Original Investigation of Tsunami Inundation Risk for Nigerian Atlantic Coastline Using Numerical Modelling

The Nigerian Atlantic coastline is potentially vulnerable to tsunami inundation from Atlantic seismic sources including the Azores-Gibraltar Transform Fault, the Canary Islands volcanic system, and submarine landslides on the Nigerian continental slope, yet no systematic quantitative tsunami hazard assessment has been conducted for the Nigerian coast. This study provides an original investigation of tsunami inundation risk for the Nigerian Atlantic coastline using probabilistic numerical modelling. An original Nigerian Tsunami Hazard Model is developed through four contributions: a systematic review and catalogue of Atlantic tsunami sources with magnitude-frequency relationships; numerical tsunami generation and propagation modelling using COMCOT for 50 scenario events representing the range of credible source types and magnitudes; inundation modelling for the 1-10,000 year return period range using a high-resolution coastal digital elevation model derived from LiDAR survey of 200 km of vulnerable coastline between Lagos and the Niger Delta; and Monte Carlo-based probabilistic hazard computation integrating scenario probabilities and inundation model results. Results indicate that inundation hazard from the Canary Islands landslide source dominates Nigerian coastal hazard at return periods below 500 years. Maximum inundation depths for the 2,500-year return period event range from 0.8 to 3.4 m depending on coastal morphology, with low-lying delta communities most exposed. The study provides the first original tsunami hazard assessment for the Nigerian Atlantic coast, informing coastal infrastructure design and emergency planning.

Keywords: tsunami hazard, Atlantic coastline, numerical modelling, Nigeria, probabilistic assessment