Under global warming, weather patterns will change, leading to increased precipitation for some areas. Even for some areas that see less precipitation on an annual basis, the rainfall may come in more intense bursts. According to the IPCC, “there is limited to medium evidence available to assess climate-driven observed changes in the magnitude and frequency of floods at regional scales because the available instrumental records of floods at gauge stations are limited in space and time, and because of confounding effects of changes in land use and engineering.”
However, “there have been statistically significant trends in the number of heavy precipitation events in some regions. It is likely that more of these regions have experienced increases than decreases, although there are strong regional and subregional variations in these trends” (IPCC SREX, 2012).
Storm water management systems, particularly those of older design, are sometimes not equipped to handle intense rainfall events, and urban flooding is certainly an issue as a result. Flooding caused by the landfall of tropical cyclones along coastal areas will be exacerbated by the increase in precipitation as well as sea-level rise. Moreover, stormwater management systems often become overwhelmed by coastal flooding, preventing proper drainage under excessive rainfall that comes with tropical cyclones. This hazard is projected to increase in severity under global warming.
Adaptation strategies over the long term include attention to stormwater management infrastructure to accommodate larger rainwater volumes, upgrading codes and standards for civil infrastructure and land use that permits rainwater catchment basins. Rapid development in urban areas without due attention to increasing flood risks can increase the risk of severe impacts under urban flooding.