Tsunami-Sediment Interactions Amplify Coastal Hazard and Reshape Inundation Dynamics in Tumaco Bay, Colombia

Abstract. Tumaco, situated on the Colombian Pacific coast, is particularly vulnerable due to its location within the Pacific Ring of Fire. Although studies on tsunami risk in the region have been conducted, the interaction between these events and sediment transport has been little explored, despite its impact on flooding dynamics. This study addresses this gap by comparing two scenarios – those with and without sediment transport – and evaluating the morphodynamic effects of tsunami events on proposed mitigation measures for Tumaco. The results show that including sediment transport in the simulations increases wave heights, flooding depth and extent, as well as coastal impacts. In particular, maximum flood depths increase by 24.4 % on Morro Island, 11.57 % on Tumaco Island, and 30.91 % on the mainland. Likewise, flooded areas increase by 4.12 %, 5.15 %, and 13.43 %, respectively, due to increases in flow density and momentum. The mitigation measures reduce the extent of flooding, although they cause local increases in wave heights due to reflection effects. It is noteworthy that in the simulations with mitigation measures, sediment transport does not cause erosion that compromises these coastal defenses. These findings underscore the importance of incorporating sediment transport into tsunami modeling to enhance hazard assessments and refine mitigation strategies, ultimately contributing to the development of more effective coastal resilience plans.