Depuis les années 1990, un changement semble être intervenu dans les politiques du risque inondation en France. Les aménagements de protection qui prévalaient depuis le XIXe siècle ont été remis en cause et l'inondation a été requalifiée comme un phénomène inévitable voire bénéfique pour l'environnement. Les discours de politique publique relatifs à la culture du risque ont remplacé ceux présentant le risque inondation comme un enjeu de sécurité publique. Les instruments d'action publique ont également changé. Les aménagements visant à inciter les riverains à vivre avec le risque inondation ont succédé à la construction de digues de protection. Notre thèse questionne la portée de ce changement d'action publique dans le domaine du risque inondation à travers l'étude d'une politique territoriale sur le Rhône. À cette fin, nous retraçons la genèse d'un instrument d'action publique, la restauration de zones d'expansion de crues, dans les forums internationaux et européens. Nous rendons compte de la traduction de cet instrument opérée sur le Rhône par une coalition de réformateurs promouvant une nouvelle problématisation des inondations. Nous suivons les controverses qui se sont déployées autour de la mise en œuvre de cet instrument localement, qui sont autant de traductions concurrentes de ce dernier. Enfin, nous questionnons les effets de l'abandon de cet instrument sur la politique territoriale, sur l'institution qui l'a porté, et sur le changement d'action publique annoncé. / Since the 1990s a shift occurred in the policies of flood risk in France. The protection structures that had been prevailing since the 19th century were questioned, and flooding was redefined as an unavoidable and beneficial for the environment. Public policy discourses about risk culture have replaced those of flood risk as an issue of public safety. The policy instruments have also changed. Facilities to encourage residents to live with flooding replaced major dykes building. The thesis questions the extent of this policy shift in the field of flood risk through the study of a local policy on the Rhône River. To that end, we retrace in international and European fora the origin of a policy instrument typical of this policy shift: the restoration of floodplains. We analyze the adaptation of this instrument to the Rhône as an opportunity for a coalition to support a new definition of floods locally. We follow the controversies and conflicts that developed around the implementation of this instrument. Finally, we question the impact of the abandonment of this instrument on the local policy itself, on the legitimacy of the coalition and on the policy shift announced.

As the world becomes more urbanized and heavy precipitation events increase in frequency and intensity, urban flooding is an emerging concern. Urban flooding is caused when heavy rainfall collects on the landscape, exceeding the capacity of drainage systems to effectively convey runoff. Unlike riverine and coastal flooding, urban flooding occurs frequently, and its risks and impacts are not restricted to areas within floodplains or near bodies of water. The objective of this dissertation is to improve our understanding of urban flooding and our capability to predict it through the development of tools and knowledge to assist with its analysis, modeling, and forecasting. To do this, three research objectives were fulfilled. First, the Stream Hydrology And Rainfall Knowledge System (SHARKS) app was developed to improve upon existing real-time hydrologic and meteorological data retrieval/visualization platforms through the integration of analysis tools to study the hydrologic processes influencing urban flooding. Next, the ability to simulate the hydrologic response of urban watersheds with large storm sewer networks was compared between the fully distributed Gridded Surface/Subsurface Hydrologic Analysis (GSSHA) model and the semi-distributed Storm Water Management Model (SWMM). Finally, the Probabilistic Urban Flash Flood Information Nexus (PUFFIN) application was created to help users evaluate the probability of urban flash flooding and to identify specific infrastructure components at risk through the integration of high-resolution quantitative precipitation forecasting, ensemble forecasting, and hydrologic and hydraulic modeling. The outcomes of this dissertation provide municipalities with tools and knowledge to assist them throughout the process of developing solutions to their site-specific urban flooding issues. Specifically, tools are provided to rapidly analyze and respond to rainfall and streamflow/depth information during intense rain events and to perform retrospective analysis of long-term hydrological processes. Evaluations are included to help guide the selection of hydrologic and hydraulic models for modeling urban flooding, and a new proactive paradigm of probabilistic flash flood guidance for urban areas is introduced. Finally, several potential directions for future work are recommended. / Doctor of Philosophy / As the world becomes more urbanized and heavy precipitation events increase in frequency and intensity, urban flooding is an emerging concern. Urban flooding is caused when heavy rainfall collects on the landscape, exceeding the capacity of drainage systems to effectively convey runoff. Unlike riverine and coastal flooding, urban flooding occurs frequently, and its risks and impacts are not restricted to areas within floodplains or near bodies of water. The objective of this dissertation is to improve our understanding of urban flooding and our capability to predict it through the development of tools and knowledge to assist with its analysis, modeling, and forecasting. To do this, three research objectives were fulfilled. First, the Stream Hydrology And Rainfall Knowledge System (SHARKS) app was developed to improve upon existing real-time hydrologic and meteorological data retrieval/visualization platforms through the integration of analysis tools to study the hydrologic processes influencing urban flooding. Next, the ability to simulate the hydrologic response of urban watersheds with large storm sewer networks was compared between the fully distributed Gridded Surface/Subsurface Hydrologic Analysis (GSSHA) model and the semi-distributed Storm Water Management Model (SWMM). Finally, the Probabilistic Urban Flash Flood Information Nexus (PUFFIN) application was created to help users evaluate the probability of urban flash flooding and to identify specific infrastructure components at risk through the integration of high-resolution quantitative precipitation forecasting, ensemble forecasting, and hydrologic and hydraulic modeling. The outcomes of this dissertation provide municipalities with tools and knowledge to assist them throughout the process of developing solutions to their site-specific urban flooding issues. Specifically, tools are provided to rapidly analyze and respond to rainfall and streamflow/depth information during intense rain events and to perform retrospective analysis of long-term hydrological processes. Evaluations are included to help guide the selection of hydrologic and hydraulic models for modeling urban flooding, and a new proactive paradigm of probabilistic flash flood guidance for urban areas is introduced. Finally, several potential directions for future work are recommended.

Coastal communities along the eastern seaboard are continuously exposed to flooding and related impacts, compromising the health and safety of their residents and especially of more vulnerable older populations. In cases where structural protection and floodproofing measures may not protect households from all types of flooding, relocation may represent the most effective long-term adaptation option. However, the extent to which older residents in Hampton Roads, Virginia are exposed to such flooding is not well understood, nor are the factors influencing their relocation attitudes. Thus, the main objective of this research is to understand both the exposure to flooding and evaluate attitudes towards relocation among older residents in Hampton Roads. This study uses a mixed methods approach to analyze flood exposure and attitudes towards relocation among older adults living in this area. First, a geospatial analysis was conducted to assess the change in flood risk in Hampton Roads over a period of 60 years and exposure to older populations, aged 60 and over. Then the survey data were used to conduct a correlation analysis to examine the relationship between survey responses and respondents' willingness to consider relocation. The geospatial analysis showed that flood exposure in this area does not increase linearly with time, with several block groups experiencing accelerated levels of flood increases from 2000-2060. Most of the municipalities which experience high overlap between flood extent and older population percentages are urban and see dramatic increases in flood exposure from 2000-2060. The statistical results show that willingness to consider relocation is correlated to several variables measuring sociodemographic characteristics, place attachment, and flood exposure, and less to other considerations influencing the decision to permanently relocate. The most influential factors driving relocation attitudes are financial, where residents would consider relocation if compensated or offered similar housing elsewhere. Finally, a large proportion of respondents (40.28%) would prefer to permanently move to either a different region or different state should flooding continue in their community. The results of this study can help community leaders and policymakers to better understand the flood outcomes and assistance needs of their older populations living in flood-prone areas. / Master of Science / Coastal communities along the Eastern United States are constantly exposed to flooding and related impacts. Hampton Roads, Virginia is experiencing higher-than-average sea level rise, which is increasing flooding and its impacts. This area is also a preferred retirement region, where older populations prefer to move. Older populations are more negatively affected by these impacts due to chronic health conditions like diabetes and hypertension, which require easy access to health care services, as well as mobility constraints. The objective of this research is to identify areas within Hampton Roads that have a significant overlap between flooding and older populations and to understand what factors are affecting older residents' attitudes towards relocation. This study answers the following questions regarding the overall objective: 1) What is the exposure to coastal flooding of older populations living in urban areas in Hampton Roads? and 2) Which aspects of socioeconomic circumstances, experiences with flooding, and flood-related concerns affect attitudes about permanent relocation among older coastal residents? To answer these questions, a geospatial analysis was conducted, followed by a survey analysis. There are high levels of overlap between older populations and flooding in urban municipalities, and flood exposure is expected to dramatically increase between the years 2000 and 2060. From the survey, older respondents favor monetary incentives for relocation as opposed to other factors. The results from this study should be used by local policymakers for more well-informed decisions that incorporate community members in the planning and relocation process.

Indiana University-Purdue University Indianapolis (IUPUI) / Paleoclimate records from North and South America were used to develop a holistic understanding of global paleo-hydroclimatic drivers across a range of boundary conditions. Here, geophysical analysis of lacustrine sediment stratigraphy at Lago de Tota, Boyaca, Colombia provided evidence for significant lake-level fluctuations through the late Quaternary and produced a record that potentially spans the last 60 ka. Seismic data revealed a series of off-lap and on-lap sequences in the upper ~20 m of sediments that indicated large amplitude changes in lake-level, driven by variability in the mean latitude of the Intertropical Convergence Zone as controlled by insolation- and ocean circulation-driven hemispheric temperature gradients during glacial/stadial and interglacial/interstadial events. In North America, late Holocene flood recurrence in the Midwest and Holocene changes in the mean latitude of the polar front jet stream were investigated through multi-proxy examinations of sediment cores collected from swale lakes in northern Kentucky and southern Indiana, and a glacially formed kettle lake in northern Indiana. These results showed that the midlatitude jet stream was displaced to the south during the late Holocene, which increased the amount of Midwestern precipitation sourced from the northern Pacific and Arctic, especially during prolonged cool conditions. During these cool periods, when atmospheric flow was meridional and a greater amount of precipitation was delivered from the northerly sources, Ohio River flooding increased. During warm conditions, when clockwise mean-state atmospheric circulation advected southerly moisture from the Gulf of Mexico into the Midwest, flooding on the Ohio River decreased. At present, streamflow in the Midwest is demonstrated here to be generally increasing, despite atmospheric conditions typically associated with reduced streamflow in the paleo-record, due in part to increasing precipitation and modern land-use dynamics. Together, these studies demonstrate the sensitivity and vulnerability of local-scale hydrological processes to synoptic climate change.

This research explores geospatial patterns in social vulnerability to flooding and experimentally examines the effect of coverage maximums on flood insurance demand. In the first chapter, I analyze census data for the City of Calgary from 1991-2016 to identify trends in social vulnerability based on flood hazard level. Using a quasi-experimental design, I estimate the short-term changes in social vulnerability attributable to the 2013 Calgary flood. The results show that the Calgary flood was associated with a 2.6% increase in postsecondary education, a 1.4% decrease in the immigrant population, a 1.7% decrease in the visible minority population, a $7,100 increase in median family income, 2.8% decrease in home ownership, 3.7% increase in housing construction and 2.2% increase in recent movers. Together, these findings suggest that the highest flood hazard areas in Calgary are generally comprised of lower vulnerability populations; absolute loss potential from floods is getting higher over time due to higher property wealth in high flood hazard areas; and flooding events are associated with a decline in social vulnerability over the short-term. In the second chapter, I examine flood insurance coverage preferences through the use of a hypothetical choice experiment. The experiment was designed to examine the effect of dwelling value and coverage limit on the probability of flood insurance purchase, while holding the probability of flooding and insurance price constant. Controlling for income, the results indicate that amount of coverage is negatively related to flood insurance demand, however, for people in high-value dwellings the opposite is observed. This may suggest an approach to flood insurance as an investment into high-value properties as a financial asset, but the trade-off in higher yearly premiums may not seem worth the investment for lower-valued dwellings. This research shows an inconsistent demand for flood insurance, dependent on dwelling value and independent of income. / Thesis / Master of Science (MSc) / In this research I analyze the population characteristics of the City of Calgary geographically in order to determine if more vulnerable populations are exposed to the hazard of flooding. I also look at the before-and-after flood population characteristics of the flooded and non-flooded areas to see if flooding makes communities more or less vulnerable following an event. My aim is to provide context for the flooding hazard in Calgary and see if a flood changes the population vulnerability of the affected areas afterwards. I also conduct a choice experiment where I provide participants with a devised flood insurance scenario. I keep some of the variables constant, such as flood probability and insurance price, but change the amount of coverage and dwelling value randomly to see if they influence the likelihood that people buy insurance. The goal of this is to understand how insurance maximums can influence consumer demand.

A counter-current two-phase flow under an applied electric field has been studied theoretically using potential flow equations. A flooding correlation has been derived taking account of applied electric field on the interface for both adiabatic and condensing system. It is found that the electric field enhances flooding phenomena in case of adiabatic system. In the case with system involving condensation the electric field enhances flooding at low liquid flow rates and at high liquid flow rates the flooding point decreases under electric field depending on the rate of subcooling. / Thesis / Master of Engineering (ME)

Evaluating and educating communities on their flood risks is an integral part of adapting to climate change and more extreme precipitation patterns. Low-income communities are often the most affected by in-land floods. They are more likely to live in floodplains and have less socioeconomic mobility. This thesis takes a two-pronged approach to evaluating flood risk. First, a flood risk model that identifies areas of high runoff in Giles County, Virginia was developed. The model accounts for land cover, soil type and elevation. The soil retention layer and Digital Elevation Model (DEM) produced a cell by cell layer of runoff. Storm data was collected from the NEXRAD program and integrated into the runoff layer. Countywide maps of low, moderate and high risk were produced. Semi structured interviews were then conducted to gauge the usability of the maps within high risk areas. Interview feedback was transcribed and coded for analysis. Themes identified throughout the interviews, were used to make adjustments to the model and maps. This experience suggests that combining technical analysis and community engagement can create a more accurate depiction of flood risk that is meaningful to those most affected. This paper also suggests that evaluating riverine flooding based on the most severe, recent storm yields a more accurate and impactful tool than previous flood modeling methods. This work takes flood modeling a step farther by receiving community input and shows that models are only as useful as they are meaningful to the most impacted communities. / Master of Urban and Regional Planning / Climate change models suggest that many communities will experience fewer precipitation events, but when precipitation events do occur they will be more intense and thus destructive. Communities can expect a higher risk of flooding, which is why it is important to plan proactively and understand where the most at-risk areas are. To help Giles County, VA understand its flood risk we created a tool that displays storm runoff. Elevation, soil type and vegetation were incorporated into the model. Storm data was integrated into the model and compared to annual precipitation levels. Countywide maps of low, moderate and high risk were produced. In order for the maps to have the maximum impact they need to be accessible to at risk populations. To gauge the accessibility of the maps to the community semi structured interviews were conducted within the high risk areas. Issues and opportunities identified through the interviews were used to make adjustments to the model and maps. The findings suggest that combining technical analysis and community engagement can create more accurate depictions of flood risks that are meaningful to those most affected. Future research efforts should include incorporating anticipated development schemes into the model and hosting more in depth community engagement activities. The importance of community engagement is highlighted in this research, as the interviews has a major impact on the outcome of the model.

Coastal communities face threats of flooding associated with episodic storm events and high tides that are increasing in severity and frequency due to climate change and sea level rise (SLR). The Mid-Atlantic U.S. is experiencing SLR at rates faster than the global average, especially in Hampton Roads, Virginia where the rate of SLR is accelerating due to land subsidence. Adaptation plans for coastal flooding are mostly made at the municipality level, ignoring the propagation of water across its administrative boundaries. Impact assessment at the watershed scale identifies areas where municipalities will need to collaborate to mitigate the flood impact. The main purpose of this project was to evaluate the impact of flooding among watersheds in Hampton Roads and identify those most at risk that overlap one or more municipal boundary. Additionally, this research assessed the impact on land use/cover and population throughout the Hampton Roads region and within a case study watershed. To meet these objectives, we used U.S. Army Corps of Engineers 50-year floodplain and NOAA intermediate SLR scenarios for 2030, 2060, and 2090 to calculate the percent land area inundated for each watershed in Hampton Roads. Further, we assessed the flood impact on populations and specific land use/covers throughout the region for each SLR scenario, as well as within the Elizabeth River watershed. Key findings show that five watersheds will see a greater increase in inundated area than the surrounding watersheds, with two that overlap multiple municipalities. The anticipated land use impacts indicate significant inundation of land occupied by military, followed by commercial, industrial, and wetland covers both in Hampton Roads and within the Elizabeth River watershed. These findings not only highlight the need for more synchronized collaboration on adaptation between municipalities in Hampton Roads, but also provide a framework for the impact assessments in similar settings globally. / Master of Science / Coastal communities face numerous threats of flooding due to storm events and high tides. These events are becoming more frequent due to climate change and sea level rise (SLR). The Mid-Atlantic U.S. is experiencing SLR at rates faster than the global average, especially in Hampton Roads, Virginia where the rate of SLR is accelerating due to sinking land. Water movement does not recognize administrative boundaries but rather reflects physical features of the land. At the same time most plans to combat rising water levels are often made within administrative boundaries. The main objective of this research is to evaluate the flood impacts at the watershed scale and identify areas where localities will need to collaborate to reduce flood impact. This research further explores answers the following questions: 1.)Which watersheds in Hampton Roads are most prone to flooding?; and 2.) How many people will be impacted by flooding, and what kinds of land uses will be impacted? To answer these questions, we used floodplain data and SLR scenarios for 2030, 2060, and 2090 to determine land area inundated for each watershed in Hampton Roads. Further, we summarized population and land use impacts within the floodplain for the entire region, as well as within a case study of the Elizabeth River watershed in Norfolk and Portsmouth. Key findings include five watersheds that will see a greater increase in inundated area with SLR than surrounding watersheds, two of which contain multiple municipalities. Finally, we identified significant impacts for military, commercial, industrial, and wetland land covers both in Hampton Roads and within the Elizabeth River watershed.

Hydrologic and material dynamics of ephemeral rivers were investigated in the Namib Desert to assess how hydrologic regimes shape the physical habitat template of these river ecosystems. An analysis of long-term hydrologic records revealed that the variation in mean annual runoff and peak discharge were nearly four times higher than the global average, rendering the rivers among the most variable fluvial systems yet described. Further, a pronounced downstream hydrologic decay characterized all of the rivers. The high spatio-temporal variability in flow was reflected in patterns of material transport. Retention of woody debris increased downstream, in contrast to patterns typically reported from more mesic systems, largely attributable to hydrologic decay. Woody debris piles were the principal retentive obstacles and played an important role in channel dynamics. They were also key microhabitats for various organisms, forming "hotspots" of heterotrophic activity analogous to patterns reported from perennial streams. Large amounts of fine particulate and dissolved organic matter (FPOM and DOM) deposited in the lower reaches of the rivers serve to fuel this heterotrophic biota. As a result of the hydrologic decay, sediment concentration (both organic and inorganic) increased downstream and the lower reaches of these rivers acted as sinks for material exported from their catchments. FPOM and DOM concentrations were among the highest reported for any aquatic system, and, contrary to patterns reported from more mesic systems, FPOM dominated the total organic load transported in these rivers. Inorganic solute concentration also increased downstream, resulting in a downstream increase in soluble salt content in floodplain soils. Soils within the river's lower reaches served as effective long-term integrators of hydrologic variability. The mean extent of floods entering the lower river was defined by an alluviation zone, evident from the convexity exhibited in the lower section of the rivers' longitudinal profiles. A downstream increase in the proportion of silt within floodplain soils is associated with increased sediment deposition. Silt deposition had a positive influence on moisture availability, plant rooting, and habitat suitability for various organisms, including fungi and invertebrates. In addition, a strong positive correlation was observed between silt, organic matter, and macronutrients. Thus, the hydrologic control of transport and deposition patterns has important implications for the structure and function of ephemeral river ecosystems. Finally, an examination of the influence of elephants upon riverine vegetation highlighted the importance of these systems as isolated resource patches interspersed in an arid and hostile landscape. Further, it illustrated that flooding was a key ecological process and that hydrologic alterations would affect the fluvial ecosystem as well as the regional landscape they drain. / Ph. D.

<p>Mosquitoes are found in extremely large numbers in the lower parts of the River Dalälven. In the year 2000 the mosquito nuisance was especially high, resulting in foundation of the Biological mosquito control project. Since 2001 mosquito larvae are controlled by using a biological pesticide BTI (Bacillus thuringiensis ssp israelensis). The mosquito fauna in the area is dominated by flood water mosquitoes, a group of mosquitoes that are very aggressive and form new generations of mosquitoes during every single flooding event during the summer. To be able to efficiently control the mosquitoes it is essential to know the extension and locality of the flooding. A flooding event is evaluated by how high the water level will reach and at which time the top of the hydrograph is accruing. There is a need for a tool for short time prediction of flooding events in the Nedre Dalälven region. In this study a hydraulic model in the software HEC-RAS has been used, here called HEC-RAS NEDA. The hydraulic model came up with good results when predicting water surface levels. The validation process made from figures of a period with large amplitude in water levels showed that the modelled water level was within ± 0,05 m from the observed water stands. It is a stable model that can handle 100-year flows with quick changes in the flow. The correspondence is good concerning the water levels and it functions well when studying the top of the hydrograph. HEC-RAS NEDA is an accurate and easy to manage tool for prediction of flooding in the lake of Bysjön, Österviken and Färnebofjärden. Modelled results have been compared with the model made by Swedish meteorological and hydrological institute on the request of Räddningsverket. The results from the two models shows large discrepancies, probably because of low accuracy data entered into the model from Räddningsverket. Räddningsverket has used the Geographical Sweden Data height data bank´and I used the height data from a laser scanned digital terrain model. Area studies have also been made according to how the area of the water surface changes with the water stand. These studies show that during the flood in year 2000, 55 km2 was flooded based on laserscanning in Färnebofjärden.</p> / <p>Mygg förekommer i extremt stora antal i området kring nedre delen av Dalälven. År 2000 var myggplågan särskilt stor vilket medförde att projekt Biologisk Myggkontroll bildades. Myggbekämpning har bedrivits i Nedre Dalälven sedan 2001 med ett biologiskt bekämpningsmedel, Bacillus thuringiensis ssp israelensis (BTI). Områdets myggfauna domineras av så kallade översvämningsmygg, en grupp stickmyggor som är mycket aggressiva och bildar nya generationer efter varje enskild översvämning under sommaren. För en effektiv bekämpning av mygglarverna krävs att man vet översvämningens omfattning och lokalisering. En översvämning bedöms med avseende på hur högt vattenståndet når samt vid vilken tidpunkt hydrografens toppvärde inträffar. Det finns ett behov av ett verktyg som kan utföra korttidsprognoser av översvämningar i Nedre Dalälven. I denna studie har en hydraulisk modell i programvaran HEC-RAS använts, här kallad för HEC-RAS NEDA. Den hydrauliska modellen fungerar bra till att användas för prediktering av vattenstånd i Nedre Dalälven. Valideringen av modellen mot värden under en testperiod med stor amplitud i vattenståndet visade att modellerade vattenstånd var inom ± 0,05 m från de uppmätta värdena. Modellen är stabil och klarar av att hantera 100-årsflöden med snabba flödesfluktuationer. HEC-RAS NEDA är ett noggrant och lätthanterligt predikteringsverktyg för översvämningar i Bysjön, Österviken och Färnebofjärden. Överensstämmelsen är god gällande nivån av vattenståndet och den fungerar bra för att studera hydrografens topp temporärt. Modellerade resultat har jämförts med karteringar som Sveriges meteorologiska och hydrologiska institut har gjort på Räddningsverkets begäran. Resultaten skiljer sig betydligt mellan HEC-RAS NEDA och Räddningsverkets modell, troligen på grund av att Räddningsverket har stora svagheter i indata till modellen. Räddningsverket har använt Geografiska Sverige Data-Höjddata och modellen HEC-RAS NEDA är framtagen med höjddata från en digital terrängmodell baserad på laserscanning. Areella studier i GIS över hur arean av vattenspegeln förändras med vattenståndet visar att Färnebofjärden under augusti år 2000 lade 55 km2 under vatten.</p>