Disaggregation of Future Regional Climate Model Data to Generate Future
Rainfall Intensity-Duration-Frequency Curves to Assess Climate Change
Impacts
Abstract
Heavy increase in urbanization, industrialization and population is
causing an increase in emissions of greenhouse gases (GHG) and this
causes variations in atmosphere. Climate change causes extreme rainfall
events and these events are expected to be enhanced in the future. Since
flooding is influencing urban areas, controlling and management of
flooding is a major necessity. Intensity-Duration-Frequency (IDF) curves
play a huge role in representing rainfall characteristics by linking
intensity, duration, and frequency of rainfall. Analysing short-duration
rainfall is crucial for urban areas due to fast responses of drainage
systems against heavy rainfall events. IDF curves were generated via the
Gumbel method for rainfalls from 5-min to 24-h in this study. However,
providing short-duration rainfall data is challenging due to the low
capacity, costs and geographic conditions. Therefore, the HYETOS
disaggregation model was applied to obtain sub-hourly data. IDF curves
are stationary since they only consider historical events. However, IDF
curves must be non-stationary and time varying based on preparation for
upcoming extreme events. This study aims to generate IDF curves under
climate change scenarios. The Regional Climate Model (RCM) HadGEM2-ES
generated under Representative Concentration Pathways (RCP) 4.5 and 8.5
scenarios and was used in the study to represent future rainfalls.
Future daily rainfalls were disaggregated into sub-hourly using
disaggregation parameters of corresponding station’s historical rainfall
data since it is impossible to estimate parameters when hourly data is
not available. With this new approach, future daily rainfall data is
disaggregated into 5-min data by complying with historical rainfall
patterns rather than complying with randomly selected rainfall
characteristics. The study concluded that future rainfall intensities
increases compared to historical IDF curves. RCP8.5 scenarios have
higher rainfall intensities for all return periods compared to RCP4.5
scenarios for all stations except a station. In addition, the accuracy
of the selected disaggregation model was verified.