Environmental Engineering Reference
In-Depth Information
Box 17.2 An example of river restoration in Denmark
PROJECT NAME: River Skjern, Denmark
BACKGROUND:
• A channelized and dredged river between 1962 and
1968 with approximately 4000 ha of fl oodplain, wet-
lands, reedbed, meadows and marshlands drained to
allow agricultural production on its fertile soils.
• Peat soils became desiccated, lowering the entire
farmed area.
• Continuous and expensive updating of the pump
systems was required to drain the low-lying ditch
systems into the river.
• Farmlands were a major source of sediment into
the river, causing severe water quality pollution and
major deposition along Ringkøbing Fjord.
AIMS:
• To restore the lower reaches of the Skjern system,
re-creating over 2200 ha of typical fl oodplain and the
sinuous course of the once multithreaded river (Figure
17.5). In 1998, the Danish Parliament, with a huge
majority, passed a Public Works Act for the work.
• To restore the natural functioning of the system to
once again provide a rich variety of habitats for
some of Europe's endangered species such as the
bittern, otter, black tern and corncrake.
TECHNIQUES USED:
• Restoration of 4 km of river and the movement of
2.7 million cubic metres of soil.
PROJECT FUNDING:
• The project was budgeted at approximately
€
319
million (National Forest and Nature Agency 1999).
BENEFITS:
• The project was completed in 2002 and by 2009
after 3 years of agreeing land acquisition deals for
farmers.
• The river has naturalized with shallow waters sup-
porting a range of migratory waders.
• In addition educational facilities, nature trails, and
picnic facilities have been developed for people; the
area is in the process of being designated a national
park.
Box 17.3 A second example of river restoration in Denmark
PROJECT NAME: The Houting Project, Denmark
BACKGROUND:
• The Houting (
Coregonus oxyrinchus
), a protected
species of fi sh, was once distributed throughout the
freshwaters that fl ow into the Wadden Sea.
• Now only 6 rivers support this species, while
industrialization has severely limited the Houting's
migration and spawning areas.
AIMS:
• To restore and maintain favourable conservation
status for Houting on the rivers Varde, Sneum, Ribe
and Vida.
TECHNIQUES USED:
• 13 in-channel obstacles (mainly weirs associated
with fi sh farms and hydro-electric power generation)
need to be removed.
• One specifi c example on the River Vida is shown
in Figure 17.6; 2 m high weir was removed and the
old millpond was separated from the river. A gravel
bed and banks installed.
PROJECT FUNDING:
• The 13.4 million Euro project was funded by the
EU-Life spawning areas for the fi sh.
BENEFITS:
• 130 kilometres of river channel habitat and 500
hectares of new nursery.
• New spawning areas have been developed for the
fi sh.
more
heterogeneity
, including wetland hollows and
fl oodplain woodland, and can support an increase in
biodiversity. From a species perspective, the enhance-
ment of poorer quality, still-water bodies, which are
created as a result of historical gravel and sand extrac-
tion, and the reinstatement of secondary channels are
also very benefi cial, acting as refuge areas for fi sh and
macro-invertebrates. The long history of fl ood defences,
multiple raised embankments and pollution from
upstream has meant that today those fl oodplains that
