If the city has become a dangerous place, due to flooding, fire, etc. Than yes, getting out is good.

But if there isn't a danger, except other people and there is enough food and water. Tthan fleeing the city, is more or less an inrational behavior, caused by fear. Although the media reporting things like widespread looting and killing and stuff. These incidents usually turn out to be incidents and on very small scale. During crisis there are in general fewer incidents of crime than in a normal situation.

A more dangerous aspect during crisis can be considerd armed people who (irrationally) fear other people, because this is one of the things that ingreas instead of reducing during a crisis.