Abstract
The assessment of the number of people exposed to natural hazards, especially in countries with strong urban growth, is difficult to be updated at the same rate as land use develops. This paper presents a remote sensing-based procedure for quickly updating the assessment of the population exposed to natural hazards. A relationship between satellite nightlights intensity and urbanization density from global available cartography is first assessed when all data are available. This is used to extrapolate urbanization data at different time steps, updating exposure each time new nightlights intensity maps are available. To test the reliability of the proposed methodology, the number of people exposed to riverine flood in Italy is assessed, deriving a probabilistic relationship between DMSP nightlights intensity and urbanization density from the GUF database for the year 2011. People exposed to riverine flood are assessed crossing the population distributed on the derived urbanization density with flood hazard zones provided by ISPRA. The validation against reliable exposures derived from ISTAT data shows good agreement. The possibility to update exposure maps with a higher refresh rate makes this approach particularly suitable for applications in developing countries, where urbanization and population densities may change at a sub-yearly time scale.
Highlights
The aim of this paper is to present a general, simple and remote sensing based procedure for the quick update of the population exposed to natural hazards in rural and urban areas
Estimated distributed population is crossed with ISPRA riverine flood hazard maps to estimate exposure
The validation with independent data shows good agreement between estimated and reference population exposed to riverine flood hazard (Figure 8), demonstrating a strong consistency in the statistical relationship expressed by (3)
Summary
The aim of this paper is to present a general, simple and remote sensing based procedure for the quick update of the population exposed to natural hazards in rural and urban areas. The level of processing required to release a final reliable version of these doi:10.20944/preprints202010.0425.v1 products lasts for several years, making their refresh rates significantly lower than the urban growth rate of many areas of the world It is worth mentioning here the provisions of the Sendai Framework for Disaster Risk Reduction [12], which requires a frequent update (e.g. yearly) of information on the population or assets exposed at national or provincial scale, to be used for the monitoring of some of its indicators, such as “Number of directly affected people attributed to disasters, per 100,000 population” (indicator B-1) or “Direct economic loss attributed to disasters in relation to global gross domestic product” (indicator C-1)
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