Dissertations / Theses on the topic 'Flood risk mitigation'

This thesis explores the reconciliation of economic development and flood risk mitigation on the Humber Estuary, England. As sea level-rise is increasing due to suspected anthropogenic climate change, the Environment Agency has taken a lead role in mitigating flood risk on the Humber estuary through the process of governance. However, in trying to balance sustainable economic development with flood risk mitigation, the Environment Agency has experienced considerable difficulty in engaging local and regional businesses within the governance process. Analysis has found that although the overall importance of managing flood risk for businesses is reported to be greater in the present and the future than in the past, it remains more important for businesses which have previous experience of flooding than those which do not. Knowledge does not appear to transfer easily between different flood events, with concerns about recent pluvial flooding not percolating into risk perceptions concerning flooding from sea water. More alarmingly, businesses which have received flood risk information from the Environment Agency were found to have lower perceptions of the importance of flood risk management that those who had not, indicating a mismatch between scientific and lay knowledges. Without an understanding of how businesses perceive flood risk and how this affects participation within a governance process, the full engagement of the private sector within flood risk mitigation governance remains unlikely, therefore jeopardising sustainable economic development objectives on the Humber.

The importance of hydraulic structures has become an essential mitigating mean for floodsthat occur more often due to climate change. Thus, the importance and safety of flooddischarge tunnels has promoted further studies and experiments on the topic to mitigatedamages, such as cavitation that arise because of high speed flows.After an experimental study on a physical model was carried out on the flood discharge tunnelin Zipingpu Water Conservancy project, a CFD model was designed and simulated in thecommercial software ANSYS Fluent. The simulations aimed to evaluate and examine the riskfor cavitation in the tunnel, examine the design problems of the structure and analyse theinstalled aerators for the mitigation of cavitation. Moreover, using CFD models as acomplementary form to physical models was analyzed.A three dimensional geometry of the discharge tunnel was built in ANSYS Spaceclaim and themesh conducted with ANSYS mesh generator. The known boundary condition such as thedesign flow conditions, velocity inlet, pressure inlets and pressure outlet were set. For themodel a multiphase VOF scheme with RANS approach, k-ϵ turbulence model and a standardwall function was set.The results from the initial simulations showed that the discharge tunnel was under cavitationrisk, since the recorded cavitation index in the tunnel was below 1.8. After having revised thelayout of the aerators in order to mitigate cavitation risk, the results from the simulations withadded aerators were sufficient to mitigate the risk as the cavitation index was still below 1.8.The results for the cavitation index remained unchanged even in the simulated models with adifferent solver setup that were used in the comparison with the experimental data in order tovalidate them.As a conclusion, it was recommended that the tunnel design has to be revised and improvedby adding more aerators and air vents to mitigate the cavitation risk. Furthermore, more studieson the discharge tunnel or similar tunnels with similar conditions should be carried out in orderto validate the results of this study and determine if numerical models are preferable to physicalmodels

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

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

This study aims to explore the possibility of environmental justice as social consensus and an institutional framework to reduce socioeconomic differences in natural disaster vulnerability through a case study of flood risk management in Johnson Creek, Portland, Oregon. First, by analyzing institutions, policies, and currently ongoing flood mitigation projects, this study investigates how federal and local governments are addressing and responding to current flood problems. Second, through flood expert surveys and GIS spatial analysis, this study examines various factors that contribute to communities' susceptibility to flood risks, and whether there exist spatial differences between physically and socioeconomically vulnerable communities within the Johnson Creek area. Lastly, this study conducted comparative analysis of perceptions using Q-methodology to explore the diverse range of meanings and understandings that flood experts and urban practitioners construct in relation to the dilemmas of environmental justice in flood mitigation practice. The findings of this study indicate that institutional blind spots and barriers in natural disaster mitigation policy and planning can be generated by flood experts' and urban practitioners' different understandings of vulnerability, different interpretations of human rights, and different perspectives on the extent of institutional responsibility to assist socioeconomically vulnerable populations.

Heavy precipitation events are expected to increase in the future, due to climate change. This predicted change will increase the risk of flooding, especially in urban areas. To mitigate these challenges and support a sustainable urban development, Nature-based solutions (NBS) can be used as a flood risk reduction measure. The NBS wetlands and constructed wetlands, composed of ponds, canals and ditches, are commonly used solutions which are multifunctional and primarily provides flood regulatory services, water quality improvements and increased biodiversity. To reach the full potential of NBS, the location and design is crucial. At present planning practise, a user friendly and time efficient tool to investigate suitable locations within a catchment is missing, where the concept of connectivity has arisen as a useful approach. In this study, the NBS concept and the potential of wetlands for flood risk mitigation have been investigated. In addition, the connectivity of two study case catchments has been analysed by using the Connectivity Index (IC index) by Cavalli et al. (2013). The aim has been to evaluate whether the IC index can be used to find suitable locations for NBS. Further, the study seeks to investigate how the IC index can be integrated into NBS planning practice in order to create useful information for the decisionmaking process. To validate the IC index result, a comparison has been performed with earlier flood events, two hydrological models, Multi criteria decision analysis and spatiotemporal soil parameters. From the obtained result and analysis, preliminary solutions have been proposed for two case studies in Sweden and Portugal. The result shows that IC index is promising as an, early stage, first assessment tool in NBS planning practice which can be used in order to allocate areas suitable for NBS. To find the most beneficial location and the site-specific design, a deeper investigation of the site-specific conditions is required. Moreover, a successful implementation is dependent on a close collaboration between different stakeholders and expertise. Finally, this study shows that realizing the potential of NBS wetlands is essential to create sustainable urban development and liveable and attractive cities.

Shire of Murray has concerns regarding the negative impact that a 100 year flood could have on existing structures built before 1997. The increase cost in construction due to landfill has an adverse effect on development in Pinjarra. Feasibility of constructing a diversion channel at upstream of Murray River to attenuate the flood level from 1 in 100 year ARI to 1 in 50 year ARI, was investigated by Kiong (2003). The Murray River Water Surface Profile along three kilometres south of Greenlands Road was modelled. Flood damages on each flood occurrence were assessed and Average Annual Damage (AAD) was calculated. The AAD is used to estimate the monetary benefit against the construction cost of the diversion channel. Groundwater along Greenlands and Fauntleroy Drains was also modelled to determine the viable depth of the designed channel, as well as the analysis of backwater. The proposed channel is designed at different scenarios (invert level at breakout point, culvert or causeway design, and diversion channel variations). The benefit cost ratio of the proposed diversion channel is calculated. Other mitigation options are suggested including detention basins for structural measure, or building a new flood-proof township for non-structural measure.

Inondations qui se produisent dans les zones urbaines sont régies par une fréquence accrue. Structures de protection contre les inondations existantes démontrent ses inconvénients. Une des solutions est émouvant de culture du risque et de trouver l'équilibre entre la forme de l'utilisation des terres et de l'urbanisation grâce à des stratégies d'adaptation, d'atténuation, de prévention et intervention et de rétablissement. La nouvelle approche globale est basée sur le concept de résilience donner une nouvelle place pour le développement et la mise en œuvre de nouvelles approches en vertu de gestion des risques d'inondation (FRM) cadres existants. Ajout de résilience à la gestion des risques d'inondation est une première étape. Grâce à une gestion des risques d'inondation opérationnelle a pour la résilience des prestations. L'indice résilience Flood (FRI) est développé dans cette thèse est une approche unique pour l'évaluation de la résistance aux inondations dans les systèmes urbains avec la priorité principale de la structure du système lorsque l'évaluation se fait sur les micro et méso échelle et sur la dimension du système lorsque la résistance aux inondations est évaluée sur macro échelle. La réflexion est mise sur le développement de la méthode par l'évaluation de la gestion des risques d'inondation existants (FRM) cadres. Grâce à l'évaluation, il est possible de constater le niveau d'intégration et de mise en œuvre de l'élément essentiel du risque d'inondation. La méthode développée pour l'évaluation de la résistance aux inondations est potentiellement applicable à tout système urbain à une échelle géographique
Floods that happen in urban areas are governed by increased frequency. Existing flood defence structures demonstrate its downsides. One of the solutions is moving to risk culture and finding the balance between the shape of land use and urbanization through adaptation, mitigation, prevention, and response and recovery strategies. The new holistic approach is based on resilience concept give a place for new development and implementation of new approaches under existing flood risk management (FRM) frameworks. Adding resilience to flood risk management is a first step. The Flood Resilience Index (FRI) is developed in this thesis is a unique approach for evaluation of flood resilience in urban systems with the main priority on system structure when evaluation is done on micro and meso scale and on system dimension when flood resilience is evaluated on macro scale. The main reflection is on the development of method by evaluation of existing flood risk management (FRM) frameworks. Through evaluation, there is a possibility to notice the level of integration and implementation of crucial element of flood risk. The developed method for evaluation of flood resilience is potentially applicable to any urban system of any geographic scale. Connections and dependences between main city elements and natural hazards (in this case urban flooding process) are defined. With its implementation, social, economical, political and cultural relations between cities will be more visible and better established and flood risk management well implemented

This thesis examines the relationships between rising water levels, vulnerable land, and sedimentation within the Chesapeake Bay watershed. Climate induced sea level rise threatens low lying coastal land, especially in regions of continuing subsidence such as the Chesapeake Bay. Alterations to shorelines over time have impacted the ability of coastal landscapes to capture and build up sediment, exposing them to continual erosion. The low lying neighborhood of Belle View along the Potomac River is the focus of the investigation due to its vulnerability to flooding and its cultural and ecological connections to the adjacent landscapes of Dyke Marsh and the George Washington Memorial Parkway. Through careful placement of breakwater infrastructure, sediment will build over time as the water rises, mitigating the effects of coastal flooding in this region. Alterations to the landscapes of the marsh and parkway allow for their cultural and recreational values to be strengthened over time as the landscape adjusts to the rising sea level.
Master of Landscape Architecture
Climate change, or the belief that human activity is altering the earth's climate, is projected to increase the occurrence of flood events due to water levels rising over time from glaciers melting. Previously, shorelines have been hardened with levee or seawall infrastructure to creates a barrier between the water and developed land. Hardened shorelines may increase water velocity and reflect wave energy in riverine landscapes, consequentially disturbing natural shorelines. This disturbance leads to the gradual loss of sediment over time and therefore a loss of ground elevation. When landscapes lose elevation, they become more vulnerable to rising water levels and flooding. This relationships between shoreline types, sedimentation, rising water, and vulnerability inspired me to discover and design a threatened landscape that would capture sediment within the river's water column to build elevation over time and protect the adjacent development from rising water. The area encompassing the low lying neighborhood of Belle View, Dyke Marsh, and the George Washington Memorial Parkway along the Potomac River is the focus of the investigation due to its vulnerability to flooding. With a careful understanding of sediment capture infrastructure dynamics, the design introduces breakwaters on the site to allow sediment to build over time as the water rises. This research and design thesis demonstrates a strategy to create landscapes that will evolve over time to mitigate future flooding events and create more resilient landscapes.

碩士
國立臺北大學
不動產與城鄉環境學系
94
Although the key instrument for government to prevent flood attacking mainly depends on engineering structures. The issue of how to appropriately employ non-structural measures for natural hazard reduction is an essential task for the policy evaluation. Land-use planning or zoning framework is often considered as a useful tool in reducing flood risk. Unfortunately, for lack of a well established mechanism to complement or compensating the regulatory taking behaviour, it is difficult for government complete using land-use regulation as an instrument in natural disaster mitigation. The transfer of development rights (TDR) is a method that both adopts the market mechanism and can be introduced for internalizing the external costs of land-use behaviour. Thus, the purpose of this article is to assess the effects when that the transfer of development rights is implemented for the flood risk management. The findings can provide essential information for supporting the decision makers in the evaluation of the appropriateness of applying TDR for hazard mitigation and risk management. We illustrated a case study over the Dahan River basin in Fuhsing, using a model developed by using environmental economic theory. We calculated the optimal amounts for development rights transfer under various hypothesized regulatory levels. The results showed the changes of flood risk owing to various hypothesized regulatory standards. Further, several suggestions for decision-making and the application of TDR are also provided in the article.

Flooding poses one of the greatest natural hazard dangers to Canadians. As human populations increase and concentrate in areas vulnerable to floods, and uncertainty about future flood risk increases with the possibility of a changing climate, major urban communities, coastal settlements and communities located within floodplains are faced with an even greater risk of floods in the coming years. Canada's policies and practices towards flood control are best described as ad hoc, and have developed over the years in response to experiences with floods. No national scale flood damage reduction program exists, and there is currently no opportunity for Canadian homeowners to purchase flood insurance. This study specifically examines how a national mitigation strategy, focused mainly on non structural techniques could help decrease damages from floods in Canadian communities. The strategy proposed here is theoretically based in EPC and IBC suggestions for a greater national mitigation strategy, as well as IDNDR research, and federal, provincial and municipal goals for sustainable development and sound land use planning objectives. Ideally, a successful non structural flood mitigation strategy for Canada would address issues at the national scale, yet be implementable at the local level in accordance with community needs, risk characteristics, and local expertise. The strategy proposed here would maximize the efficiency of federal resources and private industry as well as allow local expertise and existing mitigation schemes to be formalized, bolstered and improved. There are three major components of the non structural flood mitigation strategy. Risk avoidance measures such as early warning systems, land use and resource planning and ecological conservation all work towards reducing the chances of a dangerous flood occurring. Risk spreading measures help communities deal with flood risks by improving equity and accountability, they include tax incentives, disaster financial assistance, and flood insurance. Lastly, vulnerability reduction measures help reduce damages if a flood were to strike, and these include enforcement of building codes and the maintenance of existing protective infrastructure. An integrated, non structural flood mitigation strategy would require basin-wide cooperation between all levels of government, citizens and the private sector. This strategy is also an opportunity for communities and individuals to meet goals of environmental conservation and sustainable development. The focus in this study lies on the mitigation tools, although it is the overall process of inserting the premise of mitigation into all land use and planning decision making processes that will be the key to successful flood mitigation strategies in Canadian communities.

The role of local level governance and participation in managing climate disasters is gaining precedence in global and local (South African), discourse. In recent years, floods have caused major disasters in urban centres around the world. A lack of disaster preparedness in developing countries has resulted in much damage in urban environments. Such damage will have long-term repercussions for governance, communities and the natural environment. Heavy rainfall events are projected to become more intense and frequent due to climate change, and many recently affected areas may consequently face increased risk of flooding in future. A range of factors influences the ability to manage disasters through all phases of preparation, response and recovery at the local level. The objective of this research is to investigate the extent to which a range of factors interacts to either enhance or limit resilience to flood disasters at the local scale. This is explored through triangulating the results of three investigations into both physical and social factors of understanding and managing flood disasters. The case study of flooding in Ekurhuleni Metropolitan Municipality (EMM) in South Africa, with specific focus on the Atlasville suburb, provides the basis of the research. The research uses a multidisciplinary approach to examine disaster management, which includes perceptions and non-technical information in addition to statistical analysis. Flooding in the EMM is used as a case study to investigate how a multiple-perspective understanding of rainfall and flood events can help communities and municipalities better plan for and manage disaster events. This research argues that in order to understand the nuances of flood disasters, a combination of different sets of knowledge is necessary, as each set of knowledge plays an important part to inform how flood risks can be managed.