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The Need for Mapping, Modeling, and Predicting Flood Hazard and Risk at the Global Scale
Philip J. Ward1, Erin Coughlan de Perez1,2,3, Francesco Dottori4, Brenden Jongman1,5, Tianyi Luo6, Sahar Safaie7, and Steffi UhlemannâElmer8
1 Institute for Environmental Studies (IVM), Vrije Universiteit Amsterdam, Amsterdam, Netherlands
2 Red Cross Red Crescent Climate Centre, The Hague, Netherlands
3 International Research Institute for Climate and Society, Columbia University, New York, USA
4 European Commission, Joint Research Centre, Ispra, Italy
5 Global Facility for Disaster Reduction and Recovery, World Bank Group, Washington, DC, USA
6 World Resources Institute, Washington, DC, USA
7 United Nations International Strategy for Disaster Reduction Secretariat, Geneva, Switzerland
8 Aspen Re, Research and Development, Zurich, Switzerland
1.1. INTRODUCTION
River floods are one of the most damaging forms of natural hazards [GuhaâSapir et al., 2015], causing economic damage, fatalities, and social hardship all around the world. For example, over the period 1980â2013, flood losses exceeded $1 trillion globally, and resulted in approximately 220,000 fatalities [Munich Re, 2014]. Moreover, flood losses are increasing. While the reported losses due to floods were about USD 7 billion per year during the 1980s (adjusted for inflation), these increased to USD 24 billion per year during the period 2001â2011 (Kundzewicz et al. [2013], based on Munich Re NatCatSERVICE data). These negative impacts of flooding are projected to increase in the future [UNIDSR, 2015a] due to climate change [Arnell and Gosling, 2016; Hirabayshi et al., 2013; Winsemius et al., 2015], urbanization [GĂźneralp et al., 2015; Jongman et al., 2012], and land subsidence [Brown and Nicholls, 2015; Syvitski et al., 2009].
Flood risk management aims to reduce the negative impacts of floods. The concept of flood risk combines the probability of a flood with its potential consequences. While there are many definitions of risk, it is usually operationalized as being a function of three risk elements, namely: hazard, exposure, and vulnerability [e.g., Kron, 2002; UNISDR, 2011, 2013, 2015a]. As stated by UNISDR [2011], the hazard refers to the hazardous phenomenon itself, such as a flood event, including its characteristics and probability of occurrence; exposure refers to the location of economic assets or people in a hazardâprone area; and vulnerability refers to the susceptibility of those assets or people to suffer damage and loss (e.g., due to unsafe housing and living conditions, or lack of early warning procedures).
Reducing risk, not only to flooding but also to all natural hazards, is high on the global political agenda. For example, it is at the heart of two recent international agreements: the Sendai Framework for Disaster Risk Reduction (Sendai Framework) [UNISDR, 2015b]; and the Warsaw International Mechanism for Loss and Damage Associated with Climate Change Impacts (Loss and Damage Mechanism) [UNFCCC, 2013]. The Sendai Framework is a 15âyear, voluntary, nonbinding agreement that was adopted at the Third UN World Conference in Sendai, Japan, in 2015. The Sendai Framework aims at the following outcome: âThe substantial reduction of disaster risk and losses in lives, livelihoods and health and in the economic, physical, social, cultural and environmental assets of persons, businesses, communities and countriesâ (UNISDR, 2015b; page 12). To do this, the Sendai Framework sets out four soâcalled priorities for action, one of which (Priority 1) is Understanding Disaster Risk. To achieve this at the global level, the framework points to the need to âenhance the development and dissemination of scienceâbased methodologies and tools to record and share disaster losses and relevant disaggregated data and statistics, as well as to strengthen disaster risk modeling, assessment, mapping, monitoring and multiâhazard early warning systemsâ [UNISDR, 2015b; page 16]. The Loss and Damage Mechanism was adopted at the United Nations Framework Convention on Climate Change (UNFCC) Conference of the Parties (COP19) in Warsaw, Poland, in 2013. It promotes the implementation of approaches to address loss and damage associated with impacts of climate change, including extreme events like floods, in developing countries. One of the ways to do this is by âenhancing knowledge and understanding of comprehensive risk management approaches to address loss and damage associated with the adverse effects of climate changeâ [UNFCCC, 2013; page 6].
To contribute to the aims of the aforementioned agreements, effective risk reduction strategies are required. To achieve this at the global scale requires methods to quantitatively assess global flood risk in a holistic manner [Mechler et al., 2014]. Ideally, this could be achieved by developing detailed, highâresolution local flood models [Jonkman, 2013] for all parts of the globe. However, in reality, the data required to develop such fineâscale models do not exist in most locations, and the time required to collect such data and run the models would be prohibitive. Therefore, in the past decade, several global flood risk models have been developed.
In this chapter, a brief overview is given of recent advances in global flood hazard and risk modeling in section 1.2. In section 1.3, we discuss how global flood risk model results are contributing to highâlevel advocacy in disaster risk management (DRM) activities at the international scale. In sections 1.4â1.6, we demonstrate a number of applications of global flood risk models in international development organizations, the reinsurance industry, and flood forecasting and early warning. An example of how to communicate complex information from global flood risk models to endâusers is provided in section 1.7, using the example of the Aqueduct Global Flood Analyzer. Finally, the chapter concludes with several remarks on limitations in global flood risk models, and the way forward in section 1.8.
