One of the most important infrastructure in an urban area is its stormwater drainage system, which is used to convey the excess rainfall from the surface of the urban catchment to the natural watercourse. Conventionally, these structures are required to perform properly under the selected and generated events known as Design Rainfalls which have been statistically calculated using the recorded rainfall from the past. These events include the intensity and duration for the design rainfalls with

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... ifferent return periods or frequencies and are assumed to demonstrate the pattern and frequency of the previous rainfall events. This stationary assumption is currently questioned due to climate change. It is expected that high intensity rainfall events would be more severe and frequent. This in turn would lead to frequent flash floods as the urban stormwater drainage system would not be able to cope with the increased intensity of the storm events.