Authorities in the southern city of Krymsk, the site of catastrophic flooding, have sentenced four young men to 15 days in custody on charges of hooliganism after they interrupted a public meeting to argue that the government was hiding the true death toll. A police spokesman told the Interfax news service that the men introduced themselves as volunteer rescue workers. They “behaved aggressively and provoked a conflict with the Cossacks who were maintaining order,” the spokesman said. Among the phenomena to emerge after the July 7 flood was the stream of politically active young people who traveled to the city and volunteered to help with the cleanup, mobilized via social networks. Officials have warily accommodated the outsiders, but that tolerance had worn thin by Tuesday, when they evicted the largest camp of them from a park.