台风期间盐沼消波效应的观测研究——以珠江口芒洲湿地为例

Observational Study on Wave Attenuation Effect of Salt Marsh during Typhoon——a Case Study of Mangzhou Wetland in Zhujiang River Estuary

关键词:  芒洲湿地  台风“鹦鹉”  盐沼  消浪  减灾

Key words:  Mangzhou Wetland  typhoon 'Parrot'  salt marshes  wave attenuation  disaster reduction

摘要:

滨海盐沼可以减少风暴潮和台风浪的冲击,从而增强海岸抵御台风等自然灾害的能力,减少经济损失,在保护海岸和防灾减灾等方面起到重要作用。本研究利用2020年6月台风“鹦鹉”活动期间珠江口芒洲湿地的现场实测波浪数据来分析其消浪功能,以定量研究盐沼植被的消波效应。结果表明,台风“鹦鹉”期间,芒洲湿地测得风暴潮最大增水达0.43 m,漫滩时间大于6 h;实测波浪通过宽度100 m和230 m盐沼植被带的波高衰减率分别为90.5%和97.2%,植被减灾能力为优;根据波高衰减率经验公式的估算结果,波浪经过植被宽度100 m和200 m的波高衰减率分别为94.0%和97.0%,与实测结果基本一致。由于台风“鹦鹉”影响时间短、强度弱,现场测得水位均在1 m以下,而盐沼植被的平均株高约为2 m,植被冠顶未被淹没,因此可将植被看作透空式堤防,其茎叶的摩擦阻尼作用导致波能衰减;并且现场测得有效波高均在0.10 m以下,同时也未发生植被大量倒伏甚至茎秆断裂的情形,因此盐沼植被充分发挥了消波作用。综上,虽然芒洲盐沼面积仅为3.39 km²,但是其消波效果仍然非常显著。

Abstract:

Coastal salt marshes can reduce the impact of storm surges and typhoon waves,thereby enhancing the ability of the coast to resist natural disasters such as typhoons and reducing economic losses.Therefore,they play an important role in protecting the coast and preventing and mitigating disasters.In this study,the wave attenuation function of Mangzhou wetland in Zhujiang River Estuary was analyzed by using the field measured wave data during the typhoon 'Parrot’ activity in June 2020,so as to quantitatively study the wave attenuation effect of salt marsh vegetation.The results showed that during the period of typhoon 'Parrot’,the maximum increase of storm surge in Mangzhou wetland was 0.43 m,and the floodplain time was longer than 6 h.The wave height attenuation rates of the measured waves passing through the salt marsh vegetation zones with widths of 100 m and 230 m was 90.5% and 97.2%,respectively,and the vegetation disaster reduction ability is excellent.According to the estimation results of the empirical formula of wave height attenuation rate,the wave height attenuation rates of waves passing through vegetation widths of 100 m and 200 m was 94.0% and 97.0% respectively,which are basically consistent with the measured results.Due to the short influence time and weak intensity of typhoon 'Parrot’,the water level measured in the field was below 1 m,while the average plant height of salt marsh vegetation was about 2 m,and the crown of vegetation was not submerged.Therefore,the vegetation could be regarded as a permeable embankment,and the friction damping of its stems and leaves led to the attenuation of wave energy.In addition,the effective wave height measured in the field was below 0.10 m,and there was no large amount of vegetation lodging or even stem fracture.Therefore,the salt marsh vegetation had fully played its role in wave attenuation.In summary,although the area of Mangzhou salt marsh is only 3.39 km²,its wave attenuation effect is still very significant.