Author(s): Won Kim; Chaewoong Ban
Linked Author(s): Won Kim
Keywords: River bed; Deformation; Riparian vegetation; Sand river
Abstract: In this paper, we have tried to find something about the problems that come from riparian vegetation. It is a deformation of the river bed. Because of the vegetation encroachment, the river bed can be transformed from an even and smooth to a rough and undulated cross-section. On the part of the vegetation of the whole crosssection, the river bed may increase partially due to the deposition of the bed materials. On the other part of the cross-section, the river bed may decrease due to the scouring of the high velocity of the water. By the monitoring results since 1984, we analyze the deformation of the river bed in the Naesung River in Korea, where the sand bed is traditionally very famous. With the vegetation encroachment during the last 10 or 20 years, it was obvious that river beds had been deformed from a smooth to undulated cross-section. In the past, when there was no vegetation, the cross-section was mild and smooth, and water flowed over all of that. In 2022, the cross-section was very undulated with the heavy density of the vegetation, and water flowed in the narrow and deep part. The maximum difference of the river bed in the same cross-section will be 2-3m in 2022. We made an index to show the deformation of a river bed. The wetted perimeter and width ratio clearly explained how much deformation occurred in the cross-section of the Naesung River. It was under 1.005 before the vegetation encroachment but increased to over 1.01 in 2022.