796 DUNE EROSION AND OVERWASH IN LARGE-SCALE FLUME EXPERIMENTS G.R. TOMASICCHIO 1 , F. D’ALESSANDRO 1 , C.J.E.M. FORTES 2 , S. ILIC 3 , M.R. JAMES 3 , A. SANCHEZ-ARCILLA 4 , F. SANCHO 2 , H. SCHÜTTRUMPF 5 1. Engineering Department, University of Salento, via per Monteroni, 73100 Lecce, Italy. roberto.tomasicchio@unisalento.it; felice.dalessandro@unisalento.it 2. Laboratorio Nacional de Engenharia Civil (LNEC), Av do Brasil 101, 1700-066, Lisbon, Portugal. jfortes@lnec.pt; fsancho@lnec.pt 3. Lancaster Environmental Centre, Lancaster University, Lancaster, LA1 4YQ, United Kingdom. s.ilic@lancs.ac.uk; m.james@lancs.ac.uk 4. Universitat Politècnica de Catalunya, Laboratori d’Enginyeria Marìtima, C/Jordi Girona, 08034 Barcelona, Spain. agustin.arcilla@upc.edu 5. Institute of Hydraulic Engineering and Water Resources Management, RWTH Aachen University, Mies-van-der-Rohe-Strasse 1, 52056 Aachen, Germany. schuettrumpf@iww.rwth-aachen.de Abstract: The present paper gives a general overview of the large-scale physical model experiments performed at the LIM/UPC in Barcelona, within the EU-Hydralab III Integrated Infrastructure Initiative. The model tests have been carried out in a flume with a sandy dune exposed to a combination of water levels and wave conditions. Dif- ferent regimes of wave attacks on the sandy beach/dune system have been investigated. In particular, the study provides a unique set of large-scale physical data concerning the wave-induced dune overwash. Measurements of hydrodynamics, sediment concen- trations and beach-dune profile evolution have been carried out. Profile measurements have been used to calibrate and validate a numerical model (Kobayashi et al. 2007) to predict beach-dune profile modifications over the near-shore region. The numerical model is shown to be in agreement with the experimental data. Introduction Coastal dunes are natural barriers protecting areas along many of the world’s sandy coastlines against surge and wave action. The need for predicting the response of coasts to storms is rising steadily as the population in coastal areas grows world- wide and loads on coastal systems increase due to rising sea levels and the possibil- ity of more intense storms (Emanuel et al. 2008). Thus, it is of significant value to be able to predict the impact of a storm on a dune in terms of recession distance, eroded volume, overwash rate and probability of breaching. Several analytical and numerical models have been developed for this purpose, but many of them lack a clear physical basis and have only been tested against limited data (Larson et al. 2004).