The movement of lake water can be mainly divided into two, steady and non-steady movement. In small lakes, most of the movements are non-steady and among them, wind-driven current is distinguished. This current, as well as waves, sweeps over lake sediments. As a natural consequence, the grain size of sediments is greatly influenced by the movement of lake water.
In this paper, the author sampled sediments of three lakes such as Lake Kizaki, Yuno-ko and Lake Ohnuma and tried to find the relationship between movement of lake water and grain sizes based on the analysis of horizontal distribution of grain size. By this analysis, mean diameter, skewness coefficient and sorting coefficient are available. The current observation is performed by using current drag. As a result, the values of median diameter seem to represent the relative strength of lake water movement but not the absolute one. Skewness coefficient seems to be applicable to clarify the secondary state of lake water movements so that mud can be separated from sediment, then transported and deposited in some other places.
