The Aqueduct Global Flood Analyzer is a web-based interactive platform which measures river flood impacts by urban damage, affected GDP, and affected population at the country, state, and river basin scale across the globe, as well as 120 cities. It aims to raise the awareness about flood risks and climate change impacts by providing open access to global flood risk data free of charge.
The Analyzer enables users to estimate current flood risk for a specific geographic unit, taking into account existing local flood protection levels. It also allows users to project future flood risk with three climate and socio-economic change scenarios. These estimates can help decision makers quantify and monetize flood damage in cost-benefit analyses when evaluating and financing risk mitigation and climate adaptation projects.
Additionally, the analyzer identifies the future change in flood risk driven specifically by climate change and socio-economic development, which helps decision makers identify the drivers of future change and prioritize development focuses accordingly for strategic planning.
Global scale flood risk assessments, such as those included in the Aqueduct Global Flood Analyzer, have a large range of potential uses and applications. Following are a number of potential users:
- International development and financing organizations.International development and financing organizations (e.g. World Bank, USAID) can use the Analyzer for prioritizing investments in promising natural disaster risk reduction strategies.
- International and national disaster risk reduction (DRR) monitoring organizations. International organizations such as the United Nations and national governments can use the Analyzer to evaluate baseline risk conditions and monitor progress of risk reduction activities. An example is the progress of activities related to the implementation of the Hyogo Framework for Action (and the framework that will replace it when it expires in 2015).
- Insurance companies. The (re-)insurance industry can use the Analyzer to rapidly assess risk and projected risk trends across their portfolios, and to discuss the importance of insurance with potential new clients.
- Multinational companies. Multinationals can use the Analyzer to assess risks to their global manufacturing facilities and supply chains, and prioritize locations for further analysis and risk mitigation actions.
An example of how the data can be used comes from Nigeria, where a state-level flood risk assessment was performed for the World Bank. In the analysis, the number of affected people under several return period simulations was estimated. The results were used to open up a discussion on prioritization of flood risk management in the country.
The Aqueduct Flood Analyzer makes use of a series of models to estimate the impacts of river floods at a variety of geographic scales, including country, states, and major river basin. The impacts we look at include population exposed to floods, GDP exposed to floods, and urban damage caused by floods (in U.S. dollars).
The series of steps used by the Aqueduct Flood Analyzer includes:
- Global hydrological and hydraulic modelling. We simulate daily river runoff and flood volumes (0.5°x0.5°) for the period 1960-1999 using the global hydrological model PCR-GLOBWB and its extension for dynamic routing, DynRout. Daily precipitation, temperature, and radiation are used to estimate river runoff, and for each global 0.5°x0.5° cell, we estimate the resulting volume of water that ends up either in the river channel or on the adjacent floodplain (if flooding occurs).
- Socio-economic data (socio-economic change): for future socio-economic development, we used socio-economic data from the Shared Socio-economic Pathways (SSP). These data are produced assuming certain story lines of socio-economic development across the world. In total 5 storylines are available and future data on economic and urban development as well as population growth is available per country. We downscaled the country GDP and population estimates using a sophisticated downscaling procedure that differentiates growth estimates over urban and rural areas.
A number of caveats should be taken into account while using the hazard and risk data from the Aqueduct Flood Analyzer:
- Types of flooding. In this initial version of the Analyzer, we only simulate large-scale river flooding, and not coastal flooding, flash flooding, or pluvial flooding.
- Flood protection. The flood hazard maps represent situations with no flood protection measures (established for example through dikes and water retention areas). Hence, where such measures already exist, the flood extent (and therefore the affected population) will be overestimated. In the results displayed in the online Analyzer, the user can include a protection standard (expressed in terms of a return period in years).
- Damage estimate assumptions. To estimate urban damage, we assumed that the relationship between the inundation depth and the actual damage is the same throughout the entire world.
- Additional limitations. Further uncertainties in the hazard and risk estimates may be due to inaccuracies in the climate data used to estimate river discharges, inaccuracies in the elevation data used to simulate inundation, and model simplifications with respect to the physics.
Given the limitations described above, the results are meant to provide a first impression of the distribution of risk among countries, provinces, and basins. This provides an indication of risk magnitude, and an impression of the magnitude of future change in risk that can be expected. The results should be used to focus attention on particular vulnerable areas and open dialogues on the risks and how they can be managed. The results can certainly not be used for the dimensioning of specific flood protection measures. This would require more detailed and locally calibrated models that include additional information on local conditions, including more accurate river profiles, structures, existing flood protection, reservoir conditions and management during floods, and more accurate information on exposure and vulnerability. It would also require thorough engagement with local experts and stakeholders.
Additionally, the 120 cities included in the city layer are from Atlas of Urban Expansion from Lincoln Institute of Land Policy. It includes cities from nine geographic regions, four population size classes, and four per capita income classes. The delineations of those metro areas were the boundaries of study area of each city, provided by the Atlas of Urban Expansion. More details at http://www.lincolninst.edu/subcenters/atlas-urban-expansion/Default.aspx.
Aqueduct Global Flood Maps and Data
Aqueduct Global Flood Risk Country Rankings
Hazard modelling: A framework for global river flood risk assessments
Impact modelling: Assessing flood risk at the global scale: model setup, results, and sensitivity
- For media inquiries or general Aqueduct inquiries, contact Andrew Maddocks.
- To partner with Aqueduct and WRI, contact Charles Iceland.
- To learn more about the methodology and development of the Analyzer, contact Tianyi Luo.