Introduction

The reduction of disaster risk from multiple hazard sources is an explicitly pronounced aim in several international agendas, for example, in the Agenda 21 (UN, 1992), the Johannesburg Plan (adopted at the 2002 World Summit on Sustainable Development) and the Hyogo framework for action (UN-ISDR, 2005). Strategies and actions to ‘control, reduce and transfer risks’ on the basis of risk assessments and analyses can be subsumed under the term ‘risk management’ (UN-ISDR, 2009).

Priority 2 of the new Sendai Framework for Disaster Risk Reduction points at ‘Strengthening disaster risk governance to manage disaster risk’ and argues that ‘Clear vision, plans, competence, guidance and coordination within and across sectors as well as participation of relevant stakeholders are needed’. At the same time, the framework makes clear that a sound evidence basis is needed in order to ground decisions on risk management (Priority 1: ‘Understanding Risk’). Here, the connection between disaster risk and sustainable development becomes clear:

Decisions in the area of so-called ‘traditional’ hazards like floods or earthquakes are normally based on expert analysis, often combined with results from modelling analysis. Hereby, the calculation of the spatiotemporal probabilities of the natural hazards on the basis of recent field monitoring, but also available historical information, is crucial. However, analysed data are only available for a specific period – and are thus not representative for longer periods. This problem is enhanced when using historical data. These do, indeed, add valuable information, in particular, for the frequency and magnitude analysis of the investigated processes. However, it has to be assumed that historical data are always incomplete information covering, in particular, large-scale events, but not events with smaller magnitudes. Nevertheless, even having the incompleteness of records in mind, the added value is still evident. This principal problem is exacerbated by the observed climate change-related effects on temperature and precipitation, which will certainly lead to new uncertainties about hydro-meteorological hazards, because past events might not be representative anymore.