Citation: Cisse, C.O.T.; Almar, R.; Youm, J.P.M.; Jolicoeur, S.; Taveneau, A.; Sy, B.A.; Sakho, I.; Sow, B.A.; Dieng, H. Extreme Coastal Water Levels Evolution at Dakar (Senegal, West Africa). Climate 2023, 11, 6. https://doi.org/10.3390/cli11010006 Academic Editor: Jorge Olcina Canto Received: 22 November 2022 Revised: 20 December 2022 Accepted: 23 December 2022 Published: 26 December 2022 Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). climate Article Extreme Coastal Water Levels Evolution at Dakar (Senegal, West Africa) Cheikh Omar Tidjani Cisse 1 , Rafael Almar 2, * , Jean Paul Marcel Youm 2,3 , Serge Jolicoeur 4 , Adelaide Taveneau 5 , Boubou Aldiouma Sy 1 , Issa Sakho 6,7 , Bamol Ali Sow 8 and Habib Dieng 8 1 Laboratory Leïdi “Dynamics of the Territories and Development”, Department of Geography, University Gaston Berger, Saint-Louis BP 234, Senegal 2 Laboratory of Biostratigraphy and Sedimentology, Department of Geology, Faculty of Science and Technology, Cheikh Anta Diop University of Dakar, Dakar BP 5005, Senegal 3 Laboratory of Applied Remote Sensing, Institute of Earth Sciences, Cheikh Anta Diop University of Dakar, Dakar BP 5005, Senegal 4 Faculty of Arts and Social Sciences, Canada Department of History and Geography, University of Moncton, Moncton, NB E1A 3E9, Canada 5 Laboratory of Geophysical and Oceanographic Spatial Studies, University of Toulouse/CNRS/IRD/CNES, CEDEX 9, 31999 Toulouse, France 6 Université Amadou Mahtar Mbow de Dakar, Dakar BP 45927, Senegal 7 Normandie Université, UNIROUEN, UNICAEN, CNRS, M2C, 76000 Rouen, France 8 Laboratory of Oceanography, Environmental Sciences and Climate (LOSEC), University Assane Seck, Ziguinchor BP 523, Senegal * Correspondence: rafael.almar@ird.fr Abstract: Increasingly, it is reported that the coastline of the Dakar region is affected by coastal flooding due to extreme water levels during wave events. Here, we quantify the extreme coastal water levels as well as the different factors contributing to coastal flooding during the period 1994–2015. Severe water levels reach values of 1.78 m and increase by 8.4 mm/year. The time spent above this threshold has already increased by 1.7 over the study period and will increase by 2100 to 8 times with 0.4 m mean sea level rise and up to 20 times with 0.8 m in the IPCC low and high greenhouse gas emission scenarios, respectively. Tide is the main contributor to the extremes when combined with large wave runup, due to wave breaking which contributes to 38% of the increase in extreme events while sea level rises to 44%. Our results show that because of its prominent location, Dakar region is affected by waves coming from the Northern and Southern Hemispheres with contrasted evolutions: wave runup events increase faster (7 mm/year) during austral winter due to a maximum of the South Atlantic storm activity, and have a decreasing trend (−3 mm/year) during boreal winter (December, January, February) driven by the evolution of corresponding climate modes. Keywords: coastal flooding; extreme coastal water level; percentile; tide; waves; runup; maximum increase 1. Introduction In a global context marked by global warming leading to an increasing sea level rise of 3.4 mm/year, coastal areas are increasingly threatened by erosion and marine submersion risks [1–3]. Coastlines are vulnerable to the effects of climate change on a global scale due to sea level rise, and on a regional scale due to changes in wave climate [4–7]. In regions marked by low sea level change, a 10 cm rise could double the frequency of coastal flooding over much of the Indian Ocean, South Atlantic, and tropical Pacific [8]. These coastal floods occur due to a combination of oceanic and atmospheric factors [9,10]. They are abrupt events with diverse social, economic, cultural, heritage, morphogenic, and also ecosystem impacts [11]. Extreme events have immediate and noticeable impacts on the coast, unlike longer-term mean sea level changes [12]. According to [13], storms are among the most important driving forces inducing morphological changes in beaches and are a Climate 2023, 11, 6. https://doi.org/10.3390/cli11010006 https://www.mdpi.com/journal/climate