Procena krive protoka i rekonstrukcija poplavnog talasa u dubokom koritu sa uskim plavnim površinama

Abstract

U ovom radu razmatra se svrsishodnost primene metode razmene količine kretanja za procenu krive protoka i rekonstrukciju talasa velikih voda u dubokim koritima za veliku vodu koja imaju uske plavne površine. Ovo pitanje nametnulo se tokom procene krive protoka na hidrološkoj stanici Ub korišćenjem zabeleženog nivograma velike vode iz maja 2014. godine i rekonstrukcije odgovarajućeg hidrograma. Na ovoj hidrološkoj stanici vrednost odnosa dubine korita za veliku vodu i njegove širine u dnu znatno je veća od uobičajenih vrednosti i iznosi 1,46 (uobičajene vrednosti su mnogo manje od 1), a širina berme sa stazom za šetanje na koju se izliva voda iz glavnog korita je 2,5 m. Pored toga, korito odlikuje neujednačena rapavost zbog korišćenja različitih materijala za obradu kinete glavnog korita, kosina i bermi. Sve ovo utiče na to da presek vrlo brzo nakon izlivanja postaje hidraulički homogen, sa praktično zanemarljivom razmenom količine kratanja između glavnog korita i plavnih površina, zbog čega se vrednosti protoka dobijene metodom razmene količine kretanja razlikuju za oko 10% od vrednosti dobijenih primenom tradicionalne metode jedinstvenog preseka. S obzirom na to da za konstrukciju nove krive protoka u domenu velikih voda RHMZ nije imao dovoljno podataka, jer je stanica rekonstruisana svega godinu dana pre ovog talasa velike vode, zvaničnu krivu protoka i sve zaključke ove analize treba preispitati kada na raspolaganju bude dovoljno podataka za pouzdaniju procenu i zaključke.

In this paper, the appropriateness of the exchange discharge method for the estimation of the stage-discharge curve and the reconstruction of the flood flow hydrograph in deep compound channels with narrow floodplains is discussed. This issue has been raised while estimating the stage-discharge curve at Ub gauging station based on the recorded stage hydrograph of the 2014 May flood and an attempt to reconstruct the corresponding flow hydrograph. The ratio of the depth of the compound channel to its bottom width takes a high value of 1.46 when compared to the usual values, which are far less than one. The berm width with the walking path where the overbank flow spills, is 2.5 m. Additionally, the compound channel is characterised by different surface covers which results in non-homogeneous roughness. Because of all these facts, the compound channel starts to behave as a single unit or a simple channel shortly after the initiation of the overbank flow, i.e. the momentum transfer between the main channel and the floodplain becomes negligible. Consequently, the discharge values calculated by the exchange discharge method differ by 10% from those calculated by the traditional, single-channel method. Since the Republic Hydrometeorological Service of Serbia had no flood data from the re-established Ub gauging station for the estimation of the overbank stage-discharge curve, there is a high level of uncertainty in the official stage-discharge curve. Thus, both the curve and the conclusions derived from this analysis should be reconsidered once there is enough data for proper estimation of the curve and proper conclusions about the appropriateness of the exchange discharge model.