Preliminary observation of morphological responses totyphoon of coastal dunes
Received date: 2016-05-06
Request revised date: 2016-08-03
Online published: 2016-10-26
Copyright
Pingtan Island is located in the sea of eastern Fujian Province, which is one of the typical coastal aeolian landform regions in China, well known for its typical shape, volume and less human disturbance. On the Pingtan Island coast, which was taken as the research region for the observation of coastal dunes' morphological responses to typhoon, four areas were chosen as the field observation sample areas, separately representing the four types of coastal aeolian landforms such as coastal foredune, coastal transverse dune, coastal sand sheet and climbing dune. By using high-precision RTKGPS technology and surveying method, the elevation data before and after typhoon landed at 931 observation points and 15 transect belts in four sample areas were measured. Based on the high-precision surveying data over the four typical coastal dunes in Pingtan Island before and after the 10th typhoon (Matmo) in 2014, the morphological change of the four types of coastal dunes in response to the typhoon Matmo event is analyzed. The typical observation results suggest that the basic feature of the impact of typhoon Matmo on the morphological change of coastal dunes in Pingtan Island is the reduction of volume and height. The average elevation change of the 931 observation points in the four sample areas is 0.22 m, and the average elevation of all the observation points decreased by 0.05 m. The volume of four coastal dunes in the four sample areas reduced at an average of 0.59% after the typhoon Matmo landing, the biggest volume reduction is 2.20%, which was observed in the coastal foredune sample areas. However, the magnitudes of morphological responses are different in different types of coastal dunes and different sites over the coastal dunes. For example, the volume and height of coastal sand sheet was found to increase after the typhoon Matmo landing while other types of coastal dunes decreased. For the coastal climbing dunes the highest decrease in height was at the middle site of windward slope in front of coastal climbing dune and the smallest decrease in height was at the top site of windward slope in front of coastal climbing dune. The basic reasons for the impact of typhoon Matmo on the morphological change of coastal dunes are the strong wind erosion, the landform under the coastal dunes, the shape of coastal dunes and the differences of the distribution of coastal dunes' surface vegetation.
Key words: coastal dune; morphological responses; typhoon; observation
DONG Yuxiang , HUANG Dequan , ZHANG Xueqin . Preliminary observation of morphological responses totyphoon of coastal dunes[J]. GEOGRAPHICAL RESEARCH, 2016 , 35(10) : 1925 -1934 . DOI: 10.11821/dlyj201610011
Fig. 1 Distribution map of field observation locations in the research area and their geomorphic landscape pictures图1 研究区观测点位置图及沙丘景观 |
Fig. 2 Height surveying points and belts over coastal dunes in observation sample areas图2 观测样区的高程测点和样带 |
Tab. 1 Height change of geomorphic sites at the surveying belts over different types of coastal dunes表1 海岸沙丘不同部位的高程变化(m) |
| 样区与样带 | 海滩和海岸沙丘部位 | |||||
|---|---|---|---|---|---|---|
| 海岸前丘 | 地貌部位 | 海滩 | 迎风坡脚 | 迎风坡坡中 | 沙丘丘顶 | 背风坡脚 |
| 样带A | +0.05 | +0.18 | +0.09 | -0.18 | 0.00 | |
| 样带均值 | +0.06 | +0.25 | +0.04 | -0.28 | -0.03 | |
| 爬坡沙丘 | 地貌部位 | 沙丘前缘坡脚 | 沙丘前缘坡中 | 沙丘前缘顶部 | 沙丘中部 | 沙丘后缘 |
| 样带A | -0.22 | -0.63 | -0.17 | -0.18 | -0.23 | |
| 样带均值 | -0.24 | -0.43 | -0.10 | -0.16 | -0.24 | |
| 横向沙丘 | 地貌部位 | 迎风坡脚 | 迎风坡坡中 | 沙丘丘顶 | 背风坡中部 | 背风坡坡脚 |
| 样带A | +0.05 | -0.17 | -1.43 | -0.41 | +0.32 | |
| 样带均值 | 0.00 | -0.06 | -0.38 | -0.06 | -0.04 | |
| 海岸沙席 | 地貌部位 | 海滩 | 沙席前缘 | 沙席中部 | 沙席后缘 | |
| 样带A | -0.15 | -0.02 | +0.04 | +0.58 | ||
| 样带均值 | -0.14 | -0.03 | +0.04 | +0.22 | ||
注:“+”为高程增加,“-”为高程降低。 |
Tab. 2 Statistics of volume and height change of coastal dunes at observation locations表2 观测点海岸沙丘体积与高程变化统计 |
| 观测点 | 样区内海岸沙丘体积(m3, %) | 测点高程变化(m) | |||||||
|---|---|---|---|---|---|---|---|---|---|
| 台风前 体积 | 台风后 体积 | 体积 变化量 | 体积 变化率 | 变化值 平均值 | 高程变化 平均值 | 高程升高 均值 | 高程降低 均值 | ||
| 白鸽屿后 | 96541.7 | 94414.4 | -2127.3 | -2.20 | 0.33 | +0.02 | +0.32 | -0.35 | |
| 白犬山 | 40110.2 | 39328.1 | -782.1 | -1.95 | 0.21 | -0.18 | +0.16 | -0.21 | |
| 芦洋 | 26675.3 | 26523.7 | -151.6 | -0.57 | 0.18 | -0.02 | +0.15 | -0.21 | |
| 仙岐宫 | 80663.2 | 82291.0 | +1627.8 | +2.02 | 0.14 | -0.01 | +0.16 | -0.13 | |
| 均值 | 60997.6 | 60639.3 | -358.3 | -0.59 | 0.22 | -0.05 | +0.20 | -0.23 | |
注:“+”为增加,“-”为减小。 |
Fig. 3 Profiles of height change of main surveying points at the surveying belts over coastal dunes图3 海岸沙丘样带上主要测点的高程变化 |
The authors have declared that no competing interests exist.
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