Wave Attenuation on Muddy Bottoms – A Multidisciplinary Field Study Offshore Cassino Beach, Southern Brazil

A field experiment was performed offshore Cassino Beach, Southern Brazil. In this area mud deposits were observed, mainly originated from the Patos Lagoon. Episodically, and associated with storm waves able to transport the mud from offshore to the beach, the usual sandy beach is covered by mud. This is a unique process along the Brazilian coastline, and the field experiment aimed to record the event of mud ressuspension and onshore transport measuring the waves, near-bottom currents, concentration of suspended sediments, and changes in the characteristics of bottom sediments. The experiment occurred in May-June 2005, as the record of previous events indicate is the time of the highest probability of offshore mud to be transported onshore due to higher wave energy. Unfortunately the last event of mud deposit on the beach occurred in November 2004 (Figure 1). However, the collected data set is still valuable and will help to a better understanding of waves transformation in the inner shelf and nearshore. A major issue that might restrict data analysis was the loss of equipment due to the strong fishing activity in the area. A summary of the field experiment achievements is described in this report.