关键词: 沉积物搬运, 粒度参数, 泻湖, 潮汐汊道

Abstract:

surface sediment samples were collected from Yuehu during November- December 1998 and August-September 1999, respectively.These samples were analyzed using a Cilas940 L Laser Analyzer and by sieving (for particles with a diameter of <2 mm and >2 mm, respectively) to obtain grain size parameters. Three grain size parameters, i. e., mean grain size(μ), sorting coefficient(δ) and skewness(sk) are then calculated by a moment method.Five main sediment types are present in Yuehu according to the sediment classification scheme proposed by Shu Gao(1993, slight modification based on Folk(1980) classification scheme). The result shows the sediment appears annular distribution and is mainly composed of fine materials: From bank to center the sediment becomes finer gradually, i.e., from gravel sand, muddy sand, sandy mud to mud in turn. Sand is only distributed on ebb delta and north-east corner of the lake. There is a close relationship between mean grain size for sediment and sediment types in Yuehu where the mud area is mostly enclosed by 6  contour. The mean grain size for sandy mud is between 6 and 4 and muddy sand is between 4 and 2. In the sand and gravel sand distributed area the mean grain size is less than 2. Sorting coefficient and skewness value for sediment in Yuehu is 2.0～2.5 and 1～2 respectively. But the sediment located over flood delta is not well sorted with the sorting coefficient value between 3.0 and 3.5. At the same time the sediment near the mouth is negatively skewed with a value of 0.5 and the skewness is near 0 in a small area to the east of the center. The two dimensional model for grain size trend analysis proposed by Gao and Collins(1992 ) is adopted to identify sediment transport pathways in the study area. The net sediment transport pathways derived by using this model show that sediment is transported from bank towards the center, except the net sediment transport pathways are not obvious over ebb delta and main channel.At the same time the result shows that the north and west part of the top of the lake, flood delta and center are deposition centers. Such patterns are highly consistent with the sediment distribution pattern. Therefore this model is applicable for such a small area as Yuehu.

Key words: sediment transport, grain size parameters, Lagoon, tidal inlet