Mitigation includes activities that eliminate or reduce the chance of occurrence of the effect of a disaster. FEMA pre-disaster mitigation programs have shown that communities can dl a lot to prevent major emergencies or disasters from affecting them negatively.  If communities cannot prevent disaster, they can at least reduce the damaging impact.  For example, requiring roof reinforcement will reduce damage from hurricane winds.  Preventing new construction in floodplains or placing structures on columns in them can reduce the chance of flooded homes.