Development of Shore Platforms along the NW Coast of Italy: The Role of Wind Waves Marta Pappalardo † *, Lorenzo Cappietti ‡ , Isabel Arozarena Llopis § , Alessandro Chelli †† , and Letizia De Fabritiis † † Dipartimento di Scienze della Terra University of Pisa Pisa 56126, Italy ‡ Dipartimento di Ingegneria Civile Universit ` a di Firenze Florence 50139, Italy § Instituto Internacional del Oc´ eano (IOI) Departamento de F´ ısica Universidad Nacional-Costa Rica Heredia 40101, Costa Rica †† Dipartimento di Scienze Fisiche e della Terra ‘‘M. Melloni’’ University of Parma Parma 43124, Italy ABSTRACT Pappalardo, M.; Cappietti, L.; Arozarena Llopis, I.; Chelli, A., and De Fabritiis, L., 0000. Development of shore platforms along the NW coast of Italy: The role of wind waves. Journal of Coastal Research, 00(0), 000–000. Coconut Creek (Florida), ISSN 0749-0208. This paper investigates whether waves are active morphologic agents capable of shaping the small shore platforms that characterize the rocky coast of NW Italy. Two study areas have been selected along this coastal tract: Calafuria (Livorno) and Lerici-Tellaro (La Spezia), located ca. 120 km apart, the first being shaped in sandstone and the second in dolomite bedrock. Propagation of waves in the nearshore has been simulated by numerical modeling. From wave model results, validated with data from an offshore wave meter buoy, it is inferred that waves break directly on the coast or very close to it at Calafuria, whereas for Lerici-Tellaro shores, waves mostly break up to 150 m seaward of the shore platform. This implies that the amount of energy delivered on the platform is much greater in the first case than in the second case. Given breaking depths and the height of breakers, maximum pressure and shear stress released at the breaking point were calculated for both areas. The results showed that wave forces released onto the shore platforms both at Calafuria and at Lerici-Tellaro never exceeded the compressive strength of the platform rocks, assessed using the Schmidt hammer test. It is concluded that, in the study area and with the present oceanographic conditions, wave forces are not directly capable of causing erosion on shore platforms. ADITIONAL INDEX WORDS: Schmidt hammer, wave numerical models, compressive strength, breaking waves, wave erosion, NW Mediterranean. INTRODUCTION Shore platforms are defined as rocky landforms that may be present at the base of vertical cliffs and they can be either horizontal or gently dipping down to sea level (Stephenson, Dickson, and Trenhaile, 2013). In the international scientific literature, it is debated whether subaerial or marine processes should be considered mainly responsible for shore platform initiation and development. Early investigators (Bartrum, 1924; Dana, 1849) considered the erosive force of waves to be the most relevant shaping agent, but the contribution of subaerial weathering was equally recognized (Bartrum, 1926; Hills, 1949). The early works of Sunamura (1975, 1978) provided computational evidence of the efficiency of waves as shaping agents of shore platforms, and later studies empha- sized wave action as the formative process for the development of these landforms (Sunamura, 1992; Trenhaile, 1987, 2000; Tsujimoto, 1987). Field studies from other authors (primarily Stephenson and Kirk, 1998, 2000a,b) point to a prevalence in some case studies of terrestrial agents, whereas waves, in their view, are unable to shape coastal rocks directly. In the Italian literature, Cortemiglia (1995) developed a conceptual model for classification of rocky coasts based on a morphometric approach, wherein shore platforms are considered mainly a result of wave action. After more than 150 years of investiga- tion on this matter, a ‘‘wave vs. weathering’’ debate (Naylor, Stephenson, and Trenhaile, 2010) is still ongoing. Of the contributions published regarding the prevailing agents in shore platform formation, only a few addressed quantitatively the erosive efficiency of waves. A number of works combined the force of waves with other parameters to work out an erosive model of rocky coasts (Trenhaile 2000, 2003, 2005, 2008), whereas others inferred from field evidence that ‘‘wave erosion’’ is a relevant morphologic agent. Dickson, Kennedy, and Woodroffe (2004) recognized that the local wave climate, combined with geological and topographical features, controls the formation of shore platforms on the rocky coasts of Lord Howe Island in the southern Pacific. Further work at the same site (Dickson, 2006) highlighted that rock resistance and nearshore water depth can determine platform morphology (elevation and dip). Kennedy, Paulik, and Dickson (2011) revisited the site investigated by Dana (1849) in northern New Zealand, highlighting the contribution of subaerial weathering in platform shaping at that site; nevertheless, they recognized a major role of waves in DOI: 10.2112/JCOASTRES-D-16-00113.1 received 16 June 2016; accepted in revision 24 February 2017; corrected proofs received 20 June 2017; published pre-print online 27 July 2017. *Corresponding author: pappalardo@dst.unipi.it Ó Coastal Education and Research Foundation, Inc. 2017 Journal of Coastal Research 00 0 000–000 Coconut Creek, Florida Month 0000