Дисертації з теми "Storm and flood events"
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1
Jobin, Erik. "An Urban Rainfall Storm Flood Severity Index." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24124.
Анотація:
Extreme rainfall statistics are important for the design and management of the water resource infrastructure. The standard approach for extreme rainfall event severity assessment is the Intensity-Duration-Frequency (IDF) method. However, this approach does not consider the spatial context of rainfall and consequently does not properly describe rainfall storm severity, nor rarity. This study provides a critical account of the current standard practice and presents an approach that takes into consideration both the spatial context of rainfall storms, and indirectly incorporates runoff to produce a representative approach to assessing urban rainfall storm severity in terms of flood potential. A stepwise regression analysis was performed on a dataset of individual rainfall storm characteristics to best represent documented basement floodings in the City of Edmonton. Finally, the urban rainfall storm flood severity index was shown to be most representative of the documented basement floodings' severity when compared to that of the IDF method.
2
Anderson, Ian. "Improving Detection And Prediction Of Bridge Scour Damage And Vulnerability Under Extreme Flood Events Using Geomorphic And Watershed Data." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/823.
Анотація:
Bridge scour is the leading cause of bridge damage nationwide. Successfully mitigating bridge scour problems depends on our ability to reliably estimate scour potential, design safe and economical foundation elements that account for scour potential, identify vulnerabilities related to extreme events, and recognize changes to the environmental setting that increase risk at existing bridges.
This study leverages available information, gathered from several statewide resources, and adds watershed metrics to create a comprehensive, georeferenced dataset to identify parameters that correlate to bridges damaged in an extreme flood event. Understanding the underlying relationships between existing bridge condition, fluvial stresses, and geomorphological changes is key to identifying vulnerabilities in both existing and future bridge infrastructure. In creating this comprehensive database of bridge inspection records and associated damage characterization, features were identified that correlate to and discriminate between levels of bridge damage.
Stream geomorphic assessment features were spatially joined to every bridge, marking the first time that geomorphic assessments have been broadly used for estimating bridge vulnerability. Stream power assessments and watershed delineations for every bridge and stream reach were generated to supplement the comprehensive database. Individual features were tested for their significance to discriminate bridge damage, and then used to create empirical fragility curves and probabilistic predictions maps to aid in future bridge vulnerability detection. Damage to over 300 Vermont bridges from a single extreme flood event, the August 28, 2011 Tropical Storm Irene, was used as the basis for this study. Damage to historic bridges was also summarized and tabulated. In some areas of Vermont, the storm rainfall recurrence interval exceeded 500 years, causing widespread flooding and damaging over 300 bridges. With a dataset of over 330 features for more than 2,000 observations to bridges that were damaged as well as not damaged in the storm, an advanced evolutionary algorithm performed multivariate feature selection to overcome the shortfalls of traditional logistic regression analysis. The analysis identified distinct combinations of variables that correlate to the observed bridge damage under extreme food events.
3
Ranalli, Philip Anthony. "Small Drainage Basins and the Probable Maximum Flood: A Flood Inundation Study of an Anticipated Extreme Storm Event in West Central Florida." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000367.
4
Many, Gael. "Impacts of storm and flood events on suspended particulate matter dynamics in the Gulf of Lions. Contributions of gliders to a multi-platform approach." Thesis, Perpignan, 2016. http://www.theses.fr/2016PERP0033/document.
Анотація:
La dynamique des matières en suspension joue un rôle primordial au sein de la zone côtière en étant le principal vecteur de matière particulaire depuis les sources (rivières) vers les puits (marges continentales, canyons sous-marins, océan profond). Le suivi de cette dynamique, notamment pendant les évènements de crues des fleuves et des tempêtes, est primordial afin d’estimer les budgets sédimentaires des marges continentales, de suivre l’évolution des habitats benthiques et de déterminer le rôle de cette dynamique dans le transport de contaminants. Cette thèse a pour objet l’étude des impacts de tels évènements sur la dynamique des particules en suspension au sein du Golfe du Lion (Méditerranée). Une approche multiplateforme, couplant les différentes plateformes de mesures existantes (campagne en mer, glider, satellite, mouillage, bouée côtière) et basée sur la mesure de la turbidité en terme quantitatif et qualitatif a été adoptée. Les résultats ont permis de décrire 1) la dynamique des néphéloïdes en fonction des forçages (vents, vagues, courants) durant des évènements de crue du Rhône et de tempête marine, 2) la variabilité spatiale et temporelle de l’assemblage particulaire lors de ces mêmes évènements par une caractérisation in situ et 3) de montrer le rôle des plateformes autonomes du type gliders dans le suivi de la dynamique des matières en suspension en zone côtièreCoastal suspended particulate matter dynamics play a main role in the fate of land-derived material from the source (rivers) to sink (continental margins, submarine canyons, deep sea). The monitoring of this dynamic, especially during flooding and storm conditions, is decisive to understand factors impacting sedimentary budgets of continental margins, health of benthic habitats and spread of contaminants. The aim of this PhD is to study the impacts of such events on the suspended particles dynamics over the shelf of the Gulf of Lions (NW Mediteranean). A multi-platform approach, combining existing observation platforms (survey, glider, satellite, mooring and coastal buoy) and based on the measurement of the turbidity was adopted. Results enabled to describe 1) the impacts of forcings (winds, waves, currents) on the dynamics of nepheloid layers during flooding and storm conditions, 2) the variability of the particle assemblage during such events through an in situ characterization and 3) the role of gliders in the monitoring of suspended particles dynamics within the coastal zone
5
Ilahee, Mahbub. "Modelling Losses in Flood Estimation." Queensland University of Technology, 2005. http://eprints.qut.edu.au/16019/.
Анотація:
Flood estimation is often required in hydrologic design and has important economic significance. For example, in Australia, the annual spending on infrastructure requiring flood estimation is of the order of $650 million ARR (I.E. Aust., 1998). Rainfall-based flood estimation techniques are most commonly adopted in practice. These require several inputs to convert design rainfalls to design floods. Of all the inputs, loss is an important one and defined as the amount of precipitation that does not appear as direct runoff. The concept of loss includes moisture intercepted by vegetation, infiltration into the soil, retention on the surface, evaporation and loss through the streambed and banks. As these loss components are dependent on topography, soils, vegetation and climate, the loss exhibits a high degree of temporal and spatial variability during the rainfall event. In design flood estimation, the simplified lumped conceptual loss models were used because of their simplicity and ability to approximate catchment runoff behaviour. In Australia, the most commonly adopted conceptual loss model is the initial losscontinuing loss model. For a specific part of the catchment, the initial loss occurs prior to the commencement of surface runoff, and can be considered to be composed of the interception loss, depression storage and infiltration that occur before the soil surface saturates. ARR (I. E. Aust., 1998) mentioned that the continuing loss is the average rate of loss throughout the remainder of the storm. At present, there is inadequate information on design losses in most parts of Australia and this is one of the greatest weaknesses in Australian flood hydrology. Currently recommended design losses are not compatible with design rainfall information in Australian Rainfall and Runoff. Also design losses for observed storms show a wide variability and it is always difficult to select an appropriate value of loss from this wide range for a particular application. Despite the wide variability of loss values, in the widely used Design Event Approach, a single value of initial and continuing losses is adopted. Because of the non-linearity in the rainfall-runoff process, this is likely to introduce a high degree of uncertainty and possible bias in the resulting flood estimates. In contrast, the Joint Probability Approach can consider probability-distributed losses in flood estimation. In ARR (I. E. Aust., 1998) it is recommended to use a constant continuing loss value in rainfall events. In this research it was observed that the continuing loss values in the rainfall events were not constant, rather than it decays with the duration of the rainfall event. The derived loss values from the 969 rainfall and streamflow events of Queensland catchments would provide better flood estimation than the recommended design loss values in ARR (I. E. Aust., 1998). In this research, both the initial and continuing losses were computed using IL-CL loss model and a single median loss value was used to estimate flood using Design Event Approach. Again both the initial and continuing losses were considered to be random variables and their probability distribution functions were determined. Hence, the research showed that the probability distributed loss values can be used for Queensland catchments in near future for better flood estimate. The research hypothesis tested was whether the new loss value for Queensland catchments provides significant improvement in design flood estimation. A total of 48 catchments, 82 pluviograph stations and 24 daily rainfall stations were selected from all over Queensland to test the research hypothesis. The research improved the recommended design loss values that will result in more precise design flood estimates. This will ultimately save millions of dollars in the construction of hydraulic infrastructures.
6
Ilahee, Mahbub. "Modelling Losses in Flood Estimation." Thesis, Queensland University of Technology, 2005. https://eprints.qut.edu.au/16019/1/Mahbub_Ilahee_Thesis.pdf.
Анотація:
Flood estimation is often required in hydrologic design and has important economic significance. For example, in Australia, the annual spending on infrastructure requiring flood estimation is of the order of $650 million ARR (I.E. Aust., 1998). Rainfall-based flood estimation techniques are most commonly adopted in practice.
These require several inputs to convert design rainfalls to design floods. Of all the inputs, loss is an important one and defined as the amount of precipitation that does not appear as direct runoff. The concept of loss includes moisture intercepted by vegetation, infiltration into the soil, retention on the surface, evaporation and loss through the streambed and banks. As these loss components are dependent on
topography, soils, vegetation and climate, the loss exhibits a high degree of temporal and spatial variability during the rainfall event.
In design flood estimation, the simplified lumped conceptual loss models were used because of their simplicity and ability to approximate catchment runoff behaviour. In Australia, the most commonly adopted conceptual loss model is the initial losscontinuing loss model. For a specific part of the catchment, the initial loss occurs prior to the commencement of surface runoff, and can be considered to be composed
of the interception loss, depression storage and infiltration that occur before the soil surface saturates. ARR (I. E. Aust., 1998) mentioned that the continuing loss is the average rate of loss throughout the remainder of the storm.
At present, there is inadequate information on design losses in most parts of Australia and this is one of the greatest weaknesses in Australian flood hydrology. Currently recommended design losses are not compatible with design rainfall information in Australian Rainfall and Runoff. Also design losses for observed storms show a wide variability and it is always difficult to select an appropriate value of loss from this wide range for a particular application. Despite the wide variability of loss values, in the widely used Design Event Approach, a single value of initial
and continuing losses is adopted. Because of the non-linearity in the rainfall-runoff process, this is likely to introduce a high degree of uncertainty and possible bias in the resulting flood estimates. In contrast, the Joint Probability Approach can consider probability-distributed losses in flood estimation.
In ARR (I. E. Aust., 1998) it is recommended to use a constant continuing loss value in rainfall events. In this research it was observed that the continuing loss values in the rainfall events were not constant, rather than it decays with the duration of the rainfall event. The derived loss values from the 969 rainfall and streamflow events of Queensland catchments would provide better flood estimation than the recommended design loss values in ARR (I. E. Aust., 1998). In this research, both the initial and continuing losses were computed using IL-CL loss model and a single median loss value was used to estimate flood using Design Event Approach. Again both the initial and continuing losses were considered to be random variables and their probability distribution functions were determined. Hence, the research showed that
the probability distributed loss values can be used for Queensland catchments in near future for better flood estimate.
The research hypothesis tested was whether the new loss value for Queensland catchments provides significant improvement in design flood estimation. A total of 48 catchments, 82 pluviograph stations and 24 daily rainfall stations were selected from all over Queensland to test the research hypothesis. The research improved the recommended design loss values that will result in more precise design flood estimates. This will ultimately save millions of dollars in the construction of hydraulic infrastructures.
7
Lewis, Matthew. "Uncertainties within future flood risk storm surge inundation modelling." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601160.
Анотація:
Key uncertainties within inundation modelling of storm tide overflow were investigated for two regions. A northern Bay of Bengal LISFLOOD-FP inundation model was developed from freely available data sources, and forced with a storm surge model (IIDT) hind-cast of the 2007 cyclone Sidr flood event because no quality water-level records exist. Validation showed inundation prediction accuracy, with a Root Mean Squared Error (RMSE) on predicted water-level of...., 2 rn, which was similar in magnitude to the forcing water-level uncertainty. Indeed, when observed natural variability within five key cyclone parameters was propagated through the IID-T storm surge model, extreme water-level uncertainty was found to be very high in the Bay of Bengal, and should be considered in future work (and flood risk managers). Future flood hazard mapping uncertainty is much less in the data rich UK; however, when some key uncertainties were propagated through a North Somerset LISFLOOD•FP inundation model of the 1981 historic flood, storm tide spatial variability was found to significantly affect flood risk estimates, second only to sea level rise. A new method for prescribing the still peak water-level along a coastline was developed (Method C), which characteristics the spatial variability using a relatively short record of modelled extreme water-level events, relative to a tide gauge. Good agreement (RMSE 36 cm) was found between Method C predicted water-levels and tide gauge observations for two historic flood events in East Anglia (1953 and 2007). Furthermore, remotely sensed storm tide observations along the North Somerset coast indicated the accuracy of Method C between tide gauge observations; however, fine-scale wave and bathymetry effects need to be resolved for accurate coastal flood risk estimates in the UK. Indeed, the quantification of uncertainty, and the characterisation of natural variability, is necessary for a robust flood risk prediction.
8
Baynes, Edwin Richard Crews. "Constraining bedrock erosion during extreme flood events." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/15962.
Анотація:
The importance of high-magnitude, short-lived flood events in controlling the evolution of bedrock landscapes is not well understood. During such events, erosion processes can shift from one regime to another upon the passing of thresholds, resulting in abrupt landscape changes that can have a long lasting legacy on landscape morphology. Geomorphological mapping and topographic analysis document the evidence for, and impact of, extreme flood events within the Jökulsárgljúfur canyon (North-East Iceland). Surface exposure dating using cosmogenic 3He of fluvially sculpted bedrock surfaces determines the timing of the floods that eroded the canyon and helps constrain the mechanisms of bedrock erosion during these events. Once a threshold flow depth has been exceeded, the dominant erosion mechanism becomes the toppling and transportation of basalt lava columns and erosion occurs through the upstream migration of knickpoints. Surface exposure ages allow identification of three periods of rapid canyon cutting during erosive flood events about 9, 5 and 2 ka ago, when multiple active knickpoints retreated large distances (> 2 km), each leading to catastrophic landscape change within the canyon. A single flood event ~9 ka ago formed, and then abandoned, Ásbyrgi canyon, eroding 0.14 km3 of rock. Flood events ~5 and ~2 ka ago eroded the upper 5 km of the Jökulsárgljúfur canyon through the upstream migration of vertical knickpoints such as Selfoss, Dettifoss and Hafragilsfoss. Despite sustained high discharge of sediment-rich glacial meltwater (ranging from 100 to 500 m3 s-1); there is no evidence for a transition to an abrasion-dominated erosion regime since the last erosive flood: the vertical knickpoints have not diffused over time and there is no evidence of incision into the canyon floor. The erosive signature of the extreme events is maintained in this landscape due to the nature of the bedrock, the discharge of the river, large knickpoints and associated plunge pools. The influence of these controls on the dynamics of knickpoint migration and morphology are explored using an experimental study. The retreat rate of knickpoints is independent of both mean discharge, and temporal variability in the hydrograph. The dominant control on knickpoint retreat is the knickpoint form which is set by the ratio of channel flow depth to knickpoint height. Where the knickpoint height is five times greater than the flow depth, the knickpoints developed undercutting plunge pools, accelerating the removal of material from the knickpoint base and the overall retreat rate. Smaller knickpoints relative to the flow depth were more likely to diffuse from a vertical step into a steepened reach or completely as the knickpoint retreated up the channel. These experiments challenge the established assumption in models of landscape evolution that a simple relationship exists between knickpoint retreat and discharge/drainage area. In order to fully understand how bedrock channels, and thus landscapes, respond and recover to transient forcing, further detailed study of the mechanics of erosion processes at knickpoints is required.
9
Dunn, Catherine. "How Unusual is Tropical Storm Irene? A Case Study of Storm Deposition in Littleville Lake, Huntington, MA." Oberlin College Honors Theses / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=oberlin1400777365.
10
Abdullah, Rozi. "Rainfall forecasting algorithms for real time flood forecasting." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296151.
Анотація:
A fast catchment response usually leads to a shorter lag time, and under these conditions the forecast lead time obtained from a rainfall-runoff model or correlation between upstream and downstream flows may be infeasible for flood warning purposes. Additional lead time can be obtained from short-term quantitative rainfall forecasts that extend the flood warning time and increase the economic viability of a flood forecasting system. For this purpose algorithms which forecasts the quantitative rainfall amounts up to six hours ahead have been developed, based on lumped and distributed approaches. The lumped forecasting algorithm includes the essential features of storm dynamics such as rainband and raincell movements which are represented within the framework of a linear transfer function model. The dynamics of a storm are readily captured by radar data. A space-time rainfall model is used to generate synthetic radar data with known features, e.g. rainband and raincell velocities. This enables the algorithm to be assessed under ideal conditions, as errors are present in observed radar data. The transfer function algorithm can be summarised as follows. The dynamics of the rainbands and raincells are incorporated as inputs into the transfer function model. The algorithm employs simple spatial cross-correlation techniques to estimate the rainband and raincell velocities. The translated rainbands and raincells then form the auxiliary inputs to the transfer function. An optimal predictor based on minimum square error is then derived from the transfer function model, and its parameters are estimated from the auxiliary inputs and observed radar data in real-time using a recursive least squares algorithm. While the transfer-function algorithm forecasts areal rainfalls, a distributed approach which performs rainfall forecasting at a fine spatial resolution (referred to as the advection equation algorithm) is also evaluated in this thesis. The algorithm expresses the space-time rainfall on a Cartesian coordinate system via a partial differential advection equation. A simple explicit finite difference solution scheme is applied to the equation. A comparison of model parameter estimates is undertaken using a square root information filter data processing algorithm, and single-input single-output and multiple-input multiple-output least squares algorithms.
11
Sun, Si'ao. "Decision-making under uncertainty : optimal storm sewer network design considering flood risk." Thesis, University of Exeter, 2010. http://hdl.handle.net/10036/112863.
Анотація:
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.
12
Onen, Alper. "Analyses Of Flood Events Using Regional Hydrometeorological Modeling System." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615476/index.pdf.
Анотація:
Extreme rainfall events and consequent floods are being observed more frequently in the Western Black Sea region in Turkey as climate changes. In this study, application of a flood early warning system is intended by using and calibrating a combined model system. A regional-scale hydro-meteorological model system, consisting of Weather Research and Forecasting (WRF) model, NOAH land surface model and fully distributed NOAH-Hydro hydrologic models, is used for simulations of 25 heavy-rainfall and major flooding events
observed in the Western Black Sea region between years 2000 and 2011. The performance of WRF model system in simulating precipitation is tested with 3-dimensional variational (3DVAR) data assimilation scheme. WRF-derived precipitation with and without data assimilation and Multi Precipitation Estimates (MPE) are used in NOAH-Hydro model to simulate streamflow for flood events. Statistical precipitation analyses show that WRF model with 3DVAR improved precipitation up to 12% with respect to no-assimilation. MPE algorithm generally underestimates rainfall and it also showed lower performance than WRF model with and without data assimilation. Depending on reliability of precipitation inputs, NOAH-Hydro model produces reasonable flood hydrographs both in structure and volume. After model calibration is performed using assimilated precipitation inputs in Bartin Basin, NOAH-Hydro model reduced the average error in streamflow by 23.24% and 53.57% with
calibration for testing events. With calibrated parameters, NOAH-Hydro model forced by WRF non-assimilated precipitation input also reduced the error in streamflow but with lower rates (16.67% and 40.72%). With a proper model calibration and reliable precipitation inputs, hydrologic modeling system is capable of simulating flood events.
13
Suyanto, Adhi. "Estimating the exceedance probabilities of extreme floods using stochastic storm transportation and rainfall - runoff modelling." Thesis, University of Newcastle Upon Tyne, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386794.
Анотація:
Methods of estimating floods with return periods of up to one hundred years are reasonably well established, and in the main rely on extrapolation of historical flood data at the site of interest. However, extrapolating the tails of fitted probability distributions to higher return periods is very unreliable and cannot provide a satisfactory basis for extreme flood estimation. The probable maximum flood concept is an alternative approach, which is often used for critical cases such as the location of nuclear power plants, and is viewed as a consequence of a combination of a probable maximum precipitation with the worst possible prevailing catchment conditions. Return periods are not usually quoted although they are implicitly thought to be of the order of tens of thousand of years. There are many less critical situations which still justify greater flood protection than would be provided for an estimated one-hundred year flood. There is therefore a need for techniques which can be used to estimate floods with return periods of up to several thousand years. The predictive approach adopted here involves a combination of a probabilistic storm transposition technique with a physically-based distributed rainfall-runoff model. Extreme historical storms within a meteorologically homogeneous region are, conceptually, moved to the catchment of interest, and their return periods are estimated within a probabilistic framework. Known features of storms such as depth, duration, and perhaps approximate shape will, together with catchment characteristics, determine much of the runoff response. But there are other variables which also have an effect and these include the space-time distribution of rainfall within the storm, storm velocity and antecedent catchment conditions. The effects of all these variables on catchment response are explored.
14
Meslard, Florian. "Apports sableux par les fleuves côtiers méditerranéens et aléa de submersion marine (ASPLEC)." Electronic Thesis or Diss., Perpignan, 2023. http://www.theses.fr/2023PERP0053.
Анотація:
Obtenir des estimations précises des bilans sédimentaires sur le continuum terre-mer et comprendre comment ces bilans affectent la dynamique des littoraux est devenu un enjeu crucial dans le contexte actuel de montée du niveau marin et de recul du trait de côte. Les fleuves côtiers méditerranéens, du fait d’un caractère torrentiel lié à des événements météorologiques intenses, sont caractérisés par des épisodes de crues brefs mais violents durant lesquels la majorité du flux d’eau et de sédiments est apportée à la zone côtière en quelques jours. Ce mode de fonctionnement épisodique impacte également leurs embouchures qui peuvent se retrouver obstruées par le développement de flèche sableuse et conduire durant la concomitance des évènements de tempête et de crue à de fortes submersions en zone littorale.Cette thèse a pour objectif de mieux comprendre le fonctionnement de ces embouchures intermittentes et leurs interactions avec les apports en sédiments des fleuves qui y sont associés selon un continuum terre-mer. Une approche spatio-temporelle multi-échelles (terre-mer) couplant des données d’observations morphologiques, hydro-météorologiques et de suivi du transport sédimentaire a été appliquée sur le fleuve Têt, un exemple de fleuve côtier méditerranéen. Les résultats ont permis de 1) mieux comprendre le fonctionnement de ce système d’embouchure intermittente régie par des processus auto-allocycliques et anthropiques, 2) améliorer les estimations de flux de matières en suspension, apporter les premières estimations de flux de sable en suspension et à proximité du fond ainsi que de comprendre le rôle de la morphologie sur leur transfert vers la zone côtière et 3) améliorer la compréhension des événements concomitants de tempête et de crue sur la dynamique de réponsemorphologique et du transport sédimentaire associéObtaining accurate estimates of sediment budgets on the land-sea continuum and understanding how these budgets affect coastal dynamics has become a crucial issue in the current context of rising sea levels and retreating coastlines. The torrential nature of mediterranean coastal rivers, linked to intense meteorological events, is characterized by brief but violent flooding episodes, during which most of the water and sediment discharge is delivered to the coastal zone in a few days. This episodic behavior of operation also has an impact on their river outlet as well, which can become obstructed by the development of sandy spits, leading to heavy flooding in coastal areas during concomitant storm and flood events. The aim of this thesis is to improve our understanding of intermittent river mouths processes, and to assess their interaction with the sediment transport in a land-sea continuum. A multi-scales (land-sea) spatio-temporal approach combining morphological, hydro-meteorological and sediment transport monitoring data was applied to the Têt River, an example of a mediterranean coastal river. The results provided with 1) a better understanding of the mechanisms at this intermittent river mouth system governed by auto-allocyclic and anthropogenic processes, 2) an improved estimates of suspended solids fluxes, provided by the first estimates of suspended and near-bottom sand fluxes, as well as understanding the role of morphology on their transfer to the coastal zone, and 3) an improved understanding of concomitant storm and flood events on the dynamics of the morphological response and the associated sediment transport
15
Hepworth, Daniel Ary. "Response of a Partially Mixed Coastal Plain Estuary to Storm Events." W&M ScholarWorks, 1988. https://scholarworks.wm.edu/etd/1539617584.
16
Hubbard, Shane A. "Modeling geospatial events during flood disasters for response decision-making." Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/1973.
Анотація:
A model that emphasizes possible alternative sequences of events that occur over time is presented in paper 1 (chapter 2) of this dissertation. Representing alternative or branching events captures additional semantics unrealized by linear or non-branching approaches. Two basic elements of branching, divergence and convergence are discussed. From these elements, many complex branching models can be built capturing a perspective of events that take place in the future or have occurred in the past. This produces likely sequences of events that a user may compare and analyze using spatial or temporal criteria. The branching events model is especially useful for spatiotemporal decision support systems, as decision-makers are able to identify alternative locations and times of events and, depending on the context, also identify regions of multiple possible events. Based on the formal model, a conceptual framework for a branching events model for flood disasters is presented. The framework has five parts, an event handler, a query engine, data assimilator, web interface, and event database. A branching events viewer application is presented illustrating a case study based on a flood response scenario.
A spatiotemporal framework for building evacuation events is developed to forecast building content evacuation events and building vulnerabilities and is presented in paper 2 (chapter 3) of this dissertation. This work investigates the spatiotemporal properties required to trigger building evacuation events in the floodplain during a flood disaster. The spatial properties for building risks are based on topography, flood inundation, building location, building elevation, and road access to determine five categories of vulnerability, vulnerable basement, flooded basement, vulnerable first-floor, flooded first-floor, and road access. The amount of time needed to evacuate each building is determined by the number of vulnerable floors, the number of movers, the mover rate, and the weight of the contents to be moved. Based upon these properties, six possible evacuation profiles are created. Using this framework, a model designed to track the spatiotemporal patterns of building evacuation events is presented. The model is based upon flood forecast predictions that are linked with building properties to create a model that captures the spatiotemporal ordering of building vulnerabilities and building content evacuation events. Applicable to different communities at risk from flooding, the evacuation model is applied a historical flood for a university campus, demonstrating how the defined elements are used to derive a pattern of vulnerability and evacuation for a campus threatened by severe flooding.
Paper 3 (Chapter 4) of this dissertation presents a modeling approach for representing event-based response risk. Surveys were sent to emergency managers in six states to determine the priorities of decision makers during the response phase of flood disasters. Based on these surveys, nine response events were determined to be the most important during a flood response, flooded roads, bridges closed, residential evacuations, residential flooding, commercial flooding, agricultural damage, power outage, sheltering, sandbagging. Survey participants were asked to complete pairwise comparisons of these nine events. An analytic hierarchy process analysis was completed to weight the response events for each decision-maker. A k-means clustering analysis was then completed to form 4 distinct profiles, mixed rural and urban, rural, urban, and high population - low population density. The average weights from each profile were calculated. The weights for each profile were then assigned to geospatial layers that identify the locations of these events. These layers are combined to form a map representing the event-based response risk for an area. The maps are then compared against the response events that actually occurred during a flood disaster in June 2008 in two communities.
17
Eaton, Brett. "Morphologic channel response to flood events in a salmon spawning stream." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0027/MQ50760.pdf.
18
Safarzynska, Karolina, Roy Brouwer, and Marjan Hofkes. "Evolutionary modelling of the macro-economic impacts of catastrophic flood events." Elsevier, 2013. http://dx.doi.org/10.1016/j.ecolecon.2013.01.016.
Анотація:
This paper examines the possible contribution of evolutionary economics to macro-economic modelling of flood impacts to provide guidance for future economic risk modelling. Most macro-economic models start from a neoclassical economic perspective and focus on equilibrium outcomes, either in a static or dynamic way, and describe economic processes at a high level of aggregation. As a consequence, they typically fail to account for the complexity of social interactions and other behavioural responses of consumers and producers to disasters, which may affect the macroeconomic impacts of floods. Employing evolutionary principles and methods, such as agent-based modelling, may help to address some of the shortcomings of current macro-economic models. We explore and discuss the implications of applying consumer and producer heterogeneity, bounded rationality, network effects, social and technological learning, co-evolution and adaptive policy-making concepts into existing economic frameworks for the assessment of macro-economic impacts of floods. (authors' abstract)
19
Eaton, Brett. "Morphologic channel response to flood events in a salmon spawning stream." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21545.
Анотація:
Changes in channel morphology in response to two flood events were measured within three reaches on the Sainte Marguerite River, Quebec. The first event was the spring freshet---peaking in mid-May, 1996---while the second event---peaking on July 20, 1996---was the largest flood on record for the region. The resultant channel adjustments can be classified as either bedform evolution---in which a clear, systematic pattern of adjustment is evident---or as bedform change, in which local hydraulic and sedimen tologic conditions produce a seemingly random pattern of channel mobilization. Where bedform evolution has occurred, it is consistent with the existing paradigm for meander development. Sediment transport calculations based on the 'inverse' or 'morphologic' method were strongly correlated to reach average mobility ratios. The average rate of transport in response to the larger flood approached those reported by others for a braided system (Goff and Ashmore, 1994). Potential spawning zones within the three reaches were all subjected to significant net scour and/or fill following the second event; several potential spawning zones were significantly affected by the first event The presence of bank protection upstream of a potential spawning zone seems to be a determinant 10 the severity of the impact by promoting erosion of these zones.
20
Wadey, Matthew P. "Understanding defence failures and coastal flood events : a case study approach." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/359740/.
Анотація:
Extreme sea level events are a current global threat, whilst sea-level rise (SLR) and climate change over the 21st century will increase the frequency and severity of flooding in most coastal regions. Numerical model simulations can help to understand and predict coastal floods (e.g. flood mapping and forecasting) but in comparison to flood sources (waves and water levels) coastal flood pathways (defence failures and inundation) are presently less integrated within these models. This thesis develops and demonstrates a methodology to rapidly simulate and understand the consequences of coastal flood events, with an emphasis upon regions where the risks of flooding are not well understood and could change quickly with SLR. The Solent on the south coast of England is the case study, and is prone to frequent flooding. This region is currently differentiated from the UK east and west coasts by experiencing smaller storm surges, and is characterised by undefended sections of shoreline and small floodplains. Within the Solent is Portsmouth, a city of national flood significance (only London and Hull contain more people considered at risk of coastal flooding in the UK). However, life threatening floods have not occurred in living memory. An integrated modelling approach is developed, coupling loads and defence failures with two-dimensional simulations of floodplain inundation. Observations collated from a real storm surge and flood event are shown to generate a validation data set, which indicates that this model can predict floodplain water levels to a good level of accuracy, whilst highlighting implications of such data collection. Solent-wide analysis includes simulations of hypothetical coastal flood events based upon scenarios that cover the full range of coastal loadings (realistic waves and water levels) and defence failures (overflow, outflanking, overtopping and breaching). More detailed case-studies are also applied at two sites within the region (including Portsmouth). This analysis generates peak flood water depths and an overview of impacts across this spectrum of possible floods. This research improves the existing knowledge of coastal flooding in the case study, and highlights a number of generic concepts that should be applied to others. For example the combination of flood simulation methods with real flood event analysis is essential for optimising the interpretation of model outputs whilst supporting inferences about flood consequences associated with extreme loading events (including how these may change with SLR). Simple methods estimated that >24,000 properties are within a 1 in 200 year flood event outline; and incorporating defence failures, flood dynamics, validation and detailed case studies substantially refine the assessment of places likely to experience damages. Breach defence failures generate the worst flood impacts, although in the Solent this failure mechanism is presently less of a threat than outflanking, overflow and wave overtopping. The modelling system includes easily interpreted outputs, whilst being computationally fast; therefore with potential applications including supporting land-use and defence planning, and real-time flood forecasting and warning.
21
Kvocka, Davor. "Modelling elevations, inundation extent and hazard risk for extreme flood events." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/101761/.
Анотація:
Climate change is expected to result in more frequent occurrences of extreme flood events, such as flash flooding and large scale river flooding. Therefore, there is a need for accurate flood risk assessment schemes in areas prone to extreme flooding. This research study investigates what flood risk assessment tools and procedures should be used for flood risk assessment in areas where the emergence of extreme flood events is possible. The first objective was to determine what type of flood inundation models should be used for predicting the flood elevations, velocities and inundation extent for extreme flood events. Therefore, there different flood inundation model structures were used to model a well-documented extreme flood event. The obtained results suggest that it is necessary to incorporate shock-capturing algorithms in the solution procedure when modelling extreme flood events, since these algorithms prevent the formation of spurious oscillations and provide a more realistic simulation of the flood levels. The second objective was to investigate the appropriateness of the “simplification strategy” (i.e. improving simulation results by increasing roughness parameter) when used as a flood risk assessment modelling tool for areas susceptible to extreme flooding. The obtained results suggest that applying such strategies can lead to significantly erroneous predictions of the peak water levels and the inundation extent, and thus to inadequate flood protection design. The third and final objective was to determine what type of flood hazard assessment methods should be used for assessing the flood hazard to people caused by extreme flooding. Therefore, two different flood hazard assessment criteria were modelled for three extreme flood events. The predicted results suggest that in areas prone to extreme flooding, the flood hazard indices should be predicted with physics-based formulae, as these methods consider all of the physical forces acting on a human body in floodwaters, take into account the rapid changes in the flow regime, which often occur for extreme events, and enable a rapid assessment of the degree of flood hazard to be made in a short time period.
22
Cialino, Keith Thomas. "Fluxes of dissolved organic carbon during storm events in the Neponset River Watershed." Thesis, University of Massachusetts Boston, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3706454.
Анотація:
The transport of dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) from land to coastal environments strongly influences coastal ecosystems. The presence of first flush phenomena due to rainwater runoff traveling from land into waterways can greatly affect carbon fluxes to coastal areas. This research utilizes sensors, autosamplers, and standard watershed sampling in order to assess for the presence of first flush and its significance.
A rainfall simulator was built in order to collect runoff on two land use types. Time series data suggest that first flush of dissolved organic carbon was present for all rainfall intensities simulated on an impervious surface. At this location, approximately 40% to 51% of DOC flux occurred within the first 20% of runoff. At the permeable sampling location, first flush was observed in surface runoff collected during 12.7 and 25.4 mm hr-1 simulated storms, with 31% and 26% of DOC flux occurring within the first 22% of runoff.
Seven storm events at two locations in the Neponset River Watershed, Massachusetts, USA were monitored to study the impact of storm events on DOC export from an urban watershed. Real-time CDOM fluorescence sensor measurements were better able to capture the variability present in riverine DOC and CDOM concentrations due to runoff influxes. Using modeled flow data, estimates of total DOC export fluxes during storms were compared to estimated total annual export. Based on these calculations, the seven sampled storm events account for 7 to 10 percent of the calculated yearly flux during 4 to 5 percent of the year. Additional work is needed to collect consistent year round data using sensors at these locations.
DOC was sampled throughout the Neponset River Watershed monthly for seven years. Increased concentrations were observed following storm events and snowmelt, and were an average of 28% greater than concentrations observed during dry periods. Based on daily sampling data in September 2011, monthly fluxes may be underestimated by 38% or overestimated by 35%. More frequent sampling allows for better certainty in estimations of monthly and yearly fluxes from the watershed, but must be balanced with logistical and cost constraints.
23
Sobat, Thomas A. "The effects of storm events on the behavior of hydropsychid net-spinning caddisflies." Virtual Press, 2007. http://liblink.bsu.edu/uhtbin/catkey/1378148.
Анотація:
Physical disturbance in the form of storm events has been implicated as a major determinant of community structure in streams. But there has been limited study of this effect on individual taxa within the communities. Such work is needed because of untested assumptions regarding the behavior of bioindicator species in these systems. Development of intricate indices of insect tolerances to organic pollution have become commonplace in environmental monitoring. However, research on the effects of natural disturbance on biological water quality assessment is lacking. Hydropsychid caddisflies are relatively intolerant to organic pollution and the United States Environmental Protection Agency has outlined the use of these organisms and others as an indication of clean water. If a species is recorded as absent from samples when it is present but hidden, this false negative would bias the water quality assessment. I tested hypotheses regarding the behavior of hydropsychid caddisflies facing increased discharge, and the effect of stream size on the magnitude of this phenomenon.Three sites along the West Fork of the White River, Indiana USA were studied during nine storms between 2001 and 2004. Stratified sampling from the upper 15 cm of substrate prior to and just after a storm, and again following reestablishment of normal flow, revealed alterations of hydropsychid distributions. During storms all but one species sought refuge in the hyporheic zone at depths dependent upon storm intensity. The possibility that poor water quality resulting from increased discharge caused the hydropsychid behavior was refuted by chemical analysis. Family level biotic index (FBI) data demonstrated that increased discharge results in a reduction of stream FBI values. These results indicate that high intensity storm events influence biological monitoring and should be factored into sampling protocol.Department of Biology
24
Eshleman, Jodi L. "Nearshore wave and sediment processes an evaluation of storm events at Duck, NC /." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0004786.
25
Daniels, Joslyn B. Ramey George E. "Flood debris build-up loading and assessment of adequacy of ALDOT bridge pile bents during extreme flood/scour events." Auburn, Ala., 2005. http://repo.lib.auburn.edu/2005%20Summer/master's/DANIELS_JOSLYN_47.pdf.
26
Blackburn, Julia L. "Forecasting open water and ice related flood events using hydraulic modelling techniques." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0002/MQ59780.pdf.
27
Nyaupane, Narayan. "STATISTICAL EVALUATION OF HYDROLOGICAL EXTREMES ON STORMWATER SYSTEM." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2300.
Анотація:
Climate models have anticipated higher future extreme precipitations and streamflows for various regions. Urban stormwater facilities are vulnerable to these changes as the design assumes stationarity. However, recent climate change studies have argued about the existence of non-stationarity of the climate. Distribution method adopted on extreme precipitation varies spatially and may not always follow same distribution method. In this research, two different natural extremities were analyzed for two separate study areas. First, the future design storm depth based on the stationarity of climate and GEV distribution method was examined with non-stationarity and best fit distribution. Second, future design flood was analyzed and routed on a river to estimate the future flooding. Climate models from North American Regional Climate Change Assessment Program (NARCCAP) and Coupled Model Intercomparison Project phase 5 (CMIP5) were fitted to 27 different distribution using Chi-square and Kolmogorov Smirnov goodness of fit. The best fit distribution method was used to calculate design storm depth as well as design flood. Climate change scenarios were adopted as delta change factor, a downscaling approach to transfer historical design value to the climate adopted future design value. Most of the delta change factor calculated were higher than one, representing strong climate change impact on future. HEC-HMS and HEC-RAS models were used to simulate the stormwater infrastructures and river flow. The result shows an adverse effect on stormwater infrastructure in the future. The research highlights the importance of available climate information and suggests a possible approach for climate change adaptation on stormwater design practice.
28
Grames, Johanna, Alexia Prskawetz, Dieter Grass, Alberto Viglione, and Günter Blöschl. "Modeling the interaction between flooding events and economic growth." Elsevier, 2016. http://dx.doi.org/10.1016/j.ecolecon.2016.06.014.
Анотація:
Recently socio-hydrology models have been proposed to analyze the interplay of community risk-coping
culture, flooding damage and economic growth. These models descriptively explain the feedbacks between
socio-economic development and natural disasters such as floods. Complementary to these descriptive
models, we develop a dynamic optimization model, where the inter-temporal decision of an economic agent
interacts with the hydrological system. We assume a standard macro-economic growth model where agents
derive utility from consumption and output depends on physical capital that can be accumulated through
investment. To this framework we add the occurrence of flooding events which will destroy part of the
capital. We identify two specific periodic long term solutions and denote them rich and poor economies.
Whereas rich economies can afford to invest in flood defense and therefore avoid flood damage and develop
high living standards, poor economies prefer consumption instead of investing in flood defense capital and
end up facing flood damages every time the water level rises like e.g. the Mekong delta. Nevertheless, they
manage to sustain at least a low level of physical capital. We identify optimal investment strategies and
compare simulations with more frequent, more intense and stochastic high water level events.
29
Aidoo, Isaac Albert. "Suspended sediment dynamics during storm events in urban catchments (River Tame, West Midlands, UK)." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6012/.
Анотація:
The study used continuously monitored, high resolution turbidity, ammonia, rainfall and flow data from EA UK. Urban storm events were not systematically characterised previously leading to gaps in process understanding; previous studies used short time periods and with most of them formed on single gauges. Aimed at improving understanding with novel contributions, the objectives were characterising the events, finding their seasonal influence and the spatial scale effect on turbidity patterns. Universally adaptable quantified events characterisation and classification were developed yielding single, double and multiple events. Double and multiple events together was more than single events for both smaller and larger catchments. Thus, analysing only single events could miss key dynamics of multiple events which showed significant increases in turbidity. More anticlockwise events than clockwise were found. Anticlockwise events decreased and clockwise increased from single to multiple events. Events with more number of turbidity than discharge peaks were found. Seasonally, most attributes as well as high urban extent and effluent spillage showed significant effects on turbidity mostly in summer and autumn. All seasons but spring with more anticlockwise than clockwise events had more low flows. Winter had the highest anticlockwise events, possibly because of its wider areal rain event extent, high number of low flows as well as more distal runoff sources. In the spatial scale studies, more single events in the smaller and more multiple events in the larger catchments as well as more anticlockwise events in the smaller and more clockwise events in the larger catchment were found.
30
Kanaley, Chelsea Noelle. "Turbidity and Nutrient Response to Storm Events in the Wissahickon Creek, Suburban Philadelphia, PA." Master's thesis, Temple University Libraries, 2018. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/496177.
Анотація:
GeologyM.S.
The Wissahickon Creek is an urban stream that runs through Montgomery and Philadelphia Counties and discharges to the Schuylkill River in Philadelphia. A majority of stream segments in the Wissahickon watershed are considered impaired by the USEPA due to sediment and nutrients. Total Maximum Daily Loads (TMDLs) were implemented in 2003 for nutrients (NO3-, PO43-, NO2-, and CBOD5) and siltation. A new TMDL for total phosphorus (TP) was proposed in 2015, despite minimal data on the effectiveness of the 2003 TMDLs. This new proposal was met with concern, suggesting more data must be collected to better understand impairment in the Wissahickon Creek. The purpose of this research was to study turbidity and nutrient responses to storm events, as storm events are known to contribute significant loads of both sediment and nutrients. Twelve sites were chosen for high frequency turbidity and water level monitoring along the Wissahickon Creek and one of its main tributaries, Sandy Run. These sites were selected around three of the major wastewater treatment plants (WWTPs) to determine the relative roles of WWTPs and overland flow as sources of turbidity and nutrients during storm events. The upstream site and first downstream site at each WWTP were monitored for nutrients during storms using high frequency loggers and ISCO automatic samplers. Stream assessments were done at each site to characterize in-stream physical parameters, bank vegetation, and algae cover. High frequency turbidity data suggests that the turbidity is locally sourced, as turbidity peaks at the same time as water level, or within an hour or two, at all sites regardless of storm size. Comparisons of the turbidity response with in-stream parameters and land cover helped determine that the main factor driving the turbidity response is discharge, although bank topping and impervious cover, particularly roads, may increase turbidity responses at some sites. Similarities in nutrient, turbidity, and conductivity responses upstream and downstream of the WWTPs strongly suggest that overland flow, not WWTP effluent, is the major source of nutrients and sediment during storm events. Finally, a strong relationship between total phosphorus and high turbidity suggests that only during high discharge events is there a significant increase in TP in the Wissahickon Creek. Results from this research identify the source of turbidity and nutrients to the Wissahickon Creek during storms as primarily coming from overland flow, that the primary factor controlling the turbidity response is discharge, with some secondary influence from over-banking and the contribution of roads to land use, and a close link between TP concentrations and sediment during storms in the stream.
Temple University--Theses
31
Doyle, Micelis Clyde. "Turbidity Dynamics during High-Flow Storm Events in the Clackamas River, Oregon 2006-2012." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3884.
Анотація:
Turbidity is a useful parameter that can be utilized to help understand the water quality in a river and is an expression of the optical properties of a liquid that cause light rays to be scattered and absorbed rather than transmitted in straight lines. A total of 41 storm events occurring during water years 2006-2012 were analyzed for this study. A hysteresis index (HI) was used to assess the difference in turbidity on the rising and falling limbs of a storm-hydrograph. The upstream Carter Bridge site exhibited a clockwise (C) hysteresis in 38 of 41 storm events and counter-clockwise (CC) hysteresis in three storm events. The downstream Oregon City site exhibited clockwise hysteresis in 29 of 41 storm events and counter-clockwise hysteresis in 12 storm events. Paired t-test comparisons of calculated HI measured during storm events showed that the upstream forested site Carter Bridge had a statistically significant higher HI than the downstream Oregon City site, suggesting that particles that contribute to increasing turbidity and suspended sediment at the upstream site are delivered to the river earlier in the storm event in comparison to the downstream Oregon City site. In contrast particulate matter and suspended sediment was more likely to be higher on the receding limb of the storm hydrograph at the downstream site in comparison to the upstream monitoring location.
Multiple linear regression analysis determined the major hydrological and meteorological controls influencing turbidity over the period of a storm event. The log value of the change (Log ΔQ) in discharge explained 81% of the log value of change in turbidity (Log ΔTb) at Carter Bridge and 48% of the change in turbidity at Oregon City for all storms. Log ΔQ explained 85% and 50% variations of Log ΔTb at Carter Bridge and at Oregon City, respectively in the wet season. Log ΔQ explained 82% of Log ΔTb at Carter Bridge during the Dry Season and together with 3-day antecedent precipitation, Log ΔQ explained 84% of variation in Log ΔTb at Oregon City during the Dry Season. The findings of this study, which offers information about the dynamics that lead to increased turbidity events, could be helpful to researchers, regulatory agencies and water resource managers in maintaining high water quality in rivers.
32
Wolff, Victoria H. "Storm smart planning for adaptation to sea level rise : addressing coastal flood risk in East Boston." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/50122.
Анотація:
Thesis (M.C.P.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 2009.Includes bibliographical references (p. 67-69).
Regardless of how well we implement sustainability plans, now and in the future, the weight of scientific evidence indicates that mean sea level will continue to rise at an increasing rate over the next century. Thus, coastal lands and development lie in a precarious position, increasingly vulnerable to flood damage brought by storm surges and extreme weather events. In order to avoid disastrous losses of property, life, ecological health and social wellbeing, our cities and regions must quickly implement adaptation plans that consider plausible climate models. Coastal risk can be managed through rigid protections, soft landscape solutions, and land use decisions and regulations. In developing and implementing adaptation plans, it is important to understand the options and their applicability to different site contexts. Experts warn that today's once-in-a century flood will likely occur every two or three years by 2050!' However, Boston, like many other U.S. coastal cities, is in the early stages of devising adaptation plans that seek to reduce coastal flood risk from sea level rise. As implementation of adaptation plans may take several years or decades, Boston should act quickly to strategically consider its options. This thesis examines the effectiveness of different planning approaches to hazard mitigation in urban coastal areas and applies them to at-risk sites in East Boston under coastal flood scenarios for the years 2050 and 2100. Two sites in East Boston, one with a soft edge and one with a hard edge, create two distinct urban landscapes for design solutions.
(cont.) A menu of planning solutions that has been collected from a review of the literature and best practices is then used to inform design solutions to these problems. By applying contemporary predictions for sea level rise and the problem-specific expertise of coastal management to the site-specific realm of land use planning, I hope to provide a precedent and method for planners, particularly in the Boston area, to seriously incorporate sea level rise predictions into community discussions, regulations, and comprehensive plan making.
by Victoria H. Wolff.
M.C.P.
33
Wood, Dylan M. "Finite Element Modeling for Assessing Flood Barrier Risks and Failures due to Storm Surges and Waves." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595572799377091.
34
Mousavi, Moghaddam Seyedali. "Inundation mapping of urban areas in case of severe rainfall events using HEC-RAS." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Анотація:
The current study investigates the potential of HEC-RAS (2D) in simulating urban inundation patterns in case of sever rainfall scenarios expected in the Ferrara and Rimini cities in Italy. HEC-RAS is one to most known and used hydraulic model for river application, however, its rainfall module is relatively new and sparsely investigated. Comparison of different mesh sizes (10, 25 and 50m) indicated no significant difference in model performance. However, a significant difference was observed in simulation time. Inundation maps were obtained for 5, 20 and 100-year rainfall events. HEC-RAS model outputs are compared against ground evidence and detailed outputs obtained with other modelling scheme: filling-and-spilling algorithm and a two-dimensional (2D) hydraulic numerical model (jn Rimini). For both Ferrara and Rimini case studies, overall index of agreement between HEC-RAS and filling-and-spilling models is up to 88%, while the similarity (i.e., flood area index) between HEC-RAS and 2D hydraulic model simulation at Rimini is equal to 0.64. In general, this study provides addition insights concerning HEC-RAS potential and limitations for identifying pluvial flood-hazard spots across large urban environments.
35
Stanley, Christopher. "Flood Visualization for Urban Planning : An exploratory spatiotemporal visualization of storm water runoff in 2D and 3D." Thesis, Högskolan i Gävle, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-21822.
Анотація:
Modelling hydrologic processes is important for understanding how the water cycle works in different environments. Cities which undergo constant changes are subject to flood hazards resulting from severe rainfall. This paper aims to simulate severe rainfall, visualize the results, incorporating both spatial and temporal dimensions, and to make future recommendations for further studies on flood visualization. Visualizing the results from a rainfall simulation using GIS provides urban planners and others the means to view the dynamics of the surface runoff. At the same time, it makes accessible advanced querying and analytical tools. A hydrological model for the study area in Gävle, Sweden was used to simulate a 100-year rainfall. Through FME, the data was reduced, time-stamped and combined to a shapefile. Both 2D software, ArcGIS, and 3D software, ArcScene, were used for creating an animated flood visualization. This study shows that although 2D tested better by a group of planners and water professionals, the 3D was still considered more intuitive. The heightened sense of realism from 3D outweighs its drawbacks, and further studies are required to test different methods of 3D visualization.
36
Brenner, Iris. "Application of storm transposition to the Middle Cedar Watershed : a reanalysis of the 2008 Cedar Rapids Flood." Thesis, University of Iowa, 2019. https://ir.uiowa.edu/etd/6710.
Анотація:
On June 13, 2008, after many days of rain, the Cedar River flooded the city of Cedar Rapids. With a peak discharge of 139,987 cfs and at 19.12 feet above flood stage, the 2008 flood of Cedar Rapids was the largest flood in the city’s historic record. As rivers rose, the city had received forecasts of an incoming flood as early as June 8. Then, on June 12, it began to rain in Cedar Rapids. Finally, on June 13, 2008, the Middle Cedar crested at 31.12 feet.
This thesis project modeled a variety of rainfall patterns on June 12, 2008, to determine the effect of varying rainfall intensity and location on the magnitude of the 2008 flood of Cedar Rapids. Using a method known as Stochastic Storm Transposition (SST), I overwrote precipitation data in a hydrologic model of the Middle Cedar Watershed with rainfall data extracted from specific storm events that occurred in the Upper Midwest. We used a physically-based, semi-distributed hydrologic model known as GHOST (Generic Hydrologic Overland-Subsurface Toolkit) developed by Marcela Politano at the University of Iowa.
Traditionally, hydrologic modeling for watersheds has used design storms to create rainfall inputs in flood modeling. These design storms have uniform rainfall timing and accumulation patterns across a watershed and are determined by designated equations for a geographic region. In large watersheds such as the Middle Cedar (2,400 square miles), design storms are not physically realistic because of their uniformity. Additionally, design storms fail to capture unique storm patterns such as high intensity periods or the movement of a storm across a watershed. By implementing SST into GHOST, we used physically realistic storm events that have unique rainfall patterns and intensities within a designated return period.
SST extracts rainfall data from real storm events and transposes the storm patterns onto watersheds to provide physically realistic rainfall data for hydrologic modeling. A tool called RainyDay, developed by Professor Daniel Wright at the University of Wisconsin, provided the storm transpositions used in this research. We assigned the storm transpositions return periods created by RainyDay, corresponding to their average transposed rainfall across the Middle Cedar Watershed.
Replacing the June 12 rainfall with RainyDay’s two-year transposed storm events (average rain accumulation 1.8 inches) resulted in modeled flood peaks larger than the unaltered June 12 flood peak. Storm transpositions of 5-, 10-, and 2,000-year return periods showed even larger peaks, illustrating the potential for floods much larger than the 2008 flood.
In addition to the analysis of flood magnitude in 2008, we modeled a set of storm transposition scenarios for a variety of soil-moisture conditions. The increased discharge levels in scenarios with high soil moisture emphasize the importance of initial conditions in flooding scenarios. Finally, we modeled the effect that two-year RainyDay storms would have had on the 2016 flood of Cedar Rapids had they occurred on the day before the peak. The two-year transpositions showed that with an impending flood crest smaller than the 2008 crest, several two-year RainyDay scenarios would have resulted in floods nearly equal in magnitude to the 2008 flood event.
Our manipulation of the rainfall in the Middle Cedar Watershed on June 12, 2008, using the GHOST model provided the opportunity to re-examine the influence that a specific day of rainfall had on the 2008 flood of Cedar Rapids. The potential for higher flooding under conditions of repeated rainfall and high soil moisture illustrates the susceptibility of the Middle Cedar Watershed to future flood events under similar conditions. Applying SST in hydrologic modeling also provided an opportunity to model a variety of rainfall scenarios and to better understand watershed responses to nuanced and physically realistic rainfall patterns.
37
Reimer, Beth A. "Influences of major storm events on backbarrier salt marsh change : Masonboro Island, Southeastern North Carolina /." Electronic version, 2004. http://dl.uncw.edu/etd/2004/reimerb/bethreimer.html.
38
Wirth, Stefanie. "Lake Thun sediment record 300 years of human impact, flood events and subaquatic slides /." Zurich : Federal Institute of Technology ETH, Department of Earth Sciences, 2008. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=404.
39
Henrich, Michael. "The influence of temporal rainfall distribution and storm movement on flood depth in urban pluvial cloud burst modeling." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-265572.
Анотація:
Pluvial floods are the most difficult and to date least investigated phenomena in urban hydrology. While efforts are being made to increase the knowledge base concerning this type of flooding, a large part of the difficulty lies in the nature of the precipitation. Convective storms represent most of the larger intensity short term rainfall in urban areas and is also the raintype, that is expected to increase the most in the future. The rain cells of this type have a more distinct boundary, larger intensity, a smaller extent and a shorter life span, than frontal rains. Combined with the low availability of densely spaced rain gauge networks and also low temporal resolution of measurements in 15 minutes intervals at best, makes this rain type still very difficult to analyze and even harder to predict. The resolution of cloud radar images at 2x2km and taken every 15 minutes is too coarse and the error reduction algorithms for radar based precipitation (HIPRAD) images to analysera in patterns are not sufficient by them selves to analyze the characteristics of such rainfields and the processes occurring within these fields. The spatial variation of raincells, their development and decay, the distance between them, and the velocity and direction of their movement can however be investigated employing a combination of densely spaced rain gauges and radar images to reach a more realistic representation of short-term precipitation for the use of in hydraulic models. The movement of rain fields has been investigated with two main areas of focus: The influence of direction or directional bias, often with an interest in the most crucial case referred to as the resonance effect, and in context of areal reduction of point rainfall. Most of these studies have been carried out with statistical methods and in laboratory experiments. In this study a hydraulic model was built on the terrain model of a realcity, a 28 km area in the city of Falun, to test the recently gathered information about the temporal variation of five empirical hyetographs with different peak arrival times and peak intensities, which are representative of Swedish climate. The hyetographs were produced and provided by SMHI. The empirical rain types were derived from 20 years of rain gauge observations and confirmed by radar images. For reference purposes, a standard Chicago design storm (CDS) rain was modeled as well. The simulated scenarios were modeled as a MIKE 21 hydraulic model, as a stationary scenario and in four movement directions. It was foundthat the empirical rain types produced lower inundation depth than the CDS, in a range of 20 to 50 % lower. The effect of modeling rainfall in motion produced on average only about 4-20 % lower water depths than the corresponding non-moving scenario. In a few instances, in a single evaluation point, the moving scenarios resulted in a relative water depth of a maximum of just above 1%. It was concluded that the conceptual approach of areal reduction from movement seems to be accurate and could help improve modeling rainfall in general, and specifically for cloud burst scenarios of shorter durations in urban catchments. It was also found that further investigation of the physical processes in rainfields could serve to increase the accuracy in areal reduction of precipitation for more realistic hydraulic models and in turn reduce over design.Pluviala översvämningar är den typen, som är både svårast att reda ut och samtidigt den minst utforskade fenomenen inom urban hydrologi. Medan ansträngningar görs för att förbättra kunskapsläget, ligger den största svårigheten i nederbördens skepnad. Det är konvektiva regn som utgör de flesta av de starkare korttids regntillfällen i urbana områden och är också regntypen som förväntas att öka mest i framtiden. Regncellerna har en tydligare avgränsning, en större intensitet, mindre utsträckning, och en kortare livscykel än frontala regn. I kombination med den låga tillgängligheten av regnmätarnätverk med hög täthet i positioneringen av mätare, samt den låga tidsupplösningen av mätningar i intervaller av 15 minuter gör att konvektiva regn fortfarande är svåra att analysera och ännu svårare att förutse. Upplösningen av molnradar bilder av 2x2 km som tas varje 15:de minut är för grova och algoritmer för felreducering av bilder från radarbaserad nederbördsdata (HIPRAD) för analys av regn mönster är inte tillräckligt noggranna, för sig, för att kunna analysera egenskaperna av sådana regnfält och de processerna som karakteriserar dessa. Den spatiala variationen inom regnceller, deras utveckling och förfall, avståndet mellan dem samt riktningen och hastigheten kan ändå undersökas med hjälp av kombinationen av regnmätarnätverk och radar bilder för att uppnå mer realistiska korttids nederbördsscenarier för användning i hydrauliska model. Studier, som har undersökt regn i rörelse har varit fokuserade på två huvudområden: Betydelsen av riktningen, i vilken regnet rör sig, där den största effekten som denna riktningsbias kan uppnå, har döpts resonans effekt och i samband med ytreducering (areal reduction) av punkt nederbörd. De flesta av dessa studier har genomförts med hjälp av statistiska metoder och laboratorieexperiment. I denna studie skapades en hydraulisk modell baserad på en realistisk terräng av ett existerade urbant område, en yta på 28 km i Falun, för att testa den nyligen utvärderade informationen om temporala intensitets fördelningen som representerar det svenska klimatet. Regndatat producerades och tillhandahölls av SMHI och representerar en mätserie från regnmätare över en period av 20 år. Som referens modellerades även ett Chicago regn (CDS). Med hjälp av en MIKE21 hydraulisk modell, simulerades ett stationärt scenario och fyra rörelseriktningar för varje empirisk hyetograf. Resultaten visade att de empiriska regntyperna skapade översvämningar med 20-50% lägre vattendjup än CDS regnet. Att modellera rörelsen resulterade i 4-20% lägre vattennivåer jämfört med respektive stationär scenario. I några enstaka tillfällen, i en av evalueringspunkterna, skapade de rörliga scenarierna större resultat, med lite över 1% i det största fallet. Det drogs slutsatsen att konceptet av areal reduction genom molnrörelse verkar vara korrekt och skulle kunna hjälpa att förbättra sättet att modellera regn generellt, men också specifikt för skyfalls scenarier med korta varaktigheter över urbana avrinningsområden. Man kom ytterligare till slutsatsen att framtida studier i samband med de fysiska processerna i regnceller skulle kunna användas för att höja noggrannheten av ytreducering av nederbörd för mer realistiska hydrauliska modeller, som i sin tur kunde minska överdesign.
40
Kim, Joseph. "Enhancing Coastal Flood Resiliency in Canada Through Hazard and Life Safety Assessments." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41414.
Анотація:
Home to the world’s longest coastline, Canada has experienced devastating economic
and social from coastal flooding events. While there have been a variety of mitigation
methods employed over the years to increase a community’s resistance to coastal
hazards, it is unrealistic to think that there exists a solution to guarantee a community’s
safety under all possible flood hazards. Instead, the community’s efforts to raise their
resistance to flood hazards should be augmented with careful planning and management to increase a community’s resilience to flood hazards, allowing them to recover quickly after a natural disaster. The first step in elevating a community’s resilience is to better understand the expected hazards that it may experience.
This thesis presents two unique case studies to better understand the flooding hazards present on the Canadian coastline. A large-scale numerical model that accounts for the presence of ice was developed to investigate storm surges in Canada’s western Arctic. It was found that the quality of the climatic forcing data used, ERA5, was poor in capturing peak wind speeds, but could be compensated for by using elevated wind drag coefficients. The use of non-traditional high-water marks such as driftwood lines were validated and were shown to significantly alter expected flood return periods compared to the return periods estimated from only the incomplete tide gauge measurements present on the Arctic coastline.
The second case study extends the results of a tsunami hydrodynamic simulation on
Canada’s Pacific coastline through a life safety assessment. The performance between an agent-based and GIS-based approach to modelling tsunami evacuation were directly compared and were shown to yield different magnitudes in fatality rate and facility demand, but similar trends. Both models agreed on a mitigation option that can significantly reduce the loss of life during a tsunami.
41
Koide, Masafumi. "Significance of trace fossil Macaronichnus segregatis as an indicator of storm events in a foreshore deposit." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/145098.
Анотація:
Kyoto University (京都大学)0048
新制・課程博士
博士(理学)
甲第11332号
理博第2890号
新制||理||1431(附属図書館)
22975
UT51-2005-D83
京都大学大学院理学研究科地球惑星科学専攻
(主査)教授 増田 富士雄, 教授 瀬戸口 烈司, 助教授 前田 晴良
学位規則第4条第1項該当
42
Matar, Šadi Abdul Wahab. "Enhancing situational awareness and communication during flood crisis events using social media framework : the case of Bosnia and Herzegovina." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/14846.
Анотація:
The current thesis approaches the issue of using social media for the case of Bosnia and Herzegovina for the recurring flood crisis events. The current status of using and interacting with social media , through studying the literature of the previous facts and results towards using social media by governmental and public representatives have been investigated. Different experiences were found related to countries that are experiencing flood events and their uses of social media. On the other hand it was found that little or no information were presented for the uses of social media for crises events in Bosnia and Herzegovina case. It was found that the reasons for not having current implementation of a solution is related to the complex governmental structure that are present in the Bosnian state government, entities of Bosnia and Herzegovina, Brčko District, cantons and regions. Further investigations were initiated to identify the current uses, needs and obstacles towards the use of social media tools and services as a medium for increasing situational awareness and communication in Bosnia and Herzegovina. The considerations of the previous investigation were with respect to governmental complex structure and public needs. The results of the investigation managed to outline the current challenges with respect for each investigated sector. The outputs of the previous investigations have been used as inputs to direct and guide the system design of the proposed new system framework that is aiming for enhancing situational awareness and communication during flood crisis events using social media framework. The system design and functionalities have focused on providing sharing environment for the complex government structure and public needs with a direct focus on not distracting the current used structure and public ethnical segregations. The system framework has been tested and the reflection of governmental attitude and public results has been encouraging towards adopting this framework for future flood events in Bosnia and Herzegovina.
43
Noble, Samanthia Jean. "STORM INDUCED CHANGES IN TURBIDITY, CHLOROPHYLL, AND BRACHIONUS POPULATION DYNAMICS IN ACTON LAKE." Miami University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=miami1105465428.
44
Mendoza, Tinoco David. "Development and application of flood footprint analytical model in assessing economic impact to flooding events." Thesis, University of East Anglia, 2017. https://ueaeprints.uea.ac.uk/67843/.
Анотація:
This thesis presents a methodological approach, the flood footprint framework, to capture the total economic costs of flooding events, as some of the most damaging climatic disasters. Economic costs are constituted by physical destruction, and all cascaded disruptions caused by the direct destruction. The method uses the fundamentals of Input-Output modelling, which is founded on the conceptualisation of the circular flow of the economy, representing the complex transactions between producers and intermediate and final consumers, for each sector, in an algebraic array. The solution of the equations’ system allows quantification of direct and indirect impacts along the value chain from changes in final demand. The flood footprint model further extends to capture changes in production due to the distortions of the economic equilibrium caused by flooding events, and to simulate the economy’s recovery. Sources of flooding disruption within the model arise from capital constraints, disruptions to labour force, and behavioural changes in final consumption. The method was applied to four case studies. The outcomes support the lesson that losses from a disaster are exacerbated and disseminated to other economies throughout economic mechanisms, and those knock-on effects (or indirect damages) constitute a substantial proportion of total economic losses, where non-directly flooded sectors might be also severely affected. The main implications for adaptation strategies are the review of the dynamics of direct and indirect damages and to unveil vulnerable hotspots along the value chain. This would allow an efficient allocation of investment resources and minimisation of socioeconomic damages during post-flood economic recovery. The key contribution of this thesis is a comprehensive methodology for assessing the total economic impacts of flooding events, considering elements that had not been taken into account together before, by incorporating multidisciplinary techniques for evaluation and projection of future scenarios, and bringing the analysis to a multiregional (global) scale.
45
Ischen, Marc. "Using Two-Dimensional Numerical Models to Analyze Hydraulic Effects of Constricted Flows through the Rigolets Pass between Lake Pontchartrain and Lake Borgne." ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/922.
Анотація:
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.
46
Chan, Yuen-man, and 陳苑雯. "Field and laboratory studies of E. coli decay rate at a coastal beach with reference to storm events." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B4598864X.
47
Olsson, Jimmy. "The influence of storm movement and temporal variability of rainfall on urban pluvial flooding : 1D-2D modelling with empirical hyetographs and CDS-rain." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-387898.
Анотація:
Pluvial floods are formed directly from surface runoff after extreme rain events. Urban areas are prone to suffer from these floods due to large portions of hardened surfaces and limited capacity in the stormwater infrastructure. Previous research has shown that catchment response is influenced by the spatio-temporal behaviour of the rainstorm. A rainstorm moving in the same direction as the surface flow can amplify the runoff peak and temporal variability of rainfall intensity generally results in greater peak discharge compared to constant rainfall. This research attempted to relate the effect of storm movement on flood propagation in urban pluvial flooding to the effect from different distributions of rainfall intensity. An additional objective was to investigate the flood response from recent findings on the temporal variability in Swedish rain events and compare it to the flood depths produced by a CDS-rain (Chicago Design Storm), where the latter is the design practice in flood modelling today. A 2D surface model of an urban catchment was coupled with a 1D model of the drainage network and forced by six different hyetographs. Among them were five empirical hyetographs developed by Olsson et al. (2017) and one a CDS-rain. The rainstorms were simulated to move in different directions: along and against the surface flow direction, perpendicular to it and with no movement. Maximum flood depth was evaluated at ten locations and the model results show that storm movement had negligible effect on the flood depths. The impact from the movement was likely limited by the big difference in speed between the rainstorm and the surface flow. All evaluated locations showed a considerable sensitivity to changes in the hyetograph. The maximum flood depth increased at most with a factor of 1.9 depending on the hyetograph that was used as model input. The CDS-rain produced higher flood depths compared to the empirical hyetographs, although one of the empirical hyetographs produced a similar result. Based on the results from this case study, it was concluded that storm movement was not as critical as the temporal variability of rainfall when evaluating maximum flood depth.Pluviala översvämningar skapas från ytavrinning vid intensiva nederbördstillfällen. De uppstår ofta i urbana miljöer till följd av den höga andelen hårdgjorda ytor och ledningsnätets begränsade kapacitet. Forskning har visat att ett regnmolns rörelseriktning och hastighet påverkar avrinningsförloppet. Om molnet rör sig längs med flödesriktningen i terrängen kan en ökning i vattenlödet nedströms ett avrinningsområde uppstå. Denna effekt har visat sig vara störst om hastigheten hos regnmolnet och vattenflödet är likvärdiga. Ytterliggare en faktor som påverkar avrinningsförloppet är hur regnintensiteten är fördelad över tid. Olsson et al. (2017) har tagit fram fem empiriska regntyper som speglar tidsfördelning inom ett Svenskt regntillfälle. Inom översvämningsmodellering är det vanligt att använda ett så kallat CDS-regn (Chicago Design Storm), vilken har en given tidsfördelning. Med anledning av detta är det intressant att jämföra översvämningar genererade av ett CDS-regn och av de empiriska regntyperna. Syftet med denna studie var att utreda hur regnmolns rörelse påverkar urbana pluviala översvämningar med avseende på vattendjup, samt att jämföra denna påverkan med effekten från olika tidsfördelningar av regnintensiteter. En kombinerad dagvattenmodell (1D) och markavrinningsmodell (2D) av en mindre svensk tätort användes för att simulera olika regnscenarier. De fem empiriska regntyperna och ett CDS-regn simulerades med en rörelseriktning längs med, emot och vinkelrätt i förhållande till flödesriktningen. Även scenarier med stationära regnmoln simulerades. Maximala översvämningsdjup utvärderades i tio punkter spridda över hela modellområdet. Resultatet från simuleringarna visade att regnmolnets rörelse hade försumbar påverkan på översvämningsdjupen. De olika tidsfördelningarna av regnintensitet hade däremot betydande påverkan på de maximala översvämningsdjupen. Som mest var det det maximala översvämningsdjupet 1.9 gånger större beroende vilken regntyp som användes som indata. CDS-regnet genererade i regel de största översvämningsdjupen, även om utfallet från en av de fem empiriska regntyperna var förhållandevis likvärdigt. Regnintensitetens tidsfördelning var därmed en kritisk parameter vid den hydrauliska modelleringen av urbana pluviala översävmningar, till skillnad från molnrörelse som hade försumbar påverkan.
48
Briel, Annemarie. "Hydrological Modelling at Road Structures in a Changing Climate and Landuse." Thesis, KTH, Mark- och vattenteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171827.
Анотація:
An increase in the frequency and intensity of storm events is predicted by numerous climate researchers for the north of Europe. Not only this but also landuse change in form of clear-cutting can have an impact on the discharge of rivers and with that on road drainage structures. Extensive societal costs can be the consequences of blockage and underdimensioned structures. Hydrological models are powerful instruments that can be used to assess the future dimension requirements for road drainage structures especially in specifically vulnerable areas. In this thesis the hydrological model MIKE SHE was set up to study the discharge and water level at two pipe bridges and one culvert within the catchment of the river Hakerud in Västra Götaland, Sweden. Three scenarios were considered including a changing climate until 2050 and 2100 and a clear-cut scenario aiming to find out if the current design is sufficient for the future. This model can be used as an example model set-up for similar studies taking the recommendations of the experience gained in this thesis into consideration. For the Swedish Transport Administration further studies on this basis can contribute to decision making on the dimensioning of road drainage structures in the future to ensure a safe and robust infrastructural system.
49
Raath, Gideon. "The impact of high rainfall and flood events on Eucalyptus camaldulensis distribution along the central Breede River." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/97021.
Анотація:
Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: Eucalyptus camaldulensis Dehnh., or River Red Gum, is a commercially valuable yet recognised invasive alien plant (IAP) of riparian zones throughout South Africa. The invasive potential of E. camaldulensis is widely recognised, with specific regulations aimed at the management of E. camaldulensis. E. camaldulensis is known to use large amounts of water, reduce biodiversity, change river morphology and impact hydrological regimes of rivers. In the native range throughout Australia, E. camaldulensis displays a distinct relationship between rainfall, and flood events, for seed dispersal, germination and establishment, and consequently spatial extent, yet little is known about the relationships in the South African context. The aim of this project was to assess the impact of high rainfall and flood events on the establishment and distribution of E. camaldulensis along the Middle Breede River, between Worcester and Swellendam in the Western Cape, by establishing the current spatial extent of E. camaldulensis along the river, identifying flood events since 1950 and evaluating the impact rainfall and flood events had on the spatial extent thereof. Aerial imagery, rainfall, discharge and river level data was obtained dating back to 1980, as well as field data comprising of GPS-bounding of E. camaldulensis stands. Additionally, density measurements were obtained and interviews conducted with land users. Spatial analysis of aerial imagery, coupled with perimeter (GPS) data and density data were used to conduct spatio-temporal analysis, employing GIS and conventional statistical approaches to address the various objectives. Results indicated E. camaldulensis stands had a small overall increase in spatial extent since 1980. Flooding and rainfall events coincided with an increase in occurrence of E. camaldulensis with elevated river levels and frequent flooding, while spatial variation of this relationship was observed. The hydrological regime of the Breede River coincides with a slow increase in spatial extent of E. camaldulensis stands, but no affirmation of a positive real-world relationship was possible using the available data. Results further suggested, based on the current age class composition, that existing stands originated roughly during 1980, possibly due to commercial forestry related seeding into the river. Reduced fragmentation between stakeholders, educational programmes and improved reporting systems were recommended for improved IAP management within the area.
AFRIKAANSE OPSOMMING: Eucalyptus camaldulensis, of Rooibloekom (RB), is ‘n waardevolle kommersiële, maar erkende indringer plantspesie (IP) wat veral oewersones in Suid-Afrika indring. Die indringerpotensiaal van E. camaldulensis is welbekend, en spesifieke regulasies, gemik op die bestuur van RB en ander spesies is reeds aangeneem. E. camaldulensis is veral bekend vir sy hoë watergebruik, sy vermindering van biodiversiteit, sy vermoë om riviervorme te verander en sy algehele impak op die hidrologiese patroon van riviere waarmee dit in aanraking kom. In sy oorspronklike verspreidingsgebied in Australië toon E. camaldulensis ‘n bepaalde verhouding tussen reënval en vloedgebeurtenisse vir saadverspreiding, ontkieming en vestiging en derhalwe die ruimtelike verspreiding van die spesie; alhoewel hierdie verhouding in die Suid-Afrikaanse konteks steeds redelik onverduidelik bly. Die doelwit van hierdie studie was dus om die impak van hoë reënval en vloedgebeurtenisse op die ruimtelike verspreiding en vestiging van E. camaldulensis teenaan die Middel Breëde Rivier, spesifiek tussen Worcester en Swellendam, te evalueer. Hierdie doelwit was bereik deur die historiese ruimtelike verspreiding teenaan die rivier te meet, hoë reënval en vloedgebeurtenisse vanaf 1980 te identifiseer, en die huidige verspreiding en omtrek met GPS te meet. Digtheidafmetings, sowel as onderhoude met belanghebbendes teenaan die rivier was ook opgeneem. Visuele interpretatasie van lugfotos, sowel as omtrek (GPS) en digtheid-data was gebruik om ruimtelike analise uit te voer, deur die gebruik van GIS en konvensionele statistiese metodes, ten einde die doelwitte te evalueer. Resultate dui aan dat E. camaldulensis areas ‘n klein algemene groei getoon het sedert 1980. Hoë-reënval en gereëlde vloedgebeurtenisse het ook gepaard gegaan met ‘n groei van E. camaldulensis oppervlak, alhoewel hierdie verhouding ruimtelike variasie getoon het, met ‘n algemene groei patroon gemerk oor die volledige studietydperk. Ook geen stimulerende verhouding kon vanuit die beskikbare data bevestig word nie. Addisionele resultate het aangedui dat die verspreiding van E. camaldulensis ongeveer 1980 onstaan het, moontlik as gevolg van kommersiële bosbou-aanplanting en verwante saadverspreiding in die rivier vanaf daardie tyd. Aanbevelings ten opsigte van verbeterde indringerbestuur sluit in die beperking van huidige fragmentasie tussen belanghebbendes en betrokke verwyderingsorganisasies, addisionele onderrigprogramme sowel as die verbetering van terugvoersisteme.
50
Jacobs, Tennielle Lindsay. "A meteorological analysis of extreme flood events in the southern parts of the Eastern Cape, South Africa." Thesis, Rhodes University, 2017. http://hdl.handle.net/10962/50525.
Анотація:
Extreme flood events have been found to occur in the Eastern Cape Province of South Africa. The southern and south-eastern coastal regions are particularly susceptible to floods with daily rainfall records of up to 490 mm having been recorded here. In order to gain a better understanding of these floods, historical floods in the southern parts of the Eastern Cape have been analysed in this study. This study aimed to investigate the most extreme flood events in the history of the area and to analyse the surface observational data during the heavy rainfall events found, to contribute to the understanding of these heavy rainfall events. Seven case studies were investigated using NCEP/NCAR Reanalysis 1 data and surface observational data, to analysis the synoptic circulation and surface data tendencies during heavy rainfall events. All of the case studies that had synoptic data available showed to have a COL system present with the upper air low lying westward of the flood area. The surface synoptic situation presented an intense high pressure system lying south west or south of the country in the Atlantic Ocean between 35-45°S. Another key factor was a surface trough over the interior of the country, due to the COL, extending southwards to protrude off of the south or south eastern coastline east of the flood areas. The combination of these three systems colloquially referred to as a “Black South-Easter”, produced dangerous rainfall intensities when the winds were perpendicular to the coast. The results of the surface observations revealed temperatures increasing at night (against diurnal cycles) with increasing relative humidity preceding the heavy rainfall events. The pressure showed both increasing and decreasing trends during heavy rainfall events however in five of six cases a tight pressure gradient was present producing an influx of moist air into the flood area. Onshore winds were found to be of high importance in heavy rainfall events to bring moist air into the area. Wind speeds greater than 5m/s occurred during times of high rainfall intensities.