Frequency beach profile monitoring: implications in beach safety at Cassino beach, southern Brazil

Abstract

During the summer of 2002 and 2003, daily monitoring of beach profiles were conducted at Cassino Beach, a highly dissipative beach in southern Brazil in order to verify changes in the dynamic inner and outer bar systems which could provide additional information to beach safety programs. Distances and depths of the troughs from the water line oscillated between 55m and 0.89m respectively for the first trough, to 160m, and 1.78mfor the third trough.At low wave energy conditions, average migration rates of the first and second bar reached 4.8 m/day. The total number of accidents, in the summer 2002, were equally associated with both, dissipative and the intermediate morphodynamic states, however the accidents in the summer 2003 occurred only in the intermediate type. The presence of a deep trough imprint in the intermediate beach type, a higher hazardous morphology level. The 2003 campaign documented stable profiles, showing a low mobility and constant morphology with the same beach type, with a deep trough that reached the depth of 2.4m at a distance of 96m from the water line. It is believed that this low mobility was caused by the presence of mud bottoms at the nearshore zone.