Abstract
Situated in the South-West of Saudi Arabia, Jeddah is the biggest port city in the red sea and the kingdom's second city after Riadth. Jeddah has a population of 3500000 inhabitants. It benefits from many economic assets due mainly to its being a transit point toward the holly sites of Islam. Despite being characterized by a dry climate, by poor rain fall levels, by deficits of rain compared to evaporation, and by the irregularity of water flow systems along with the functional degradation of its hydraulic networks, Jeddah underwent many unexpected floods- three big ones in 2009, 2010, and 2011. The human tolls as well as the material losses were huge: hundreds dead, thousands of damaged buildings which were built on slopes or close to river beds with legal permits. Such floods were studied by local and national authorities as well as scholars in order find adequate solutions. It is within this framework and with modelization statistics and cartographic analyses in mind that we will attempt to understand what caused such floods:
-Natural causes (geo-morphological specifics, climate change, intensive rainfall),
- Human causes: lack of hazard culture, urban extension and planification, and the absence of viable strategies of prevention