Evaluation of tsunami inundation in the plain of Martil (north Morocco): Comparison of four inundation estimation methods

Abstract

The Alboran Basin may be subject to tsunami hazards. If such an event were to occur, it is expected that the urbanised and densely populated areas of northern Moroccan coastline would be affected. Precise inundation hazard maps are needed for tsunami risk management in this region. In this article, we argue that the diversity of hazard mapping methods ensures the robustness of the scientific knowledge about the exposure of a territory. Hence, the main objective of this study is to analyse the exposure of the plain of Martil (north of Morocco), by using four hazard mapping methods to create inundation maps for two scenarios of tsunamis generated by extreme submarine mass failure (SMF) in the Alboran Sea, of 0.9 ​km³ and 3.8 ​km³ respectively. A digital terrain model of the plain was used to explore four methods of inundation mapping. The static method identified 4.32 ​km² and 19.83 ​km² of flooded areas for each scenario using water height values as inundation thresholds. The hybrid and the volumetric methods use the volume of water to determine the inundation extent. For the first scenario, 3.51 ​km² of the plain were inundated using the hybrid method, and 20.11 ​km² for the second scenario. The results of the volumetric methods are 2.32 ​km² and 7.82 ​km² respectively for the first and second scenario. Finally, the fourth method relies on numerical hydrodynamic modelling of tsunami inundation (Freshkiss3d® code). With this method, 4.55 ​km² of the plain were flooded in the first scenario, and 24.12 ​km² for the second. The comparison of the results highlights that the most sensitive areas to tsunami inundation are the lowest topographic ones, being the beaches and the wadis floodplains. This result raises questions on the current coastal development and the preparedness of its population, thus calling for more attention to engage on tsunami risk management related questions.