Determination of Infragravity Wave Conditions at a Nearshore Location With a Non-Uniform Coastline: Case Study of Baía de Todos os Santos, Brazil

Abstract

The Petrobras energy company plans to build a new terminal in the Baía de Todos os Santos, Brazil. This paper describes a study in which an estimate has been provided for infragravity (or low-frequency, LF) wave conditions at this future LNG Regasification Terminal location. To aid the design of the terminal, numerical simulations of the propagation of these waves into the bay have been performed. At the proposed terminal location, within a large coastal bay, LF waves can be related to long waves bound to the local primary sea and swell waves (bound LF waves) and to low-frequency waves that propagate into the bay after being made free near the bay entrance (free LF waves). While most of the primary waves will not fully penetrate into the bay, the long LF waves can. Due to the large area of the bay (approximately 40 km × 30 km), detailed modelling of all complex coastal processes related to infragravity waves was not efficient. Therefore, a practical approach has been followed in this study. For a first evaluation, an estimate has been made of bound LF wave conditions at the terminal location inside the bay and at the mouth of the bay. This estimate is based on an equilibrium method using the local primary wave climate and assuming a flat bottom. In a second stage, free LF wave penetration into the bay has been simulated using the shallowwater model Delft3D-FLOW. By applying the practical approach described in this paper, infragravity wave conditions (bound and free) have been efficiently estimated at the future terminal location for yearly-averaged and extreme primary wave conditions. The results show that the LF wave climate at the terminal will be very mild, corresponding to beneficial conditions for terminal operations. The outcome of this study will be taken into account in the further design of the terminal.