Original paper

Time-focused investigation of river channel morphological changes due to extreme floods

Rusnák, Miloš; Lehotskeý, Milan


The typical morphological response of the meandering rivers to large floods is the lateral shift of their channel which triggers the formation of a new morphological structure from the initial destruction by erosion over deposition of new sediments and stabilization of vegetation. The article deals with the effect of extreme flood events on lateral channel shift and bar pattern with relation to changes of the riparian zone land cover structure by using multitemporal analyzes of aerial photographs (three time horizons – 1987, 2002 and 2009) in the GIS environment on the example of the 13.2 km long less regulated and laterally partly-confined meandering reach of the Ondava River (Eastern Slovakia). The photographs were chosen in a way to capture the morphological changes that occurred after floods. The average lateral channel shift per year was 1.17 m in 1987–2009, maximum 217 m. The river has eroded in total 35.6 ha and deposited 31.6 ha. Gravel bars in 1987, 2002 and 2009 spread a channel total area of 21.1 ha, 17.8 ha and 19.7 ha. The most eroded category is that of arable land, followed by grasslands and pastures and shrubs. We conclude that in case of the Ondava River, low magnitude high frequency floods, instead of causing destruction of the system, led to the stabilization of the channel, erosion of the concave bank and to the formation of the meandering planform. In contrast, the short recurrence interval of extreme floods led to an increased in tensity of erosion processes, a change of the meandering planform to slightly braided one, straightening of the channel and formation of gravel bars.


bank shiftfloodgismultitemporal