Author(s): Jiaqi Lin; Sameh A. Kantoush; Tetsuya Sumi

Linked Author(s): Sameh A. Kantoush, Tetsuya Sumi, SAMEH KANTOUSH

Keywords: Sediment replenishment; Numerical simulation; Stockpile erosion; Hydro-morphological Impacts; Telemac-2D

Abstract: Sediment replenishment (SR) is a widely adopted river management strategy globally, yet its long-term implementation in Japan exhibits distinct characteristics that warrant deeper investigation into its geomorphological impacts. This study examines the erosion of SR stockpiles and their downstream effects in the Naka River using field analysis and a two-dimensional depth-averaged hydromorphodynamic numerical model (Telemac-2D). We evaluated the influence of flushing flow (magnitude and frequency) and stockpile configuration (location and geometry) using key metrics such as transport ratio (TR) and the Hydro- Geomorphological Index of Diversity (HMID). Results show that higher-magnitude flushing flows are less effective in promoting stockpile erosion; instead, an optimal discharge of about 40% of the bankfull flow, applied with typical duration an d frequency, achieves the optimal erosion effectiveness. Introducing a second flood pulse or using a double-stockpile SR arrangement enhanced erosion as well, increasing TR by 1.5% and 3%, respectively. Regarding the downstream impacts, the additional sediment supply from SR site stimulated the formation of riffles and bars, elevating HMID values locally. These findings offer important insights for predicting SR erosion and associated hydro-morphological changes in the Naka River, while providing practical guidance for designing effective sediment replenishment in similar fluvial systems worldwide.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.126

Year: 2026