Beach Morphodynamics and Characterization of Sand Bars in Mesotidal Environments

High frequency monitoring aims at characterizing the changes that occur in beach environments and the mobility of sand bars near the coast. This study was carried out on the coast of Futuro Beach, Fortaleza (CE), in the northeast of Brazil. From June to July 2007, daily profiles of high frequency were carried out for 30 days in a row in order to characterize the position and migration pattern of the sand bars in an environment of sediments with different modal classes. The morphodynamics of the beach was characterized according to the conceptual model proposed by Masselink and Short (1993) to classify the effects of tides in beach morphology. For this study, video images were also collected to assess sand bars in the area. The video-imagery data showed that there are two sand bars on that beach: one of them, which emerges at the low tide, is located near the coast in the intertidal zone and the other one, which is constantly submerged, is located farther from the coast. The width of the beach profiles varied between 80 m and 137 m with average migration of sand bars of 4.08 m/day. The surveys also enabled to verify that the average value of the sand bar migration was 4.64 m/day at three monitoring points. Taking into account that the causes of the migration processes and the behavior of sand bars are not fully understood yet, studies of changes registered in beach profiles, such as the migration rates of sand bars in the surf zone, are important to comprehend these phenomena and to select the best monitoring frequency.