Climate change is predicted to alter the rainfall patterns in the future, and extreme rain events with large rainfall volumes will become more frequent and intense which increases the flood risk. A clear trend can be seen, where more and more people decide to relocate from rural to urban areas. The concentration of people, infrastructure, businesses and social services in urban areas makes them particularly vulnerable to floods due to the large economic consequences that ensue. Analyzing the future flood risk is therefore of high importance in order to adapt to the changing climate and lower the consequences of future floods. Estimating the flood risk of an area is complicated and usually abstract, especially as i) the definition and understanding of risk varies a lot, ii) there is a large shortage of consistent data and iii) decision management plans are made several years ahead even though it’s hard to predict how cities will evolve. In a hydro-economical flood risk analysis, the risk is expressed in monetary terms, here in terms of Expected Annual Damage (EAD). In order to calculate the true risk of an area, EAD, for any given year there is a need of calculating all consequences for “all” events. With today’s technical limitations it is not possible to compute all possible events in an effective way, which makes the practice both time-consuming and expensive, therefore usually only a several events are considered. Among others, this paper aim to give a better understanding of how this several events should be picked to still get a good estimation. A flood risk assessment of the city Tierp, Sweden, was performed as part of the master thesis for use as decision support. The flood hazard was mapped through hydrodynamic modelling using the 2D-modelling program MIKE21 developed by DHI. The model simulated the future flood extent in the year 2100 by using precipitation corresponding to the return periods 1, 2, 5, 10, 20, 30, 50, 100, 200 and 500 years, with a climate factor of 1.25. The economic consequences were evaluated in the DHI program City Adaptation Decision Support System (CADSS) where the flood maps were overlaid with assets of different categories with assigned damage costs. The program allowed calculation of the flood risk in terms of an expected annual damage (EAD), and the choice and combination of return periods when calculating the EAD was assessed to see how it affects the outcome. Furthermore, sustainable drainage systems (SuDS) were implemented in the hydrodynamic model and a hydro-economic analysis was performed through a cost-benefit analysis to find the optimum design return period of the structures. The flood risk assessment showed that Tierp would face an EAD of 4 304 181 SEK in the year 2100 if climate change predictions proved accurate. The accuracy of the EAD calculation was found to increase with the number of included return periods, where the inclusion of lower return periods was seen to have a larger impact on the outcome compared to higher return periods. The hydro-economic optimization of mitigation structures concluded that the optimum design return period is 50 years, and the benefit of implementing SuDS of larger dimensions is minimal. However, more dimensions need to be included in the optimization to validate this result.  Flood risk assessments have a large potential for being used as decision support in Sweden, but lack of national damage cost data makes the result uncertain and difficult to validate. More research would also be required to better understand the relation between floods and the damage they cause for Swedish conditions. / I takt med klimatförändringarna förutspås extrema regnhändelser med stora regnmängder och hög intensitet att öka i framtiden. Samtidigt väljer allt fler människor att flytta från landsbygden in till städerna vilket bidrar till att exponering av sårbara värden som människor, infrastruktur och verksamheter koncentreras. Det i sin tur innebär att risken för översvämning ökar, då översvämningarna förväntas ske mer frekvent samtidigt som risken för att konsekvenser uppstår till följd av översvämningen ökar. För att förebygga översvämningar eller minska risken i framtiden krävs en hållbar stadsplanering, där första steget är att försöka estimera översvämningsrisken inom ett område. Uppskattning av översvämningsrisken är komplicerat. Dels eftersom i) definitionen och kunskapen av risk varierar mycket, ii) det råder stor brist på data och iii) planering och beslut görs flera år i förväg, samtidigt som det är svårt att förutsäga hur städerna kommer att utvecklas. I en ekonomisk riskanalys av översvämningar uttrycks risken i monetära termer som i denna rapport definierats som förväntad årlig skada (Expected Annual Damage, EAD). För att beräkna den verkliga risken för ett område, EAD, för ett visst år måste man beräkna alla konsekvenser för ”alla” händelser. På grund av dagens tekniska begränsningar är det inte möjligt att beräkna alla sannolika händelser på ett effektivt sätt vilket gör det både tidskrävande och dyrt. Syftet med denna rapport är därför bland annat att ge en bättre förståelse för hur ett urval av händelser kan göras för att ändå ge en bra uppskattning. En del av masteruppsatsen bestod i att kartlägga översvämningsrisken i staden Tierp, Sverige. Översvämningsrisken simulerades genom hydrodynamisk modellering med hjälp av 2D-modelleringsprogrammet MIKE 21, utvecklat av DHI. Med hjälp av modellen simulerades den framtida översvämningsutbredningen år 2100 vid nederbörd med återkomsttiderna 1, 2, 5, 10, 20, 30, 50, 100, 200 och 500 år, med en klimatfaktor på 1,25. De ekonomiska konsekvenserna utvärderades i DHI-programmet City Adaptation Decision Support System (CADSS) där översvämningskartor jämfördes med kategoriserade byggnader och dess respektive förväntade skadekostnader. Med hjälp av CADSS kunde översvämningsrisken i form av EAD beräknas, och kombinationen av olika återkomstperioder vid beräkningen av EAD kunde bedömas för att se hur det påverkar resultatet. Utöver detta implementerades hållbara skyfallslösningar i den hydrodynamiska modellen och en hydroekonomisk analys utfördes genom en kostnads-nyttoanalys för att hitta den optimala designåterkomsttiden för lösningarna. Bedömningen av översvämningsriskerna visade att Tierp skulle drabbas av en EAD på 4 304 181 SEK år 2100 om de förväntade klimatförändringarna visar sig vara korrekta. Noggrannheten i EAD-beräkningen visade sig öka med antalet inkluderade återkomsttider, där inkluderandet av lägre återkomsttider visade sig ha en större inverkan på resultatet jämfört med högre återkomsttider. Den hydroekonomiska optimeringen av begränsningsstrukturer ledde till slutsatsen att den optimala återkomstperioden är 50 år, och att nyttan av att införa skyfallslösningar dimensionerade för större återkomsttider är minimal. Fler dimensioner måste dock inkluderas i optimeringen för att bekräfta detta resultat.  Bedömningar av översvämningsrisker har en stor potential att användas som beslutsstöd i Sverige, men bristen på nationella uppgifter om skadekostnader gör resultatet osäkert och svårt att validera. Det krävs även mer forskning för att bättre förstå relationen mellan översvämningar och de skador de orsakar för svenska förhållanden.

There is a growing interest in tidal energy, owing to its predictable nature in comparison to other renewable sources. In the case of the UK, its importance also lies on the availability of exploitable areas as well as their total capacity, which is estimated to cover more than 20% of the country demand. However, the level of development of this kind of technology is still far behind other types of renewable energy. However, several studies focused on a variety of individual devices, followed by more recent research on the deployment of large arrays or tidal farms. Potential sites for energy extraction can be found in narrows between islands and the coast or estuaries. The latter present some advantages for the installation and the connection to the grid but estuaries are often prone to flood risk from tides and surges. Therefore, the objective of this thesis is to evaluate the effect that very large groups of turbines could have on peak water levels during flooding events in the case of being deployed in estuarine areas. For that purpose, a new methodology has been developed, which implies the use of a numerical model (MIKE 21 by DHI), and it has been demonstrated against a real case study in the UK: the Solway Firth estuary. Another objective has consisted of integrating in this thesis the results from detailed CFD modelling and optimisation techniques involved in the project. A literature review has been carried out in order to identify the current state of the art for the different subjects considered in the thesis. Different aspects of the numerical model used for this study (MIKE 21) have been presented and the modelling of the turbines within the code has been validated against experimental and CFD data. The procedure to include large numbers of turbines in the code is also developed. An analysis has been done of the different estuaries existing in the UK suitable for tidal energy extraction, identifying their main geometrical features. Based on this, idealised models of estuaries have been used to assess the influence that the channel geometry could have on the impact of tidal farms under extreme water levels. The effect has been measured by comparing the results of the numerical model between the case with and without turbines under different flooding scenarios. Finally, the same methodology has been applied to a real case study selected from the previous group of estuaries namely the Solway Firth. An initial model has been created, according to the available data at the start of the research, which contained some errors related to the water depth at the intertidal areas in the upper estuary. Therefore, when a more realistic dataset became available, an improved model was created. The improved model has been used to assess the effects of tidal farms in the estuary under a coastal flooding event. It is concluded that there is significant influence of the channel geometry over the locations where the maximum changes in water levels due to the tidal farms will happen. Nevertheless, the effects seem to be more relevant in terms of the decrease rather than the increase of peak water levels for all geometries and the maximum changes seem to be in the order of dm. This is in agreement with the results of the Solway Firth models and can be summarised as a positive net effect over flood risk. On the other hand, a concern has been raised about the impact on intertidal areas, which could be the subject of future research.

Natural disasters disrupt our daily life and cause many sufferings. Among the various natural disasters, flood is one of the most catastrophic. Assessing flood risk helps to take necessary precautions and can save human lives. The assessment of risk involves various factors which can not be measured with hundred percent certainty. Therefore, the present methods of flood risk assessment can not assess the risk of flooding accurately.  This research rigorously investigates various types of uncertainties associated with the flood risk factors. In addition, a comprehensive study of the present flood risk assessment approaches has been conducted. Belief Rule Base expert systems are widely used to handle various of types of uncertainties. Therefore, this research considers BRBES’s approach to develop an expert system to assess the risk of flooding. In addition, to facilitate the learning procedures of BRBES, an optimal learning algorithm has been proposed. The developed BRBES has been applied taking real world case study area, located at Cox’s Bazar, Bangladesh. The training data has been collected from the case study area to obtain the trained BRB and to develop the optimal learning model. The BRBES can generate different "What-If" scenarios which enables the analysis of flood risk of an area from various perspectives which makes the system robust and sustainable. This system is said to be intelligent as it has knowledge base, inference engine as well as the learning capability.

京都大学 / 0048 / 新制・課程博士 / 博士(情報学) / 甲第18620号 / 情博第544号 / 新制||情||96(附属図書館) / 31520 / 京都大学大学院情報学研究科社会情報学専攻 / (主査)教授 多々納 裕一, 教授 矢守 克也, 教授 堀 智晴 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20681号 / 工博第4378号 / 新制||工||1680(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 角 哲也, 准教授 竹門 康弘, 准教授 Sameh Kantoush / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24887号 / 工博第5167号 / 新制||工||1987(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 角 哲也, 教授 堀 智晴, 教授 山上 路生 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Among the various natural calamities, flood is considered one of the most catastrophic natural hazards, which has a significant impact on the socio-economic lifeline of a country. The Assessment of flood risks facilitates taking appropriate measures to reduce the consequences of flooding. The flood risk assessment requires Big data which are coming from different sources, such as sensors, social media, and organizations. However, these data sources contain various types of uncertainties because of the presence of incomplete and inaccurate information. This paper presents a Belief rule-based expert system (BRBES) which is developed in Big data platform to assess flood risk in real time. The system processes extremely large dataset by integrating BRBES with Apache Spark while a web-based interface has developed allowing the visualization of flood risk in real time. Since the integrated BRBES employs knowledge driven learning mechanism, it has been compared with other data-driven learning mechanisms to determine the reliability in assessing flood risk. Integrated BRBES produces reliable results comparing from the other data-driven approaches. Data for the expert system has been collected targeting different case study areas from Bangladesh to validate the integrated system.

The high frequency and cost of flooding in Canada has demonstrated the need for effective risk assessment (Public Safety Canada (PSC), 2010). In response to this need, the United States Federal Emergency Management Agency (FEMA) developed HAZUS, a hazard risk assessment tool which relies on a geographic information system (GIS) (FEMA, 2015). Unfortunately, in many rural communities in Canada, only aggregate population data may be available. In those cases, the ability to further partition aggregated data may prove essential in generating robust and accurate risk assessments. The results of this study show that HAZUS can be adapted for use in Canada and provides a new methodology for conducting hazard estimations in areas where available data is coarsely aggregated. There was a strong relationship between nighttime light and population density. High populations were associated with developed land cover classification. These relationships can be used to increase the accuracy of HAZUS predictions. / October 2016

Thailand has been often affected by severe flood events over the past century. The 2011’s Thailand Flood Catastrophe was the costliest in country’s history, and it was ranked to be the second most damaging natural hazard in the world in terms of economic losses. The Chao Phraya River Basin was noted to be the most vulnerable area prone to flooding in Thailand. The dynamics of flood risk in the river basin have changed drastically over the past fifty years. In particular, flood exposure increased due to rapid urbanization and population growth. Since 2012, integrated flood risk management has been addressed to be the major framework of water-related disasters with the goal of losses and damage reductions. However, there is currently little research in Thailand on how to quantify flood risks and mitigate flood inundation damage on the relation between the occurrence of flood events and their consequential socio-economic implications. In this study, a tradition method in flood risk assessment is implemented by integrating 2D hydrodynamic modelling and the assessment of socio-economic impact of floods into the Chao Phraya River Basin. More specifically, the fully 2D version of the LISFLOOD-FP model code was used to model flood inundation processes. The output of the model was then used to map inundation depth and assess the levels of physical/environmental risk associated to flood hazards on multiple receptors/elements at risk. The European Flood Directive and the KULTURisk methodology were applied to quantify flood risks in monetary terms for residential, industrial, and agricultural sectors. The 2011 flood event was used for model calibration, while a hypothetical flood event with a return period of 100 years was simulated to identify the potential flood losses. Depth-damage functions comprising of JRC-ASIA, the Flemish, and JICA models were used to estimate potential damage for residential and industrial structures. The results showed that LISFLOOD-FP could satisfactorily reproduce the flood inundation extent obtained from satellite imagery in 2011. The model performance (Critical Success Index or F1) was of 56%, with a Bias of 112%. The latter meant the total inundated area was 12% larger than flood extent’s observation. Moreover, the model could simulate flood levels with overall Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) of 2.03 m a.s.l. and 1.78 m a.s.l., respectively. For the estimation of flood damage and losses, the Flemish model showed the strongest agreement with the reported flood damage in the residential sector, while JICA-ASIA model underestimated flood damage for industrial sector by just 1%. The KULTURisk methodology also well-estimated crop losses in the 2011 event which an overestimation about 21% from the reported value. Apart from that, fully 2D numerical method could not perfectly represent 1-in-100 year flood inundation due to non-consideration of important features such as the precise river channel topography, hydraulic infrastructures, and flood protection schemes in the river basin. Lack of such features results in an overestimation of flood damage and losses for 1-in-100 year flood comparing to the national flood hazard map and damage assessment which are simulated and estimated by JICA’s study. Such features can be better handled by using a coupled 1D/2D numerical method in order to simulate flood inundation extent more realistically and estimate flood losses. This could help the Thai government to better prepare a budget for flood risk prevention. In addition, even if the Flemish model indicates a good representation of relative flood damage to housing structures, the government should establish depth-damage curves specific for Thailand.

This study addresses flood risk assessment in the Catalpa Creek watershed, located in northeast Mississippi, USA. Employing the Hydrological Modeling System (HEC-HMS) and the River Analysis System (HEC-RAS), integrated models were developed and calibrated, to predict flood behavior within the watershed. The study conducted flood frequency analyses for return periods ranging from 2 to 100 years and generated flood inundation maps, pinpointing flood-prone areas. Mitigation measures for flood risk management were recommended. The results underscore the effectiveness of the integrated modeling approach for simulating and understanding the complex dynamics of flood events. The research identified critical flood-prone zones, emphasizing the importance of proactive flood risk management. The calibrated hydrological model serves as a valuable tool for stormwater management, water resource planning, and watershed assessment. The study provides insights into flood risk in the Catalpa Creek watershed, offering valuable guidance to regional decision-makers. This study lays the foundation for future investigations in floodplain encroachment, sediment transport, stream restoration, and flood inundation hazard mapping.