Urbanizing the floodplain: Global changes of imperviousness in flood-prone areas

Abstract:

Urban encroachment on floodplains increases exposure and vulnerability
to floods while population changes and climate change are expected to
exacerbate those risks despite the installation of flood control
structures. Although there is a large body of work studying the
mechanisms of how urbanization and land use changes in general can
affect flood risks, long-term global maps of urban encroachment at high
resolutions do not exist to our knowledge. With the advent of big-data
geospatial processing tools, global-scale
reconstructions (~35 years) of water occurrence and urban areas
derived from Landsat observations have been made available. We combine
these data products with surface reflectance data from the same
sensors to derive global maps of flood occurrence and changes in
impervious surface area annually (1985-2018), which we then used to identify urbanized
areas that had previously flooded. This observational dataset enables the
identification of hotspots (both in space and time) of urban
encroachment on the floodplain with many implications on flood risk
mitigation and urban design policies.