The EPID (electronic portal imaging device) was designed for in vivo imaging of patients during radiotherapy treatment. The ability of EPIDs to promptly acquire two dimensional data, lends them to be considered for use in quality assurance of the linac. This thesis set out to investigate the possibility of using a radionuclide, technetium 99 m (Tc99m), to produce a flood field for the calibration of an EPID, because using a beam calibrated EPID to measure the beam is self-referential. The difference in relative response between the energy spectrum of a 6MV beam and the Tc99m was investigated using EGSNRC DoseXYZ Monte Carlo Modelling. The relative output ratio was calculated to be less than 1.6%. The dose response of the EPID with respect to dose rate was checked using different activities of Tc99m and found to be linear. The flatness from a phantom was calculated, with a model in MATLAB, for a range of heights, overlaps, thickness, and deformations, to find the optimum balances between signal strength and flatness. This model was checked for accuracy using diagnostic radiographic film. The culmination of the energy response, linearity and the calculated flatness is a flood field taken with a flood phantom on the EPID with low signal strength. To get a signal to noise ratio of 3% the mean of over 2000 flood field images were used. This accuracy was not adequate for clinical use but the averaging of pixels it is accurate enough for QA.

Floods cannot be prevented, but their devastating effects can be minimized if advance warning of the event is available. The South African Disaster Management Act (Act 57 of 2002) advocates a paradigm shift from the current "bucket and blanket brigade" response-based mind set to one where disaster prevention or mitigation are the preferred options. It is in the context of mitigating the effects of floods that the development and implementation of a reli able flood forecasting system has major significance. In the case of flash floods, a few hours lead time can afford disaster managers the opportunity to take steps which may significantly reduce loss of life and damage to property. The engineering challenges in developing and implementing such a system are numerous. In this thesis, the design and implement at ion of a flash flood forecasting system in South Africa is critically examined. The technical aspect s relating to spatio-temporal rainfall estimation and now casting are a key area in which new contributions are made. In particular, field and optical flow advection algorithms are adapted and refined to help pred ict future path s of storms; fast and pragmatic algorithms for combining rain gauge and remote sensing (rada r and satellite) estimates are re fi ned and validated; a two-dimensional adaptation of Empirical Mode Decomposition is devised to extract the temporally persistent structure embedded in rainfall fields. A second area of significant contribution relates to real-time fore cast updates, made in response to the most recent observed information. A number of techniques embedded in the rich Kalm an and adaptive filtering literature are adopted for this purpose. The work captures the current "state of play" in the South African context and hopes to provide a blueprint for future development of an essential tool for disaster management. There are a number of natural spin-offs from this work for related field s in water resources management. / Thesis (Ph.D.Eng.)-University of KwaZulu-Natal, Durban, 2007.

Storm sewer systems play a very important role in urban areas. The design of a storm sewer system should be based on an appropriate level of preventing flooding. This thesis focuses on issues relevant to decision-making in storm sewer network design considering flood risk. Uncertainty analysis is often required in an integrated approach to a comprehensive assessment of flood risk. The first part of this thesis discusses the understanding and representation of uncertainty in general setting. It also develops methods for propagating uncertainty through a model under different situations when uncertainties are represented by various mathematical languages. The decision-making process for storm sewer network design considering flood risk is explored in this thesis. The pipe sizes and slopes of the network are determined for the design. Due to the uncertain character of the flood risk, the decision made is not unique but depends on the decision maker’s attitude towards risk. A flood risk based storm sewer network design method incorporating a multiple-objective optimization and a “choice” process is developed with different design criteria. The storm sewer network design considering flood risk can also be formed as a single-objective optimization provided that the decision criterion is given a priori. A framework for this approach with a single objective optimization is developed. The GA is adapted as the optimizer. The flood risk is evaluated with different methods either under several design storms or using sampling method. A method for generating samples represented by correlated variables is introduced. It is adapted from a literature method providing that the marginal distributions of variables as well as the correlations between them are known. The group method is developed aiming to facilitate the generation of correlated samples of large sizes. The method is successfully applied to the generation of rainfall event samples and the samples are used for storm sewer network design where the flood risk is evaluated with rainfall event samples.

Die Vorteile der Kernschätzung gegenüber dem Abzählen von Ereignissen in Zeitintervallen werden dargestellt. Für das beiden Methoden gemeinsame Glättungsproblem gestattet die Kreuzvalidierung eine Lösung. Für die Hochwasserereignisse der Oder im Zeitraum 1350 bis 1850 wird eine Abnahme der Häufigkeit nach ca. 1675 gefunden; weitergehende Aussagen bedingen eine Homogenisierung der Daten. Die dargestellte Methodik wird gegenwärtig in das Computerprogramm XTREND implementiert. / The advantages of kernel estimation over counting of events within time intervals are shown. Cross validation offers a solution for the smoothing problem which is common to both methods. As regards ooding events of the river Oder in 1350 to 1850, a decrease in the frequency after about 1675 is found. More detailed results demand homogenized data. The method is currently being implemented into the computer program XTREND.

Flooding in the Assiniboine River Basin has increasingly resulted in major crop and infrastructure losses. Since the early 2000’s, flood events have occurred more frequently and with greater impact. As floodwaters travel over agricultural fields, soil particles and nutrients are carried downstream. These particles and nutrients are a major factor in water quality degradation contributing nitrogen and phosphorus to Manitoba’s rivers and lakes. This practicum aims to increase the storage capacity of existing wetlands in a prairie landscape so that a 100-year storm event can be managed on-site. A site in Broughton’s Creek Watershed was. It was determined that the quantity of runoff could be significantly reduced and the quality of water would increase. This approach could be applied to other locations within the Assiniboine River Basin to create a landscape resilient to flood events and downstream water quality degradation. / October 2016

The study is a contextual analysis of flood victimization. Victimization is defined as the social, psychological, and physiological aftermath experienced by victims of a disaster. Disaster researchers concentrate on the victims' characteristics to explain the varying degrees of their victimization, providing only ambiguous results. Theorists such as Kreps, Wildavsky, and Douglas contend that the outcomes of disasters are contingent upon social structure. This analysis treats victimization as one such outcome. The condition and behavior of individuals can be explained by the presence of disaster and the conditions of social organization. A model explains victimization based on individual's attributes (individual resources), his social environment, and the disaster characteristics. This study uses the 1984 Mingo Creek Flood Victims Survey data to test the model. The data contain information measuring victimization. The survey data are linked with 1980 Census tract data. The tract data provide indicators of the social networks. This tract information, the contextual variables, taps the social conditions, including poverty, unemployment, geographic mobility, and family patterns. This study uses factor analysis to identify the dimensions of victimization. Regression tests the relationship between the contextual variables, the individual resource variables, the disaster characteristic variables, and victimization. The results of the analysis show that victimization is multidimensional with different types of variables being significant predictors for each dimension of victimization, one variable indicating the intensity of the disaster, the dollar value of damage victims experienced, is found to be a significant predictor of the psychological, physiological, and social disruption aspects of victimization. Variables measuring the family and unemployment patterns in the victims' census tract are significant predictors of the psychological and social disruption aspect of victimization. The findings provide general support for the proposed model of victimization. However, victimization is multidimensional with each dimension having a unique set of predictors. Based on the findings, this study suggests that future research focus on measurement and conceptualization of the characteristics of disasters and the victims' social environment.

Shifting climatic regimes can increase or decrease the frequency of extreme hydrologic events (e.g., high and low streamflows) causing large societal and environmental impacts. The impacts are numerous and include human health and safety, the destruction of infrastructure, water resources, nutrient and sediment transport, and within stream ecological health. It is unclear how the hydrology of a given region will shift in response to climate change. This is especially the case in areas that are seasonally snow covered as the interplay of changing temperature, precipitation, and resulting snowpack can lead to an increased risk of flood or drought. This research aimed to understand the ways temperature and precipitation are changing using general circulation models and observed weather station data in the northeastern United States. With the knowledge that general circulation models do not accurately represent precipitation statistics and trends from the historical period, a large network of climate stations was utilized to further investigate shifts in precipitation. A hydrology model was utilized for further study of regional hydrology. The model used was the Regional Hydro-Ecologic Simulation System, which was calibrated to snow coverage and streamflow for a historical time period. The hydrology model was used to investigate the relationship of snow and streamflow in a changing climate. We characterized climate change and related impacts in the northeastern United States and estimated a decrease in snowfall of 50% and the number of days below freezing by 45 days by the end of the century. We also showed that precipitation is not only becoming more intense, but it is also more persistent -- a finding that may have significant hydrological implications including increased flood risk throughout the year. The 95th percentile of daily precipitation has increased by 0.5 mm per day per decade, while the probability of successive days with precipitation increased by 0.6 percent per decade. We also explored the role of snowpack in a changing climate. We found that temperature plays a larger role than precipitation in shifting hydrologic regime, because the warming-induced reduction of snowpack reduced the maximum flows more than the increasing precipitation increased the maximum flows. However, because of the increasing intensity and persistence of precipitation, instantaneous peak flows occurring outside of the snowmelt season will likely continue to increase during all times of the year. We shed light on the complexity of the modes of climate change and the interactions that increases in temperature and precipitation can have on the hydrology of a region.

Les conditions de vie offertes par la montagne anti-atlasique aux populations ne sont guère favorables au travail de la terre : la pluviosité est très irrégulière et insuffisante, le sol est squelettique et caillouteux car il se développe à partir d'un substrat géologique ancien et sur des pentes fortes. Pour pallier ces conditions hostiles, la société montagnarde de l'Anti-Atlas marocain s'est efforcée depuis des siècles, peut-être même depuis des millénaires, d'aménager pratiquement toutes les pentes pour y fixer la terre arable et surtout pour y récupérer tout le ruissellement pluvial afin d'en imbiber les terres. Ces aménagements sont aujourd'hui parfois fossilisés par l'abandon de l'activité agricole et sont menacés de ruine ou de disparition. Cette situation est évidente dans toutes les contrées anti-atlasiques que nous avons parcourues. C'est une oeuvre et un savoir-faire paysans qui sont donc en danger. Il est important de les étudier alors que ces artefacts sont encore partiellement fonctionnels et qu'ils peuvent encore participer à l'enrichissement du potentiel culturel de cette montagne méridionale déjà si riche, par ailleurs, de paysages et de vestiges architecturaux de toute sorte. / The living conditions of the population in the Anti-Atlas Mountains are not ideal for agriculture: rains are very irregular and insufficient; the soil is skeletal and stony, as it develops from an old geological substratum and on steep slopes. To make up for those hostile conditions, for centuries and perhaps for millennia, the mountain society of the Moroccan Anti-Atlas has endeavoured to manage the slopes so as to preserve arable land and especially to capture rainfall runoff, so as to imbibe the land with it. Nowadays, those structures are sometimes fossilized and threatened with disrepair and destruction now that agricultural activities have come to an end. This situation is striking in all the Anti-Atlas areas I have travelled through. The work and the skills of local farmers are therefore in danger of being lost. It is essential to study those artifacts while they are still partly functional, as they can still enrich the cultural potential of this southern mountainous area, already rich of its many landscapes and architectural vestiges.

The objective of this study was to determine if numerical models commonly used for large scale applications could also be used to model flow through flood control structures in the Rigolets Pass between Lake Borgne and Lake Pontchartrain. For this purpose a small scale physical model was built. It showed that bi-stable flow can develop downstream of a constriction. Small changes in the distribution of the approaching flow significantly impacted flows downstream of the constriction. This behavior could not be properly reproduced by a small scale 2-dimensional RMA2 model of identical dimensions. A large scale RMA2 model of the Rigolets testing possible locations and geometries of flood control structures showed that this pass is very sensitive to variations in the cross sectional flow area. Even minor reductions can significantly increase headlosses and velocities. To reduce negative impacts a flood control structure should be built in a wide and shallow area of the pass.

La pratique de la planification urbaine reste un défi dans les villes d'Afrique sub-saharienne et l'occupation de l'espace urbain se fait en grande partie en déphasage avec les normes urbanistiques. L'analyse du contexte de production et d'occupation de l'espace urbain ainsi que des conséquences qui découlent d'une planification urbaine inconséquente permet de faire un lien entre les problèmes de développement et les risques d'aggravation des inondations.A Cotonou, le phénomène est plus qu'inquiétant. Les problèmes de planification se posent en termes d'occupation des zones impropres à l'habitat, de fragilité des surfaces bâties et de qualité des ouvrages d'assainissement. Les conditions d'insalubrité de l'habitat et la situation sanitaire des zones potentiellement inondables ainsi que la gestion de l'environnement sont autant de défis pour les autorités locales ; l'occupation anarchique de l'espace, la perte progressive de contrôle et de régulation de l'action publique étant des causes de cette situation.Les propositions formulées dans cette recherche sont relatives aux contraintes physiques, pluviométriques, climatologiques et aux stratégies d’adaptation des populations face aux inondations. Elles intègrent également l'amélioration de la gouvernance urbaine, l'assainissement urbain et la gestion de l'environnement construit. / The practice of urban planning remains a key challenge in Sub-Saharan Africa cities since the urban land use is out of phase with the urbanistic standards. The analysis of the context of urban space production and occupation as well as of the consequences that result from an inconsistent urban planning allows us to draw a link between development problems and the risks of aggravating flood situations. The phenomenon is more than worrisome in Cotonou. The planning problems can be presented in terms of occupation of land that are unsuitable for habitat, of vulnerability of inhabited areas and of quality of wastewater facilities. The unhygienic conditions of the habitat and the sanitary situation of potentially flood-prone areas as well as the environment management are among the numerous challenges for cities councils, which are caused by the anarchic occupation of land, the gradual loss of control and regulation by the public hands.The proposals made by this research are related to the physical and climatological constraints and to the strategies for adaptation of the communities to floods. They include besides urban governance improving, urban sanitation and built environment management.