Wpływ działalności bobrów na lokalne procesy fluwialne w wybranych rzekach Równiny Łowicko-Błońskiej
The influence of beaver activity on local fluvial processes in selected rivers on the Łowicz-Błonie Plain

Summary/Abstract: In this article the influence of beavers activity on the fluvial processes in lowland rivers has been discussed. Beavers were introduced to the middle Rawka in 1983 and sites of their activity were found in the Bzura river in 1996. General zoological papers emphasise the fact that beavers live in burrows. Nowadays, beavers in Central Poland live mostly in lodges dug in high river banks. Detailed research has been conducted in selected sectors of lowland rivers on the Łowicz-Błonie Plain: in the regulated channel of big river (Bzura), meandering channel of a medium-size river (Rawka) and in the regulated channel of a small river (Igla).Beavers mostly influence fluvial processes and alter valley floors because they construct dams and thus create ponds in small valleys. In small rivers and valleys beaver activity results in retention of large volumes of water and produces a local rise of water level. In the case of large rivers the environment is transformed only locally in the immediate vicinity of the bank with lodges. Beaver activity in a meandering river is limited to slowing down the water-flow and weakening of lateral erosion – often only in a single river bend. At a different location beavers’ activity accelerated the cutting of a meander neck, cutting off of the bend and the creation of an oxbow lake. At a straight river, in favourable conditions, they may initiate the process of lateral erosion.

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