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

As a result of the global climate change, extreme precipitation is occurring more frequently which increases the risk of flooding, especially in urban areas. Urbanisation is widely discussed regarding urban flooding where an increase of impervious surfaces limits the infiltration and increases the surface runoff. Flooding events in urban areas are increasing around the world and can cause large damages on infrastructure and buildings, which makes the cities vulnerable. Urban flood models are an important tool for analysing the capacity of the drainage systems, to predict the extent of the events and to find optimal locations to implement measures to prevent damages from flooding. In this project, a sensitivity analysis in MIKE FLOOD, a coupled 1D-2D flood model developed by DHI is presented, where sewer- and surface systems are integrated. The aim with this project is to investigate how the result of a coupled flood model vary in relation to changes in input parameters. The sensitivity analysis is performed to evaluate how different parameters impact the model output in terms of water depth and variations in cost of flooded buildings, roads, rail- and tramways. The analysis is applied in a case study in Lundby-Lindholmen, Gothenburg city, Sweden. The results show that modelling without infiltration influenced the model output the most, with the largest increase both in terms of cost and water depth over the investigated area. Here the correlation between the initial water saturation and location of the applied pre-rain was highlighted. The model outputs were less sensitive to changes in surface roughness (expressed as Manning value) than without infiltration but did lead to measurable changes in surface water depth and distribution while the flood damage cost didn’t show any major changes. Additionally, the coupled flood model was evaluated in terms of handling changes in magnitudes of rain-events. Data indicates the shorter the return period, the smaller the flood propagation, as well as the flood damage cost decreases with shorter return periods. The data evaluated supports the use of this coupled model approach for shorter return periods in terms of flood propagation.

This research investigates flood-risk communication challenges in Canada, emphasizing the need for tailored strategies to address diverse household preferences and values. In Chapter 2, we examine Canadian household experiences with flood-risk information, aiming to identify new communication needs and bridge the gap between households and flood-risk managers. The interviews reveal previously overlooked flood risk information needs. The importance of tailored communication strategies was highlighted by household participants as they emphasized the need for information that caters to their unique circumstances and requirements. Moreover, fairness emerged as a crucial aspect of flood-risk communication, prompting a call for equitable practices to address vulnerabilities affecting specific households. In Chapter 3, we investigate household values and preferences on flood-risk information through a survey of at-risk households in Canada, uncovering diverse preferences, values and needs for tailored risk information. Additionally, significant differences in flood-risk knowledge, accessibility, and transparency are observed among risk-status groups, with higher awareness among those who perceive themselves at risk. Overall, this research emphasizes the importance of understanding diverse values and preferences within households regarding flood-risk information. Strengthening flood-risk communication strategies and addressing information gaps can lead to more informed risk perceptions and improve awareness among at-risk households in Canada / Thesis / Master of Arts (MA) / This research focuses on how people in Canada receive information about flood risks and how we can improve it. In Chapter 2, we talked to Canadian households to learn about their experiences with flood-risk information. We found that the current way of giving this information might not meet everyone's needs. People want information that fits their specific situations, and they stressed the importance of fairness in how the information is shared. In Chapter 3, we conducted a survey among households at risk of flooding in Canada to find out what kind of information they prefer. We discovered that people like to get clear and direct messages with detailed risk information that is customized for them. We also noticed that some people who think they are at higher risk of flooding are more informed about the risks. This means it's essential to consider how people see their own risk levels when communicating with them effectively. Overall, this research shows that flood-risk information needs to be tailored to people's different preferences and values. By doing this, we can help individuals and communities better understand and prepare for flood risks. We recommend working together with different groups involved in flood-risk management to improve how we communicate these risks. By doing so, we can create a more informed and inclusive flood-risk communication system that helps communities stay safe during flood events in the future.

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Yes / This paper reviews and discusses the recent studies of natural flood management (NFM) and its associated microbial risks in the UK and suggests set of numerical modelling approaches for their respective investigation. This study details the importance of precise numerical representation of the NFM to flood inundations and microbial risks caused by NFM measures. Possible future numerical advancements of the numerical modelling for the NFM and microbial activities are also discussed here.

This thesis l concerned with the mathematical modelling of open channel flows governed by the Saint-Venant equations, which are used as a prediction or identification tools. A survey of the literature in these fields identified the problems in need of Immediate research. Numerical test runs were then devised which led to projecting a clear picture as follows. The performance of twn widely used Implicit finite difference schemes, the 4-point box and 6-point staggered schemes were compared In a wide range of circumstances. it is concluded that both schemes produce 'very close results, but the staggered scheme is prone to convergence problems In some extreme cases. It was also noted that a sharp change in geometric configuration of compound channels produced discontinuous features on the aim ulated depth and discharge hydrographs. The inability of the staggered scheme In handling a head-discharge relationship as a downstream boundary condition was tackled by proposing and implementing a scheme of second order accuracy. As model data are generally corrupted withh errors and noise, their effects together with that of other factors on the Identified friction parameters we Investigated. The results demonstte the paramount Importance of the effect of a choice of objective function on the Identified parameters. While the individual values of the identified M2nning n may vary from one flood event to another, their mean is shown both numerically and rigorously to be dependent upon the choice of objective function. It is shown that an objective function formulated by using absolute errors performs ideally and produces reliable results even in the presence of autocorrelated Gaucian noise samples. The mean of the Identified parameters is also found to be adversely affected if the observation station is affected by localized disturbances. Sensitivity of objective functions to the variation In the value of the friction parameter Is also found to be an Important factor, as Insensitivity leads to ill-conditioning.

The complex hydroclimatic response of the Upper Colorado River Basin (UCRB) to climate circulation patterns and their descriptive indices creates significant challenges to water managers, especially given the uncertain future of the climate. This dissertation addresses fundamental questions that surround extreme flooding in the UCRB by combining paleoflood field techniques, two analytical geochronology techniques and several numerical climate data analysis techniques. The three manuscripts included in this dissertation focus on the Dolores River Basin (DRB), a sub-basin within the UCRB in order to answer theoretical questions about the timing and climate patterns associated with extreme floods.It has become widely accepted that extreme flooding in the Lower Colorado River Basin (LCRB) is linked to a period when the frequency and intensity of El Nino periods was higher. Within the UCRB, and more specifically, the DRB, the linkages are less clear. The paleoflood chronology that we developed indicates that the peak episodes of flooding in the DRB occurred between roughly 300 A.D. and 1200 A.D. This period of flooding is out of phase with many floods in the LCRB, whose peak floods dominantly clustered in the last 700 years; a period of time coincident with the termination of large floods in the DRB. The chronology that I developed utilizes accelerator mass spectrometry radiocarbon (AMS 14C) and optically stimulated luminescence (OSL) to provide a detailed flood history, highlighting the importance of utilizing independent age control. Alternative, or less accurate chronologies would have resulted had we used AMS 14C or OSL alone, suggesting that some previously studied basins may have incorrect chronologies. The detailed flood chronology of this study has subsequently allowed us to contextualize extreme floods relative to middle--late Holocene climate variability.In an effort to provide a hydroclimatic context for flooding in the DRB, numerical analyses were applied to contemporary climate and streamflow data in order to identify the possible mechanisms that modulate precipitation and streamflow in the Western U.S. and more specifically, the DRB. Results from these techniques indicate that the DRB maintains a complex response to a major North Pacific, low-frequency circulation pattern. The North Pacific circulation modulates the low-frequency component of the DRB's precipitation and flooding, although the high frequency modulation remains very poorly characterized.

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A new stochastic rainfall field model is described which employs the Turning Bands Method (TBM) to transform a unidimensional Gaussian process, generated by the fractional differencing process along a line, into a multidimensional space-time Gaussian process with a specified space-time correlation structure. Transformations are applied to give the rainfall process a non-Gaussian and non-stationary structure. A correction factor is introduced into the model to take account of the effect of topography on rainfall. The model has been applied to the small upland Wye catchment in mid Wales (area 10.55 km2) and shown to reproduce satisfactorily the statistics and correlation structure of observed hourly point rainfall. As an extension to the rainfall field model, a new technique of conditional simulation has been used to generate the rainfall fields. The conditionally simulated rainfall fields reproduce exactly the observed point rainfalls at measurement points and likely realizations of rainfall fields between points. Rainfall fields generated by the above mentioned rainfall field model and the conditional simulation technique are fed directly into the Systeme Hydrologique European (SHE) model and the sensitivity of runoff prediction errors to (i) level of space-time correlation (ii) sampling of rainfall with different schemes in space and (iii) antecedent conditions are explored. It is found that in case of Wye catchment the errors deriving from sampling procedure used are generally small when rainfall fields were based on observed correlation structure. Sensitivity of errors to different correlation levels give the impression that errors increase with a decrease in correlation level. Further it is noticed that this trend of errors is more pronounced in `dry' catchment conditions as compared to `wet' catchment conditions. Overall the results for the small Wye catchment illustrate that the catchment acts as a smoother of the spatially distributed rainfall input at this spatial scale and for the rainfall regime in question. However, the results imply that for the typical raingauge densities encountered for larger catchments, significant errors may occur.