Vulnerability of flash flooding in Riyadh, Saudi Arabia

In recent years, hazardous flash flooding has caused human deaths and damages to urban infrastructures in Saudi Arabian cities. This study has computed, mapped, and analyzed the physical vulnerability, social vulnerability, and overall composite flash flood vulnerability (CFVI) indices using a simulated flood and 2006 census data on seven social variables for 153 neighborhoods of the City of Riyadh, the capital of the Kingdom of Saudi Arabia. The physical vulnerability index was computed by ranking a potential flood depth map created by simulating a 6 h of high-intense rainfall in the city. The social vulnerability index was constructed by standardizing the social data variables. Finally, the two indices were multiplied to create the CFVI. The CFVI map revealed that the low-lying central and southern half of the city is highly vulnerable; northern and northeastern peripheral neighborhoods are moderately to highly vulnerable; and the mountainous western neighborhoods are the least vulnerable to flash flooding. Low-income and unemployed expatriate families living in densely populated central, south, and southeastern neighborhoods are more vulnerable to flooding than rich Saudi families living in the sparsely populated northern half of the central city, western, northwestern, and southwestern neighborhoods. The CFVI map will help city planners to formulate effective flood control measures to protect the city residents and urban infrastructures from future flood damage. This flood vulnerability research can be expanded to other Saudi cities by incorporating more physical and social variables.