Flood risk and damage analysis of the 2023 floods in Meža River catchment, SloveniaBarbosa i Llauet, Oriol (Avtor) Rusjan, Simon (Mentor) Vidmar, Andrej (Komentor) flood damageflood hazardflood riskflood risk managementFwDETKRPANMeža riverSloveniawater depth estimationIn August 2023, Slovenia experienced devastating floods across the country. The mountainous regions, like the Meža River catchment, were the most affected. According to current estimates, the event caused €3 billion in direct damage and potentially up to €6 billion in indirect damage. The inundation extended far beyond the expected flood hazard areas in particular regions, exposing the hydraulic models' inherent uncertainties and limitations. The substantial transportation and deposition of debris and sediments obstructed the hydraulic conductivity of various river sections, leading to hydromorphological changes, extensive fluvial erosion, and flooding in areas previously unaware of their high flood risk, emphasising the challenges that externalities pose for hydraulic models. This master’s thesis examines the flood risk and damage resulting from the 2023 floods in the Meža River catchment. The flood extent was delineated using post-event orthophotos, while flood hazard modelling was conducted with the Floodwater Depth Estimation Tool (FwDET). This method, tested under the extreme conditions experienced by the Meža River, was compared with national flood hazard maps to assess its suitability. The flood damage analysis was performed using KRPAN software, which provided detailed statistical data on the event's impact, offering insights into the damages by asset types and sectors. Based on the post-flood event data, the flood hazard results reasonably accurately assessed water depths in areas that had undergone significant hydromorphological changes. FwDET performed substantially better in regions with milder channel slopes and wider floodplains, regardless of the hydromorphological modifications encountered. The most important hazard alterations in the Meža River were attributed to extensive fluvial erosion, sediment transport, and debris deposition. At several locations, the obstruction of hydraulic conductivity of bridges resulted in greater damage to urban assets. The estimated flood damage for the Meža River catchment in our analysis amounted to €77.7 million, with residential and industrial assets being the most affected. The flood return period was estimated to exceed 250 years, underscoring the exceptional nature of the event. The impact was particularly severe near remote torrential streams and urban areas affected by hydraulic conductivity obstructions, some of which had not been previously modelled. The damage-derived return period aligned with the FFA results, indicating a positive correlation between the available hydrologic data and the results obtained from FwDET and KRPAN. Given the satisfactory results and reduced time and cost associated with data analysis using this methodology, we recommend incorporating FwDET into the Slovene Flood Risk Management scheme. This tool could complement hydraulic models, offering more flexible flood mapping and enabling faster post-event risk and damage assessments.[O. Barbosa i Llauet]20242024-09-06 07:45:40Magistrsko delo/naloga160973sl