Field observations of sediment transport across the rocky coast of east Taiwan: impacts of extreme waves on the coastal morphology by Typhoon Soudelor
Description
Large boulders and mixed sediments were deposited across the beach after Typhoon Soudelor, 2015, along the east coast of Taiwan. The field observations of these sedimentary features resulting from the extreme waves provide the real data to validate the parameters predicted by the hydrodynamic models on areas with similar topographic conditions. Although the maximum inundation distance is only 170 m due to the lack of beach buffer zone, the largest boulder weighs over 1 ton and the maximum run-up can reach 11.9 m. The grain distribution of the overtopping and beach face sediments exhibited reverse directions of coarsening, reflecting different stages of wave propagation. The formation of the higher extreme wave berm and the destruction of the lower swell berm on one of the sites displayed the power of the storm surges and suggested the important role of the run-up on the evolution of the berm. Extreme values of the run-up, flow velocity, and weight of the clast make it difficult to distinguish the origin of the event if they were found in the geologic records. A comprehensive understanding on the occurrence of the sediments and the depositional environment should be incorporated to differentiate the storm and tsunami events.