Wave Energy and Longshore Sediment Transport Gradients Controlling Barrier Evolution in Rio Grande do Sul, Brazil

Abstract

This paper aims to verify how wave energy and longshore sediment transport rates could have influenced the evolution of the Rio Grande do Sul Holocene barriers in the last 5000 y, assuming that wave climate conditions did not change much during the Middle and Late Holocene. Calculations of wave energy based on visual observations and longshore sediment transport show that both wave energy and sediment transport decrease as the coastline becomes concave (embayed) and increase as the coastline becomes convex (projected). These variations alongshore create a positive and negative imbalance, respectively, in the sediment budget. The long-term operation of these processes has produced progradational barriers in embayments and retrogradational barriers along projections. In the transition zones between embayed to convex coastlines, neither depositional nor erosional processes predominate, creating a sediment balance and producing aggradational barriers.