An estimation of the probable maximum precipitation for river basins in the Czech Republic

摘要

The hydro-meteorological evaluation of a flood event in July 1997 (the Odra flood in Central Europe) demonstrated that new procedures to estimate design floods for the reservoir outflow structures in the Czech Republic (CR) were needed. Therefore, the techniques of the estimation of Probable Maximum Precipitation (PMP) were developed in a national research project (1998-2000), and the activity focused on the improvement of the area related PMP estimates was going on within a present national project. In the frame of the evaluation of the next extreme precipitation event in August 2002 (the Labe flood in the CR and Germany), we compared the catchments related precipitation with the PMP estimates. In this paper, an outline of the PMP estimation techniques is given and the use of data from the Czech gauges is described, the aim being the statistical derivation of the point and area PMP estimates for precipitation duration of 1 to 5 days. The use of radar data in assessing the maximized area reduction factor is discussed and the relationship resulting from the radar measurements over the CR territory is presented. An evaluation of the radar-based area rainfall enabled us to transform the point PMP to the area PMP estimate designed for the river basins in CR. In the last part of the paper, the results obtained by comparing the rainfalls in 1997 and 2002 flood events with the PMP estimates are presented. The comparison showed that the maximum area rainfalls over small Czech catchments (the 3rd order river basins) did not exceed 63% of the corresponding PMP values.