving these impact factors was proposed for coal mine flood risk assessment model. After obtaining the all factors related information, the weights of these factors were calculated by pair-wise comparison method, which depend on the specialists’ opinions. A risk assessment analysis approach based on AHP was created for combining these factors and calculating the results.
Finally, based on the result from risk assessment model, a risk assessment indication map was generated using GIS software. By comparing our assessment result with the Wuda coal flood risk map from Shenhua Group, we noticed that the distribution and levels of coal mine flood risk are similar. Some other auxiliary techniques, for instance, the geological drilling and geological radar detection, were used to validate the result of our study. These techniques also proved the final result is reasonable and acceptable. After the investigation and evaluation, some conclusions and suggestions, were proposed for coal mine companies to avoid or reduce the risk from coal mine flood.
The results indicate that the methodology is effective and practical; thus, it has the potential to forecast the ood risk for coal mine ood risk management. Therefore, it can be used as a final risk assessment model for mine flooding in coal fire area. In the future, we will conduct such risk analysis to mitigate the impact from coal mine flood disasters.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Wang, Shengxiao.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.
Includes bibliographical references (leaves 162-174).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts also in Chinese.
Abstract --- p.i
TABLE OF CONTENT --- p.vi
LIST OF TABLES --- p.ix
LIST OF FIGURES --- p.x
Acknowledgements --- p.xiii
Chapter 1. --- Introduction --- p.1
Chapter 1.1 --- Coal mine disasters in China --- p.1
Chapter 1.2 --- Coal mine flood in China --- p.4
Chapter 1.3 --- Background of Wuda coal mine area --- p.6
Chapter 1.4 --- Research objectives --- p.9
Chapter 1.5 --- Structure of the thesis --- p.11
Chapter 2. --- Background --- p.12
Chapter 2.1 --- Coal mine flood --- p.12
Chapter 2.1.1 --- Classification of coal mine flood --- p.12
Chapter 2.1.2 --- Current rescuing situation of coal mine flood --- p.13
Chapter 2.2 --- The Longwall coal mining --- p.14
Chapter 2.3 --- Coal mining Subsidence --- p.19
Chapter 2.3.1 --- Subsidence Mechanisms --- p.19
Chapter 2.3.2 --- Subsidence and Fissures --- p.20
Chapter 2.3.3 --- Previous investigations --- p.22
Chapter 2.4 --- Coal fire and fissures --- p.24
Chapter 2.4.1 --- Definition and Classification --- p.24
Chapter 2.4.2 --- Combustionmechanism --- p.27
Chapter 2.4.3 --- Production of coal fire - Minerals and Burnt rock --- p.29
Chapter 2.4.4 --- Ground temperature related to the coal fire --- p.31
Chapter 2.4.5 --- Fissures caused by Coal fire --- p.32
Chapter 2.4.6 --- Detecting Coal Fires Using Remote Sensing --- p.34
Chapter 2.5 --- Assessment methods review --- p.37
Chapter 3. --- Description of the study areas & data sets --- p.39
Chapter 3.1 --- Study area --- p.39
Chapter 3.2 --- Geography --- p.40
Chapter 3.2.1 --- Geographical position --- p.40
Chapter 3.2.2 --- Climate --- p.41
Chapter 3.3 --- Geology --- p.42
Chapter 3.3.1 --- Geology structure --- p.42
Chapter 3.3.2 --- The stratigraphy of coal --- p.43
Chapter 3.4 --- Hydrology --- p.46
Chapter 3.4.1 --- Hydrogeological characteristics --- p.46
Chapter 3.4.2 --- Surface hydrological characteristics --- p.46
Chapter 3.5 --- Three major coal mine overviews of the assessment area --- p.48
Chapter 3.5.1 --- Suhaitu coal mine --- p.48
Chapter 3.5.2 --- Huangbaici coal --- p.51
Chapter 3.5.3 --- Wuhushan coal --- p.53
Chapter 3.6 --- Data available --- p.55
Chapter 3.6.1 --- Data available for this research --- p.55
Chapter 3.6.2 --- Collection materials and data for reference --- p.55
Chapter 4. --- Investigation and Analysis of Risk Factors --- p.57
Chapter 4.1 --- Currentstatus of Wuda Coalfield --- p.57
Chapter 4.2 --- Water source --- p.58
Chapter 4.2.1 --- Rain fall --- p.58
Chapter 4.3 --- Surface Condition --- p.59
Chapter 4.3.1 --- Flood ditches and surfacerunoff --- p.59
Chapter 4.3.2 --- Stripping digging pits --- p.61
Chapter 4.3.3 --- Slag heap --- p.67
Chapter 4.3.4 --- Water yield of three main coal mine --- p.71
Chapter 4.4 --- Water conductors investigation --- p.72
Chapter 4.4.1 --- Faults --- p.73
Chapter 4.4.2 --- Fissures investigation --- p.75
Chapter 4.4.3 --- Investigation and analysis of fissures --- p.81
Chapter 4.4.4 --- Abandoned tunnel and (illegal) private coal mine --- p.83
Chapter 4.4.5 --- Subsurface Detection- Geological radar --- p.84
Chapter 5. --- Methodology and Information acquisition --- p.87
Chapter 5.1 --- Evaluation Index System --- p.87
Chapter 5.1.1 --- Methodologies in Establishing the Evaluation Index System --- p.87
Chapter 5.1.2 --- Principles for Establishing Evaluation Index System --- p.88
Chapter 5.1.3 --- Method in Establishing Evaluation Index System --- p.89
Chapter 5.1.4 --- Flow chart --- p.90
Chapter 5.2 --- Storm Rainfall Design --- p.91
Chapter 5.3 --- Drainage network and fill sinks extraction --- p.94
Chapter 5.3.1 --- Surfacerunoff model --- p.94
Chapter 5.3.2 --- Fill Sinks (peaks) --- p.96
Chapter 5.3.3 --- Flow Direction --- p.97
Chapter 5.3.4 --- Flow accumulation --- p.98
Chapter 5.4 --- Traditional methods of derived Fissures area and depth --- p.101
Chapter 5.5 --- The method of obtaining coal fire information --- p.103
Chapter 5.5.1 --- Remote sensing data --- p.105
Chapter 5.5.2 --- Land use classification --- p.105
Chapter 5.5.3 --- Temperatureretrieval based on TM/ETM+ --- p.107
Chapter 5.5.4 --- Results of coal fire retrieval --- p.110
Chapter 5.6 --- The method of obtaining coal mine subsidence area --- p.113
Chapter 5.7 --- Illegal private coal mine detecting --- p.115
Chapter 5.8 --- The Analytic Hierarchy Process (AHP) --- p.118
Chapter 5.8.1 --- Introduction of AHP --- p.118
Chapter 5.8.2 --- The procedure of AHP --- p.120
Chapter 6. --- Evaluation and validation --- p.122
Chapter 6.1 --- Workflow --- p.122
Chapter 6.2 --- Develop a decision hierarchy structure --- p.122
Chapter 6.2.1 --- Choosing evaluation indicator --- p.123
Chapter 6.3 --- Weights distribution --- p.124
Chapter 6.3.1 --- Establishment of comparison matrix --- p.125
Chapter 6.3.2 --- Weight Calculation and Consistency Check --- p.127
Chapter 6.3.3 --- Global weight calculation and global consistency check --- p.131
Chapter 6.4 --- Data Preparation and Classification --- p.133
Chapter 6.4.1 --- Rainfall classification --- p.134
Chapter 6.4.2 --- Classification of surface condition --- p.135
Chapter 6.4.3 --- Classification of conductor --- p.138
Chapter 6.5 --- Result of Factor weight overlay --- p.140
Chapter 6.4.1. --- Results --- p.140
Chapter 6.4.2 --- Compare with Risk Map from Shenhua Group --- p.143
Chapter 6.4.3 --- Fieldwork Validation --- p.145
Chapter 7. --- Conclusions and suggestions --- p.150
Chapter 7.1 --- Results and conclusions --- p.150
Chapter 7.2 --- Eliminate potentialdangerous source --- p.152
Chapter 7.3 --- Flood prevention measures recommended --- p.153
Chapter 7.3.1 --- Mainly measures for flood prevention --- p.154
Chapter 7.3.2 --- General prevention and control of surface water --- p.155
Chapter 7.3.3 --- Establish mechanisms and systems to prevent coal mine flood --- p.156
Chapter 7.3.4 --- Strengthen the basic work to prevent coal mine accidents --- p.158
Chapter 7.3.5 --- Investigation and remediation work to prevent coal mine accidents --- p.159
Chapter 7.4 --- Future work --- p.160
References --- p.162

The aim of this thesis is to devise a method for objective classification of floodplain based on spatially accurate data from UAV that allows identification of the fundamental features of floodplain and channel arising from or affecting by the floods activities. Background research is focused on floodplain forming processes; types of flood on our territory and its geomorphological effects, as well as a brief description unmanned aerial vehicle and their applicability in natural science and the flood. Proposed method was carried out on the test section - a part of meander of Javoří stream in Šumava Mountain - then was tested on complex meander belt of the same stream. Proposed method is based on applicability of standard objective classification. Elementary products from photogrammetric analysis - 2D orthophoto and 3D digital surface model - are used as basic input data. Another aim of theses is to discuss applicability of this method for assessment of fluvial form, its limits and potential development. The results indicated that success of classification will increase significantly the involvement of 3D data to classification, which from standard data from the UAV, despite the lack of absence multispectral bands doing a very valuable source of information for mapping and analysis, for example, the...

The purpose of this study is to analyze the combined effects of storm surge and inland rainfall on the floodplain of a coastal bayou in the Houston area using dynamic hydraulic modeling. HEC-RAS, a one dimensional flow model, was run for both the steady and unsteady states in order to analyze the linkage between inland flooding and storm surge. First, the steady model was run to give a basic understanding of the watershed. The unsteady HEC-RAS model was then evaluated in the unsteady state which allowed both rainfall and storm surge from Hurricane Ike to be introduced dynamically. This allowed for a more accurate representation of the timing of flooding characteristics of Horsepen Bayou, and the modeled hydrographs generated an excellent match against measured data in Horsepen Bayou. Using this model it was discovered that the timing of both rainfall and storm surge play a significant role in the magnitude of flooding.

Floods and droughts are frequent in Central America and cause large social, economic and environmental impacts. A crucial step in disaster risk reduction is to have a good understanding of the causing mechanisms of extreme events and their spatio-temporal characteristics. For this, a key aspect is access to a dense network of long and good-quality hydro-meteorological data. Unfortunately, such ideal data are sparse or non-existent in Central America. In addition, the existing methods for hydro-climatic studies need to be revised and/or improved to find the most suitable for the region’s climate, geography and hydro-climatic data situation. This work has the ultimate goal to support the reduction of risks associated with hydro-climatic-induced disasters in Central America. This was sought by developing ways to reduce data-related uncertainties and by improving the available methods to study and understand hydro-climatic variability processes. In terms of data-uncertainty reduction, this thesis includes the development of a high resolution air temperature dataset and a methodology to reduce uncertainties in a hydrological model at ungauged basins. The dataset was able to capture the spatial patterns with a detail not available with existing datasets. The methodology significantly reduced uncertainties in an assumed-to-be ungauged catchment. In terms of methodological improvements, this thesis includes an assessment of the most suitable combination of (available) meteorological datasets and drought indices to characterise droughts in Central America. In addition, a methodology was developed to analyse drought propagation in a tropical catchment, in an automated, objective way. Results from the assessment and the drought propagation analysis contributed with improving the understanding of drought patterns and generating processes in the region. Finally, a methodology was proposed for assessing changes in both hydrological extremes in a consistent way. This contrasts with most commonly used frameworks that study each extreme individually. The method provides important characteristics (frequency, duration and magnitude), information that can be useful for decisions within risk reduction and water management. The results presented in this thesis are a contribution, in terms of hydro-climatic data and assessment methods, for supporting risk reduction of disasters related with hydro-climatic extremes in Central America.
Översvämningar och torka inträffar ofta i Mellanamerika och orsakar stora skador på samhälle, ekonomi och miljö. En kritisk del av riskreduceringen är förståelsen av mekanismerna bakom extremhändelserna, och deras rumsliga och tidskarakteristik. En nyckelfaktor är tillgång till långa tidsserier av rumsligt täckande hydrometeorologiska data av bra kvalitet. I Mellanamerika är sådana ideala data tyvärr sällsynta eller saknas helt. Dessutom behöver befintliga metoder för hydro-klimatisk analys revideras och/eller förbättras för att identifiera de mest lämpade metoderna för regionens klimat, geografi och situationen vad gäller hydrologiska och meteorologiska data. Det övergripande syftet med denna avhandling har varit att stödja arbetet med riskreducering i Mellanamerika vid hydrologiska extremhändelser som sätts igång av extrema väderhändelser. För att bidra till detta utvecklades metoder för att minska datarelaterade osäkerheter och för att förbättra tillgängliga metoder för att studera och förstå de processer som ligger bakom variabiliteten i hydrologi och klimat. Dataosäkerheten minskades genom utveckling av ett nytt dataset för lufttemperatur med hög rumslig upplösning och en metodik för att begränsa osäkerheten i modellberäknad vattenföring i ett område där det saknas observationer. Det nya datasetet kunde fånga rumsliga mönster på en detaljnivå som hittills inte varit möjlig. Metodiken möjliggjorde en klar minskning i osäkerheten hos vattenföringen i ett avrinningsområde som behandlades som om det saknade data. Avhandlingen innehåller också en metodik för att fastlägga den mest lämpade kombinationen av tillgängliga klimatdataset och torkindex för att karakterisera torka i Mellanamerika. Därutöver utvecklades en metod för att studera torkans fortplantning i ett tropiskt avrinningsområde på ett objektivt och automatiserat sätt. Slutligen föreslås en metod för att hantera förändringar av både översvämning och torka på ett konsistent sätt  som förenklar användningen av resultaten  för en beslutsfattare. Dessa metoder bedömdes användbara för att förbättra karakteriseringen och förståelsen av extrema hydrologiska händelser i Mellanamerika. Resultaten i denna avhandling ger bidrag till förståelsen av hydrologiska och klimatextremer genom förbättrade data och analysmetoder som i förlängningen kommer att stödja riskreduceringsarbetet i Mellanamerika.
Las sequías e inundaciones son frecuentes en Centroamérica y causan grandes problemas sociales, económicos y ambientales. Un aspecto crucial en la reducción del riesgo consiste en entender los mecanismos que causan dichos eventos, y sus características espacio-temporales. Para lograr esto es necesario tener acceso a una red de datos hidro-meterológicos densa, con series largas, y de buena calidad. Desafortunadamente, este no es el caso en Centroamérica. Además, los métodos para hacer estudios hidro-climáticos requieren ser evaluados y/o mejorados para asegurar su aplicabilidad en la región (su clima, su geografía y los datos disponibles). Este trabajo tiene como meta apoyar la reducción del riesgo de desastres asociados a eventos hidro-meteorológicos extremos en Centroamérica. Esto se consigue a partir de la reducción de incertidumbres asociadas a los datos, y de la mejora de métodos para el estudio de la variabilidad hidro-climática. Para reducir la incertidumbre de los datos, este trabajo incluye el desarrollo de una base de datos de temperatura de alta resolución y el desarrollo de una metodología para reducir las incertidumbres en datos simulados de caudal. Con la nueva base de datos se logra reconocer patrones espaciales a un nivel de detalle no antes captado por otras bases de datos. Por otro lado, la metodología redujo significativamente las incertidumbres de los datos simulados de caudal. En cuanto a métodos, esta tesis incluye una evaluación para encontrar la mejor combinación de índices de sequía y base de datos para la caracterización de sequías en la región. Además, se desarrolló una metodología para analizar la propagación de la sequía en una cuenca tropical, de una manera objetiva y automatizada. Los resultados de estos dos pasos ayudaron a mejorar la comprensión de los patrones y los mecanismos de generación de las sequías. Finalmente, se incluyó un método para evaluar los cambios en los patrones de sequías e inundaciones de una manera consistente, y no de manera individual como usualmente se ha hecho. Así fue posible obtener la frecuencia, duración y magnitud en ambos extremos hidrológicos. Esta información podría constituir una herramienta  útil para el manejo del riesgo y del recurso hídrico.

Floods are one of the most damaging types of weather-related disasters which pose serious hazards to human property and life in many parts of the world. Extreme weather events like floods will become more frequent and severe due to climate change. In addition, major flooding can result from heavy rainfall during an extreme event in one or more sub-catchments in a large basin. Global climate change can further increase the intensity of extreme events and cause rises in sea level. Change of temperature, potential evaporation and rainfall are also the results of global climate change.