Disasters stir a desire to help, and the record-breaking rains that triggered massive flooding in western Japan — killing 200 people and inflicting widespread destruction — have prompted groups of volunteers to take action, seeking to offer rapid assistance to communities hit by the calamity.

But areas and organizations hosting volunteers are warning them to avoid hindering relief operations, and encouraging them to engage in recovery efforts that are truly needed. As of Thursday, some 7,000 people remained in shelters, according to the Fire and Disaster Management Agency.

American Joy Jarman-Walsh, 49, a long-term Hiroshima resident who teaches tourism and business at Yasuda Women’s University, is volunteering now as she did four years ago.