Extreme Water Levels

Exceedance probability—the likelihood that water levels will exceed a given elevation—is based on a statistical analysis of historic values. 

This interactive map provides annual and monthly exceedance probability levels for select water level stations with at least 30 years of data. When used with real-time station data, exceedance probabilities can be used to evaluate current conditions and determine whether a rare event is occurring. This station-specific information may also be instrumental in planning for the possibility of dangerously high or low water events at a local level.