The Role of Global Data Sets for Riverine Flood Risk Management at National Scales

Over the last two decades, several data sets have been developed to assess flood risk at the global scale. In recent years, some of these data sets have become detailed enough to be informative at national scales. The use of these data sets nationally could have enormous benefits in areas lacking existing flood risk information and allow better flood management decisions and disaster response. In this study, we evaluate the usefulness of global data for assessing flood risk in five countries: Colombia, England, Ethiopia, India, and Malaysia. National flood risk assessments are carried out for each of the five countries using six data sets of global flood hazard, seven data sets of global population, and three different methods for calculating vulnerability. We also conduct interviews with key water experts in each country to explore what capacity there is to use these global data sets nationally. We find that the data sets differ substantially at the national level, and this is reflected in the national flood risk estimates. While some global data sets could be of significant value for national flood risk management, others are either not detailed enough, or too outdated to be relevant at this scale. For the relevant global data sets to be used most effectively for national flood risk management, a country needs a functioning, institutional framework with capability to support their use and implementation. Plain Language Summary To adequately manage flood risk, it is important to understand where flood risk is greatest. This is done by carrying out a flood risk assessment, which combines flood hazard maps with data for exposure (who or what is flooded) and vulnerability (how affected exposure is by flooding). At the national level, flood risk assessments have typically been limited to countries with the necessary data and expertise to develop such assessments. In recent years, several flood risk data sets have been developed with global coverage, which means national flood risk can now be assessed in any country. We investigate how useful global data sets are for assessing national flood risk in five countries: Colombia, England, Ethiopia, India, and Malaysia. We find that there is significant disagreement between national flood risk estimates, suggesting not all global data sets are up to the task. Beyond that, we show that the usefulness of global flood risk data for national flood risk management is also determined by the national context in which they