Wave run-up on stepped slopes

Abstract

Abstract

In the design of coastal structures such as seawalls or breakwaters, it is necessary to calculate the wave run-up height so as to define the height of structures. Thus, precise estimation of the wave run-up height would bring about the engineering safety and economy. Most formula for the wave run-up calculation are empirical formula, introduced from laboratory experimental data and have been proposed for either the wave run-up on smooth slopes or on rubble-mound slopes. The research on stepped slope is, however, still limited. In this study, an existing form of the wave run-up formula that accounts for the roughness of surface slopes was applied to forecast the wave run-up on stepped slopes. Empirical parameters in the formula were determined from the experimental data in laboratory. The experiments were conducted with a regular wave flume of 60 cm wide, 80 cm deep and 16 m long. The depth of water in a uniform section of the flume was 35 cm. Regular waves were generated at the frequencies of 0.83, 1.00, 1.17, 1.33, 1.50 and 1.67 Hz. For the case of smooth slopes, the slope ranged from 15 to 25 degrees and for the case of stepped slopes, the slope ranged for 14 to 27 degrees. The step riser heights were 2, 3, 4 and 5 cm. The experimental results showed that the wave run-up decreased as the riser heights increased, due to increasing friction. The wave run-up formula for both smooth and stepped slopes is proposed with satisfactory precision

Keywords : Empirical formula; Seawall; Stepped slope; Wave run-up; Wave steepness