Articles | Volume 19, issue 11
Research article
24 Nov 2015
Research article |  | 24 Nov 2015

Novel indices for the comparison of precipitation extremes and floods: an example from the Czech territory

M. Müller, M. Kašpar, A. Valeriánová, L. Crhová, E. Holtanová, and B. Gvoždíková

Abstract. This paper presents three indices for evaluation of hydrometeorological extremes, considering them as areal precipitation events and trans-basin floods. In contrast to common precipitation indices, the weather extremity index (WEI) reflects not only the highest precipitation amounts at individual gauges but also the rarity of the amounts, the size of the affected area, and the duration of the event. Furthermore, the aspect of precipitation seasonality was considered when defining the weather abnormality index (WAI), which enables the detection of precipitation extremes throughout the year. The precipitation indices are complemented with the flood extremity index (FEI) employing peak discharge data. A unified design of the three indices, based on return periods of station data, enables one to compare easily inter-annual and seasonal distributions of precipitation extremes and large floods.

The indices were employed in evaluation of 50 hydrometeorological extremes of each type (extreme precipitation events, seasonally abnormal precipitation events, and large floods) during the period 1961–2010 in the Czech Republic. A preliminary study of discrepancies among historic values of the indices indicated that variations in the frequency and/or magnitude of floods can generally be due not only to variations in the magnitude of precipitation events but also to variations in their seasonal distribution and other factors, primarily the antecedent saturation.

Short summary
Three proposed indices combine return periods of precipitation totals or discharges with the size of the affected area. Precipitation indices also determine actual duration of either extreme or seasonally abnormal precipitation events. A unified design of the indices enables one to easily compare inter-annual and seasonal distributions of events, which is demonstrated by 50 maximum events in the Czech Republic during the period 1961-2010, including the June 2013 floods.