Recently, the Kingdom of Saudi Arabia (KSA) has been facing significant changes in rainstorm patterns (rainstorm intensities, frequencies, distributions) causing many flash flood events. The city of Jeddah is located in a coastal plain area, in the middle of the western side of the KSA, which represents a clear case of changing rainstorm patterns. Jeddah has been hit by many rainstorm events, which increased dramatically since 2009 (e.g., one in 2009, one in 2011, one in 2015, and another one happened in 2017). However, in 2018 about six rainstorms occurred. Two major flash flood events occurred in the city in November 2009 and in January 2011. There were significant impacts of these two events causing severe flooding. During these events, 113 persons were announced dead (in the 2009 event), and infrastructures and properties were damaged (roads and highways, more than 10,000 homes and 17,000 vehicles). In addition to that, dam failure occurred in the 2011 event. This situation gives clear evidence in changing the climate system that could cause more storms in the future across the KSA. Generally, Jeddah city has a lack of short-duration data in rainfall stations. In addition to that, there are a limited number of studies that have been done in determining rainstorm patterns. Consequently, the approach of the current study will focus on understanding and determining rainstorm patterns in the period between 2011 and 2017 depending on some digital rainfall stations that have been installed recently in Jeddah city. Rainstorm pattern and the method of distribution are the most crucial factors affecting peak flow and volume calculations. Our findings showed that there are two pattern types for the rainstorms in Jeddah city. Finally, a comparison with SCS-type II distribution was carried out.
Part of the book: Rainfall