Oana IONUŞ Mihaela DOBRE Elisabeta CIOCAN
The main objective of the study is to use the statistical models to analyse the probability of flood and the joint of temporal variability of the flood peaks and their seasonality. The case study refers to the 2013 spring floods on the Jiu River, Filiași-Craiova sector. Thus, in order to obtain several features of the maximum discharge, the maximum values, the increasing and decreasing time also the frequency of occurrence, one of largest floods is analysed. The data used were recorded at 3 hydrometrical stations on the Jiu River for a common period of 10 years.
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The hydrological analysis is based on two methods of the maximum flow values: Mann-Kendal test and Gumbel distribution. In the first part, we have identified if it’s a trend or not in the data series of the annual maximum discharge using Mann-Kendall trend test and the results were obvious, both statistically and graphically. The annual trend at two hydrometrical stations is of decrease (Test Z values: -1.58, Filiași hydrometrical station and -0.81, Răcari hydrometrical station), while at the hydrometrical station that closes the analysed sector is an increasing trend (Test Z value: 0.62, Podari hydrometrical station).
The Gumbel distribution is used to process the data from a long observation period of the maximum values. Applying this method to the flood data registered at the three hydrometric stations along the Jiu river are corresponding certain return periods (years) as follows: 1,140 cm/s registered at Filiași hydrometrical station has a 15 years return period; 1,447 cm/s reached at Răcari hydrometrical station has a 24 years return period; 1,309 cm/s recorded at Podari hydrometrical station has a 27 years return period. The above-mentioned values confirm the magnitude of the maximum flow at Răcari and Podari hydrometrical stations and anticipate the potential damage.
The flood frequency analysis using statistical models is important and also required in Romania given that the statistics of extreme events plays an important role in the engineering practice of water resources management.
Abstract: The paper presents the results of investigation of the 24-hour maximum precipitation in the region of North-Eastern Bulgaria by applying the relative criterion of Fukui. According to this criterion, 24-hour precipitation equal to or exceeding 10% of the yearly rainfall amount is “extraordinarily heavy rainfall” and this rainfall has significant effects on river flow, soil, natural and agriculture vegetation. The criterion was applied to 24 stations from the National meteorological network during the period 1992-2008. The territorial and temporal distribution of 24-hour maximum precipitation and their impact on the natural complex and the society are analyzed.
Abstract: The present paper analyses the types of synoptic situations that generated obvious weather instability within Oltenia between May 25 and June 6. Weather instability is usually associated with pronounced coolings that brought to the occurring of monthly minimum values or event o absolute minimum values for May and June during the abovementioned interval. In certain years, in the same period, there occurred rain showers that generated great precipitation amounts and floods in certain parts of Oltenia, while other times, hail registered exceptional dimensions and, consequently, important material damages (June 2, 1995, Marinică, 1995, 2005). We consider this paper is extremely useful for the researchers involved in weather forecast and climatology.
Abstract: The present paper (a case study) aims at analyzing the synoptic conditions registered between the 18th and the 23rd of September 2005, which led to extremely abundant rainfalls fallen on 12-24 hour intervals and to severe floods in Oltenia, as well as within all the southern regions of the country. The registering of such a situation in the mentioned interval brought to the sixth flood wave in Romania, which had catastrophic consequences. Such synoptic situation usually appears in rainy years in autumn and display an unusual intensity of the precipitation phenomena once in 30-35 years. Rainy years are usually registered in the years characterized by a minimum solar activity. The study also approaches this issue from the point of view of the climatic risk. The results are important for the study of the climatic risk of the increased rainfalls as well as for the forecast activity.