Abstract
Weeding of levee is one of the important river management to maintain safety against flood. In Japan, many citizen-based river groups are engaged in weeding, however, their actual states have not been thoroughly investigated. In order for an effective collaboration with river managers and citizen groups, it is necessary to investigate quantitatively how many times and staffs of the citizen-based river groups related to weeding of embankment. We extracted 207 groups through questionnaires and interviews. The result shows that the total active mass of river groups are accounted for about 210,000. With this active mass, river groups are able to weed 3% of river section managed by the government. Also economic value for activities of river groups was estimated to be 1.6 % (0.013 million yen) of official cost for weeding.
