Probability Analysis of Historical Flood Data

In addition to routinely collected hydrometric data, information on past river water levels at a site can often be gathered from various other sources such as residents and archives. However these sources generally have varying reliability, overlapping and broken periods of record, and no well-defined reference levels—features that have made the probability analysis of this data difficult. The paper describes a simple method of incorporating such data into probability analyses and illustrates it by application to the probability analysis of ice breakup stages on the Peace River at Fort Vermilion, Alberta, Canada. There is generally little standard hydrometric information on such water levels, yet they are often a very significant component of the annual maximum water levels in cold regions. In such situations the analysis of historical data is particularly important.