台风期间港湾海岸湿地侵蚀、淤积的环境动力学机制初探——以福建罗源湾为例

Environmental Dynamic Mechanisms for Sediment Erosion and Accretion over Embayment Coastal Wetland during Typhoon Event:A case study from Luoyuan Bay,Fujian China

为了探讨港湾海岸湿地在台风期间发生冲淤变化的过程和机制,利用流速仪观测了台风"凤凰"过境期间福建罗源湾海岸湿地(包括盐沼中下部和光滩)的环境动力过程。结果表明,台风登陆期间盐沼中下部和光滩的滩面淹没时间增长约2 h,近底层流速平均值变化很小,但流速波动变化幅度很大,底部切应力显著增大,滩面发生侵蚀;台风登陆后,随着风浪作用的减弱,流速波动显著减小,底部切应力逐渐减小,悬沙发生沉降,滩面表现为淤积。台风期间的滩面侵蚀、淤积主要受底部切应力的控制。

In order to understand the processes and mechanisms of sediment erosion and accretion caused by typhoon event,in situ measurements of water level,tidal current speed and direction were carried out using Acoustic Doppler Velocimeter（ADV,Vector by Nortek）,Electromagnetic Current Meter（EMCM,AM HR by ALEC）,and miniature pressure sensor（MkV/D by ALEC） at two sites over coastal wetlands in Luoyuan Bay,during the period when typhoon ＂FUNG-WONG＂ was impacting region.Observed results showed that the water inundation time increased about 2 h in the tidal cycle during the typhoon landing,and the mean value of current speed varied slightly,but the fluctuation of current speed during a short time significantly increased,then the bottom shear stress also increased obviously,which brought about seabed erosion.After the typhoon landed,the current speed fluctuation decreased significantly,and the bottom shear stress also decreased obviously,then the suspended sediment settled on the seabed heavily,which resulted in seabed accretion.The sediment erosion and accretion during the typhoon event over embayment coastal wetlands was controlled by the variations of bottom shear stress.