An Exploratory Study on the Impact of Climate Change on Design Rainfalls in the State of Qatar

Abstract: The Intergovernmental Panel on Climate Change (IPCC), in its Fourth Assessment Report AR4 predicts a more extreme climate towards the end of the century, which is likely to impact the design of engineering infrastructure projects with a long design life. A recent study in 2013 developed new design rainfall for Qatar, which provides an improved design basis of drainage infrastructure for the State of Qatar under the current climate. The current design standards in Qatar do not consider increased rainfall intensity caused by climate change. The focus of this paper is to update recently developed design rainfall in Qatar under the changing climatic conditions based on IPCC’s AR4, allowing a later revision to the proposed design standards, relevant for projects with a longer design life. The future climate has been investigated based on the climate models released using a stationary approach. Annual maximum series (AMS) of predicted 24-hour rainfall data for both wet (NCAR-CCSM) and dry (CSIRO-MK3.5) scenarios for the Qatari grid points in the climate models have been extracted for three periods: current climate 2010-2039, medium-term climate (2040-2069) and end-of-century climate (2070-2099). A homogeneous region of the Qatari grid points has been formed and L-Moments based regional frequency approach is adopted to derive design rainfall. The results indicate no significant changes in the design rainfall in the short term 2040-2069, but significant changes are expected towards the end of the century (2070-2099). New design rainfall has been developed taking into account climate change for 2070-2099 scenario and by averaging results from the two scenarios. IPCC AR4 predicts that the rainfall intensity for a 5-year return period rain with a duration of 1 to 2 hours will increase by 11% in 2070-2099 compared to the current climate. Similarly, the rainfall intensity for more extreme rainfall, with a return period of 100 years and a duration of 1 to 2 hours, will increase by 71% in 2070-2099 compared to the current climate. Infrastructure with a design life exceeding 60 years should add safety factors, taking the predicted effects of climate change into due consideration.