Volume 544, 15 February 2016, Pages 339–353
Highlights
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- Beavers came back to the Carpathian rivers after an over three hundred year absence.
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- Beavers' dam cascade system changed fluvial erosion, transport and sedimentation.
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- Beaver activity changed the headwater valley morphology.
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- Beaver damming and ponding affect fluvial systems in montane regions.
Abstract
Beaver (Castor sp.) can change the riverine environment through dam-building and other activities. The European beaver (Castor fiber)
was extirpated in Poland by the nineteenth century, but populations are
again present as a result of reintroductions that began in 1974. The
goal of this paper is to assess the impact of beaver activity on montane
fluvial system development by identifying and analysing changes in
channel and valley morphology following expansion of beaver into a
7.5 km-long headwater reach of the upper Wisłoka River in southeast
Poland. We document the distribution of beaver in the reach, the change
in river profile, sedimentation type and storage in beaver ponds, and
assess how beaver dams and ponds have altered channel and valley bottom
morphology. The upper Wisłoka River fluvial system underwent a series of
anthropogenic disturbances during the last few centuries. The rapid
spread of C. fiber in the upper Wisłoka River valley was
promoted by the valley's morphology, including a low-gradient channel
and silty-sand deposits in the valley bottom. At the time of our survey
(2011), beaver ponds occupied 17% of the length of the study reach
channel. Two types of beaver dams were noted: in-channel dams and
valley-wide dams. The primary effect of dams, investigated in an
intensively studied 300-m long subreach (Radocyna Pond), was a change in
the longitudinal profile from smooth to stepped, a local reduction of
the water surface slope, and an increase in the variability of both the
thalweg profile and surface water depths. We estimate the current rate
of sedimentation in beaver ponds to be about 14 cm per year. A
three-stage scheme of fluvial processes in the longitudinal and
transverse profile of the river channel is proposed. C. fiber reintroduction may be considered as another important stage of the upper Wisłoka fluvial system development.
Graphical abstract
Keywords
- Beaver ponds;
- Fluvial processes;
- Land use change;
- Silting;
- Grain size;
- Fluvial system
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