Jeddah Gets Caught in the Rain: Urbanization and Storms

A new study from KAUST has highlighted how urbanization can increase rainfall in cities, using Jeddah as a case study. Located on the Red Sea, Jeddah experiences winter storms that can cause heavy rainfall, strong winds, and flash flooding. While such storms can be dangerous, they are also an important water source for Saudi Arabia, a country facing water scarcity challenges. In fact, Saudi Arabia has a national goal to double its rainfall harvesting efforts by 2030.

The research team, led by Ibrahim Hoteit and postdoctoral fellow Thang Luong, investigated how urbanization affects rainfall during storms in Jeddah. The city’s urban heat island effect, where buildings and roads absorb heat during the day and release it at night, plays a significant role in altering storm patterns. In particular, the team simulated rainfall during 10 severe storms under two scenarios: one with the urban environment and another with pre-settlement land cover.

The results were striking: the urban heat island effect caused an increase in rainfall over Jeddah by 26 percent compared to the surrounding desert during storms. The concrete surfaces, roads, and buildings of Jeddah absorbed sunlight and enhanced turbulence, causing warm air to rise and collide with moist air from the Red Sea. This interaction intensified the storms, leading to heavier and prolonged rainfall. In contrast, the desert scenario showed lower rainfall.

The team’s model also successfully replicated the 2009 Jeddah flood event, which claimed lives and caused significant damage. This modeling capability is crucial for improving flood forecasting, policy, and urban planning to mitigate future storm damage.

KAUST researchers continue to investigate the most critical elements of urbanization that drive increased rainfall and how the spread of urban areas along the Red Sea coast might impact storm evolution.

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