Soil aggregate stability and pore structure are key indicators of soil degradation. Waves generated by the water-level fluctuations could severely deteriorate soil aggregates, which eventually induce soil erosion and several other environmental issues such as sedimentation and flooding. However, due to limited availability of the hydrological alteration data, there is a limited understanding of soil aggregates, intra-aggregate pore dynamics, and their relationships under periodically flooded soils. The present study has relied on long-term hydrological alteration data (2006-2020) to explore the impacts of inundation and exposure on soil aggregates and pore structure variations. Soil samples from increasing elevations (155, 160, 163, 166, 169, and 172 m) in the water-level fluctuation zone of the Three Gorges Reservoir were exposed to wet-shaking stress and determined soil structural parameters. The overall inundation and exposure ratio (OvI/E) gradually decreased from 1.87 in the lowest to 0.27 in the highest elevation, respectively. Predominant distribution of macropores was recorded in lower elevations, while micropores were widely distributed in the upper elevations. The mean weight diameter (MWD) was significantly lower in the lower (2.4-3.7 mm) compared to upper (5.3-6.0 mm) elevations. The increase in MWD has increased the proportion of micropores (PoN < 50 mu m), with R-2 = 0.59. This could suggest that the decrease in flooding intensity can create favorable conditions for plant roots growth. The strong flooding stress in lower elevations (i.e., higher values of the OvI/E) accelerated the disintegration of soil aggregates and considerably increased the formation of macropores due to slaking and cracking. The findings of the present study emphasize the need to restore degraded soils in periodically submerged environments by implementing vegetation restoration measures. This could enhance and sustain aggregate stability, which was also proved to increase functional pores under hydrological alterations.

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.