Process-based flood risk assessment for Germany

Stefan Lüdtke,Kai Schröter,Tobias Sieg,Sergiy Vorogushyn,Mostafa Farrag,Nivedita Sairam,Bruno Merz,Viet Dung Nguyen,Heidi Kreibich,Fabio Brill,Patric Kellermann

doi:10.5194/egusphere-egu21-13034

Abstract

&lt;p&gt;Floods affect people worldwide and account for more than USD 100 billion losses on average every year. Hazard, Exposure and Vulnerability are the three components that influence flood risk. Flood Risk Management (FRM) decisions especially, with respect to new flood defense schemes and resilience initiatives are generally taken based on the assessment of impacts for hazard scenarios. Current large-scale studies are comprehensive in terms of sectors covered in impact assessment. However, these studies often deploy generalized data and methods on the model components resulting in coarse risk estimates with low spatial resolution.&lt;/p&gt;&lt;p&gt;In this study, we use process-based models with 100m resolution on the national scale within a systems approach to develop and simulate a 5000 year flood event catalogue for Germany. The events are then analyzed per economic sector, including residential, commercial and agriculture sectors. The risk chain includes continuous simulation of high-resolution hazard maps, obtained from coupled hydrology and hydraulic models; NUTS3-level exposure asset values further disaggregated to ATKIS land-use data and calibrated object-level vulnerability models that provide high-resolution quantification of economic damage. Spatial dependence of flood events is addressed by the continuous simulation approach. For each model component in the risk assessment (hazard, exposure and vulnerability), uncertainty in data and methods are integrated into the risk predictions. Based on these simulations, we present a sector-wise flood risk assessment for Germany along with the reliability of the risk estimates. This process-based, systemic flood risk assessment is valuable for policy making, adaptation planning and estimating insurance premiums.&lt;/p&gt;

Highlights

Integrated flood risk management approaches are implemented in many countries worldwide (Merz et al, 2010; Sayers et al, 2013)
We apply the process-based Regional Flood Model (RFM) to simulate a 5000-year flood event catalog for all major catchments in Germany and derive risk curves based on the losses per economic sector
The agriculture sector gets affected by small return period floods and only contributes to less than 3% to the total risk

Summary

Introduction

Integrated flood risk management approaches are implemented in many countries worldwide (Merz et al, 2010; Sayers et al, 2013). These approaches consider that flood defenses might fail and focus on mitigating the consequences of flooding, acknowledging that entirely preventing floods is not possible. In Germany, the events in 1993, 1995 and the extreme event in 2002 triggered various policy decisions toward more systemic risk management approaches (Petrow et al, 2006; Rözer et al, 2020). Nationwide risk assessments are important to support national risk management and climate change adaptation policies (Merz et al, 2010). The European Flood Directive (ES, 2007) requests the European Union member states to provide risk management plans for all areas with potentially significant flood risk.

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