Physico-chemical Variability of Alluvial Sediments in a Floodplain Area of the Downstream Vltava (Moldau) River in the Czech Republic after the Most Recent Catastrophic Flood in 2013

The physico-chemical parameters of the Fluvisols that have developed in long-term deposited river sediments at a depth of 0–10 cm (topsoil) and 30–40 cm (subsoil) were determined immediately after the catastrophic flood in 2013 across the area of Veltrusy Castle (290 ha), which is situated in the inundation zone of the downstream Vltava River. We investigated the soil texture, the active and exchange reaction, the total electric conductivity, the content of total carbon and nitrogen, the available content (Mehlich 3) of selected nutrients (Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn), and the total content of risk elements (As, Be, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, V and Zn), for which the maximum allowed content in soils is laid down in the relevant legislation. An analysis was also made of a sample of the most recent coarse sandy-gravel mineral sediment and of the fine organic-clay sediment. A comparison was made between the data for topsoil affected by the most recent erosion and by the accumulation of sediments, on the one hand, and the subsoil, which was probably unaffected by this most recent flood. The comparison was made on woody plots (42), grassy plots (19) and ploughed field plots (31). The results showed that the most recent flood in the area had mainly affected the texture of the soil cover by accumulation of sandy-gravel sediments and to some extent the content of some elements present in organic clayey sediments. Surprisingly, it was detected a low effect of the most recent flood, and on the salinity and the content of total carbon, nitrogen and other elements.