Author(s): Hyoungchul Park, Jin Hwan Hwang

Linked Author(s): Jin Hwan Hwang

Keywords: Emergent vegetation; Vegetation arrangement; Longitudinal dispersion coefficient; Standardized Morisita index;

Abstract: Aquatic emergent plants significantly affect the dispersion of pollutant in the river and ocean. They grow with diverse spatial arrangements such as random, uniform and clumped pattern depending on the environmental conditions, kind of vegetation, etc. Thus, this paper investigated the effect of spatial arrangement of vegetation on longitudinal dispersion by conducting laboratory experiments with artificial emergent vegetation. Various types of arrangements are considered and quantified numerically by applying the standardized Morisita index, which are originated from the study of ecology. The results of experiments reveal that the hydraulic parameters such as the mean velocity and longitudinal dispersion coefficient are changed depending on the value of standardized Morisita index. The mean velocity in the vegetated channel is smaller than that in non-vegetation. Emergent vegetation makes the vertical distribution of stream-wise velocities uniform but causes fluctuation in lateral direction. In particular, for the 2D clumped arrangement, the spatial heterogeneity of velocity in the lateral direction increases evidently. The longitudinal dispersion coefficient changes from 13.5 to 101.7 cm2/s depending on the standard Morisita index. It can be explained from the variation of spatial heterogeneity of velocity in both lateral and vertical directions, which depends on the type of vegetation arrangement.

DOI: https://doi.org/10.3850/38WC092019-1171

Year: 2019