GIS-Based Spatial Mapping of Flash Flood Hazard in Makkah City, Saudi Arabia
Dawod, Gomaa M., Mirza, Meraj N., Ghamdi, Khalid A. Al-, Journal of Geographic Information System
Hazards of flash floods are vital in terms of human lives loss and economical damages. Makkah city, west of Kingdom of Saudi Arabia (KSA), exhibits two unique features that increase the hazardous flood consequences: 1) its topography is very complex; 2) about three million Muslims are gathered annually in Makkah to perform Hajj over a two-week period in the winter, which is the main rainfall season in Saudi Arabia. Due to the increasing interest in flood impacts over the last couple of decades, extensive flood estimation studies have been carried out in different countries, such as USA , Egypt [2,3], Nigeria , South Korea , China , and Saudi Arabia [7,8]. This paper aims to develop a GIS approach for assessing the flash flood hazards for Makkah metropolitan area, utilizing the most up-to-date and precise available data sets.
2. Flood Estimation
Flood estimation methods aim to model the rainfall-runoff relationships, and can be categorized into three groups according to their complexity. Simple approaches, such as the rational method and empirical formulas, estimate the peak discharge quickly and with little number of inputs. The Curve Number (CN) is an example of moderate flood estimation methods. Detailed, or complex, models are able to identify the causes of problems rather than producing a simple description of overall conditions . The CN method is quite used in engineering design and flood management projects, particularly in the USA [10-13].
Geographic Information Systems (GIS) and Remote Sensing (RS) techniques have been utilized as efficient tools in flood risk assessment [14,15]. For example, Change et al.  applied GIS to study the time-based relationship between flood hazards and land use changes. Also, Jasrotia and Singh  uutilized the CN method to study the runoff and soil erosion within a GIS environment. Moreover, Chen et al.  tested a GIS model, which consists of a storm-runoff model and an inundation model, to model flood hazards. In addition, Dongquan et al.  developed a GIS batch process to delineate catchments and compute their geomorphologic parameters. Furthermore, Guptaa, and Panigrahya  has utilized several data sources and two runoff models in a GIS platform to investigate the flood characteristics and variations of large basins in India. Additionally, Gogoase et al.  utilized GIS to develop inundation maps foe extreme flood events. Moreover, Karmakar et al.  proposed a methodology for six major damage centers in the Upper Thames River watershed, Canada to assess the flood risks, i.e. flood probability of occurrence, vulnerability to flood, and exposures of land use and soil type to flood.
3. Flash Floods in Makkah City
Makkah city is located in the south-west part of KSA, about 80 Km east of the Red Sea (Figure 1). It extends from 39[degrees]35' E to 40[degrees]02'E, and from 21[degrees]09' N to 21[degrees]37' N. The area of the metropolitan region (the study area) equals 1593 square kilometres. The topography of Makkah is complex in nature, and several mountainous areas exist inside its metropolitan area. The winter is considered as the main rainy season in Saudi Arabia. The annual rain over Makkah city, for a period extending from 1966 to 2009, varies from 3.8 mm to 318.5 mm, with an average of rainfall equals 101.2 mm (Figure 2). Due to the complexity of Makkah's topography, flash floods occur periodically with significant variations in magnitude. Mirza and Ahmed  have reported that the extreme flood …
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Publication information: Article title: GIS-Based Spatial Mapping of Flash Flood Hazard in Makkah City, Saudi Arabia. Contributors: Dawod, Gomaa M. - Author, Mirza, Meraj N. - Author, Ghamdi, Khalid A. Al- - Author. Journal title: Journal of Geographic Information System. Volume: 3. Issue: 3 Publication date: July 2011. Page number: 225+. © 2010 Scientific Research Publishing, Inc. COPYRIGHT 2011 Gale Group.