This study aims to investigation of settling characteristics of cohesive sediment in small rivers. For this, the settling experiments are conducted using kaolinite and natural sediments sampled in 5 small rivers in Korea. (i,e., Jeungsancheon; Bangchukcheon; Ilwolcheon; Jangseongcheon; and Changpyeongcheon).
Through the settling test, this research comprehends the relationship between each other by measuring the floc size and settling velocity and calculating the density and fractal dimension through the measured values. Base from the results of this study, the following un-clusions are as follows.
Through the floc size and settling velocity relationship graph, it was determined that adhesion similarity settling velocity of Jangseongcheon and Lake Apopka appears directly proportional to the floc size. However, for kaolinite, Jeungsancheon, Bangchukcheon, Ilwolcheon, and Changpyeongcheon are determined to have slight influence of floc size or almost no correlation in settling velocity with floc size.
In respect of floc density, kaolinite, Jeungsancheon, Bangchukcheon, Ilwolcheon showed tendencies that as the density decreases the floc size increases. While for Jangseongcheon, Changpyeongcheon, and Lake Apopka, results showed minimal proportion or no tendency. Also, the density value measured by using the mass cylinder displays a result of big difference between density of primary particle and similarity density in Jangseongcheon and Changpyeongcheon as compared to Jeungsancheon, Bangchukcheon, and Ilwolcheon.
In terms of the fractal dimension, kaolinite, Jeungsancheon, Bangchukcheon, and Ilwolcheon showed of decreasing fractal dimension along win increase of flug size as in case of flug density, while Jangseongcheon, Changpyeongcheon, and Lake Apopka showed minimal reverse proportions or no tendency. Such difference in the results is comprehended as a composition of fractal structure with self-similarity along with the organic matter content. That is, in case of kaolinite, Jeungsancheon, Bangchukcheon, and Ilwolcheon which follows fractal theory, inverse proportionality. However the organic cohesive sediments from Jangseongcheon, Changpyeongcheon showed minimal inverse proportionality or no change at all. This way, Jeungsancheon, Bangchukcheon, Ilwolcheon of Geumgang river and Jangseongcheon, Changpyeongcheon of Yeongsangang river, which showed different characteristics, appear necessary to consider settling velocity from different viewpoint respectively and determine the effect of such characteristic on transference and dispersion of cohesive sediment.
Henceforth, the further studies are necessary to accurately represent the river characteristics by sample collections from different sites with in the same time. Furthermore, it is also necessary to investigate the characteristics of cohesive sediment, from Geum river system and Yeongsang river system, by collecting more samples form both river system.