Makkah is the holiest site for all Muslims. Millions of Muslims arrive to Makkah from all over the World annually. They perform Hajj "pilgrimage", the famous annual worship for those who could afford it once in their life time. The number has increased significantly during the last few years, due to the increase of those who arrive for Umrah (visit to Al-Masjed Al-Haram "the Holy Mosque"). The number of arrivals for pilgrimage and visit has to be taken into consideration with the number of the city population, which exceeds one million inhabitants. The city of Makkah is located in the western part of Saudi Arabia, which is known for its arid and semi-arid climate.

 

Therefore, massive flooding is a rare phenomena in Makkah, but it could be highly devastating when it occurs. It might cause considerable destruction on various local infrastructures. The objective of this research is to assess the potential impacts of flooding on road network in Makkah, based on various data; Statistical data on rainfall and roads, maps, aerial photos, images…etc.

 

This research argues that new techniques, such as Geographic Information Systems and Remote Sensing provide better alternatives for more accurate spatial planning of road networks. Hence, ArcGis 9.3 and ERDAS Imagine 9.1 have been the principal tools for the study. They were used for modeling the impacts of this natural phenomenon on road networks, as man-made features. Layers of roads network, drainage system network of Makkah, its catchment area, contorts, and Digital Elevation Model (DEM) were overlaid. Velocity, speed of running water and height of flow were calculated. Final assessment was made based on the results.

 

It is hoped that the outcomes of this study will contribute to the enhancement of the decision making process in the area, based on a solid scientific rationale. Consequently, different levels of modifications of road network structures and other related infrastructure accordingly are proposed. This research might be considered as a new classic model for further research in other cities within Saudi Arabia and elsewhere with similar physical conditions.