Numerical simulation of extreme wave runup during storm events in Tramandaí Beach, Rio Grande do Sul, Brazil

Abstract

We present a high resolution analysis of the interaction of irregular waves with natural and urban structures leading to extreme wave runup. Horizontal runup data, instantaneous flooding maps, and wave propagation beyond the coastline are numerically predicted. The novel methodology combining the Wave Watch III, SWAN and SWASH models to achieve accurate and computationally feasible simulation of waves at different time and spatial scales, from the formation process at deep water up to the total energy dissipation in the swash zone, is proposed. An access to the LIDAR database has provided a high resolution (15cm–25cm) of the subaerial surface which is essential for accurate representation of the hydrodynamic interactions with the beach profile. The suggested approach has been applied for evaluation of wave runup related to six storm events in Tramandaí Beach in Southern Brazil. This allowed for an identification of critical vulnerable overwashing areas as well as, critical information on flooding zones. The results are in agreement with the runup measurements performed in January 2014. The numerical methodology employed in this work has been also compared with the survey and conventional empirical model data. It was discovered that the empirical models lead to the systematic overestimation of the runup results.