Future precipitation characteristics of eight Tier I Urban Conglomerates amongst designated smart cities of India under selected Shared Socio-economic Pathways

Increased incidences of pluvial floods from rainfall affect key economic and cultural hubs of many countries of the world. Future-proofing India’s 100 designated smart cities against pluvial flooding through Integrated Urban Water Management (IUWM) is an important requirement that calls for assessments of the future characteristics of rainfall in these cities and the likely impacts of alterations of these characteristics under Shared Socio-economic Pathways (SSPs) of the Sixth Assessment Report (2021) of the Intergovernmental Panel on Climate Change. In this study, potential future alterations in Intensity-Duration-Frequency (IDF) characteristics of precipitation were explored by using reanalysis outputs of hourly precipitation of the period 1955–2014 from a selected Global Climate Model (GCM), namely MIROC6. In this study, the MIROC6-simulated precipitation data of three future periods, namely 2015–2040, 2041–2070 and 2071–2100, under four SSPs, namely SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5, at a 0.25°×0.25° grid over India were used. It emerged from the analyses that, generally, for all four SSPs, the north-central, eastern and western parts of the country encompassing 69 smart city locations and the southern peninsular region containing 29 locations would have high future precipitation intensities. The number of smart cities having significant positive trends of 1-hour annual maximum precipitation was found to increase from 35 under SSP2-4.5 to 68 and 72 under SSP3-7.0 and SSP5-8.5 respectively. The historical 1-hr precipitations of 100-year return period and their % deviations in the three future periods under four SSPs showed that the aerial extents of positive deviations generally increase from SSP1-2.6 to SSP4-8.5, particularly during 2041-70 and 2071–2100, and that 81 smart city locations exhibit high positive deviations under SSP5-8.5 during 2071–2100. These results indicate that future precipitation intensities, and hence pluvial floods, are likely to increase over the designated smart cities, and accounting for the increasing vulnerabilities of these cities to urban pluvial flooding due to increased short-duration rainfall would be vital for effective IUWMs.