Floods in the Upper Part of Vistula and Odra River Basins in the 19^th and 20^th Centuries / Powodzie W Górnej Części Dorzeczy Wisły I Odry W XIX I XX Wieku

The discussion of floods in this paper covers the section of the Odra River basin from its source down to the mouth of the Nysa Klodzka River and the section of the Vistula River basin down to the Krakow profile. The area of the upper part of Odra River basin is 13,455 km2 and the length of the river bed in this section is ca. 273.0 km. In the reach examined, the Vistula River is 184.8 km long and has a catchment area of approximately 8,101 km2. Geographical and environmental conditions in the upper part of the Vistula and Odra Rivers basins are conducive to floods both in the summer and winter seasons. The analyses conducted for the 19^th and 20^th centuries demonstrate that two main types of floods can be distinguished. Floods with a single flood wave peak occurred in the following years in the upper Odra River basin: 1813, 1831, 1879, 1889, 1890 and 1896, and on the Vistula River they were recorded in 1805, 1813, 1816, 1818, 1826, 1830, 1834, 1844 and 1845. In the 20^th century, similar phenomena were recorded on the Odra River in 1903, 1909, 1911, 1915, 1925, 1960, 1970 and 1985, and on the Vistula River they occurred in 1903, 1908, 1925, 1931, 1934, 1939, 1948, 1951, 1970, 1972, 1991, 1996, 1997 and 1999. The second category includes floods with two, three or more flood wave peaks. These are caused by successive episodes of high rainfall separated by dry periods that last for a few days, a fortnight or even several weeks. Such floods occurred on the upper Odra River in 1847, 1854, 1880, 1888, 1892, 1897 and 1899; while on the Vistula River only two (1839 and 1843) floods featured two flood wave peaks. In the 20^th century on the upper Odra River, floods of this type occurred in 1902, 1926, 1939, 1940, 1972, 1977 and 1997; on the upper Vistula River, they were recorded in 1906, 1915, 1919, 1920, 1940, 1958, 1960 and 1987.