Latest Research News on Flood : Apr 2022

Flood risk and flood management

Risk management has been established as a well defined procedure for handling risks due to natural, environmental or man made hazards, of which floods are representative. Risk management has been discussed in many previous papers giving different meanings to the term—a result of the fact that risk management actually takes place on three different levels of actions: the operational level, which is associated with operating an existing system, a project planning level, which is used when a new, or a revision of an existing project is planned, and a project design level, which is embedded into the second level and describes the process of reaching an optimal solution for the project. The first two levels will be briefly described in the paper. It will be emphasized that the transition from the first to the second level is a dynamic process. As the value system of a nation changes, and as the natural boundary conditions are modified by human actions or global changes, an existing system will be found not meeting the demands of the present society, and actions on the second level are initiated. The decisions for change depend on the changes in options available for handling a flood situation, as well as on the changes in risk perception and attitudes towards risk. On the third level, the actual cost of a design are evaluated and compared with the benefits obtained from the planned project. In particular, on this level the residual risk is considered, i.e. the risk which remains even after a project is completed and fully operational.[1]


Review article “Assessment of economic flood damage”

Damage assessments of natural hazards supply crucial information to decision support and policy development in the fields of natural hazard management and adaptation planning to climate change. Specifically, the estimation of economic flood damage is gaining greater importance as flood risk management is becoming the dominant approach of flood control policies throughout Europe. This paper reviews the state-of-the-art and identifies research directions of economic flood damage assessment. Despite the fact that considerable research effort has been spent and progress has been made on damage data collection, data analysis and model development in recent years, there still seems to be a mismatch between the relevance of damage assessments and the quality of the available models and datasets. Often, simple approaches are used, mainly due to limitations in available data and knowledge on damage mechanisms. The results of damage assessments depend on many assumptions, e.g. the selection of spatial and temporal boundaries, and there are many pitfalls in economic evaluation, e.g. the choice between replacement costs or depreciated values. Much larger efforts are required for empirical and synthetic data collection and for providing consistent, reliable data to scientists and practitioners. A major shortcoming of damage modelling is that model validation is scarcely performed. Uncertainty analyses and thorough scrutiny of model inputs and assumptions should be mandatory for each damage model development and application, respectively. In our view, flood risk assessments are often not well balanced. Much more attention is given to the hazard assessment part, whereas damage assessment is treated as some kind of appendix within the risk analysis. Advances in flood damage assessment could trigger subsequent methodological improvements in other natural hazard areas with comparable time-space properties.[2]


FLOOD DAMAGE, VULNERABILITY AND RISK PERCEPTION – CHALLENGES FOR FLOOD DAMAGE RESEARCH

In this contribution it is argued that the current challenge in flood damage research consists in developing a better understanding of the interrelations and social dynamics of flood risk perception, preparedness, vulnerability, flood damage and flood management, and to take this into account in a modern design of flood damage analysis and flood risk management. Accordingly, the sections of this contribution are organised as follows: In the next section the relationship between flood damage, vulnerability and risk perception is analysed and clarified. Section three deals with state-of-the-art approaches to flood damage analysis. The fourth section discusses the shortcomings of the current approaches with a special focus on the disregard for socio-economic factors and methods. Finally, the contribution concludes with an outlook, presenting current EU research efforts to improve state-of-the-art approaches to flood damage analysis.[3]


Flood power

Channel boundary shear stress and stream power per unit boundary area are very useful concepts in assessing the role of rare, great floods in producing major geomorphic responses in fluvial systems. These variables were determined for the largest known flash floods in small drainage basins and for six historic dam-failure floods, predominantly in the United States. The largest values (shear stress exceeding 2×103 Nm−2 and power per unit area exceeding 1×104 Wm−2) occurred in narrow, deep flows in exceptionally steep bedrock streams. An optimum drainage area of approximately 10 to 50 km2 seems to be associated with the most powerful flash floods.[4]


Rethinking the relationship between flood risk perception and flood management

Although flood risk perceptions and their concomitant motivations for behaviour have long been recognised as significant features of community resilience in the face of flooding events, there has, for some time now, been a poorly appreciated fissure in the accompanying literature. Specifically, rationalist and constructivist paradigms in the broader domain of risk perception provide different (though not always conflicting) contexts for interpreting evidence and developing theory. This contribution reviews the major constructs that have been applied to understanding flood risk perceptions and contextualises these within broader conceptual developments around risk perception theory and contemporary thinking around flood risk management. We argue that there is a need to re-examine and re-invigorate flood risk perception research, in a manner that is comprehensively underpinned by more constructivist thinking around flood risk management as well as by developments in broader risk perception research. We draw attention to an historical over-emphasis on the cognitive perceptions of those at risk to the detriment of a richer understanding of a wider range of flood risk perceptions such as those of policy-makers or of tax-payers who live outside flood affected areas as well as the linkages between these perspectives and protective measures such as state-supported flood insurance schemes. Conclusions challenge existing understandings of the relationship between risk perception and flood management, particularly where the latter relates to communication strategies and the extent to which those at risk from flooding feel responsible for taking protective actions.[5]


Reference

[1] Plate, E.J., 2002. Flood risk and flood management. Journal of hydrology, 267(1-2), pp.2-11.

[2] Merz, B., Kreibich, H., Schwarze, R. and Thieken, A., 2010. Review article” Assessment of economic flood damage”. Natural Hazards and Earth System Sciences, 10(8), pp.1697-1724.

[3] Messner, F. and Meyer, V., 2006. Flood damage, vulnerability and risk perception–challenges for flood damage research. In Flood risk management: hazards, vulnerability and mitigation measures (pp. 149-167). Springer, Dordrecht.

[4] Baker, V.R. and Costa, J.E., 2020. Flood power. In Catastrophic flooding (pp. 1-21). Routledge.

[5] Birkholz, S., Muro, M., Jeffrey, P. and Smith, H.M., 2014. Rethinking the relationship between flood risk perception and flood management. Science of the Total Environment, 478, pp.12-20.

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