京都大学 / 新制・課程博士 / 博士(工学) / 甲第23171号 / 工博第4815号 / 新制||工||1752(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 田中 茂信, 准教授 田中 賢治, 准教授 佐山 敬洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

A flood inundation study is presented for a watershed located in south central Virginia. A HEC-RAS hydrodynamic model of the main river network was developed to assess the impact of a number of hydrologic events, including the Probable Maximum Flood (PMF), in the area of interest. The primary goal of the study was to transform discharge hydrographs produced by HEC-HMS, an event-based hydrologic model, into water surface elevations and flood inundation spatial extents. Initially, a river terrain model was constructed using data from publicly available sources and filed survey campaigns. HEC-GeoRAS and ArcGIS were used to document and integrate the considerable amount of data required for building the model. Then, a calibration process was performed using stage-discharge predictor curves. The HEC-RAS unsteady flow component was employed for routing the discharge hydrographs through the modeled river network. Flood inundation maps, as well as longitudinal water surface elevation and channel velocity profiles were generated for the study reaches. As part of the flood inundation study, an uncertainty quantification analysis was carried out on the boundary roughness of the floodplains. The objective was to measure the extent to which flood inundated areas, water surface elevations, and channel velocities were influenced by variations on this empirically-based model coefficient. Finally, the impact of various hydraulic characteristics of the modeled river on the sediment transport process is examined. This characterization is intended to provide a better understanding of a subsequent sediment transport modeling effort to be performed under severe flooding conditions. / Master of Science

På grund av osäkerheter i indata, parametrar och modellstruktur kan det finnas stora osäkerheter i översvämningskarteringar. Trots detta sker oftast ingen osäkerhetsanalys vid översvämningskarteringar i praktiken vilket gör att beslutsfattare och andra användare kan uppfatta resultaten som mer korrekta än vad de egentligen är. En orsak till att osäkerhetsanalys ännu inte blivit en vedertagen del i översvämningskarteringar kan vara att modellerare på konsultbyråer och myndigheter inte har tillräcklig kunskap om ämnet. Att tillgången på data kan vara begränsad underlättar inte heller vid osäkerhetsanalyser. Dessutom saknas exempel på hur osäkerheter kan analyseras i MIKE 11, vilket är en av de vanligaste modellerna som används vid översvämningskarteringar på konsultbyråer. Syftet med examensarbetet var tvåfaldigt. Det första var att ge en generell kunskapsöverblick över aktuell forskning om osäkerheter och osäkerhetsanalys vid översvämningskarteringar för att öka kunskapen hos konsulter och beslutsfattare. Det andra syftet var att med ett exempel visa hur osäkerheter kan uppskattas i en översvämningskartering skapad i MIKE 11 då det finns begränsad tillgång på data. En litteraturstudie visade att det ofta finns stora osäkerheter i flödesberäkningar och den geometriska beskrivningen och att det finns väldigt många sätt att analysera dessa på. Några av metoderna som används är Monte Carlo simuleringar, Oskarpa mängder, Scenarioanalys, Bayesiansk kalibrering och Generalized Likelihood Uncertainty Estimation, GLUE. En fallstudie gjordes där en hydraulisk modell av Kungsbackaån skapades med MIKE 11. Den metod som var praktiskt genomförbar att använda för att uppskatta osäkerheterna i detta arbete var scenarioanalys. Totalt utfördes 36 olika modellsimuleringar där kalibreringsflöde, Mannings tal och scenarioflöde varierades. Scenarioanalys ger inte någon exakt beräkning av osäkerheterna utan endast en subjektiv uppskattning. Resultatet av scenarioanalysen visade att då havsnivån i Kungsbackafjorden var 0,92 m skiljde de simulerada vattennivåerna som mest med 1,3 m för 100-årsflödet och med 0,41 m för beräknat högsta flöde, BHF. Även osäkerheterna i utbredningen för de två flödena undersöktes och visade sig vara som störst i flacka områden trots att osäkerheten i vattennivåerna var mindre där. / Due to uncertainty in data, parameters and model structure, there may be large uncertainties in flood inundation models. Despite of this, uncertainty analysis is still rarely used by practitioners when creating flood maps. A reason why uncertainty analysis has not yet become customary in flood inundation modeling may be due to a lack of knowledge. Low availability of data can sometimes also make it more difficult to do an uncertainty analysis. Moreover, no examples exist of how uncertainties can be analyzed in MIKE 11, which is one of the most common models used in flood mapping at consultant agencies. The aim of this study was twofold. Firstly, to provide a general overview of current research on uncertainty and uncertainty analysis for flood inundation modeling. This in order to increase knowledge among consultants and decision makers. Secondly, to give an example of how uncertainties can be estimated in a flood inundation model created in MIKE 11 when there is limited access to data. The research overview showed that there is often considerable uncertainty in the discharge calculations and geometrical description in hydraulic models, and that there are many different ways to analyze the uncertainties. Some methods that are often used are Monte Carlo simulations, fuzzy sets, scenario analysis, Bayesian calibration and Generalized Likelihood Uncertainty Estimation, GLUE. A case study was performed in which a hydraulic model was built for the River Kungsbackaån in MIKE 11. A scenario analysis was carried out to show the uncertainties in the hydraulic model. Overall, 36 different model runs were made in which the calibration discharge, Manning's number and design flow were varied. Scenario analysis cannot provide a precise estimate of the uncertainty, it can only give a subjective estimate. The results of the scenario analysis showed that when the sea level in Kungsbackafjorden was 0,92 m the simulated water levels differed at most by 1,3 m for the 100-year discharge and by 0,41 m for the calculated maximum flow. Also, the flood extent of the two discharges were investigated. The greatest uncertainty in the extent was found in the flat areas even though the uncertainty in water levels was smaller there.

Hydrological extremes associated with climate change are becoming an increasing concern all over the world. Frequent flooding, one of the extremes, needs to be analyzed while considering climate change to mitigate flood risk. This study forecasted streamflow and evaluated the risk of flooding in the Neuse River, North Carolina considering future climatic scenarios, and comparing them with an existing Federal Emergency Management Agency (FEMA) flood insurance study (FIS) report. The cumulative distribution function transformation (CDF-t) method was adopted for bias correction to reduce the uncertainty present in the Coupled Model Intercomparison Project Phase 6 (CMIP6) streamflow data. To calculate 100-year and 500-year flood discharges, the Generalized Extreme Value (GEV) (L-Moment) was utilized on bias-corrected multimodel ensemble data with different climate projections. The delta change method was applied for the quantification of flows, utilizing the future 100-year peak flow and FEMA 100-year peak flows. Out of all projections, shared socio-economic pathways (SSP)5-8.5 exhibited the maximum design streamflow, which was routed through a hydraulic model, the Hydrological Engineering Center’s River Analysis System (HEC-RAS), to generate flood inundation and risk maps. The result indicates an increase in flood inundation extent compared to the existing study, depicting a higher flood hazard and risk in the future. This study highlights the importance of forecasting future flood risk and utilizing the projected climate data to obtain essential information to determine effective strategic plans for future floodplain management.

付記する学位プログラム名: グローバル生存学大学院連携プログラム / 京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19975号 / 工博第4219号 / 新制||工||1653(附属図書館) / 33071 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 立川 康人, 教授 寶 馨, 教授 堀 智晴 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20679号 / 工博第4376号 / 新制||工||1680(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 寶 馨, 教授 立川 康人, 准教授 佐山 敬洋 / 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24213号 / 工博第5041号 / 新制||工||1787(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 立川 康人, 教授 角 哲也, 准教授 佐山 敬洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

A mesoscale evaluation is performed to determine the impacts of climate change on terrestrial hydrological components and the Net Irrigation Water Requirement (NIWR) throughout the Chesapeake Bay watershed in the mid-Atlantic region of the United States. The Noah-MP land surface model is calibrated and evaluated against the observed datasets of United States Geological Survey (USGS) streamflow gages, actual evapotranspiration from USGS Simplified Surface Energy Balance (SSEBop) Model and soil moisture from Soil Analysis Climate Network (SCAN). Six best performing Global Climate Models (GCM) based on Multivariate Adaptive Constructed Analogs (MACA) scheme are included for two future scenarios (RCP 4.5 and RCP 8.5), to assess the change in water balance components, change in NIWR for two dominant crops (corn and soybeans) and uncertainty in GCM projections. Using these long-term simulations, the flood inundation maps are developed for future scenarios along the Susquehanna River including the City of Harrisburg in Pennsylvania. The HEC-RAS 2D model is calibrated and evaluated against the high-water marks from major historical flood events and the stage-discharge relationship of the available USGS streamgages. Finally, the impacts of climate change are assessed on flood inundation depth and extent by comparing a 30-yr and 100-yr flood event based on the historical and future (scenario-based) peak discharge estimates at the USGS streamgages. Interestingly, flood inundation extent and severity predicted by the model along the Susquehanna River near Harrisburg is expected to rise in the future climate scenarios due to the greater frequency of extreme events increasing total precipitation. / Master of Science / Climate change is inevitable due to increased greenhouse gas emissions, with impacts varying in space and time significantly throughout the globe. The impacts are strongly driven by the change in precipitation and temperature which affect the control of the movement of water on the surface of the Earth. These changes in the water cycle require an understanding of hydrological components like streamflow, soil moisture, and evapotranspiration. Development of long-term climate models and computational hydrological models (based on mathematical equations and governed by laws of physics) has helped us in understanding this climate variability in space and time. This study performs a long-term simulation using the datasets from six different climate models to analyze the change in terrestrial hydrological components for the entire Chesapeake Bay watershed in the mid-Atlantic region of the United States. The simulations provide an understanding of the interplay between various land surface processes due to climate change and can help determine future water availability and consumption. To illustrate the usefulness of such long-term simulations, the crop water requirement is quantified for the dominant crops in Chesapeake Bay watershed to project water availability and support the development of mitigation strategies. Flood inundation maps are also developed for a section of Susquehanna River near the City of Harrisburg in south-central Pennsylvania using the streamflow from long-term simulations. The flood inundation depth and extent for major flood events such as Tropical Storm Agnes (1972) and Tropical Storm Lee (2011) are compared along the Susquehanna River, which can aid in managing flood operations, reduce the future flood damages and prioritize the mitigation efforts for endangered communities near the City of Harrisburg.

I framtiden förutspås kraftig nederbörd bli vanligare förekommande på grund av klimatförändringar och global uppvärmning, vilket kan leda till fler och större översvämningar. Med översvämningskartering kan fastighetsskador och dödsfall undvikas och kartorna kan användas som beslutsunderlag inom samhällsplanering. Gävle kommun har pekat ut Västra Kungsbäck i Gävle som utredningsområde för bl.a. bostäder och verksamheter och i framtiden kan området bli en ny stadsdel. I norra delen av Västra Kungsbäck rinner Kungsbäcken, vilket innebär en översvämningsrisk som noga måste utredas innan eventuell exploatering. Studien utfördes i två delar – en fallstudie på Kungsbäcken där syftet var att simulera och kartlägga översvämningars utbredning i området till följd av kraftig nederbörd, och en enkätundersökning med syfte att undersöka hur planhandläggare tolkar översvämningskartor med osäkerhetszon och hur dessa tolkningar skiljer sig mot experters. Inledningsvis modellerades Kungsbäckens avrinningsområde i HEC-HMS med meteorologiska data från SMHI och modellen kalibrerades till en tidigare översvämningshändelse. Sedan simulerades kraftig nederbörd för att uppskatta resulterande vattenföring, som i den endimensionella modellen HEC-RAS, användes för flödessimulering. Därefter skapades översvämningskartor som visar översvämningars utbredning i Västra Kungsbäck. Därtill användes också i ArcGIS ett nyutvecklat verktyg för att skapa en översvämningskarta med osäkerhetszon där osäkerheten visualiseras. Kartan användes i enkätundersökningen, där 41 planhandläggare från slumpmässigt utvalda svenska kommuner och två experter med sakkunskap inom relaterade ämnesområden, fick bedöma översvämningsrisk på tre olika platser i översvämningskartan. Resultaten visar på den generella översvämningsrisk som råder i Västra Kungsbäck. Betydande översvämningar kan drabba stora delar av området till följd av kraftig nederbörd. Dock finns stor osäkerhet i modellerad översvämning, varför fler studier krävs och mycket stor försiktighet måste vidtas inför eventuell planläggning, kanske till den grad att området inte alls bör bebyggas. Inget definitivt svar finns på hur planhandläggare tolkar översvämningskartan med osäkerhetszon eftersom tolkningarna kraftigt skiljer sig åt. Planhandläggarna är olika personer med olika förmågor, där bl.a. utbildningsnivå och erfarenhet av kartläsning, verkar ha påverkan på tolkningarna och efterföljande bedömning av översvämningsrisk. Resultaten både bekräftar och skiljer sig från tidigare forskning. Planhandläggare med en utbildning på avancerad nivå var i denna studie mindre säkra att sina bedömningar var korrekta jämfört med planhandläggare med endast grundutbildning. Anmärkningsvärt är att de flesta planhandläggare verkar bedöma översvämningsrisken statiskt, enbart utifrån presenterad översvämningskarta. Bara ett fåtal planhandläggare visar upp ett försiktigare förhållningssätt, där de utöver presenterad översvämningskarta, även bedömer översvämningsrisken med hänsyn till eventuella framtida förändringar i nederbördsmängd och resulterande flöde. Med anledning av skillnaderna i tolkning och bedömning krävs fler studier för att fastställa hur översvämningskartor bäst ska utformas för att tolkas och uppfattas korrekt. / Climate change and global warming is expected to cause extreme precipitation to occur more frequently in the future, with more severe floods as a consequence. Flood inundation mapping can prevent property damage and fatalities and the maps can be used as a basis for decision-making in spatial planning. Gävle municipality has chosen Västra Kungsbäck in Gävle for investigation regarding e.g. housing and may become a new neighborhood in the future. The stream Kungsbäcken flows though the northern part of Västra Kungsbäck, which results in flood risk that must be carefully investigated ahead of potential development. The study was conducted in two parts – a case study of Kungsbäcken where the purpose was to simulate and map flood inundation extent caused by extreme precipitation, and a survey with the intention to examine how planners interpret flood inundation maps with an uncertainty zone and how these interpretations differ from those of experts. Initially, the drainage area of Kungsbäcken was modelled in HEC-HMS with meteorological data from SMHI and the model was calibrated to a previous flooding event. Extreme precipitation was simulated to estimate the resulting discharge, and the one-dimensional HEC-RAS model was used for hydraulic simulation. Afterwards, flood inundation maps were created showing flood inundation extents in Västra Kungsbäck. Additionally, a newly developed tool was used in ArcGIS to create a flood inundation map with an uncertainty zone, where the uncertainty is visualized. This map was used in the survey, where 41 planners from randomly selected Swedish municipalities and two experts in related fields of study, were asked to evaluate flood risk in three locations in the flood inundation map.The results show the general flood risk in Västra Kungsbäck. Extreme precipitation can cause significant flooding affecting large parts of the area. There is, however, considerable uncertainty in modelled flood, hence additional studies are required and planning the area must be done with great caution, perhaps to the extent that the area should not be developed at all.  There is no definitive answer to how planners interpret the flood inundation map with an uncertainty zone because the interpretations vary. The planners are different people with different qualifications, where e.g. level of education and map experience, appear to have an effect on the interpretations and subsequent evaluations of flood risk. The results both confirm and differ from previous studies. Planners with a postgraduate degree were in this study less certain that their evaluations were correct compared to those with only an undergraduate degree. It is remarkable that most planners appear to evaluate the flood risk statically, only based on the presented flood inundation map. Only a few planners show a more careful approach, where they evaluate flood risk beyond the presented map, according to expected increased amount of precipitation and resulting discharge. As a result of the different interpretations and evaluations, further studies are needed to determine how flood inundation maps best should be designed to be correctly interpreted and understood.

This study deals with the investigation of characteristics of a flash flood and development of design of flood mitigation facilities occurred in G&uuml / zelyurt in North Cyprus on 18th of January, 2010 and development of design of flood mitigation facilities. Hydrologic and hydraulic modeling of this flood event has been utilized to develop solutions for preventing the region from the flood. Topographical maps and soil properties are used in hydrological modeling. The data are inserted into a geographical information system program (ARC-GIS) where basin properties are obtained. Since there is no any stream flow gauging station along the creeks in the study area, the synthetic unit hydrograph is developed by using Soil Conversation Service Method to obtain design flood hydrographs. In hydraulic modeling, the cross-section data of Fabrika Creek and Bostanci Creek are taken by using global navigation satellite system (GNSS) device and total station. These data are entered into the HEC-RAS program. Flood inundation maps are generated for both creeks. After hydrological and hydraulic modeling, two solutions are proposed. The first one is to build a detention basin for storing water and a lateral channel. for diverting extra flow from Bostanci Creek to Fabrika Creek. The second solution is to build a lateral channel from Bostanci Creek to G&uuml / zelyurt Dam for diverting all water during a flood event. Based on hydrologic, hydraulic, and cost analysis, the first solution is accepted to be the feasible solution. In addition, flow carrying capacities of the creeks are improved.