Performance of coastal sea-defense infrastructure at El Jadida (Morocco) against tsunami threat: lessons learned from the Japanese 11 March 2011 tsunami

Abstract

This paper seeks to investigate the effectiveness of sea-defense structures in preventing/reducing the tsunami overtopping as well as evaluating the resulting tsunami impact at El Jadida, Morocco. Different tsunami wave conditions are generated by considering various earthquake scenarios of magnitudes ranging from <i>M</i>_w = 8.0 to <i>M</i>_w = 8.6. These scenarios represent the main active earthquake faults in the SW Iberia margin and are consistent with two past events that generated tsunamis along the Atlantic coast of Morocco. The behaviour of incident tsunami waves when interacting with coastal infrastructures is analysed on the basis of numerical simulations of near-shore tsunami waves' propagation. Tsunami impact at the affected site is assessed through computing inundation and current velocity using a high-resolution digital terrain model that incorporates bathymetric, topographic and coastal structures data. Results, in terms of near-shore tsunami propagation snapshots, waves' interaction with coastal barriers, and spatial distributions of flow depths and speeds, are presented and discussed in light of what was observed during the 2011 Tohoku-oki tsunami. Predicted results show different levels of impact that different tsunami wave conditions could generate in the region. Existing coastal barriers around the El Jadida harbour succeeded in reflecting relatively small waves generated by some scenarios, but failed in preventing the overtopping caused by waves from others. Considering the scenario highly impacting the El Jadida coast, significant inundations are computed at the sandy beach and unprotected areas. The modelled dramatic tsunami impact in the region shows the need for additional tsunami standards not only for sea-defense structures but also for the coastal dwellings and houses to provide potential in-place evacuation

Tsunami hazard and buildings vulnerability along the Northern Atlantic coast of Morocco –the 1755-like tsunami in Asilah test-site

“…The code also allows employing a nested grid system with increasing grid resolutions in order to fulfil the need for tsunami simulations at different scales from the source zone to the high resolution target coast where inundation maps are computed (Wang 2009). COMCOT code has been used to study several tsunami events such as the 1755 Lisbon tsunami Omira et al 2013), the 2003 Algeria tsunami (Wang and Liu 2005) and, more recently, the 2004 Indian Ocean tsunami (Wang and Liu 2006).…”

“…Hazard and vulnerability are the main components of any comprehensive risk assessment. For the tsunami phenomenon, the hazard assessment along a threatened coast is often covered by numerical modeling of the resulting inundations through the deterministic method (Tinti and Armigliato 2003;Tinti et al 2005;Løvholt et al 2006;Baptista et al 2011;Omira et al 2011;Omira et al 2013) or the probabilistic analysis (González et al 2009;Omira et al 2016). In addition, vulnerability study is trans-disciplinary and multi-dimensional, covering social, economic, physical, political, engineering and ecological aspects and dimensions (Post et al 2009).…”

“…1) while evaluating their sensibility to the effect of the tidal variation. This is achieved by: i) performing highresolution inundation modeling using the scenario-based approach described in Tinti and Armigliato (2003) and other recent applications along the Moroccan coastline (Omira et al 2010;Omira et al 2011;Omira et al 2013;Benchekroun et al 2015;Wronna et al 2015), and ii) investigating the building vulnerability using an approach based on a combination of the results of tsunami hydrodynamic modeling, information collected during the building inventory and the use of GIS tools allowing multicriteria analysis and vulnerability mapping. This building vulnerability assessment method is based on the BTV model proposed by Omira et al (2010).…”

Tsunami impact and vulnerability in the harbour area of Tangier, Morocco

“…The main limitation consists of excluding various building types such as harbour structures and historical buildings, for which no damage levels were assigned, since damage curves associated with such building types were not assessed. Also, in the methodology there is no consideration of existing sea-barriers and/or protective structures that could reduce the tsunami impact and inundation as investigated in Omira et al (2013), and hence, affect the reliability of the damage results presented.…”

“…In spite of the recent attempts addressed to the compilation of tsunami catalogue (Kaabouben et al 2009), the identification of tsunami deposits (Medina et al 2011), the mapping of tsunami inundation (Omira et al 2010(Omira et al , 2013Renou et al 2011) and the assessment of tsunami building vulnerability (Omira et al 2010;Atillah et al 2011), tsunami hazard and vulnerability along the Moroccan coasts remain poorly investigated. Detailed tsunami hazard assessment generally faces the lack of highresolution bathymetric and topographic data required to perform inundation simulations.…”