Transcript Dias nummer 1

River Skjern: Presentation of speaker 1
• Mogens Bjørn Nielsen
• Experience includes:
• Geomorphologist
Hydrologist
• River Skjern: project
steering and projecting
• River Brede: Project leader
• Head of Rivers,
Landscape and Planning
Department in the Region • The EU-Life River
Restoration Project with
of Aarhus
UK: Project leader
• www.aaa.dk
• In 15 years responsible for
the sea dike to the Wadden
• [email protected]
Sea and river dikes in the
Region of South Jutland
River Skjern, Denmark
• Background: River Brede – example on
benefits for biodiversity
• Aims and considerations in the River
Skjern Nature Project
• The challenge in projecting to secure flood
defence with nature benefits
• The results in the field
• The democratical process
R. Brede: Before EFC = regulated
R.Brede Restored In the back and still regulated in the front
R.Brede The meadows as water reservoir at high discharges
EFFECT ON FLORA
- EXAMPLE RIVERBANKS PLANTS
Number of species
200
192
other species
Wetland-species
176
155
157
148
150
116
112
94
95
153
127
117
133
104
100
50
0
96
North riverbank
99
94
95
96
South riverbank
99
94
95
96
99
Both riverbanks
Number of species of riverbank plants on the two riverbanks of River
Brede before and after restoring.The river was on this reach restored in
late 1994 between the investigations in summer 94 and summer 95.
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EFFECT ON FLORA
-EXAMPLE MEADOW PLANTS
Number of species
97
other species
Wetland-species
100
82
81
75
80
71
69
68
63
56
60
49
49
48
40
20
0
94
95
Area 1
96
99
94
95
96
99
Area 2
Number of species on 3 areas along River Brede before
and after restoring. The river was on this reach restored
in late 1994 between the investigations in summer 94 and
summer 95.
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94
95
Area 3
96
99
Geography
• North Sea region
• Coastal humid
climate
• Lowland
• Intensive farming
Skjern River
• Catchment: 2500 km2
• Discharge: 35-100
m3/sec
• 5000 t N/year
• 100 t P/year
• 30,000 t sediments/year
• The lower part regulated
and diked in 1962-68
• The “inland delta”
drained for intensive
farming
River Basin and Project Area
Regulation scheme
Objectives
• Restore meandering and
natural dynamics and
secure against flooding
outside project area
• Improve conditions for
flora and fauna
• Ensure high water quality
in the river system and
the Fjord
• Improve the basis for
outdoor leisure
From regulation to restoration
Regulation and drainage
• 1800: Inland delta: 4000
ha of wetlands, unique in
Denmark
• 1900: Small scale
regulation starts
• 1962-68: Main regulation
and drainage scheme
• 1970-86: Increasing
environmental concern
Restoration
• 1987: Parliament decision:
The river to be restored for
self-purification
• 1988: Grants for land
acquisiton
• 1995: Detailed surveys and
design started
• 1998: Public works act
• 1999: Earth works started
• 2002: Restoration complete
Environmental Concerns
Nature lost
Pollution
• A unique riparian
system
• Part of a major
migration corridor
• Poor conditions for
Salmon and Whitefish
• Biotopes of rare
species disapered
• Ochre
• Nutrient leakage
• No retention
Farmer’s concern
• Land shrinkage
Design Considerations
Land shrinkage
• large areas now lower
than the river and even
below sea level
• either let the river flow
through shallow lakes
and restore the inland
delta by time
• or restore it separated
from lakes and wetlands
by levés
• Decreasing earth works
• Landscape priorities
• Using existing dikes for
delimitation where
possible
• Using existing bridges
• Protection of sensitive
flora and fauna
• Utilisation of old
meanders
• Authenticity
Construction and earth works
•
•
•
•
•
•
•
2 new bridges
Road to be elevated
5 bridges decommissioned
2 pumping stations decommissioned
Dikes to be removed
Re-meandering
Total earth works: 3 million m3
Before: Highway for water bordered by dikes
Before: Secondary drainage channel
R. Skjern ready to bend again
Before
Nature areas and intensive farmland
side by side
The tributary R. Omme also restored
Discharge
Total earth works: 3 million m3
Democratical process
Know how on restoration
- the art of restoration and
aesthetic
- authenticity/originality
- the physical dimension
- the biological dimension
the hydrological dimension
Democratical process
Political dimension
-
protect environment and nature
- quality objectives for streams,
lakes and coastal waters
- NGO’s and interest groups
- Investments
- Public interests
Regional plans and goals
Know how on restoration
- the art of restoration and
aesthetic
- authenticity/originality
- the physical dimension
- the biological dimension
the hydrological dimension
Democratical process
Landowners
Political dimension
-
protect environment and nature
- quality objectives for streams,
lakes and coastal waters
- NGO’s and interest groups
- Investments
- Public interests
Regional plans and goals
Know how on restoration
- the art of restoration and
aesthetic
- authenticity/originality
- the physical dimension
- the biological dimension
the hydrological dimension
-
private landownership
-
involvement
-
negotiations
compensations
exchange of land
Democratical process
Landowners
Political dimension
-
protect environment and nature
- quality objectives for streams,
lakes and coastal waters
- NGO’s and interest groups
- Investments
- Public interests
Regional plans and goals
Know how on restoration
- the art of restoration and
aesthetic
- authenticity/originality
- the physical dimension
- the biological dimension
the hydrological dimension
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-
private landownership
-
involvement
-
negotiations
compensations
exchange of land
Practical dimension
-
project management
and leadership
- tenders
contractors
Goals
Success criteria
Methods
Cooperation
Time & budget
Quality assessment
Recommendations on lowland stream restoration
Include consideration on the catchment area and the whole stream valley in the
project plan
Secure the hydrological connection between the stream and its valley.
Establish many crossings between the straight, regulated course and the new
meandering, restored course, in order to secure rapid colonisation by aquatic
plants and other organism
Restoration projects involving excavation of the former floodplain must take into
consideration existing vegetation niches worthy of preservation.
Restoration of streams by means of large-scale excavation should start during
periods of low discharge (in Denmark this period is July to September). The
construction work should be finished before the spawning season for trout and
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How to gain the most ’nature’ for the invested money in restoring streams
and wetlands
1.
Stable investments and long-lasting projects
2.
Low costs to buy areas and laying out the project
3.
Low cost to maintenance after completion
4.
Large areas better than spots
5.
Several purposes at the same time
6.
Political and local back-up
7.
Cooperation between authorities and ‘interest groups’
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A way to better ecosystem in streams and wetlands
Prevention is better and cheaper than treatment
1.
Stop the accident
2.
Preserve what still is in a natural condition
3.
Stop drainage and further regulation
4.
Proper maintenance and recreational use
5.
Use market economics: Socio-economic effects plus links to agricultural
land-use and subsidies
6.
Rehabilitation and restoring when 1 to 6 have been considered and used
International cooperation is necessary
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