Evaluation of coastal vulnerability and exposure to erosion and submersion risks in Bou Ismail Bay (Algeria) using the coastal risk index (CRI)

Abstract

The Algerian coastal zone is under high pressure occurring from natural origin (seismic and tsunamis risks, erosion/accretion, salt water intrusion, etc.) and from human sources (pollution, loss of biodiversity, economic value, etc.). The lack of data, particularly time series over natural coastal process, is an impediment for decision making. In many cases, the implemented coastal protection measures even exacerbate the vulnerability of these zones, particularly the hard engineering solutions. The aim of this work is to produce coastal vulnerability and exposure index maps to erosion and marine submersion, by adapting the coastal vulnerability index (CVI) into coastal risk index (CRI) according to the new vision of the risk adopted by the International Panel on Climate Change (IPCC). This index turned out to be a relevant tool to adjust coastal planning and management decision making, by confirming the vulnerability of some physiographic units and give at local and regional levels a broad image of coastal zone sensitivity to erosion and submersion. This index should be integrated in Integrated Coastal Zones Management policy and management decision making. The mapping of coastal vulnerability and exposure in Bou Ismail Bay shows that it is 80% moderately vulnerable to erosion and submersion. Also, 45% of the bay is highly exposed to coastal hazards. Some sectors are more vulnerable and exposed than others especially in the East side of the bay. The mapping of coastal risk index using coastal hazard component, combined with vulnerability and exposure maps, has led us to identify the degree of erosion and submersion risk in Bou Ismail Bay. The risk mapping shows that 40% of the bay is at high risk level; it means that some procedures should be made to decrease the level of sensitivity and improve resilience of this heavily populated area.