Sandwave characteristic，evolution and erosion protection of wind farm in the western South China Sea

The development of seabed sand waves has many adverse effects on the installation, construction, and subsequent operation and maintenance of offshore wind farms. Based on the survey results of a wind farm in the South China Sea, we analyzed the developmental characteristics, migration pattern, and control mechanism of seabed sand ridge in the field. Results show that there are spatial differences in the development of linear sand waves in the study area. Linear sand waves usually develop on the top and tail of the sand ridge; crescent sand waves and curved sand waves develop on the flat terrain in the sand ridge trough; and forked sand waves are the predecessor of linear sand waves. The sand waves in the north migrated southward as a whole due to falling tidal flow, while the sand waves in the southern part of the study area migrated northward as a whole due to rising tidal flow, and the transition zone was the area where sediments converged on both sides, reflecting a long-term stable state. The development of sand waves in the study area experienced three evolutionary stages, namely, crescent or curved sand waves, bifurcated sand waves, and linear sand waves. With the evolution of sand waves, the scale of sand waves gradually increased and the mobility gradually weakened. To protect wind turbine pile base from scouring, bionic water grass mats, rocks, or hydraulic fabrics can be applied around the pile foundation to increase the stability of the seabed and reduce the scour around the pile base.