In the context of global warming, it is very critical to delineate areas of high flood vulnerability and risk. Climate and hydrologic surveying using traditional methods is not always available and depends on external factors. So, the use of geographical information system and remote sensing is of high importance as a decision support system. This approach is of low cost and can cover a long period for surveying. This study aims to provide decision makers a framework of GIS based on multicriteria analysis for flood risk mapping. Classified remote sensing image layers are used to complete GIS-multicriteria results. Results show that the high to very high-risk levels affect the majority of the study area, particularly the south-west and north-east zones. The comparison between GIS and remote sensing approaches shows the same areas of risk and reveals that it is a reliable methodology that greatly enhances decision making.
TopStudy Area Characteristics
Medjerda is one of the main rivers of the Maghreb and the major river in Tunisia if considering the length of its watercourse, the drainage area of the basin, and the volume of waters it carries (Ben Mansour, 2011). The river source is located beyond the Algerian borders (Figure 1), precisely Constantine (Souk Ahras), and then flows eastwards to the Mediterranean Sea (Gulf of Tunis). A 90,000 ha are irrigated with water of the Medjerda (Ben Khalfallah et al., 2018).
The study area is performed in the vicinity of the main stations of the Medjerda River located in Bou Salem Area and its vicinity (Figure 1).
The interannual monthly rainfall for 2014/2015 is around 546.9 mm (INM, 2015).
The situation of the city of Bou Salem is essentially the result of the crossing of Oued Mejadra and its significant flows in periods of rain. These flows cross the urban area and cause damage to homes and traffic routes.
The town of Bou Salem is surrounded by other tributaries in particular (Figure 31):
Oued Tessa and Mellègue from the South
Oued Bouhertma in the west of the city
Oued Boujaarine in the east of the city
According to the general population census of 2014, the study area is populated by 20,098 inhabitants. Since 1881 the population has multiplied by 850 people until it reached 8,716 in 1975.
Tunisia is periodically affected by floods and sometimes catastrophic floods which can cause significant human losses and material damage.
During the last century, the city of Bou Salem has experienced several floods, the most recent of which were in 1973, 2000, 2003, 2012 and even 2015.