Overall, NBS are attractive adaptation options for stormwater management and to reduce impacts of pluvial and fluvial flooding in cities  compared, and in combination, with grey infrastructure. Cities with combined sewer infrastructure are likely to see benefits from NBS due to reductions in stormwater quantity and reduced sewage overflows. Cities where a large proportion of residents lack access to piped infrastructure and drink surface water may see large benefits, especially to human health, from NBS investments . Where future large-scale upgrades or installation of grey infrastructure will be necessary, new and growing cities may have more opportunity to realise large net benefits from investments in NBS. Older cities, and new, rapidly urbanising areas that lack large-scale water infrastructure may see the greatest benefits from enhanced NBS, relative to cities where heavy investments infrastructure upgrades have already been made. Cities facing climate changes that include more frequent or extreme precipitation may also see large water quality benefits from investment in NBS . Overall, there is increasing evidence that NBS for addressing stormwater is cost effective , especially in cities facing a need to update current infrastructures.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report