In situ abrasion of marked pebbles on two coarse-clastic beaches (Marina di Pisa, Italy)

In this paper pebbles marked by passive integrated transpon ders from two artificial coarse-grained beaches at Marina di Pisa (Tuscany, Italy) were analyzed in order to measure the in situ abra sion rate. The beaches (Cella 7 and Barbarossa) were set up in 2006 as a form of coastal protection. They are both composed of pebbles (30-to-90 mm diameter) and bounded longshore by huge groynes. They differ in length (250 m and 110 m respectively) and in the prese nce of an additional defense structure, 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 differen ces of pebbles released on Cella 7 and on Barbarossa. The RFID technology (Radio Frequency Identification) was used to track the pebbles due to its reliability and limited costs. The tracers were released on the beaches in March 2009 along closely-spaced crossshore transects. The recovery campaign was carried out in May 2009. A total of 127 pebbles was detected, 83 of which were recov ered. Huge beach reworking during the storms determined high burial rates and consequently the loss of a definite amount of tracers. The pebbles that were recovered showed a significant increase in roundness, in particular the tracers that were released on Bar barossa. The average pebble weight loss measured at Cella 7 was slightly lower, which means lower 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 energy of the storms occurred during the experiment.

[1]  M. C. Powers.  A New Roundness Scale for Sedimentary Particles , 1953 .

[2]  P. Kuenen.  EXPERIMENTAL ABRASION: 6. SURF ACTION , 1964 .

[3]  Robert L. Folk,et al.  Petrology of Sedimentary Rocks , 1974 .

[4]  E. Matthews.  Measurements of beach pebble attrition in Palliser Bay, southern North Island, New Zealand , 1983 .

[5]  J. Latham,et al.  Abrasion of a series of tracer materials on a gravel beach, Slapton Sands, Devon, UK , 1998, Geological Society, London, Engineering Geology Special Publications.

[6]  E. Pranzini.  Updrift river mouth migration on cuspate deltas: two examples from the coast of Tuscany (Italy) , 2001 .

[7]  C. Moses,et al.  Life expectancy of shingle beaches: measuring in situ abrasion , 2002, Journal of Coastal Research.

[8]  Enzo Pranzini,et al.  ‘Back to the Beach’: Converting Seawalls into Gravel Beaches , 2003 .

[9]  Jonathan C. Allan,et al.  The use of Passive Integrated Transponder (PIT) tags to trace cobble transport in a mixed sand-and-gravel beach on the high-energy Oregon coast, USA , 2006 .

[10]  M. Coli,et al.  The Marble Beaches of Tuscany* , 2008 .

[11]  Philip D. Osborne,et al.  Seasonal patterns of coarse sediment transport on a mixed sand and gravel beach due to vessel wakes, wind waves, and tidal currents , 2009 .

[12]  A. Samet Hasiloglu,et al.  Shape Properties of Natural and Crushed Aggregate using Image Analysis , 2010 .

[13]  Giuliano Benelli,et al.  Radio Frequency Identification (RFID) technology applied to the definition of underwater and subaerial coarse sediment movement , 2010 .

[14]  G. Benelli,et al.  Transport trajectories of “smart” pebbles on an artificial coarse-grained beach at Marina di Pisa (Italy): Implications for beach morphodynamics , 2010 .

[15]  Duccio Bertoni,et al.  On the profile evolution of three artificial pebble beaches at Marina di Pisa, Italy , 2011 .