A Study of Tsunami Reflection on Not-Armoured and Armoured Beach

An experimental study has been carried out to investigate the tsunami reflection on not armoured and armoured beaches. The experiments were conducted in the glass-walled wave channel of 22.5 m length, 1.00 m width, and 0.50 m depth. First, natural beach material with a diameter of 0.35 mm and specific gravity of 2.63 was placed on 1/5 slope. Incident and reflecting wave heights were measured and the tsunami reflection coefficient (Hr/Hi) was calculated. Then, natural gravel and natural aggregate on diameters of 10 mm and 13.8 mm were placed the natural beach material throughout the slope, separately and each 5 cm thick, incident and reflecting wave heights were measured again, and reflection coefficients for these cases were calculated. These experiments, conducted with 1/5 slope, were repeated with 1 /2.5 and 1/6.5 slopes. In all slopes, armoured and not armoured surfaces, reflection coefficient decreases when dimensionless run-up height and dimensionless wave height increase. When slope increases, reflection coefficient increases too and when the diameter of armour unit increases, reflection coefficient decreases. After evaluation of the experimental results, the parameters that affect the tsunami reflection coefficient were determined. These parameters were written as a dimensionless group using Buckingham’s Pi theorem. The regression analysis is carried out and empirical relationship is proposed. All experiments were repeated slope 1:3.5 for verification of the proposed relationship, and the results from this relationship and experimental results have been compared, and it was shown a good agreement between the results.