The significance of meander restoration for the hydrogeomorphology and recovery of wetland organisms in the Kushiro River, a lowland river in Japan

Published source details Nakamura F., Ishiyama N., Sueyoshi M., Negishi J.N. & Akasaka T. (2014) The significance of meander restoration for the hydrogeomorphology and recovery of wetland organisms in the Kushiro River, a lowland river in Japan. Restoration Ecology, 22, 544-554.
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This study is summarised as evidence for the following.

	Action	Category
	Raise water level to restore degraded freshwater marshes Action Link

Raise water level to restore degraded freshwater marshes

A before-and-after study in 1999–2011 of a floodplain in Hokkaido, Japan (Nakamura et al. 2014) reported that following restoration of the natural meandering river course, the area of emergent herbaceous vegetation increased. Statistical significance was not assessed. Marshes covered approximately 50 ha of the floodplain around 10 years before restoration began, then 77 ha around five years after restoration began. More specifically, there were increases in the area of stands dominated by knotweed Polygonum thunbergii (before: 0 ha; after: 36 ha) and stands dominated by common rush Juncus effusus (before: 0 ha; after: 9 ha) – mostly in a recently (<9 months old) relandscaped area. In contrast, there were decreases the area of mixed common reed Phragmites australis and sedge Carex spp. stands (before: 27 ha; after: 19 ha) and wet meadows dominated by reed canarygrass Phalaris arundinacea (before: 22 ha; after: 13 ha). Methods: The Kushiro River was channelized and straightened in the 1970s. Between 2007 and 2011, its natural course was restored (2007–2010: former meandering channel excavated and reflooded; 2011: flood embankments removed and straightened section backfilled). Flooding frequency increased in the surrounding floodplain, and the water table rose to near the ground surface. Vegetation was mapped before (1999) and after (2011) restoration, from aerial photographs and with field surveys.

(Summarised by: Nigel Taylor)