FLOOD RISK ASSESSMENTS - RESULTS, APPLICATIONS AND FUTURE REQUIREMENTS

Andreas Kortenhaus,Hocine Oumeraci

doi:10.9753/icce.v34.management.15

Andreas Kortenhaus, Hocine Oumeraci

Open Access

https://doi.org/10.9753/icce.v34.management.15

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Abstract

This paper summarises and discusses the key results of two research projects one of which was a 4-year joint research project in Germany (XtremRisK) and the other comprised applications of the XtremRisK results to selected cases in Denmark (HARIMA-DK) within the framework of the European Flood Directive on the generation of hazard and risk maps for preselected areas. The former project focused on improving and expanding the existing knowledge, methods and models on flood risk assessments for extreme storm surges with respect to (a) extreme storm surge for current conditions and scenarios for climate change, (b) failure mechanisms of flood defences, (c) assessment of tangible and intangible losses, (d) integrated flood risk analysis involving the aforementioned developments and its implementation for two selected pilot sites (representative for an open coast and an urban estuarine area in Germany). The HARIMADK project used these results, applied it and produced flood risk maps for selected coastal areas in Denmark. The key results of both projects are briefly summarised, lessons learned are discussed and some conclusions for future flood risk studies are finally drawn.

Highlights

In the past, storm surges and river floods have frequently led to failures of flood defences which caused major damages, along German rivers and coastlines
The German research project XtremRisK (Extreme storm surges at open coasts and estuarine areas: Risk assessment and mitigation under climate change aspects, www.xtremrisk.de) has defined the risk of flooding as the combination of the probability that the flood occurs and the related consequences to people and assets (Oumeraci et al, 2012)
Within XtremRisK a deterministic approach has been developed which combines empirical methods and numerical modelling to analyse the non-linear interaction between the storm surge constituents and to determine extreme storm surge scenarios

Summary

Introduction

Storm surges and river floods have frequently led to failures of flood defences which caused major damages, along German rivers and coastlines. Due to climate change and increasing intensities of rainfall and storm surges it may be expected that the risk of flooding will still increase. Taking into account the uncertainties associated with the impacts of climate change, the unpredictability of extreme events and the various combinations of loading conditions, it is inevitable to use a probability-based approach to account for any flood hazard assessment. Mid- and long-term changes of the potential socio-economic consequences of any flood event are impossible or very hard to predict but should be accounted for when dealing with any future impacts of hazards. Risk-based approaches are more widely used to date for assessing both future changes and their consequences in a very transparent and quantifiable way. Definitions and methodologies are not consistent in literature and there is an ongoing discussion to which detail flood risk assessments need to and can be performed (see e.g. Oumeraci et al, 2012)

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Conclusion