Dissertations / Theses on the topic 'Flooding, Urban areas'

This research is the first of its kind in Bangladesh. It focuses upon flood losses in urban sectors of the country’s economy. The broad research question is whether flood impacts in urban or non-agricultural sectors are important in Bangladesh, given that it is currently an agricultural economy. The research examines the applicability of existing urban flood impact assessment methods, and develops methods suitable to Bangladesh. An important aim is to accumulate a knowledge base of flood impacts in the urban or non-agricultural sectors. With appropriate modifications, flood loss assessment methods generated in developed countries may be applied in a developing country such as Bangladesh. However, the ‘synthetic’ approach of constructing standard potential flood loss data sets is not feasible. Using surveys of actual floods, the construction of reasonably high-quality ‘average’ data sets proves to be feasible, as floods in Bangladesh are not sparse. The construction of data sets through regressions is preferred because it is more realistic and cost-effective. The widely used unit-loss model is found to be applicable to appraisals of urban protection schemes. However, the successful application of the model depends on the accuracy of land use and land level survey data, and detailed hydraulic and hydrological information. In Bangladesh, this form of modelling is found to be suitable for project appraisals ranging from small to intermediate scale. Some methods, however, are suitable for up to full scale appraisals. The major achievement of the research is that flood loss potential for urban Sectors has been thoroughly investigated, providing flood loss data of a significantly higher quality that are available hitherto in Bangladesh. In providing these data the research is a significant advance upon the methods recommended within the existing FPCO Guidelines for project assessment, and those used in recent FAP urban protection studies. The assessments methods developed and the standard damage data sets constructed may now be used to appraise urban protections, which will also facilitate evaluation of agricultural projects more comprehensively through incorporating non-agricultural losses that can be averted in such schemes. The research reveals that the urban sectors of the economy are highly vulnerable to floods. Induced by rapid urbanisation, potential urban flood losses in Bangladesh are expected to be progressively more important in the future. Poverty is found to be fundamental to flood hazard vulnerability: the poorest of the poor have the most to lose in proportional (to value) terms. A high priority can now be given to protect urban and commercial centres in Bangladesh. Given limited resources in Bangladesh, low-cost non-structural measures are also important. Local knowledge and informal flood warning systems have a positive bearing on resilience building. Community cohesion, together with family kinships, are also important in this respect. Different types of floods (e.g. river flood, flash flood and tidal surge) are associated with differential impacts: tidal floods prove the most destructive. Flood impacts at the macro-level are not found to be as severe as those at the micro-level. The findings suggest that floods deepen poverty and help widen the income gap between rich and poor. This problem poses further research questions regarding ‘equity’ and sustainable development. Project appraisal methods using conventional ‘economic efficiency analysis’ need to be re-calibrated in order to confront the problems relating to inequity and sustainable development, especially in the context of existing socio-economic conditions in Bangladesh.

The research presented in this Thesis aims at defining the strengths and weaknesses of an Improved 1D/1D model when compared with a more accurate 1D/2D model. Although both coupled-models (sewer/surface) solve the St.\ Venant equations in both layers, the latter uses a higher approximation (2D two-dimensional) on the surface layer. Consequently, the 1D/1D model is computationally more efficient when compared to the 1D/2D model, however there is some compromise with the overall accuracy. The hypothesis is that "The inundation extent of urban flooding can be reproduced by 1D/1D models in good agreement with the 1D/2D models if the results are kept within certain limits of resolution and under certain conditions". The Thesis starts by investigating ways of improving an existing 1D/1D model to rival the more accurate 1D/2D model. Parts of the 1D/1D model code are changed and new algorithms and routines implemented. An innovative GIS tool translates the 1D output-results into 2D flood-inundation-maps enabling a thorough comparison between the two models. The methodology assures the set-up of two equivalent models, which includes a novel algorithm for calibrating the 1D/1D model vs.\ the 1D/2D model results. Developments are tested in two distinctly different case studies of areas prone to flooding. The conclusion is that the 1D/1D model is able to simulate flooding in good agreement with the 1D/2D model; however, it is found that features such as topography, density of the urbanised areas and rainfall distribution may affect the agreement between both models. The work presented herein is a step forward in understanding the modelling capabilities of the analysed coupled-models, and to some extent may be extrapolated to other models. Research is growing in urban flooding and this work may well prove to be a strong foundation basis for future research.

Climate change increases the intensity, duration and/or frequency of climate-related events such as floods. These events can become major disasters when they occur in vulnerable urban regions. Coastal resort towns and tourism cities can be particularly vulnerable to these disasters due to their geography and highly variable seasonal populations. Moreover, despite the increasing risk, urban development in many coastal cities continues to take place on low-lying land, aggravating existing exposure and vulnerabilities. Resilience has become a popular concept in urban planning and policy especially in the context of adaptation to climate change but it is not an easy concept to understand and articulate in policy goals. These difficulties, coupled with the increasing risks associated with climate-related disasters, call for a reconsideration of the concept and its application in the field of urban planning. Responsibility for building resilience usually falls to local governments but they may lack the necessary resources and struggle to respond. In Australia, there is also a lack of a consistent policy direction across different local government areas.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>Griffith School of Environment<br>Science, Environment, Engineering and Technology<br>Full Text

<p>This MSc thesis contributes with new information on how vulnerability to tropical cyclone (TC) induced flooding has evolved at two coastal lowland study sites in the town of Corinto in Nicaragua over a period of 50 years. The research was done through rain station data analyses, semi-structured interviews, and focus group discussions. Analyses of changing poverty, human mobility, housing conditions, and occurrence of flood-related diseases were used as additional indicators supporting the overall vulnerability assessment.</p><p>The recent increase in the North Atlantic TC activity can not be seen in the data from Corinto. The both studied neighborhoods built on dump-sites and mangrove marsh have clearly become less exposed, less sensitive, and more resilient to external stress brought by TCs. These two sites have been developing into different directions since one has reached a more prosper status whereas the other is still rather marginal. The former has been supported by the local government while the latter has been growing in a less regulated way.</p><p>This thesis suggests that there are coastal communities in developing countries, which are able to cope with and adapt to extreme climate events even though this kind of vulnerability has been predicted to increase due to global warming.</p>

A two-dimensional numerical model (RiverFLO-2D) has been enhanced to simulate flooding of urban areas by developing an innovative wet and dry surface algorithm, accounting for variable rainfall, and recoding the model computer program for parallel computing. The model formulation is based on the shallow water equations solved with an explicit time-stepping element-by-element finite element method. The dry-wet surface algorithm is based on a local approximation of the continuity and momentum equations for elements that are completely dry. This algorithm achieves global volume conservation in the finite element, even for flows over complex topographic surfaces. A new module was implemented to account for variable rainfall in space and time using NEXRAD precipitation estimates. The resulting computer code was parallelized using OpenMP Application Program Interface, which allows the model to run up to 5 times faster on multiple core computers. The model was verified with analytical solutions and validated with laboratory and field data. Model application to the Malpasset dam break and Sumacarcel flooding event show that the model accurately predicts flood wave travel times and water depths for these numerically demanding real cases. To illustrate the predictive capability of the enhanced model, an application was made of the city of Sweetwater flooding in Miami-Dade County, FL caused by the Hurricane Irene. The simulation starts with dry bed and rainfall is provided by NEXRAD estimates. Integrating NEXRAD rainfall estimates, developing a novel dry-wet area algorithm and parallelizing RiverFLO-2D code, this dissertation presents a proof of concept to accurately and efficiently predict floods in urban areas, identifying future improvements along this line of research.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO<br>PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO<br>Esta dissertação busca enfatizar a necessidade de adaptação à mudança climática principalmente em zonas costeiras de baixa altitude (LECZ) com o objetivo de destacar a importância dos espaços livres públicos em estratégias de adaptação de áreas urbanas costeiras sujeitas à inundação no contexto da mudança climática. Estas áreas são consideradas as mais vulneráveis devido à grande concentração de população, riqueza e centros comerciais em risco de inundações costeiras e terrestres, além de apresentar um alto grau de degradação do subsistema natural, por causa das atividades humanas e influências marítimas. O contexto da mudança climática agrava o grau de vulnerabilidade, ao projetar um aumento na intensidade das chuvas e tempestades, a temperatura média, e elevação do nível do mar. Em paralelo, o rápido crescimento populacional forma megacidades costeiras reproduzindo um modelo de ocupação insustentável. Assim, este trabalho pretende contribuir para a discussão de soluções práticas para adaptar as zonas costeiras para os efeitos das alterações climáticas que incorporam o espaço livre público, como um aspecto fundamental da adaptação. Somando à adaptação, pode-se observar outros ganhos em termos de bem estar humano e promoção de melhoria da qualidade de vida das populações urbanas. Para apoiar o argumento dessa dissertação, usa-se exemplo de design urbano que utiliza espaços livres públicos como estratégias de adaptação - Londres, Nova Orleans, Nova York, Roterdão, Cho Hi Minh City, Jakarta e Melbourne.<br>This thesis aims to investigate the role of open public in adaptation coastal areas subject to flooding to the impact of climate change by emphasize the need to adapt to climate change mainly in coastal areas of low altitude (lecz). These areas are considered the most vulnerable due to a large concentration of population, wealth and commercial centers at risk of inland and coastal flooding, and a high degree of degradation of the natural subsystem because of human activities and maritime influences. The context of the climate change aggravates this state of vulnerability by increasing the intensity of rainfall and storms, average temperature, rising sea level, parallel to rapid population growth forming coastal megacities. Thus, this thesis aims to contribute to the discussion of practical solutions to adapt coastal urban areas to the effects of climate change incorporating public space, as a fundamental aspect of adaptation. Adding to adapt, can be observed other gains in human well-being and promote improvement of the urban population quality of life. To support the argument this thesis uses example of urban designs that utilizes open public spaces as strategies for adaptation - London, New Orleans, New York, Rotterdam, Cho Hi Minh City, Jakarta and Melbourne.

O presente trabalho apresenta a carta de risco a movimentos de massa e enchentes em escala de semidetalhe (1:10.000) realizado na bacia hidrográfica das Furnas inserida no Município de Santana de Parnaíba-SP. Na bacia hidrográfica das Furnas foram identificados os inventários das ocorrências no bairro Cidade São Pedro, entre o período de 2002 a 2014 foram registradas 70 ocorrências provenientes dos processos de movimentação de massa e eventos hidrológicos (enchentes), causando prejuízos sócio-econômicos e ambientais. A partir desse conhecimento, essa pesquisa objetivou investigar a compartimentação da aptidão física e identificar os tipos de uso e ocupação da terra que atuam diretamente na potencialidade do risco. Na carta de risco a movimentos de massa e enchentes prepondera a avaliação de dano potencial à ocupação, determinado segundo diferentes graus de risco, resultante da conjugação da probabilidade de ocorrência de manifestações naturais ou induzidas e das consequências sociais e econômicas decorrentes. Para este documento, foram estabelecidos cinco unidades homogêneas correspondentes à aptidão física e às restrições para o assentamento urbano, definidas como área de instabilidade ocorrente, área de instabilidade ocorrente de forma pontual, área de instabilidade potencial iminente, área de instabilidade potencial e área de instabilidade potencial com cobertura vegetal. Os resultados da pesquisa podem subsidiar o poder público no planejamento urbano, direcionando as tomadas de decisões referente ao parcelamento do solo possibilitando à redução das potencialidades de risco, bem como a prevenção de medidas de mitigação dos eventos.<br>This study presents the mass movement and floods risk map of the Furnas basin, Santana de Parnaíba - SP in a semi-detailed scale of 1:10.000. There was identified, in the Furnas basin, the inventories of mass movement and flood occurrences at Cidade São Pedro neighborhood. In the period between 2002 and 2014. Were recorded 70 occurrences of mass movement processes and hydrological events (floods), causing socio-economic and environmental damage. Based on this records, this study investigated the partitioning of physical aptitude and identified the types of use and occupancy of land that act directly on the potential risk. The mass movement and floods risk map preponderates assessing potential damage to the occupation, determined by different risk levels, resulting from the conjugation of the probability of occurrence of natural or induced events and social and economic consequences arising. For this document, there was set out five homogeneous units corresponding to the physical aptitude and urban settlement restrictions, and defined as occurrant instability area, pontual occurrant instability area, imminent potential instability area, potential instability area and potential instability area with vegetation coverage. The research results may help guide the government in urban planningby directing decision making regarding the land subdivision allowing the reduction of potential risk as well as the prevention and adoption of mitigation actions to the events.

This thesis investigates the effectiveness of Low Impact Development Infrastructure (LIDI) and Green Infrastructure (GI) in reducing flooding resulting from heavy rainfall events and sea-level rise, and in improving stormwater quality in the City of Miami Beach (CMB). InfoSWMM was used to simulate the 5, 10, and 100-year, 24-hour storm events, total suspended solids (TSS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) loadings, and in evaluating the potential of selected LIDI and GI solutions in North Shore neighborhood. Post-development results revealed a decrease of 48%, 46%, and 39% in runoff, a decrease of 57%, 60%, and 62% in TSS, a decrease of 82%, 82%, and 84% in BOD, and a decrease of 69%, 69%, and 70% in COD loadings. SWMM 5.1 was also used to simulate the king tide effect in a cross section in Indian Creek Drive. The proposed design simulations successfully demonstrated the potential to control flooding, showing that innovative technologies offer the city opportunities to cope with climate impacts. This study should be most helpful to the CMB to support its management of flooding under any adaptation scenarios that may possibly result from climate changes. Flooding could be again caused as a result of changes in inland flooding from precipitation patterns or from sea-level rise or both.

<p>The main objective of this study is to understand and asses flood risk perception among people living in Msimbazi Valley in Das es Salaam, Tanzania. Many of the people I have interviewed are experiencing flooding every year but it is rarely considered disastrous. Looked at individually they may not be disasters but cumulatively they may be. The rapid urbanisation, in this part of the world, forces people to live on hazardous but central land because of the livelihood opportunities available there. The government and the local communities are well aware of the risk of floods in the area and are considered as a serious threat to the families. People are still living in these areas because they find the benefits big enough to make up the risks.</p>

The University Area (UA), a low-income, unincorporated neighborhood in Hillsborough County, Florida, is a site of sustainable redevelopment by the local government and nonprofit organizations. Throughout the past decade, the transitions in local and state political climates have significantly impacted the residents’ ability to advocate for infrastructural and environmental improvement to the site. This thesis discusses the findings of a research project dedicated to exploring resident perspectives of stormwater management, infrastructure, and the redevelopment currently occurring the University Area. Drawing from theoretical concepts in political ecology, environmental justice, and the interplay of agency and structure, this research investigates the impacts of flooding on the UA’s residents and infrastructure; specifically, the ways it affects the population’s interaction with their environment. Data were collected using a mixed methods approach including participant observation; semi structured interviews with residents, developers, and community organization employees; ground truthing the area to verify the location of the stormwater drains present in a selection of the UA; a historical review of the area’s land use; and analysis of critical environmental justice databases. Findings indicate that flooding in the University Area is related to historical oppressive housing strategies against minority and low-income populations. Results found that flooding in UA is caused by a combination of faulty infrastructure (impervious surfaces and a subpar, unmaintained stormwater system), increasing rain events (climate change), and the lack of municipality support (power dynamics). The oppressive power dynamic present in the relationship between the residents and their respective property owners and the county municipality services exacerbates problems with flooding. Redevelopment plans in the University Area must address the effects of historical marginalization and disenfranchisement of the current residents with respect to housing segregation and lack of municipality support. Without these considerations, the cycle of disenfranchisement faced by the current residents of the UA will likely continue and worsen over time.

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.<br>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.

Flooding of cities is a serious threat to the development and life of people. Urban areas at risk of flooding are particularly affected by the worsening effects of deluge, which is observed everywhere in the world. Floods are subject to urban areas of all types ‒ from small towns to large cities and megacities.

碩士<br>國立成功大學<br>建築學系<br>103<br>Due to the effects of worldwide environmental changes, natural or artificial causes and urban overdevelopment, the odds for urban areas to suffer from flood risk is on the rise. Under the idea of living around water resources, the increasing urbanization and high density development has reducing the amount of available spaces in urban areas and limiting other methods for flood to be resolved naturally are the main issues with the urban areas today. The urban flood risk revolves around our everyday lifestyle, architectural design structures and the natural surroundings, the relationship between these three important aspects should not be underestimated. This study will demonstrate an example of flood control architect structural plan that can be adapted to today's climate changes, natural causes and other architectural restrictions. Furthermore impels the coexistence and symbiosis between urban spaces, natural surroundings and our everyday lives. This research will examine the flood response programs and actions taken by urbanized Taiwanese communities through a series of related article reviews, from community size level flood response plan to a single flood control architectural design. In addition, the paper oversees Taiwanese present flood related policies and architectural restrictions. Followed by recommendations for new architectural restriction policies to the existing one. In the process of discussing the new flood control design, the paper can point out the three main categories within this topic: Disaster Adaption, Low-Carbon Sustainability and Urban Greening. By collecting and analyzing international and domestic urban area architectural cases, one can further outline additional five environmental related architectural terminologies, they are Urban Context, Terrain Sculpting, Unique Style/ Established Landmark and Buried Massing. These five architectural terminologies and three categories along with urban landscape are the important elements of a good flood control construction. Lastly, this study will demonstrate a flood control architectural construction based on the Tainan Kun-Shan community surroundings and circumstances. Take such demonstration as a example of flood response architectural design and its feasibility to other Taiwan urban areas. Through multiple design practice and competitions, new architecture typologies are explored. Flooding response planning are simulated with Kun-Shan community, Yong-Kang Dist as the site to demonstrate the feasibility of this framework. Scenarios of sustainable, disaster preventing urban area environments are proposed in attempt to achieve the symbiosis of natural and artificial scenery. This “Architectural Design for Flooding Response in Tainan Urban Areas” of this research concludes 3 major targets, 8 area strategies, and 10 architecture strategies. This may provide a better basis of operation direction for future planning and designs of Urban areas in Tainan.

碩士<br>國立臺灣科技大學<br>電子工程系<br>103<br>Vehicular Ad-hoc Networks(VANETs) have many kinds of applications such as increasing driving safety, decreasing traffic congestion and offering better driving services.When the vehicle has a service request,it broadcast its request to roadside unit by broadcasting and register. However,when there are multiple road side units selectable, how to effectively pick out a road side unit in the network topology can have a stable connection environment has become an important issue.However,when there are multiple roadside units which can be selected,how to effectively pick out a road side unit which has a stable connection environment under the network topology has become one of an important issue.The traditional method, Flooding, provides a good reachability but it may causes “Broadcast Strom Problem”, resulting in bandwidth abusing. Depend on if it can broadcasts the packets successfully that will affect the accuracy of road side unit which was selected in this study.Therefore, we propose the restricted flooding whcich ensures bidirectional broadcasting on any roads, such that it can be suitable for any scenarios. The simulations are conducted with network simulator NS2. The simulation results show that the proposed scheme can achieve high Packet Delivery Ratio.

碩士<br>國立臺灣大學<br>生物環境系統工程學研究所<br>107<br>In recent years, the effects of climate change and extreme weather have caused more and more rainfall intensity, more and more flooding events, and the increased rainfall intensity to move the garbage and leaves on roads. If the garbage and fallen leaves block road drains, it will increase the probability of urban flooding events. This study analyzes urban flooding simulations with various methods of coupling one sewer flow model and one overland flow model. The runoff enters the sewer system by manholes and road drains respectively. The flooding simulation results show that the road drainage method has better evaluation results. However, there are still some errors compared with the observation data. Therefore, this study considers the blockage of road drains and sets the 0% to 100% clogging factors as the set value with reference to relevant literature. This study uses three kinds of road drain clogging scenarios for urban flooding simulation. 1. All road drains are not clogged, 2. All road drains are clogged, 3. road drains around road trees are clogged. And use Accuracy(ACC), Probability of Detection(POD), Precision or Predictive(PPV), Threat Score(TS) and the water level at the WL gauge to analyze which clogging scenarios have better urban flooding simulation results. In this study, the Muzha sub-catchment area of Wenshan District in Taipei City is selected as the research area. Two historical flooding events are used to evaluate the above scenarios. The best flooding simulation result is this scenario in 20% clogging factor of road drains around road trees.

碩士<br>國立臺灣大學<br>生物環境系統工程學研究所<br>102<br>In recent years, extreme rainfall events become more frequent due to global climate anomaly. The flood disasters are more serious especially in metropolitan because of its high population density and excessive development. Therefore, it leads to the increment of the flood risk. This research takes Wayaogou Drainage located in New Taipei City as the study area which is highly developed and selects four adjustment strategies based on the characteristics of urban areas to analyze flood mitigation. This study evaluates the mitigation performance of these four strategies separately by using the simulated results obtained from flood inundation modeling. The flood inundation model is verified by the flood event occurred on August 12, 2009 to check the numerical accuracy. The above selected adjustment strategies are building retention, green roof, permeable pavement and ecological detention pond, respectively. Two different rainfalls (5-year and 10-year return periods) are input into the flood inundation model to analyze the benefits and limitations of these four strategies. The simulated results show that the flood area reduced after applying the adjustment strategies. Among the four strategies, building retention can decrease the most flood area. Regarding the aspect of adaptation benefits (e.g. the ratio of reduction of flood areas to adaptation areas), the strategy of the ecological detention pond is more efficient than others. It can obviously reduce flood areas in its surrounding region. For 10-year return period rainfall, the peak discharge in channels will approach to the safety value and be prevented from overbanking by applying the selected strategies, except for ecological detention pond. Eventually, the contribution of the four strategies is presented in flood risk map. Through conducting these adjustment strategies, they all descend the flood risk and then ascend the flood resilience in Wayaogou drainage.

碩士<br>國立臺灣大學<br>生物環境系統工程學研究所<br>101<br>Recently, flooding hazard in urban areas becomes progressively serious due to climate variations and urbanization. In this work, Taichung metropolitan is selected to be a study area and the flood degree and damage are investigated according to its land-use change processes. The simulation model, coupled the 1-D river routing model, the storm water management model and 2-D inundation routing model, to study the interaction of regional drainage, sewerage and surface runoff. Besides the urbanization factor of Manning’s n value considering in the above model, the other factors (i.e. infiltration and building blockage effect) are also introduced in the model. This present model is validated based on the data of Typhoon Kalmaegi flooding event in 2008. The simulated results have good agreement with the measured data. In this work, to quantitatively evaluate the effect of inundation on the urban area, the urbanization factors such as Manning’s n value infiltration and building blockage effect are conducted in the present model. Three different land-uses of Taichung metropolitan (i.e. the scenarios of land-use in 1997, 2007 and 2017 for future urbanization) are introduced to further discussion. According to the urbanization of 1997 scenario, the impact assessments on flood degree and flood damage losses are investigated. Furthermore, the entire catchment basins (i.e. Fa-Tzu River and Hann Creek basin) are divided based on the spatial distribution of land-use into several sub-basins for discussing the flood hazard under different urbanization factors. Finally, the simulated results in the present work are presented by using geographic information system. The quantitative assessments of flooding losses are displayed. The simulated results show that the downstream area of catchment basin not only suffers large damage but also becomes the major area where is impacted by flooding inundation. In addition, the density of building construction plays an important role to affect the evaluation of the impact of urbanization. Under the quantitative results of impact assessment, the change of flooding losses is more sensitive than flood degree. Thus, the index of flooding losses is more representative in predicting the flooding hazard.

Increasing global mean temperature or global warming has the potential to affect the hydrologic cycle. In the 21st century, according to the UN Intergovernmental Panel on Climate Change (IPCC), alterations in the frequency and magnitude of high intensity rainfall events are very likely. Increasing trend of urbanization across the globe is also noticeable, simultaneously. These changes will have a great impact on water infrastructure as well as environment in urban areas. One of the impacts may be the increase in frequency and extent of flooding. India, in the recent years, has witnessed a number of urban floods that have resulted in huge economic losses, an instance being the flooding of Mumbai in July, 2005. To prevent catastrophic damages due to floods, it has become increasingly important to understand the likely changes in extreme rainfall in future, its effect on the urban drainage system, and the measures that can be taken to prevent or reduce the damage due to floods. Reliable estimation of future design rainfall intensity accounting for uncertainties due to climate change is an important research issue. In this context, rainfall intensity-duration-frequency (IDF) relationships are one of the most extensively used hydrologic tools in planning, design and operation of various drainage related infrastructures in urban areas. There is, thus, a need for a study that investigates the potential effects of climate change on IDF relationships. The main aim of the research reported in this thesis is to investigate the effect of climate change on Intensity-Duration-Frequency relationship in an urban area. The rainfall in Bangalore City is used as a case study to demonstrate the applications of the methodologies developed in the research Ahead of studying the future changes, it is essential to investigate the signature of changes in the observed hydrological and climatological data series. Initially, the yearly mean temperature records are studied to find out the signature of global warming. It is observed that the temperature of Bangalore City shows an evidence of warming trend at a statistical confidence level of 99.9 %, and that warming effect is visible in terms of increase of minimum temperature at a rate higher than that of maximum temperature. Interdependence studies between temperature and extreme rainfall reveal that up to a certain range, increase in temperature intensifies short term rainfall intensities at a rate more than the average rainfall. From these two findings, it is clear that short duration rainfall intensities may intensify in the future due to global warming and urban heat island effect. The possible urbanization signatures in the extreme rainfall in terms of intensification in the evening and weekends are also inferred, although inconclusively. The IDF relationships are developed with historical data and changes in the long term daily rainfall extreme characteristics are studied. Multidecedal oscillations in the daily rainfall extreme series are also examined. Further, non-parametric trend analyses of various indices of extreme rainfall are carried out to confirm that there is a trend of increase in extreme rainfall amount and frequency, and therefore it is essential to the study the effects of climate change on the IDF relationships of the Bangalore City. Estimation of future changes in rainfall at hydrological scale generally relies on simulations of future climate provided by Global Climate Models (GCMs). Due to spatial and temporal resolution mismatch, GCM results need to be downscaled to get the information at station scale and at time resolutions necessary in the context of urban flooding. The downscaling of extreme rainfall characteristics in an urban station scale pose the following challenges: (1) downscaling methodology should be efficient enough to simulate rainfall at the tail of rainfall distribution (e.g., annual maximum rainfall), (2) downscaling at hourly or up to a few minutes temporal resolution is required, and (3) various uncertainties such as GCM uncertainties, future scenario uncertainties and uncertainties due to various statistical methodologies need to be addressed. For overcoming the first challenge, a stochastic rainfall generator is developed for spatial downscaling of GCM precipitation flux information to station scale to get the daily annual maximum rainfall series (AMRS). Although Regional Climate Models (RCMs) are meant to simulate precipitation at regional scales, they fail to simulate extreme events accurately. Transfer function based methods and weather typing techniques are also generally inefficient in simulating the extreme events. Due to its stochastic nature, rainfall generator is better suited for extreme event generation. An algorithm for stochastic simulation of rainfall, which simulates both the mean and extreme rainfall satisfactorily, is developed in the thesis and used for future projection of rainfall by perturbing the parameters of the rainfall generator for the future time periods. In this study, instead of using the customary two states (rain/dry) Markov chain, a three state hybrid Markov chain is developed. The three states used in the Markov chain are: dry day, moderate rain day and heavy rain day. The model first decides whether a day is dry or rainy, like the traditional weather generator (WGEN) using two transition probabilities, probabilities of a rain day following a dry day (P01), and a rain day following a rain day (P11). Then, the state of a rain day is further classified as a moderate rain day or a heavy rain day. For this purpose, rainfall above 90th percentile value of the non-zero precipitation distribution is termed as a heavy rain day. The state of a day is assigned based on transition probabilities (probabilities of a rain day following a dry day (P01), and a rain day following a rain day (P11)) and a uniform random number. The rainfall amount is generated by Monte Carlo method for the moderate and heavy rain days separately. Two different gamma distributions are fitted for the moderate and heavy rain days. Segregating the rain days into two different classes improves the process of generation of extreme rainfall. For overcoming the second challenge, i.e. requirement of temporal scales, the daily scale IDF ordinates are disaggregated into hourly and sub-hourly durations. Disaggregating continuous rainfall time series at sub-hourly scale requires continuous rainfall data at a fine scale (15 minute), which is not available for most of the Indian rain gauge stations. Hence, scale invariance properties of extreme rainfall time series over various rainfall durations are investigated through scaling behavior of the non-central moments (NCMs) of generalized extreme value (GEV) distribution. The scale invariance properties of extreme rainfall time series are then used to disaggregate the distributional properties of daily rainfall to hourly and sub-hourly scale. Assuming the scaling relationships as stationary, future sub-hourly and hourly IDF relationships are developed. Uncertainties associated with the climate change impacts arise due to existence of several GCMs developed by different institutes across the globe, climate simulations available for different representative concentration pathway (RCP) scenarios, and the diverse statistical techniques available for downscaling. Downscaled output from a single GCM with a single emission scenario represents only a single trajectory of all possible future climate realizations and cannot be representative of the full extent of climate change. Therefore, a comprehensive assessment of future projections should use the collective information from an ensemble of GCM simulations. In this study, 26 different GCMs and 4 RCP scenarios are taken into account to come up with a range of IDF curves at different future time periods. Reliability ensemble averaging (REA) method is used for obtaining weighted average from the ensemble of projections. Scenario uncertainty is not addressed in this study. Two different downscaling techniques (viz., delta change and stochastic rainfall generator) are used to assess the uncertainty due to downscaling techniques. From the results, it can be concluded that the delta change method under-estimated the extreme rainfall compared to the rainfall generator approach. This study also confirms that the delta change method is not suitable for impact studies related to changes in extreme events, similar to some earlier studies. Thus, mean IDF relationships for three different future extreme events, similar to some earlier studies. Thus, mean IDF relationships for three different future periods and four RCP scenarios are simulated using rainfall generator, scaling GEV method, and REA method. The results suggest that the shorter duration rainfall will invigorate more due to climate change. The change is likely to be in the range of 20% to 80%, in the rainfall intensities across all durations. Finally, future projected rainfall intensities are used to investigate the possible impact of climate change in the existing drainage system of the Challaghatta valley in the Bangalore City by running the Storm Water Management Model (SWMM) for historical period, and the best and the worst case scenario for three future time period of 2021–2050, 2051–2080 and 2071–2100. The results indicate that the existing drainage is inadequate for current condition as well as for future scenarios. The number of nodes flooded will increase as the time period increases, and a huge change in runoff volume is projected. The modifications of the drainage system are suggested by providing storage pond for storing the excess high speed runoff in order to restrict the width of the drain The main research contribution of this thesis thus comes from an analysis of trends of extreme rainfall in an urban area followed by projecting changes in the IDF relationships under climate change scenarios and quantifying uncertainties in the projections.

博士<br>國立臺灣大學<br>生物環境系統工程學系暨研究所<br>92<br>Taiwan is in the subtropics, with an average annual precipitation of 2,500 mm. Rainfall is temporally and spatially non-uniform. Moreover, rivers in Taiwan are short and steep and become torrential during heavy storms. Therefore, typhoons cause severe flooding damage on the alluvial plains where most communities and industries are concentrated, because information about the hazard risk associated with typhoons is lacking. Losses due to flooding damage increase with the economic development of Taiwan. 　The aim of this study is to analyze such flooding damage and propose a method for developing a series of models for evaluating losses due to flooding damage. The following three models are established; (a) a model based on the method of classified quartile curves, (b) a grey model GM(1,3) of the spatial index, and (c) a model based on the index method of assessing hazard potential. The first model uses a statistical method to generate inundation depth-loss curves. Combining the curves with basic data on buildings yields an estimate of the monetary value of the flooding damage. The second model associates the basic data and losses of property in the project area with inundation maps simulated by the 2-D unsteady hydraulic model, to develop a grey model GM(1,3) of the spatial index. Various inundation maps of various return periods are applied to determine the property losses under the above conditions to gain the hazard risk of flooding damage in an urban area. The third model integrates grey relational analysis with the analytic hierarchy process to compute hazard potential indices. Each village in the project area is then assigned to a class using the two breaking points method to evaluating appropriately the hazard potential indices. Decision-makers can use the map of classified hazard potentials in the project area to design a strategy for preventing flood-disasters.

The severity and frequency of flooding-related catastrophes are increasing, and lands adjacent to rivers that were formerly the hub for city growth and commerce now face constant threats of flooding. As flood risks have become more at the forefront of legislative consciousness, with governments increasing flood-protection and mitigation measures for flood-prone areas, landowners within such areas are left with little support and direction for their lands. In exploring the issues facing landowners within flood-prone lands, this practicum focuses on whether governments should be directly involved in finding solutions for landowners to ensure a situation where both private landowners and governments benefit. The research concludes that development within flood-prone areas should be avoided, and that municipalities should, given adequate capacity and ability, relocate existing residents from flood-prone areas to repurpose the area for flood-mitigation measures. The research recommends that the City of Brandon become a member, and participate in the Red River Basin Commission, while also exploring opportunities to play a leadership role in the implementation of a similar commission for the Assiniboine River Basin.<br>February 2017

碩士<br>國立臺灣大學<br>生物環境系統工程學研究所<br>107<br>In recent years, due to climate change and extreme weather events, the rainfall intensity has increased. This phenomenon also has the same trend in summer typhoons, which increases the frequency of flooding disasters. At present, the flooding simulation usually sets up a single rainfall station for model simulation. Although this method is faster and simpler to construct, the single rainfall station may not be able to represent the rainfall situation of a whole area. In addition, the drainage method in the metropolitan area usually collects rainwater from the inlet and the side ditch. If the garbage and the fallen leaves accumulate due to heavy rainfall, the water inlet will not reach the designed water collecting effect, which may cause the metropolitan area the product of flooding. In this study, we investigated the effects of rainfall data from different spatial distributions on flooding simulations in urban areas, using rainfall observation data and radar echo data to simulate flooding. Comparison of single rainfall station, multi-rainfall station Thiessen&apos;&apos;s Method rainfall setting, multi-rainfall station Thiessen&apos;&apos;s Method Partition rainfall setting, Inverse Distance Weighted rainfall and radar echo rainfall. Through the methods of Accuracy (ACC), Probability of Detection (POD), Threat Score (TS), Precision or Predictive value (PPV), it is estimated that what kind of rainfall setting has better performance for flooding simulation in the urban area. Then set different clogging rates to compare the clogging rate values closer to the real city blockage, and compare the clogging rates with the Taipei city flooding map. In this study, Jieshang drainage and Hougang drainage basin in Shilin Distrinct, Taipei, is selected as the study area. Two short duration and one long duration rainfall events are used for simulation and analysis. Due to the closeness to real rainfall collection phenomena, the simulated results from Inverse Distance Weighted rainfall setting has a better agreement whether the duration of rainfall event is short or long. And set different clogging rate to get the clogging factor 20% as the closest to the real urban area clogging rate. It is also comparable to the flooding simulation map of Taipei City. The result of setting a 20% clogging rate can make the indicators have better performance.