Changing characteristics of monsoon rainfall for an urban smart city catchment in the South Indian Peninsula

Changing monsoon rainfall characteristics in rapidly urbanizing catchments pose major challenges for flood mitigation, especially in smart cities. Conventional long-term trend analyses often smooth out short-duration extremes, masking recent high-intensity events that drive urban flooding. This study investigates the rainfall variability in the Ernakulam District, a coastal city using 120 years of gridded data. A complementary framework combining the Mann–Kendall tests with the Innovative Trend Pivot Analysis Method (ITPAM) was applied to assess statistical significance and visually classify trend magnitudes across different sub-series. Annual rainfall ranged from 3009 -3469 mm, with strong spatial variability and higher intensities in the eastern region. While long-term statistical tests showed insignificant trends for the recent decades, ITPAM successfully captured the extreme rainfall events of the last decade that traditional methods overlooked. The findings highlight the need for short-period trend analysis to detect localized intensification and support resilient flood-management strategies in rapidly urbanizing environments.