Abstract: Through the physical model test in the wave flume, the influence of the artificial trapezoidal ecological reef on the infragravity wave characteristics in the complex island reef environment is discussed, and compared with the case of no reef. The wave propagation, reflection and attenuation effects of the artificial trapezoidal ecological reef in the complex island reef terrain are systematically analyzed. The experimental study shows that the wave height is significantly reduced in the rear area of the ecological reef. The ecological reef effectively weakens the wave breaking near the reef, which reduces the wave added value, and makes the wave height of short wave and low frequency long wave near the reef smaller. The existence of ecological reefs also helps to reduce the maximum run-up of waves on slopes ; the amplitude of wave attenuation increases with the decrease of the pore size of the ecological reef. It is also found that when the wave height and spectral peak period of the incident wave increase, the ecological reef has a more obvious effect on the short-wave wave height, low-frequency long-wave wave height and wave elevation. However, with the increase of water depth of reef flat, the effect of ecological reef on weakening wave energy shows a decreasing trend. The reflection coefficient in the presence of ecological reefs is generally greater than that in the absence of ecological reefs.

Key words: ecological reef, infragravity wave, low frequency long wave, complex reefs, wave characteristics