This chapter describes the Disaster Impact Model, which shows how three preimpact conditions–hazard exposure, physical vulnerability, and social vulnerability–act together with event-specific conditions (hazard event characteristics, improvised disaster response, and improvised disaster recovery) to produce a disaster’s physical and social impacts. Physical impacts comprise casualties and damage whereas social impacts consist of psychosocial, demographic, economic, and political impacts. These disaster impacts can be reduced by three preimpact emergency management interventions–hazard mitigation, emergency preparedness, and recovery preparedness. Local officials can be more effective in managing their communities’ exposure to environmental hazards if they understand the elements of the Disaster Impact Model and the ways in which these elements are related.