黄岛金沙滩现代波痕沉积特征与水动力关系

Characteristics of Ripples both in Morphology and Sediments in Golden Beach Coastal Zone,Huangdao and the Relationship with Hydrodynamics

黄岛金沙滩为典型的无障壁高能海岸,后滨发育有风成波痕,前滨滩槽和近滨上部可见大量浪成波痕。本文通过对上述3种环境下波痕的形态、沉积物粒度特征及前滨波痕形成水动力条件进行分析研究发现:1)后滨风成波痕波长、波高、迎流面及背流面相对浪成波痕较小,但波痕指数较大,而前滨滩槽、近滨上部波痕由陆向海波长、迎流面、背流面变小。2)风成波痕沉积物粒度波峰较粗,而浪成波痕沉积物粒度波谷较粗,从前滨到后滨沉积物粗组分减少,细组分增多;风成波痕、前滨滩槽波痕粒度频率分布曲线呈"双峰"特征,而近滨上部波痕粒度频率分布曲线主体呈"单峰"特征,风成波痕、滩槽波痕沉积物缺少悬浮组分;波痕沉积物分选-峰度图、分选-偏度图可以较好地判别沉积环境。3)平均粒径与流速、水深、弗劳德数Fr有很好的线性关系,前滨退潮时形成波痕的水动力条件具有水体浅、流速小和水动力弱的特点,可能与退潮时水速、水深变化较快有关。4)对前滨波痕沉积特征与相应流速、水深分别进行逐步回归分析,获得了形成环境的流速、水深的回归关系式。

The Golden Beach is a typical high-energy coast without barrier, with wind ripples being developed in the backshore and wave ripples in the upside of the nearshore and swales in the foreshore. This paper analyzes the morphology, the sediment granularity and the hydrodynamic conditions of these three kinds of ripples developed in different environments, and it is found that, 1） The wind ripples in the backshore have a longer wavelength, a lower wave height, but a bigger ripple index as compared to the wave ripples. Both the wavelength and the scale of the wave ripples increase from the land to the sea. 2） For the wind ripples, it is the crest sediments that contain more coarse grains, while for the wave ripples, it is the valley sediments that contain more coarse grains, and the coarse grains increase their number from the backshore to the foreshore. The sediments of the wind ripples and the wave ripples in the swale lack the suspension components. The frequency distributions of the ripple grain size in the backshore and the foreshore take bimodal forms, while the frequency distribution of the ripple grain size in the upside of the nearshore takes a unimodal form. Using the sorting-kurtosis figure and the sorting-skewness figure of the ripple sediments, it is easy to distinguish the sedimentary environment. 3） The mean grain size of the sediments has a certain linear relationship with the flow velocity, the water depth and the Froude number Fr. According to theexperimental results, the ripples in the foreshore formed in the falling tide indicate a weak hydrodynamic condition, which may be related to the quick change of the flow velocity and the water depth. 4） The regression equations between the sedimentary characteristics, the flow velocity and the water depth are obtained after the stepwise regression analyses.