Evaluating the influence of Cynodon dactylon on the wave force and wave erosion in the water-level fluctuation zone of the Three Gorges Reservoir Area

Abstract

Wave erosion is the main erosion type in the water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir Area (TGRA). Despite vegetation can effectively mitigate wave erosion in the WLFZ, its influence on the wave force and wave erosion remains unclear. Therefore, the wave experiments were conducted under 3 Cynodon dactylon coverage rates (0, 30% and 60%) and 9 wave conditions (3 wave heights of 4, 6 and 8 cm combined with 3 wave periods of 1, 2 and 3 s) to analyse the wave force (expressed as the wave pressure on the slope surface and the pore water pressure in the slope) and wave erosion rate, and the factors influencing wave erosion were identified. The results indicated that the wave pressure, pore water pressure and wave erosion rate increased by 19.14%–104.75%, 16.84%–65.04% and 23.33%–91.64%, respectively, as wave height increases. The wave pressure decreased by 1.50%–31.23% followed by an increase by 22.05% to 87.10% with the increase of wave period, whereas the pore water pressure and wave erosion rate decreased by 28.33%–53.59% and 20.46%–63.59%, respectively. However, these quantities decreased by 2.10%–50.84%, 17.06%–40.23% and 17.28%–82.18%, respectively, with the increase of Cynodon dactylon coverage rate. It was also discovered that the pore water pressure and Cynodon dactylon coverage rate attained the highest positive and negative correlation coefficients with the wave erosion rate, respectively. In addition, pore water pressure accumulation is the most critical influence factor on wave erosion, and Cynodon dactylon could effectively reduce the pore water pressure via its roots, thus improving the slope wave erosion resistance. This study could be useful to understand the mechanism of plants on controlling wave erosion and could provide a scientific reference for wave erosion control and the ecological construction in the WLFZ.