What is the “flood stage” of a river and how is it figured?
Most people think that flood stage is the point where water begins to overflow its banks. However, this is not necessarily true. Actually, flood stage is the point at which overflow of the natural banks of a stream begins to present a potential flood damage hazard to the area. Therefore, it does not solely depend on the level where water leaves its banks.
In many instances, flood stage may actually be several feet above bank full because no significant property damage occurs until the water level reaches a higher stage. Input from local officials and emergency managers is used to set flood stage thresholds.