Author(s): Taro Yamamoto; Norio Ishida; Daigo Inagaki; Kiyotaka Sagai

Linked Author(s):

Keywords: River Channel Re-meandering; Wetland Restoration; Sediment Control

Abstract: The Kushiro wetland is the largest wetland in Japan. The wetland area has been decreasing over the past 50 years, and the vegetation transitioned from reed or sedge meadow to alder forest. One of the assumed major factors of vegetation transition is the increasing sediment intrusion into the wetland. Because of this, the wetland restoration project was commenced in 2003 and some practical efforts have been conducted for reduction of sediment intrusion into the central area of the wetland. One of the most essential efforts of sediment reduction is the old channel restoration in the Kayanuma district in the Kushiro River. This is the re-meandering work that switched from straightened channel to old abandoned channel to enhance the river environment and to make floodwater inundate easily to reduce the amount of sediment discharge into the central wetland. The switching work was carried out in 2010. After this work was completed, inundation occurred around the channel during annual floods, especially in the huge flood that caused a large amount of sediment accumulation in 2016. The amount of overflowed water and sediment was estimated by field observation. The result showed a reduction of 50% water and 40-90% sediment. We developed the 2D model with shallow water and suspended load for evaluation of the restoration work. The result of the model calculation led the estimation of around 30% decrease of sediment intrusion into the wetland after implementation of restoration.

DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P1738-cd

Year: 2025