Dissertations / Theses on the topic 'Hydrological hazard'

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This research presents the numerical simulation to reproduce the transport and deposition processes of the sludge flow on March 15, 2017, strongly impacting the town of Pampapacta in Punta Hermosa-Peru.The debris flow initiation process in the basin was represented by hydrographs obtained from the estimated volumes of stormwater runoff and solid materials. The sludge flow was modeled in Flo2D to calculate hazard maps with the discharge event and others with different return periods.The numerical simulation results show acceptable results in relation to what happened. The model used to assess the hazard due to debris flow can predict and delineate, with acceptable precision, potentially hazardous areas for a landslide. The application of the proposed methodology to assess the hazard of disasters due to debris flows in basins and streams is useful to understand the extent of the impact of the mud flow during extreme weather events, as well as to develop emergency plans and formulate disaster policies.

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

O aumento da ocorrência de desastres hidrológicos relacionados a inundações bruscas tem recebido maior atenção dos diversos órgãos em suas diferentes escalas, com o objetivo de reduzir ao máximo suas causas. Justamente por isso, as medidas não estruturais são medidas de extrema importância na prevenção de tais desastres. Uma dessas medidas deve ser o mapeamento de áreas de perigo de inundações. Portanto, o objetivo do presente trabalho foi propor e avaliar o perigo de inundações bruscas por meio de modelagem hidrogeomorfológica na bacia do arroio Forromeco-RS. Para isso, foi utilizado o modelo CAESAR-LISFLOOD, para representar os processos hidrológicos em escala de bacia e canal. Em escala de bacia foram gerados hidrogramas a partir da criação de chuvas de projeto para diferentes tempos de retorno (TR), considerando como base o maior evento registrado nessa bacia associado a um TR de 22 anos. Esses hidrogramas foram utilizados nas simulações em escala de canal para gerar os diferentes mapas de inundação em termos de profundidade e velocidade do fluxo da água. Para analisar as áreas de perigo de inundação, foram determinados os índices de perigo (IP) associados aos diferentes TR, a partir da profundidade e a velocidade d’água. Através das análises do resultado de IP foi criado o mapeamento final de perigo associado a três tempos de retorno (5, 22, e 100 anos). Além disso, estabeleceu-se três zonas para identificar os níveis de perigo, considerando o cenário mais crítico dos três mapas. Os resultados mostraram que a maior área inundada se encontra em alto perigo, ocupando 77% da área total, o que significa que as pessoas que moram nessa região estão em perigo tanto em casa, como fora delas. Ao mesmo tempo as construções estão em alta possiblidade de serem danificadas.
The increase in the occurrence of hydrological disasters related to flash floods has begun to be more important for several organs at different scales in order to reduce their magnitude and frequency as much as possible. Precisely because of it, non-structural measures are extremely important measures for preventing such disasters. One of these important measures might be the mapping of flood hazard areas. Therefore, the objective of the present work was to propose and evaluate the flash flood hazard by means of hydrogeomorphic modeling of the Forromeco river basin, Rio Grande do Sul state. Thus, the CAESAR-LISFLOOD model was used to represent the hydrological processes at basin and channel scale. At basin scale hydrographs were generated from the creation of hyetographs for different return periods (RP), considering the largest event recorded in this basin. These hydrographs were used in the channel scale simulations to generate the different flood maps in terms of depth and velocity of water flow. In order to analyze the flood hazard areas, the hazard indexes (HI) associated with the different RPs were determined from the depth and water velocity. Through the IP analysis, the final hazard mapping associated with three RPs (5, 22, and 100 years) was created. In addition, three zones were established to identify the hazard levels, considering the most critical scenario of the three maps. The results showed that the largest flood area is in high degree hazard, occupying 77% of the total area. It indicates that people are in danger both inside and outside houses. At the same time buildings are in high possibility of being damaged.

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

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Fundação de Amparo à Pesquisa do Estado de Minas Gerais
O recente aumento do número de inundações e movimentos de massa na região densamente povoada no sudeste do Brasil, o presente estudo analisa as alterações espaciais e temporais na precipitação durante o período de 1978-2014, nas regiões montanhosas dos estados brasileiros do Rio de Janeiro e Santa Catarina. Avaliou-se a presença de tendência nas series sazonais, anuais e do conjunto de índices extremos de precipitação onde foi usado o software Rclimdex. As series são calculados a partir das series precipitação diária. Com base nos resultados observou-se que nas escalas anuais e sazonais se tem um aumento de precipitação, exceto para a temporada de inverno na região montanhosa de Rio de Janeiro. Além disso, foram encontradas de mudanças abrutas em diferentes anos para as séries de tempo analisadas, diferenças espaciais nas tendências em estações individuais e tendências associadas com elevação sugerem que apesar da proximidade destas duas regiões, os impactos do clima não são uniformes em todo o sudeste do Brasil. Os mecanismos de clima responsáveis pelas tendências de precipitação observada são identificados, mas trabalho adicional é necessário para isolar as causas. Por outro lado, o número de desastres naturais de tipo hidrológico como os movimentos de massa/enchentes estão aumentando. Este tipo desastre mostrou correlações positivas significativas com os índices 1-day (máximo de precipitação anual em um dia) e o 5-dias (máximo de precipitação anual em cinco dias consecutivos), sendo assim índices que podem ser úteis indicadores de eventos de risco hidrológicos para estas regiões.
In order to understand the rising number of flash floods and mass movements in the densely populated region of southeastern Brazil, this study analyzes the spatial and temporal changes in precipitation from 1978 to 2014. We focus on the sensitivity of mountainous regions, specifically the Rio de Janeiro (RJMR) and Santa Catarina (SCMR) regions. Daily rainfall observations are aggregated into annual and seasonal indices, and RClimdex is used to evaluate a suite of precipitation and extreme event indices. Results show positive annual and seasonal precipitation trends during all seasons except for the winter season in the RJMR. Diverse change points in their time series, spatial differences in the trends at individual stations, and trends associated with elevation suggest that despite the close proximity of these two regions, climate impacts are not uniform across all of southeastern Brazil. Climate mechanisms responsible for the observed precipitation trends are identified, but additional work is needed to isolate the causes. Statistically significant positive correlations are discovered between mass movements/flash floods events and annual maximum 1–day and 5–day consecutive precipitation, and these indices may be useful indicators of natural hazard events for this region.

Master of Landscape Architecture
Department of Landscape Architecture/Regional and Community Planning
Timothy Keane
The City of Manhattan, Kansas is looking for possible solutions to mitigate flooding along Wildcat Creek within the Wildcat Creek Watershed. Recent flooding has caused substantial property damage. The project presented here brings recreation into the community by designing a golf course in a location along Wildcat Creek that addresses flooding issues, increases infiltration, and improves water quality. The golf industry has a long way to go to become more sustainable. The world is facing many challenges related to water and hydrology. Much of the opposition towards the golf industry is because critics see it as environmentally unfriendly. Golf has the potential to become a catalyst for change in the way we design and develop the landscape around us. The golf industry can become a leader in sustainable design while taking on hydrological concerns within the community. This project demonstrates the application of a golf course to help mitigate flooding along Wildcat Creek with the use of vulnerability and suitability analysis as a guide to site selection. This method of analysis illustrates the process of identifying and protecting areas vulnerable to degradation by designing a golf course in a suitable location to utilize water hazards to store flood water, provide more floodplain access to effectively increase infiltration capacity, reduce runoff rates, and improve water quality. The report explains the relationship between golf course design and environmental practices as they relate to hydrology on a theoretical site in Manhattan, Kansas. By integrating golf course design theory and environmentally sound stormwater management practices, water hazards on the golf course can become the fundamental elements used in strategizing the design of the golf course. A conceptual plan was created to maximize the infiltration capacity of the site as well as allow increased floodplain access, and provide a place to store flood water. A golf course can then be properly sited and designed hydrologically around the use of water hazards to help reduce flooding and improve water quality within the watershed.

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.

Le changement climatique requiert une adaptation de la gestion des extrêmes hydrologiques (crues et étiages). Nos recherches proposent un cadre d’analyse de l’effet du changement climatique sur ces extrêmes dans le bassin transnational de la Meuse, par un chaînage de modèles (atmosphérique – hydrologique - hydraulique) liant le gradient régional de pression à l’écoulement mesuré à l’exutoire d’un bassin. Le forçage climatique est obtenu par l’agrégation de données climatiques historiques et de données multi-modèles issues de l’expérience CMIP5. En forçant deux sous-bassins de la Meuse (situés en France et en Belgique) à l’aide d’une première estimation de la variabilité climatique potentielle, nous montrons que les indicateurs de crues et d’étiages ainsi que les débordements de rivière peuvent être fortement impactés par le changement climatique anthropique. Cette analyse de vulnérabilité constitue un outil pour tester la robustesse de stratégies d’adaptation au changement climatique
Climate change requires to adapt management of streamflow extremes (floods and low flows). Our researches provide a framework to analyze climate change effect on the streamflow extremes in the transnational Meuse river basin, through a modelling chain (atmospheric model – hydrological model – hydraulic model) linking the pressure gradient force to the flow at the outlet of a basin. The climate forcing is obtained by blending historical data and multi-model data for the CMIP5 experience. By forcing two sub-basins of the Meuse river (located in France and Belgium) with the potential climate variability, we show that flood and low flows indices as well as river overflowing might be strongly impacted by the anthropogenic climate change. This analysis of catchment vulnerability is a robust tool to test climate resiliency of adaptation strategies for water management

Dissertação de mestrado em Geografia (área de especialização em Planeamento e Gestão do Território)
Vivemos atualmente numa “sociedade de risco” que se define pela inexistência de risco zero, sendo por isso o acesso à informação sobre os riscos a que os cidadãos estão sujeitos no território, uma obrigação legal no sentido de sensibilizar e garantir a adoção de medidas fundamentais para a sua gestão. O risco hidrológico é normalmente classificado como natural e tem bastante incidência no território nacional. Naturalmente, o concelho de Braga não é exceção. Neste território os fenómenos de cheias, inundações e alagamentos são frequentes, originando consequências negativas a nível ambiental, social e económico. É neste contexto que a Geografia, como ciência autónoma, mas também como ciência interface, pode contribuir para que seja elaborado um instrumento de apoio à gestão do risco hidrológico. Na presente dissertação é proposta uma metodologia para a elaboração de uma cartografia de risco hidrológico, para o concelho de Braga, baseada num modelo que envolve três componentes de risco, sendo eles: a perigosidade, a exposição e a vulnerabilidade social. Estes são baseados num conjunto de particularidades naturais, humanas e mistas, que podem ser responsáveis pelo desencadeamento da materialização do risco hidrológico. Esta cartografia de risco permitiu identificar as áreas de risco hidrológico: “muito baixo”, “baixo”, “médio”, “elevado” e “muito elevado”, do território em estudo, o que possibilitou estabelecer áreas prioritárias no que respeita à implementação de medidas de gestão, promovendo o planeamento e ordenamento do território.
We currently live in a “risk society” that is defined by the absence of zero risk, and that’s why the access to risk information by citizens it’s a legal obligation to raise awareness and ensure the adoption of fundamental measures for their management. The hydrological risk is one of the multiple risks classified as natural, with a strong impact on the portuguese territory. In fact, the municipality of Braga is no exception. In this territory, hydrological phenomena are frequent, causing negative consequences in the environment, in the society and in the economy. In this context Geography, as an autonomous science, but also as an interface science, can contribute to the elaboration of an instrument to support the management of hydrological risk. So, in this dissertation, a methodology is proposed for the elaboration of a hydrological risk mapping, for the municipality of Braga. This is based on a model that involves three risk components: probability of the hazard, exposure and social vulnerability. These are based on a set of natural, human and mixed characteristics, which may be responsible for the materialization of hydrological risk. This risk mapping made it possible to identify the areas of hydrological risk: "very low", "low", "medium", "high" and "very high", allowing the establishment of priority areas to implement management measures, promoting territorial planning.

Railroad bridges and culverts in the United States are often subject to extreme floods, which have been known to washout sections of track and ultimately lead to derailments. The potential for these events is particularly high in the western U.S. due to the lack of data, inadequate radar coverage, and the high spatial and temporal variability of storm events and terrain. In this work, a hydrologic model is developed that is capable of effectively describing the rainfall-runoff relationship of extreme thunderstorms in arid and semi-arid regions. The model was calibrated and validated using data from ten storms at the semi-arid Walnut Gulch Experimental Watershed. A methodology is also proposed for reducing the amount of raingages required to provide acceptable inputs to the hydrologic model, and also determining the most appropriate placement location for these gages. Results show that the model is capable of reproducing peak discharges, peak timings, and total volumes to within 22.1%, 12 min, and 32.8%, respectively. Results of the gage reduction procedure show that a decrease in the amount of raingages used to drive the model results in a disproportionally smaller decrease in model accuracy. Results also indicate that choosing gages using the minimization of correlation approach that is described herein will lead to an increase in model accuracy as opposed to selecting gages on a random basis.

abstract: Aquifers host the largest accessible freshwater resource in the world. However, groundwater reserves are declining in many places. Often coincident with drought, high extraction rates and inadequate replenishment result in groundwater overdraft and permanent land subsidence. Land subsidence is the cause of aquifer storage capacity reduction, altered topographic gradients which can exacerbate floods, and differential displacement that can lead to earth fissures and infrastructure damage. Improving understanding of the sources and mechanisms driving aquifer deformation is important for resource management planning and hazard mitigation. Poroelastic theory describes the coupling of differential stress, strain, and pore pressure, which are modulated by material properties. To model these relationships, displacement time series are estimated via satellite interferometry and hydraulic head levels from observation wells provide an in-situ dataset. In combination, the deconstruction and isolation of selected time-frequency components allow for estimating aquifer parameters, including the elastic and inelastic storage coefficients, compaction time constants, and vertical hydraulic conductivity. Together these parameters describe the storage response of an aquifer system to changes in hydraulic head and surface elevation. Understanding aquifer parameters is useful for the ongoing management of groundwater resources. Case studies in Phoenix and Tucson, Arizona, focus on land subsidence from groundwater withdrawal as well as distinct responses to artificial recharge efforts. In Christchurch, New Zealand, possible changes to aquifer properties due to earthquakes are investigated. In Houston, Texas, flood severity during Hurricane Harvey is linked to subsidence, which modifies base flood elevations and topographic gradients.
Dissertation/Thesis
Doctoral Dissertation Geological Sciences 2018

The world’s freshwater resources are being placed under increasing pressure owing to growth in population, economic development, improved standards of living, agricultural intensification (linked mainly to irrigation), pollution and mismanagement of available freshwater resources. Already, in many parts of the Orange River Catchment, water availability has reached a critical stage. It has become increasingly evident that water related problems can no longer be resolved by water managers alone, owing to the problems becoming more interconnected with other development related issues, as well as with social, economic, environmental, legal and political factors. With the advent of climate change and the likelihood of increases in extreme events, water managers’ awareness of uncertainties and critical reflections on the adequacy of current management approaches is increasing. In order to manage water resources effectively a more holistic approach is required than has hitherto been the case, in which technological, social and economic development are linked with the protection of natural ecosystems and with dependable projections of future climatic conditions. To assess the climate risk connected with rural and urban water management, and to develop adaptive strategies that can respond to an increasingly variable climate that is projected into the future and help to reduce adverse impacts, it is necessary to make connections between climate related hazards, climate forecasts as well as climate change, and the planning, design, operation, maintenance, and rehabilitation of water related infrastructure. Therefore, adaptive water resources management (AWRM), which in essence is “learning by doing”, is believed to be a timely extension of the integrated water resources management (IWRM) approach as it acknowledges uncertainty and is flexible in that it allows for the adjustment of actions based on information learned about the system. Furthermore, it is suggested that climate risk management be imbedded within the AWRM framework. The objective of the research presented in this thesis is to develop techniques to integrate state-of-the-art climate projection scenarios – which forms part of the first step of the adaptive management cycle – downscaled to the regional/local scale, with hydro-climatic hazard determination – which forms part of the first step in the risk management process – in order to simulate projected impacts of climate change on hydro-climatic hazards in the Orange River Catchment (defined in this study as those areas of the catchment that exist within South Africa and Lesotho). The techniques developed and the results presented in this study can be used by decision-makers in the water sector in order to make informed proactive decisions as a response to projected future impacts of hydro-climatic hazards – all within a framework of AWRM. Steps towards fulfilling the above-mentioned objective begins by way of a comprehensive literature review; firstly of the study area, where it is identified that the Orange River Catchment is, in hydro-climatic terms, already a high risk environment; and secondly, of the relevant concepts involved which are, for this specific study, those pertaining to climate change, and the associated potential hydro-climatic impacts. These include risk management and its components, in order identify how hazard identification fits into the broader concept of risk management; and water resources management practices, in order to place the issues identified above within the context of AWRM. This study uses future projections of climate from five General Circulation Models, all using the SRES A2 emission scenario. By and large, however, where techniques developed in this study are demonstrated, this is done using the projections from the ECHAM5/MPI-OM GCM which, relative to the other four available GCMs, is considered to provide “middle of the road” projections of future climates over southern Africa. These climate projections are used in conjunction with the locally developed and widely verified ACRU hydrological model, as well as a newly developed hydro-climatic database at a finer spatial resolution than was available before, to make projections regarding the likelihood and severity of hydro-climatic hazards that may occur in the Orange River Catchment. The impacts of climate change on hydro-climatic hazards, viz. design rainfalls, design floods, droughts and sediment yields are investigated, with the results including a quantitative uncertainty analysis, by way of an index of concurrence from multiple GCM projections, for each of the respective analyses. A new methodology for the calculation of short duration (< 24 hour) design rainfalls from daily GCM rainfall projections is developed in this study. The methodology utilises an index storm approach and is based on L-moments, allowing for short duration design rainfalls to be estimated at any location in South Africa for which daily GCM rainfall projections exist. The results from the five GCMs used in this study indicate the following possible impacts of climate change on hydro-climatic hazards in the Orange River Catchment: · Design rainfalls of both short and long duration are, by and large, projected to increase by the intermediate future period represented by 2046 - 2065, and even more so by the more distant future period 2081 - 2100. · Design floods are, by and large, projected to increase into the intermediate future, and even more into the more distant future; with these increases being larger than those projected for design rainfalls. · Both meteorological and hydrological droughts are projected to decrease, both in terms of magnitude and frequency, by the period 2046 - 2065, with further decreases projected for the period 2081 - 2100. Where increases in meteorological and hydrological droughts are projected to occur, these are most likely to be in the western, drier regions of the catchment. · Annual sediment yields, as well as their year-to-year variability, are projected to increase by the period 2046 - 2065, and even more so by the period 2081 - 2100. These increases are most likely to occur in the higher rainfall, and especially in the steeper, regions in the east of the catchment. Additionally, with respect to the above-mentioned hydro-climatic hazards, it was found that: · The statistic chosen to describe inter-annual variability of hydro-climatic variables may create different perceptions of the projected future hydroclimatic environment and, hence, whether or not the water manager would decide whether adaptive action is necessary to manage future variability. · There is greater uncertainty amongst the GCMs used in this study when estimating design events (rainfall and streamflow) for shorter durations and longer return periods, indicating that GCMs may still be failing to simulate individual extreme events. · The spatial distribution of projected changes in meteorological and hydrological droughts are different, owing to the complexities introduced by the hydrological system · Many areas may be exposed to increases in hydrological hazards (i.e. hydrological drought, floods and/or sediment yields) because, where one extreme is projected to decrease, one of the others is often projected to increase. The thesis is concluded with recommendations for future research in the climate change and hydrological fields, based on the experiences gained in undertaking this study.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

abstract: This doctoral thesis investigates the predictability characteristics of floods and flash floods by coupling high resolution precipitation products to a distributed hydrologic model. The research hypotheses are tested at multiple watersheds in the Colorado Front Range (CFR) undergoing warm-season precipitation. Rainfall error structures are expected to propagate into hydrologic simulations with added uncertainties by model parameters and initial conditions. Specifically, the following science questions are addressed: (1) What is the utility of Quantitative Precipitation Estimates (QPE) for high resolution hydrologic forecasts in mountain watersheds of the CFR?, (2) How does the rainfall-reflectivity relation determine the magnitude of errors when radar observations are used for flood forecasts?, and (3) What are the spatiotemporal limits of flood forecasting in mountain basins when radar nowcasts are used into a distributed hydrological model?. The methodology consists of QPE evaluations at the site (i.e., rain gauge location), basin-average and regional scales, and Quantitative Precipitation Forecasts (QPF) assessment through regional grid-to-grid verification techniques and ensemble basin-averaged time series. The corresponding hydrologic responses that include outlet discharges, distributed runoff maps, and streamflow time series at internal channel locations, are used in light of observed and/or reference data to diagnose the suitability of fusing precipitation forecasts into a distributed model operating at multiple catchments. Results reveal that radar and multisensor QPEs lead to an improved hydrologic performance compared to simulations driven with rain gauge data only. In addition, hydrologic performances attained by satellite products preserve the fundamental properties of basin responses, including a simple scaling relation between the relative spatial variability of runoff and its magnitude. Overall, the spatial variations contained in gridded QPEs add value for warm-season flood forecasting in mountain basins, with sparse data even if those products contain some biases. These results are encouraging and open new avenues for forecasting in regions with limited access and sparse observations. Regional comparisons of different reflectivity -rainfall (Z-R) relations during three summer seasons, illustrated significant rainfall variability across the region. Consistently, hydrologic errors introduced by the distinct Z-R relations, are significant and proportional (in the log-log space) to errors in precipitation estimations and stream flow magnitude. The use of operational Z-R relations without prior calibration may lead to wrong estimation of precipitation, runoff magnitude and increased flood forecasting errors. This suggests that site-specific Z-R relations, prior to forecasting procedures, are desirable in complex terrain regions. Nowcasting experiments show the limits of flood forecasting and its dependence functions of lead time and basin scale. Across the majority of the basins, flood forecasting skill decays with lead time, but the functional relation depends on the interactions between watershed properties and rainfall characteristics. Both precipitation and flood forecasting skills are noticeably reduced for lead times greater than 30 minutes. Scale dependence of hydrologic forecasting errors demonstrates reduced predictability at intermediate-size basins, the typical scale of convective storm systems. Overall, the fusion of high resolution radar nowcasts and the convenient parallel capabilities of the distributed hydrologic model provide an efficient framework for generating accurate real-time flood forecasts suitable for operational environments.
Dissertation/Thesis
Ph.D. Civil and Environmental Engineering 2012