Author(s): Hyo Seop Woo; Chang-Rae Jang; Sung-Uk Choi

Linked Author(s): Hyoseop Woo

Keywords: Flood risk; Flow regime; Numerical analyses; Riparian vegetation; Willow patches

Abstract: This study presents a representative case of the “from white river to green river” phenomenon, describing riparian forestation in a 1.8 km reach of the upper–middle Nakdong-gang River, Korea. Following the construction of the Andong Dam in 1976 and the Imh a Dam in 1991, the reach experienced substantial alterations in flow regime and sediment transport. These changes enabled the colonization of vegetation on formerly unvegetated sandbars between 1991 and 1994, resulting in the establishment of willow-dominated riparian forests by 2024. To mitigate the perceived flood risk associated with forested floodplains, river managers have periodically cleared woody vegetation, most recently in 2024, without conducting prior scientific evaluations. Numerical hydraulic modeling conducted in this study shows that the complete removal of woody and herbaceous vegetation can lower the flood stage by 0.65 m under the 100-year design flood. These findings underscore the importance of vegetation management strategies being based on scientific assessments rather than arbitrary clearance practices.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.158

Year: 2026