Environmental Engineering Reference
In-Depth Information
Table 17.2
The main human activities that have infl uenced river systems in Europe.
Activity
Reason
Impact
Land drainage
Agricultural
Loss of fl oodplains and wetlands, increased sediment supply
to the river, increased fl ood peak through decreased storage;
Disconnection.
Flood
protection
Urban and economic
Isolation and loss of fl oodplains, loss of biodiversity;
Increased discharge.
Reservoirs
and dams
Water supply and hydro-
electric power
Ecological deterioration downstream river;
Fundamental change upstream, river to lake; increase in
contamination; disruption to the transfer of sediment from
upstream change.
Weirs
Mill systems
Prevents fi sh passage to upstream reaches; reduces access to
spawning grounds, causing sedimentation locally.
Channelization
Erosion prevention;
Flood control;
Drainage of surrounding land;
Navigation;
Infrastructure.
Disrupts the physical equilibrium of the watercourse;
Reduced riparian vegetation and increased water temperature
(range of temp. change too);
Increase in fl ow velocity and hence reduces habitat and
biodiversity.
Dredging
Gravel and sand extraction
increases capacity.
Spoil heaps and levees.
Over widening and deepening of the river;
instability and bank collapse;
Removal of natural bed material;
Raised bank full height; reduced spillover.
Water
abstraction
Drinking water and
agriculture
Lowering of river water levels and the fl oodplain water table.
Urban
expansion
Increased populations and
economic growth
Increase in hard surfaces, greater and faster runoff;
Loss of riparian corridor and fl oodplains;
Poor water quality; sewage, spillages.
Water quality
Population increase;
Increased industrialization;
Intensive farming, increases
use of fertilizers.
Poor water quality, increased sedimentation, reduced riparian
vegetation.
terms of economical viability and potential ecological
gain. This has created the opportunity for river restora-
tion to be taken more seriously as a viable alternative
to present management practices, as there is an
increasing acknowledgement that it is not always pos-
sible or acceptable to channelize and/or regulate rivers
(see Petts 1984 ).
disconnected fl oodplains which, in a natural riverine
environment, would not only have been of much
higher value ecologically but would also have increased
the storage capacity of the rivers in times of high fl ow,
thus reducing the need to mitigate against fl ood
impacts downstream.
17.3 CURRENT DISTURBANCES
AND THREATS
17.2.3 Disconnection of European rivers
and their fl oodplains
Today the rivers and fl oodplains of Europe have impor-
tance for a wide range of plants and animals, however,
very few of them can be truly defi ned as natural and
this has serious implications for the associated ecosys-
tems. The naturally diverse physical and biological
habitats of Europe's river systems have declined in
quality and area, particularly over recent decades.
No river system should be considered in isolation from
its fl oodplain and yet throughout Europe there have,
historically, been high demands on these areas; as a
result many are now left with a legacy of land manage-
ment and fl ood defence strategies often based on
unnecessarily over - engineered solutions. The result is
