Characteristics of Sand Waves of the Changyun Sand Ridge and Taiwan Shoal in the Taiwan Strait

Seabed topography reveals fundamental information of the earth system at multiple scales. Geomorphologic studies provide insights into the interaction between the hydrosphere and solid earth. We reviewed previous studies of the dynamic seabed environment in the Taiwan Strait and classified the sand waves of the Changyun Sand Ridge and Taiwan Shoal by compiling and analyzing the Crestline distribution and sand wave geometries. We identified five types of sand waves coexisting in the western Changyun Ridge, including long bed trochoidal (LT-type), symmetrical (S-type), trochoidal (T-type), sinusoidal (Sin-type) sand waves, and mega-ripples (Mr-type). Their heights (amplitudes) and wavelengths range from 4.5 to 37 m and 244 to 2,115 m, respectively. In Taiwan Shoal, trochoidal sand waves almost cover the entire area, while the sinusoidal and bimodal sand waves spread in the middle and western portions; the wave heights and wavelengths range from 0.3 to 10 meters and 5 to 1,700 meters, respectively. However, further time-dependent bathymetric and oceanographic investigations are required to simulate the long-term behavior of potential bedform variation along with extreme events. Monitoring the migration of sand waves will also contribute to understanding seabed stability and thus offshore engineering designs in the Taiwan Strait.