A study of beach profile and sediment grain size distribution was conducted at Tombolo Beach, at Manatí in the north-central coast of Puerto Rico from 2008 to 2012. Beach profile measurements, beach sediment collection and field observations were conducted to describe beach width, inclination and sediment grain size characteristics in monthly basis. Sediment grain size was described based on Folk parameters (Folk, 1974). Description of physical variables such as wave height, occurrence of storm and cold front systems were evaluated to identify possible causes of geomorphic changes in the study site. Focal group was also used as a tool to collect information related with natural and human events occurring in the area. Results showed that subaerial beach suffered changes from reflective and dissipative, and vice versa, during the study period. Sediment grains size and composition also showed changes by period and location. Major beach profile and sediment grain size changes were found in less protected beach stations during the occurrence of swells generated by cold fronts arriving from the North Atlantic. An important water retreat event was observed in the study area from April 2009. Detail data are not available yet to identify causes that produce water retreat but definitively produce geomorphic changes in the beach and its sediment sources. A new study will conducted to identify possible causes that produce water retreat event in the area as a coastal uplift. This assessment was done to generate information that may use to develop a coastal management plan to the site.

This research was supported in part by The National Science Foundation (NSF) (Informal Science Project 0638966) and The Conservation Trust of Puerto Rico. “Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation or the Conservation Trust of Puerto Rico.