Risk indices and risk matrix have been used among governmental agencies for assessing risks and ranking alternatives protection measures. The popularity of risk matrices can be associated with its characteristics to quick assessing risk and providing inexpensive solutions. The risk assessment is associated with flood protection as: economic, environmental, and life-safety. Economic risks are reasonably well dealt with by the well-known traditional cost-benefit analysis, insurance, and financial markets. Environmental risks are difficult to assess by traditional methods in flood project evaluation. Environmental consequences cannot be directly measured, while social risks represent the most challenge to quantify. It may be possible to estimate the number of fatalities, and cost of damaged infrastructures, while the social aspects cannot be measured. This paper is proposing a flood risk matrix technique for assessing risks in urban arid and extreme arid regions demonstrated through case-study application on the catchment of Taibah University (TU) and Islamic University (IU) in Medina, KSA. The study focused on assessing the geographical impacts of the flash flood inundated depths for different frequencies from 5 to 100 years return periods leading to identification of the flood channels, and its floodplains that may be vulnerable to different degrees of flood hazards.