impact (noun): a marked effect or influence
Floods can have a major impact on people living near the river.
In risk analysis, impact is used to describe the size of an effect associated with a risk event. High-impact events are more serious than low-impact events.
impact (verb): to have a noticeable effect on
The flood could impact several communities.
The use of impact as a verb has only recently become acceptable. It should not be overused and should be restricted to events that have large, significant or serious effects. Consider using affect or influence instead:
The flood could affect several communities
See also affect, effect