During the flood event and immediately after its end, the significance of field measurements increases, and these can then serve for the quality evaluation of flood hydrographs, both as stage and above all discharge ones.
As field measurements we regard above all measurement of discharge with the current meter, surface velocity measurement with floats, and marking the maximum flood water surface. The CHMI hydrology workers during the flood event in August 2002 were performing all these types of measurements. About 130 current meter discharge measurements were made, as well as 50 - 70 flood marks in the vicinity of gauging stations and other flood marks in other places in the terrain.
Several surface velocity measurements were made with the help of floats, some of them being very significant, e.g. on the Vltava (Moldau) in Prague immediately after the peak - see the table.
Date Time h(cm) S(sq.m) Q(cu.m/s)
14.8. 15.30 785 2114 5210
15.8. 11.30 600 1720 3550
16.8. 11.10 445 1480 2500
17.8. 09.15 365 1350 1920
18.8. 13.45 259 1124 1410
All these measurements, supplemented later with the surveying of cross-sections, will be used for the evaluation of peak discharges, the extrapolation of rating curves, and the ensuing derivation of flood discharge hydrographs.
Information & Contact:
Ing. Pavel Sercl
CHMI Czech Hydrometeorological Institute
Na Sabatce 17
143 06 Praha 4 - Komorany
tel:00420/244 032 347
