Improving flood damage assessment models in Italy

Flood damage assessments are often based on stage-damage curve (SDC) models that estimate economic damage as a function of flood characteristics (typically flood depths) and land use. SDCs are developed through a site-specific analysis, but are rarely adjusted to economic circumstances in areas to which they are applied. In Italy, assessments confide in SDC models developed elsewhere, even if empirical damage reports are collected after every major flood event. In this paper, we have tested, adapted and extended an up-to-date SDC model using flood records from Northern Italy. The model calibration is underpinned by empirical data from compensation records. Our analysis takes into account both damage to physical assets and losses due to foregone production, the latter being measured amidst the spatially distributed gross added value

Validation of flood risk models: Current practice and possible improvements

[EN] Although often neglected, model validation is a key topic in flood risk analysis, as flood risk estimates are used to underpin large investments and important decisions. In this paper, we discuss the state of the art of flood risk model validation, using as input the discussion among more than 50 experts at two scientific workshop events. The events aimed at identifying policy and research recommendations towards promoting more common practice of validation, and an improvement of flood risk model reliability. We pay specific attention to different components of the risk modelling chain (i.e. flood hazard, defence failure, and flood damage analysis) as well as to their role in risk estimates, to highlight specificities and commonalities with respect to implemented techniques and research needs. The main conclusions from this analysis can be summarised as the need of higher quality data to perform validation and of benchmark solutions to be followed in different contexts, along with a greater involvement of end-users in the application on flood risk model validation.The authors acknowledge with gratitude all the participants and the speakers at the workshop in Delft (December 2014) and at the special session at FloodRisk2016 (October 2016); as the main content of the papers was derived from the information presented and the fruitful discussions at these two events. As such, it may include subjective considerations by the authors and may not reflect the individual statements presented at these events. We also acknowledge the EuropeaBallio et an Geoscience Union (EGU), the Panta Rhei Initiative, the FloodRisk2016 Scientific Committee, and Deltares for supporting these events.Molinari, D.; De Bruijn, KM.; Castillo-Rodríguez, J.; Aronica, GT.; Bouwer, LM. (2019). Validation of flood risk models: Current practice and possible improvements. International Journal of Disaster Risk Reduction. 33:441-448. https://doi.org/10.1016/j.ijdrr.2018.10.022S4414483

The failed-levee effect: Do societies learn from flood disasters?

Human societies have learnt to cope with flood risks in several ways, the most prominent ways being engineering solutions and adaptive measures. However, from a more sustainable point of view, it can be argued that societies should avoid or at least minimize urban developments in floodplain areas. While many scientists have studied the impact of human activities on flood risk, only a few studies have investigated the opposite relationships, i.e. the impacts of past flood events on floodplain development. In this study, we make an initial attempt to understand the impact of the occurrence of flood disasters on the spatial distribution of population dynamics in floodplain areas. Two different methodologies are used to uncover this relationship, a large-scale study for the USA and a case-study analysis of the 1993 Mississippi flood. The large-scale analysis is performed at county level scale for the whole of the USA and indicates a positive relationship between property damage due to flood events and population growth. The case-study analysis examines a reach of the Mississippi river and the territory, which was affected by flooding in 1993. Contrary to the large-scale analysis, no significant relationship is found in this detailed study. However, a trend of dampened population growth right after the flood followed by an accelerated growth a decade later could be identified in the raw data and linked to explanations found in the literature