**2. Study area**

A cosmopolitan city, a major nerve center of the Red Sea and a dynamic port city, Jeddah is located in the Alhijaz region, on the Red Sea coast, developed on Tihamah coastal plain. It is the main urban center of the West (**Figure 2**). Its

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**Figure 3.**

*Geological map of Jeddah city.*

*Flood Risk and Vulnerability of Jeddah City, Saudi Arabia*

**3. Geological and geomorphological framework**

geographical location on the ancient trade routes and its status as a seaport and airport through which the vast majority of pilgrims travel to the two holy cities Mecca and Medina have made it the most cosmopolitan city in all of Saudi Arabia. While the population was estimated at nearly 1 million in the late 1970s, it rose to 1.4 million in 1986, exceeding 3 million in 2010 [4]. It now stands at nearly 3.5 million, with a rate of 3.5% according to the municipality of Jeddah, which represents

According to Monnier and Guilcher, the morphological setting is characterized by the Tihamah littoral plain with a maximum width of 40 km, located at the foot of the highly dissected Precambrian granitic mountains of Alhijaz whose peaks reach several hundred meters. The plain is surmounted by a crest of basalts forming part of a set of castings called harrats (lava flows today in inversion of relief), coming from mouths located at a hundred kilometers inside and going back to the old Pleistocene based on their stratigraphic relations [5] in [6]. The existence of geomorphological phenomena related to the eustatic variations of the Red Sea during the Pleistocene is noted. The stability (or geological instability) of the coastal plain is related to the earthquakes associated with the formation of the Red Sea. Most faults, diaclases, and cracks take parallel and orthogonal directions to the Red Sea. Hydrologically, there are 24 watersheds in the context of the flooded area. Sixteen watersheds are directed toward the city of Jeddah to the west, and the rest flows in a southwesterly direction toward the great valley of *Wadi* Fatimah [7]. The study area is composed of Precambrian-Cambrian formations, overlain by a succession of Cretaceous-Tertiary sedimentary rocks and Tertiary-Quaternary basaltic lava flows and Quaternary-to-recent alluvial deposits (**Figure 3**).

*DOI: http://dx.doi.org/10.5772/intechopen.82073*

14% of the population of Saudi Arabia.

*Flood Risk and Vulnerability of Jeddah City, Saudi Arabia DOI: http://dx.doi.org/10.5772/intechopen.82073*

*Recent Advances in Flood Risk Management*

damage at the social, psychological, economic, health, and environmental levels [3]. The roads where turned into torrents and saw dozens of cars washed away. The present work illustrates a spatial analysis of flood risk based on multisource data (satellite, DEM, cartographic and statistical) and aims to identify flood-prone areas to determine the vulnerability of the Jeddah area so as to avoid urban extension in

A cosmopolitan city, a major nerve center of the Red Sea and a dynamic port city, Jeddah is located in the Alhijaz region, on the Red Sea coast, developed on Tihamah coastal plain. It is the main urban center of the West (**Figure 2**). Its

risk areas and to develop adequate management of the environment.

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**Figure 2.** *Study area.*

**2. Study area**

*Floods in 2009 and 2011. Source: Internet.*

**Figure 1.**

geographical location on the ancient trade routes and its status as a seaport and airport through which the vast majority of pilgrims travel to the two holy cities Mecca and Medina have made it the most cosmopolitan city in all of Saudi Arabia. While the population was estimated at nearly 1 million in the late 1970s, it rose to 1.4 million in 1986, exceeding 3 million in 2010 [4]. It now stands at nearly 3.5 million, with a rate of 3.5% according to the municipality of Jeddah, which represents 14% of the population of Saudi Arabia.
