In assigning probability it is important to adjust probabilities based on location. Data on hazards tends to be applied across a jurisdiction, but impacts may vary greatly based on location within the jurisdiction. For example, the primary immediate impact of highway and rail accidents tend to be restricted to the neighborhood of the transportation corridor. The further one is from that corridor the lower the probable impact.

It is also important to account for changes to the environment that have occurred after the hazard data was gathered. For example, increased construction of new housing and commercial facilities increases the potential for urban runoff flooding. The closing and environmental cleanup of an industrial facility may reduce the potential for explosion, fire, or hazardous waste release.