In this study, we discuss the energy dissipation characteristics of stepped embankments by using both the regular and irregular waves in a physical wave flume. The present stepped obstacle is different from those of traditional stepped dikes with fixed horizontal and vertical stage surface as previously investigated by many experts and scholars, the angle of the present stepped surface varies with the slope of the embankment surface, with various interaction angles between the incident waves and the rough stepped surfaces. The stepped embankments were composed of six types of stepped arrangements under five different slopes to analyze the wave run-up heights and reflection coefficients. The results showed that Case F and Case G have better mitigation effects on wave run-up, and the maximum run-up height and reflection coefficient reduced more than 50%. Case F was most performance, while Case D is less effectiveness. The influence of the step shape factor on the wave reflection is minor compared to the embankment slope. Actor on the wave reflection is minor compared to the embankment slope.
Recently, with the change of leisure patterns and the demand for activity spaces, many energy dissipation technologies that provided the maintenance of natural ecology and landscape in the sea, and new energy-dissipation structures have been extensively developed and investigated to reduce wave energy and coastal erosions effectively. Scholars have studied various offshore embankments, including changing the shape of the submerged embankment (Shih and Weng, 2016), the permeability characteristics of the submerged embankment, the number of submerged embankments and the distance between the submerged structures (Shih et al., 2013, 2014), to explore the interaction between waves and structures and their dissipation effectiveness. In addition to reducing the visual barriers of coastal protection facilities, it can further enhance the utilization of coastal spatial resources. One of the most important considerations in the design of Coastal protection technique and structures is the characteristics of wave run-up, wave overtopping, and energy dissipation. Ahrens et al. (1985) analyzed some of the existing formulas for calculating wave run-up and methods that can be widely applied to various conditions for accurately predictions. By using various methods to increase the surface roughness of the coastal protection structures, it is possible to moderately reduce the wave run-up height and the volume of wave overtopping. The coastal areas were traditionally protected by throwing blocks, ramps or gravel. In the past, stepped energy dissipating structures were applied to solid-bed works on spillways and riverbed with concrete blocks, which could be divided into sub-drop water consumption (as energy-dissipating units) to stabilize the riverbed. Chanson (2015) explores the associated dyke overflow spillway and precast concrete block protection systems and emphasizes that the safe operation of the dyke-overflow protection system depends on good structural design and easy periodic maintenance. Ward (2003) determined the range of design storm conditions in several design configurations based on aesthetics and safety reasons, to determine the basic seawalls and stepped revetments of existing coastlines, their experiments on gravel and concrete step-by-step bank revetment showed that the concrete step revetment is more durable than the gravel-type step revetment.
