Experimental study on wave attenuation and beach profile evolution under the protection of submerged flexible vegetation

• Published in: Journal of hydrology (Amsterdam) Vol. 638; p. 131478
• Main Authors: Gong, Shangpeng, Xu, Sudong, Li, Mingxuan, Wang, Yiran, Yin, Kai, Chen, Yimei, Chen, Jie
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2024
• Subjects: Cross-shore profiles; Flexible vegetation; Regular wave; Sediment transport; Spectrum analysis; Wave attenuation; Wave attenuation; Flexible vegetation; Cross-shore profiles; Spectrum analysis; Regular wave; Sediment transport
• ISSN: 0022-1694
• DOI: 10.1016/j.jhydrol.2024.131478

•Flume experiments were conducted to assess the impact of submerged flexible vegetation on regular wave attenuation and beach morphology.•The presence of vegetation prevented further erosion of the beach, resulting in a reduction of 7% to 63% in experiments.•The attenuation caused by vegetation results in the wave breaking point being closer to the shoreline on vegetated sand, leading to shoreline retreat.•A dimensionless equation was developed to characterize the behaviour of the cross-shore beach profile under the protection of flexible vegetation. Coastal protection methods are evolving from hard engineering techniques to natural enhancement approaches. Aquatic vegetation provides an environmentally friendly solution by effectively dissipating waves and resisting erosion. Laboratory flume experiments were conducted to investigate the effect of submerged flexible vegetation on the regular wave attenuation and cross-shore profiles on the artificial plane beach under varying hydraulic conditions. Variations in the waveform, wave spectrum, and wave height were analysed in the vegetation zone. Results show vegetation distorts the waveform and accelerates the attenuation process of the wave energy, and wave height evolution behaves differently from the theoretically obtained attenuation by Mendez and Losada (2004) due to the underestimating vegetation-induced attenuation and neglecting sediment-induced attenuation. Additionally, the formation process of the winter and summer profiles of the vegetated beach was analysed by the screenshots. Regenerated wave breaking becomes more apparent with increasing wave periods. The critical surf similarity parameter of the vegetated beaches was found to be lower than that of a smooth, impermeable slope because of the energy dissipation. Vegetation did not alter the type of the beach profiles, as compared to the final profiles and their characteristic parameters of the unvegetated beaches. Instead, it reduced the erosion depth and brought the eroded area closer to the shoreline. Dimensionless parameters were formulated to characterize the response of the cross-shore beach profile under the shelter of flexible vegetation, and an empirical equation about maximum erosion depth was developed within the scope of the experiment.