Extreme Waves

Abstract Knowledge of coastal storm regimes is essential to ensure an economic and sustainable development in the coastal area. In recent decades, wave storms have been responsible for several fatalities and economic losses along the Algiers coast. The aim of this paper is to present a detailed analysis on wave storm events during the past 40 years, including an assessment of the potential impacts of various storm events along the Algiers coasts according to their intensity and direction based on the different historical events. Thus, this paper gives an estimation of return periods of extreme significant wave heights and extreme storm events. For this purpose, the wave storm events occurring in the Algiers coasts, based on the storm power index (SPI) developed by Dolan and Davis (1992), were characterized and classified. Five storm categories were defined in terms of their power index, subdivided into 31 categories, taking into consideration their propagation directions. The temporal analysis shows a progressive increase in the number of storm events and their intensity during the last decade, which explains the increased damage recorded recently in the Algiers coastlines. A spatial analysis of these extreme and catastrophic storms being responsible in these damages has shown that the nature of coastal storm damages on the local scale depends on several factors, mainly power of these storms and their direction; in view of the complex morphology of the Algiers coastlines. These two factors were considered during the extreme value analysis, and allowed us to estimate the return period of the storm events already observed based on their SPI and direction. A return period of 59 years has been estimated for the catastrophic storm of 2015, which caused significant erosion resulting a loss of more than 15 000 m2 of coastal lands.