Abrasion rates of coarse sediments on two artificial pebble beaches at Marina di Pisa (Italy)

In this paper pebbles marked by passive integrated transponders from two artificial coarsegrained beaches at Marina di Pisa (Tuscany, Italy) were analyzed in order to measure the in situ abrasion rate. The beaches (Cella 7 and Barbarossa) were set up in 2006 as a form of coastal protection and differ in length (250 m and 110 m respectively) and in the presence of a submerged breakwater 50 m off the coastline at Cella 7. The aim of the study is to reckon the abrasion rate of individual pebbles and evaluate abrasion differences of pebbles released on Cella 7 and on Barbarossa. The RFID technology (Radio Frequency Identification) was used to track the pebbles. The tracers were released on the beaches in March 2009 along closelyspaced cross-shore transects. The recovery campaign was carried out in May 2009. A total of 127 pebbles was detected, 83 of which were recovered. The pebbles that were recovered showed a significant increase in roundness, in particular the tracers that were released on Barbarossa. The average pebble weight loss measured at Cella 7 was slightly lower, which means higher mobilization rate at this site rather than at Barbarossa. The resulting values are significant considering the short time frame of the research (two months) and the limited energyof the storms occurred during the experiment