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River channel deformations under different phases of hydrological regime and various energy floods

Chernov Alexey V., Korableva O. V., Zavadsky Alexandr S.

Geography and Tourism

2017

Vol. 5, No. 2

67--74

The paper presents the results of the regular bank erosion monitoring on three rivers of the Eastern European (Russian) Plain: the Kerzhenets River (left tributary of the Volga River), the Sherna River (left tributary of the Klyazma River) and the Tarusa River (left tributary of the Oka River). The first two rivers are characterised by wide floodplains and meandering channels, the third one is distinguished by an incised straight channel and a narrow floodplain. Results of the bank erosion monitoring carried out twice a year – after a spring snowmelt flood and a summer low-water period - over the last 5-15 years allowed the authors to arrive at the following conclusions: 1. Bank erosion and channel lateral migration were observed only during the flood events. No channel deformations were observed during the low-water periods on the rivers of the humid temperate climate zone. 2. Bank erosion and channel lateral migration were observed only during the years with the highest flood magnitude, regardless of the stream bed sediment grain size composition. In the years with moderate flood events, bank erosion occurred, but its rates were inconsiderable and comparable to the measurement accuracy limit. During dry years, no channel deformations were observed. 3. As a consequence of the meander development and its sinuosity changes, zones of the maximum concave bank retreat change their locations along the meander. First, the maximum erosion rate zone occupies most of the concave bank length, then moves towards the lower limb and concentrates at the meander apex when reaching the maximum sinuosity. 4. Formation of cutoffs in a high-sinuosity meander is mainly associated with intrinsic mechanisms of the meander self-development and to a lesser extent with a flood magnitude. In this case, the main factor of the cutoff process is a very fast increase in the channel longitudinal profile gradient, rather than flood discharge.

Przekształcenia powierzchni brzegów rzecznych przez procesy mrozowe

Augustowski K., Kukulak J.

Landform Analysis

2013

Vol. 24

3--10

Zbadano skutki procesów mrozowych na podciętych brzegach rzek w okresie listopad–kwiecień przełomu lat 2011/2012 r. Erozję powierzchni brzegów w dorzeczu Czarnego Dunajca (Kotlina Orawska, Pogórze Gubałowskie) oraz w dorzeczu Ropy (Beskid Niski) badano metodą prętów pomiarowych i łapaczami materiału osypiskowego. Procesy mrozowe były tam aktywne w 4–5 okresach multigelacji. Wykazano, że spowodowały największą erozję powierzchni brzegów skalistych, mniejsza była erozja brzegów zbudowanych ze żwirów średnich i grubych, a najmniejsza brzegów zbudowanych z piasków i glin. Na rozmiary tej erozji miała wpływ nie tylko litologia utworów i stopień ich spoistości, ale także obecność i gęstość spękań.

The effects of frost processes on undercut riverbanks in the period November-April, at the turn of 2011/2012 were examined. Erosion of the riverbanks in the Czarny Dunajec basin (Orava Basin, Gubałówka Hills) and in the Ropa basin (Low Beskid) was studied by erosion pins and catchers of bank sediments. There were 4–5 multigelation periods. It has been shown that the frost processes caused the largest erosion in area of rocky banks; erosion was smaller on banks built with medium and coarse gravels, and the smallest on banks built with sands and clays. The size of this erosion was influenced not only by lithology and the degree of cohesion, but also the presence and density of cracks.