Flood Frequency Analysis Summary

Flood frequency analysis is used to estimate the magnitude or frequency of flooding for a watershed. Historical data is used in a statistical model to predict how often a flood of a given scale is likely to recur, or to predict the greatest flood likely within a given time period. This module describes the techniques used to do this statistical analysis and make these predictions.

This module also describes some of the limitations of these methods and how the statistics relate to the flood criteria used for the design of structures to be built within the watershed. Since it is based primarily on historical data and climate invariance, the predictions of flood frequency analysis are likely to become less and less accurate as our climate changes and exceeds the bounds of historical precedent.