Floods and floodplain changes of the River Morava, the Straznicke Pomoravi region (Czech Republic) over the past 130 years

The development of the River Morava floodplain has been influenced by several natural and anthropogenic factors. This paper focuses on variations in flood activity and channel changes of the River Morava in the region of Straznicke Pomoravi (southeastern Czech Republic). Floods are analysed in terms of measured peak water stages, H-k (Rohatec, 1886-1920) and peak discharges Q(k) (Rohatec/Straznice, 1921-2010) evaluated with respect to their N-year return period (H-N or Q(N)). The frequency of floods with Q(k) >= Q(2) reaches a significant maximum in March, followed by July. According to flood series compiled from 1881 onwards, their frequency peaked in the 1961-1970 decade with the most severe events occurring in July 1997 (Q(100)), March 2006 and June 2010 (Q(50)). During the study period the natural dynamics of the original anabranching channel patterns were significantly modified by human intervention, such as the abandonment of some anabranching channels, channel straightening, enlargement of the main channel, flood-dike construction, and the creation of the Bat'a shipping channel. These changes resulted in decreased frequency and a reduction in the extent of floodplain inundations compared to the period prior to channel modifications in the 1930s.