Flash floods risk analysis in ephemeral streams: a case study on Wadi Mekerra (northwestern Algeria)
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ORIGINAL PAPER
Flash floods risk analysis in ephemeral streams: a case study on Wadi Mekerra (northwestern Algeria) Kh. Korichi 1,2 & A. Hazzab 1 & M. Atallah 1
Received: 28 October 2015 / Accepted: 1 August 2016 / Published online: 11 August 2016 # Saudi Society for Geosciences 2016
Abstract The number and intensity of water-related disasters are increasing tremendously. Floods and inundations in the Mediterranean countries are often caused by torrential rains. In Algeria, floods have left more than 1000 dead and caused loss of around 550 million euros. In Mekerra Basin, northwestern Algeria, the flooding risk is growing. This paper diagnoses the causes and the flood damage that generates Wadi Mekerra. Besides, the legislative texts are also discussed. Predicting the flooding risk is done through numerical modeling of two typical flood waves. It is a comparison between two numerical models, Van Leer finite volume scheme and Petrov Galarkin finite element scheme with recorded hydrographs. Based on these results, several additional actions are recommended at the end of this work. Keywords Flash floods . Ephemeral Wadi . Mekerra watershed . Risk assessment . Flood control . Geomorphological analysis . Numerical model
Introduction Recently, more than 360,000 people have lost their lives because of more than 300 disasters in the world, while 200 million have been directly affected in which the cost of damage reached $180 billion (UN Daily News, 2009). * Kh. Korichi [email protected]
1
Modeling and Calculation Methods Laboratory, Saïda University, BP 138, 20002 Ennasr Saïda, Algeria
2
Hydraulics Department, Faculty of Technology, University of Djillali Liabes, Sidi Bel Abbes, BP 89, 22000 Sidi Bel Abbes, Algeria
Jonkman and Vrijling (2008) divide the floods into three types: drainage flood, river floods, and flash floods. The statistics showed that the average mortality rate is higher in the flash floods because they are unexpected and developed rapidly. From 1975 to 2001, 1816 local floodings were reported worldwide resulting more than 175,000 people dead. Other types of inundation caused by dam breaks, storms, and tsunamis can be even more devastating in terms of loss of life. Hand et al. (2004) noted that most extreme events that occurred in the twentieth century have been accompanied by flash floods and inundations, especially in summer and early fall. For example, the 1967’s flood in Lisbon, Portugal, has killed 464 people. In 1975, the Banqiao dambreak in China generated floods that caused approximately 231,000 deaths. Outburst floods are often caused by heavy or excessive rains over a short period of time less than 6 h (National Weather Service, NWS, 2009). In UK, the flash floods have peak time less than 3 h for watersheds around 5–10 km2, while in the USA, the peak time can reach 6 h for catchments of 400 km2 (Georgakakos and Hudlow, 1984). This is due, in particular, to the population growth, urbanization, climate change, and environment degradation. Their effects are devastating, especially, for d
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