台风群后海岸爬坡沙丘形态变化特征

依据福建平潭岛海岸爬坡沙丘在2016年夏秋季台风“尼伯特”“莫兰蒂”“鲇鱼”组成的台风群登陆前后一年内8次形态高精度测量数据,探究典型海岸爬坡沙丘在台风群登陆后的年内形态变化过程及其特征。结果表明:(1)台风群造成海岸爬坡沙丘体积减少了0.13%、沙丘高度最大降低1.43 m,且不同部位高度变化存在一定差异,特别是后缘因地表植被破坏高度变化最明显。(2)台风群中单个台风作用下海岸爬坡沙丘形态变化虽明显,但未发现存在累积效应。(3)海岸爬坡沙丘形态在台风群后的近一年内以体积增加、沙丘高度增加为主,特别是爬坡沙丘前缘部位有明显的变化规律。(4)海岸爬坡沙丘形态对台风群的响应特征是台风群(强度、数量)、海岸爬坡沙丘原形态、植被盖度、海滩类型及周边环境等因素综合作用的结果,而台风群过后爬坡沙丘形态恢复变化与其形成发育因素相类似,其中海滩沙源和风况是关键性因素。

Morphological change of coastal climbing dunes in Pingtan Island of China after typhoon group

Pingtan Island is located of the eastern coast of China’s Fujian Province, which is one of the typical coastal dunes in China, well-known for its typical shape, volume, and limited human disturbance. The island was severely impacted by a group of three typhoons (Nepartak, Meranti, and Megi) during summer 2016. Field investigations were conducted on the island before and after the typhoon group landed almost a year, with using high-precision RTK GPS technology and surveying methods. We analyzed morphological change of coastal climbing dunes after the typhoon group. The results indicated that: (1) The maximum height change among coastal climbing dunes was 1.43 m, and dune volume decreased slightly by 0.13%; the changes in height differed between climbing dune sites, for example, the maximum height changes at the trailing edge of climbing dunes varied because of the destruction of vegetation. (2) Coastal climbing dunes showed no cumulative effects in their responses to the typhoon group, despite an individual typhoon showing obvious impacts on coastal dune morphology. (3) The basic morphological change of coastal climbing dunes after typhoon was comprised of increases in volume and height. Especially, the front part of climbing dunes has obvious change rule. (4) In general, the morphological change of coastal climbing dunes were mainly due to the typhoon intensity and quantity, to dune type and previous morphology, vegetation density, beach type, the trend of the coastline, the surrounding environment, and so on. The morphological recovery and change of climbing dune after typhoon group are similar to its formation and development factors, among which the supplies of beach sands and wind condition play a critical role.