Dune restoration experiments during a typhoon season on Taiwan's Si-Cao coast

The restoration of coastal dunes, a common form of soft protection, can not only save considerable construction and maintenance costs but also facilitate the maintenance of coastal ecological environments and natural landscapes. Taiwan sustains frequent typhoons and its Si-Cao coast has been seriously affected by previous storms. Restoration of the sand dunes of the Si-Cao coast is necessary and urgent, and the influence of typhoons should be fully considered in dune restoration. Therefore, four test sets were created to perform dune restoration experiments in the northern section of the Si-Cao coast by using different methods, materials, and layouts. We compared topographical and vegetation survey results preceding and following four typhoons, and used this information to identify suitable construction methods for typhoon-affected dunes. These results indicated that artificial vegetation did not perform ideally because the growth of vegetation was slow under the influence of typhoons. Oyster bamboo racks were found to have a positive effect on sand trapping, and provided a shelter that enabled plants to grow naturally. Sand accumulation between two fences was substantial, but moderately dispersed. After consecutive typhoons, vegetation coverage showed a downward trend in all four test sets; however, the sand fence set had the highest protective effect on vegetation. Spinifex littoreus exhibited a strong ability to resist typhoons; after a slight decrease, its coverage improved markedly. According to these results, we provide recommendations for dune restoration on the Si-Cao coast.