Dyke relocation on the river Elbe near Lenzen, Germany

Title Dyke relocation on the river Elbe near Lenzen, Germany
Description
Preview image No image
Preview image caption
Creators fullname Laszlo Cseh
Contributors fullname
NWRM
Site information
Climate zone
cool temperate dry
Mean annual rainfall
300 - 600 mm
Mean rainfall unit
mm/year
Average temperature
9
Mean runoff
704
Mean runoff unit
600 - 750 mm
Type
Case Study Info
Light or indepth?
In-depth
Average slope range
0-1%
Vegetation class
Prior to the project implementation, the area was subject to agricultural use. After implementation it was converted to alluvial forests and half-open pasture landscapes.
Design and implementations
Application scale
River Basin
Installation date
2011
Age
3
Performance timescale
Immediate
Area (ha)
1031
Area subject to Land use change or Management/Practice change (ha)
420
Size
420
Size unit
ha
Design capacity description
The newly created retention area of 420 ha between the old dyke and the new one can comprise up to 16 million m3.
In times of extreme flood events the measure allows lowering the water level of up to 40 cm in the area.
Max water retention capacity
16
Max water retention capacity unit
mio m3/month
Basis of design
Through the NWRM, 36% of a 20-25 years flood flow (3250 m3/sec) would take place in the newly created floodplain.
Constraints
no information on physical / biophysical constraints
Favourable preconditions
Preconditions which led to the implementation of the measure were not natural, but mainly due to the fact that the old dyke had been constructed very close to the river bed.
Management change from
Agricultural land use.
Management change to
Landscape conservation measures.
Inflow volume
2300
Inflow volume unit
m3/sec
Outflow volume
1667,5
Outflow volume unit
m3/sec
Peak flow rate
3250
Public consultation
1
Design contractual arrangement
No data
Design consultation activity
Activity stage Key issues Name Comments
Implementation phase
Guided tours
Guided tours take place in the project area.
Implementation phase
Visitor centre
A visitor centre informs about the project.
Design land use change
No data
Design authority
Authority type Role Responsibility Name Comments
NGO
Implementation
Trägerverbund Burg Lenzen e.V.
Other
Initiation of the measure
Biosphere Reserve "River Landscape Elbe-Brandenburg"
Management of the biosphere reserve.
Other
Implementation
Brandenburg State Office of Environment, Health and Consumer Protection
Regional authority with different responsibilities (nature conservation, water management, etc.).
Responsible for the construction of the new dyke.
Farmers
Initiation of the measure
Large-scale farmer
Manager of a large-scale farm (about 3600 ha) situated in the area. Interested by promoting regional development activities.
Monitoring
Federal Waterways Engineering and Research Institute (BAW)
Research institute accompanying the project.
Lessons, risks, implications
Key lessons
The project shows a successful combination of nature conservation, flood protection and other objectives (agricultural, regional development, and others).
It is said that public communication activities should have been made in a more intensive way, in particular at the beginning of the project.
From an ecological perspective, an earlier / deeper connection to the Elbe would have been better to improve the lateral connectivity and morphological dynamic of the river. The latter would have also helped to minimize sedimentation processes in the new floodplain area, which can be expected in the middle and long term.
The highest effect of the measure can be stated next to the first opening of the dyke (on the "evil place") and it decreases towards the downstream part of the dyke relocation. Further downstream from the dyke relocation, the measure does not have any effect anymore on the water level. Upstream, the positive effect diminishes with an increasing distance. This shows that the measure has a very clear, but mainly regionally working impact. In order to solve the important flood problems of the Elbe river, it is indispensible to carry out other dyke relocation measures.
The measures are suitable to be applied also elsewhere. However, areas free of settlement are needed.
The continuous persuasion works from a few - and over several years - is highlighted as one key factor for the successful implementation of the project. The prior implementation of research projects ensured the effectiveness of the measure design, but was also very useful for providing support for public discussion.
Financing difficulties
1
Financing difficulties information
The large costs of the project led to important financing problems. Thanks to the multifunctionality of the measures applied (nature conservation, flood protection), financing from different sources was possible. However, none of them was sufficient on itself.
financing funding solutions
Different financing sources had been combined to collect sufficient funds. Furthermore, to benefit from all financing sources, a private body was needed as applicant, and an association has been created with different stakeholders for this purpose.
Transferability
The preconditions in terms of stakeholder engagement were quite particular - going back to changes in the framework of the political turnover in Germany. However, from a technical point of view, dyke relocations can be implemented in any other area were sufficient settlement free areas exist.
Success factor(s)
Success factor type Success factor role Comments
Attitude of relevant stakeholders

The commitment of stakeholders to the project was key to its successful implementation, as the process lasted several years.
Financing possibilities

Thanks to the multifunctionality of the measures applied (nature conservation, flood protection), financing from different sources was possible. However, none of them was sufficient on itself and only a combination of different sources led to sufficient funds.
Successful coordination between authorities
Communication activities
Conducted assessments (incl. economic)

Hydrologic research projects created a sound basis for decision making and ensured the effectivity of the measure. The scientific studies provided furthermore support to the public discussion.
Legal obligations

Legal obligations existed for "renovating" the dyke in order to comply with current standards.
Existing institutional framework

From an institutional point of view it had been advantageous that the responsible nature conservation authority and the water authority are part of the same state environmental agency. They coordinated internally their position.
Financing
Financing type Comments
National funds
Sub-national funds
Funds from the State of Brandenburg.
Other
The association managing the project brought in money in alliance with different nature conservation NGOs.
Barrier
Barrier type Barrier role Comments
Other
secondary barrier
No major barriers to implementation are reported, apart from the need for substantial funding, but which could be resolved.
Driver
Driver type Driver role Comments
Organisation committed to it
main driver
It was only due to the continued commitment of local stakeholders that the project could be implemented.
Past flooding events
main driver
Reducing the local flood risk was a main driver for the implementation of the measures.
Legal obligations
main driver
There had been legal obligations to adjust the old dyke to current requirements - which temporarily coincided with the development of the project idea.
Financing share
Financing share type Share Comments
National funds
93
75% From the German government and 18% from the state of Brandenburg.
Private funds
7
From the project management association.
Policy, general governance
Policy description
The project was implemented mainly to reduce the flood risk, but also to restore alluvial forests in the area.
Policy target
Target purpose
Peak-flow reduction
Runoff control
Improved Biodiversity
Pollutants Removal
Policy pressure
No data
Policy area
No data
Policy impact
No data
Policy wider plan
No data
Policy requirement directive
No data
Socio economic
Direct benefits information
Increased flood protection and biodiversity benefits.
Ancillary benefits information
Benefits for the regional development: The project area got quickly established as a regional attraction on the international Elbe bike trail. In connection with a centre for environmental education and a visitor centre for the area a sustainable increase of the number of visitors occurred.
Furthermore, during the construction period, there had been some socio-economic effects in terms of employment and local consumption.
Costs investment
13000000
Costs investment information
11.5 million euros for the construction of the new dyke (include 0.71 million euros for planning). 1.5 million euros for opening the old dyke (include 240 000 euros for planning).
Costs operation maintenance
n/a
Costs maintenance information
Maintenance costs exist for maintaining the dyke.
Costs total
13000000
Costs total information
11.5 million euros for the construction of the new dyke (include 0.71 million euros for planning). 1.5 million euros for opening the old dyke (include 240 000 euros for planning).
Compensations annual information
no information
Compensations basis information
no information
Compensations nr beneficiaries information
Land in the newly created floodplain only belonged to two farmers.
Compensations scheme information
Compensation payments have been made for the abandonment of agricultural areas, for the herewith induced operating adaptations of the farming activity, the dissolution of current land tenures and the land use difficulties of furthermore cultivated areas.
Information on Economic costs - income loss
Agricultural activities have been abandoned, but which were (after the German reunification) anyway not very adapted to the new market situation.
Ecosystem improved biodiversity
1
Information on Ecosystem improved biodiversity
Alluvial forests have been initiated by planting respective tree species. Furthermore, an half-open pasture landscape is maintained. An impact has been stated amongst others with regards to the development of a diverse avifauna.
Ecosystem provisioning services
1
Information on Ecosystem provisioning services
Agricultural activities have been abandoned. No information on other potential provisioning services.
Information on Economic costs other annual
Hunting rights have been limited in the area.
Ecosystem impact climate regulation
No information available
Biophysical impacts
Retained water
16
Retained water unit
mio m3/month
Information on retained water
16 million m3 of water can be retained by the new floodplain area in case of flood events.
Increased water storage
38095
Increased water storage unit
m3/ha
Information on increased water storage
In terms of flood events, up to 16 million m3 can be retained in the 420 ha of the newly created floodplain area.
Peak flow rate reduction
36
Peak flow rate reduction unit
%
Information on Peak flow rate reduction
In times of extreme flood events (ocurring every 20-25 years), 36% of the flood flow is taking place in the floodplain.
Information on Increased groundwater level
Problems with upward seed are mentioned in the area next to the relocated dyke.
Information on Ecosystem flood control volume
The created floodplain is limited by a (relocated) dyke - no separation of the effects is possible.
Information on Ecosystem flood control return periods
Effects with regards to the following flood events have been calculated:
a) Flood events recurring every 1-2 years = 1500 m3/s
b) Flood events recurring every 3-5 years = 2300 m3/s
c) Flood events recurring every 20-25 years = 3250 m3/s
Water quality overall improvements
N/A info
Information on Water quality overall improvements
An effect on water quality is assumed through the retention of nitrogen and phophorous in the floodplain.
Information on Water quality Improvements (P)
Retention of P is assumed, no measurements took place.
Information on Water quality Improvements (N)
Retention of N is assumed, no measurements took place.
Soil quality overall soil improvements
Not relevant for this application
Information on Soil quality overall soil improvements
With regards to the impact of the measure, it is not about the quality of the soil, but its change back to its alluvial character.
Reducing flood risks quantity change
Depending on the importance of the flood event, the effect of the measure has been calculated as being the following (compared to the previous status, prior to the dyke relocation):
a) Flood events recurring every 1-2 years = 1500 m3/s
b) Flood events recurring every 3-5 years = 2300 m3/s
c) Flood events recurring every 20-25 years = 3250 m3/s
Share of the flow taking place in the newly created floodplain:
a) 8.6 %, b) 27.5 %, c) 36 %
Difference of the water level:
a) 9.2 cm, b) 28 cm, c) 38.9 cm
Monitoring maintenance
Monitoring impacts effects
1
Monitoring location
Catchment outlet
Administrative annual cost information
no information
Monitoring parameters
The following aspects are monitored (Damm et al. 2011):
- Hydrology: 12 groundwater gauges are supervised by the association carrying the project
- Hydraulics: Construction of 4 dyke gauges through the large-scale nature conservation project, steady reading of the meter by the state office, analysis through the Federal Waterways Engineering and Research Institute
- Soils: Two permanent observation plots of the Land Brandenburg, complemented by an evaluation at the end of the project
- Forestry: Examination of the planted alluvial forests in 2009 (evaluation)
- Fishes: Examination of the flood channels in 2009 and 2010, in time intervals further observations in cooperation with research institutes
- Birds: Examination in the framework of the evaluation of the project continuously 2007-2010, continued by the state of Brandenburg
- Vegetation: surveys through cooperation between the project management association, the state of Brandenburg and different research institutes
Performance
Performance impact estimation method
Catchment outlet
Performance impact estimation information
Substantial modeling exercises and numerical calculations had been undertaken to predict the effect on flood peaks. A two-dimensional, hydro-dynamic numerical model has been used (it compares the previous situation without dyke relocation with the one with dyke relocation).
The impact of the measures with regards to flood protection could be directly observed during the extreme flood event in January 2011.
Measures
sources
Nwrm type In-depth
Nwrm geolocation 11.478521,53.097326
General
National Id
Germany_01
Site name
Stretch of the Elbe river near Lenzen
Summary
In the framework of the large-scale nature conservation project "Lenzener Elbtalaue", a dyke along the river Elbe (in Germany) has been relocated. This created a new retention area with a diverse floodplain, including alluvial forests, half-open pasture landscapes and other typical habitats of lowland floodplains. With 420 ha it is the biggest application of this type of measure in Germany so far. The project successfully combines flood protection and nature conservation objectives. Since the cutting of the old dyke in 2009, the measure could proof its effectiveness during several high water events.
Location description
The measures are applied on a stretch of the Elbe river in Germany, next to Lenzen, between the Elbe kilometers 473.5 and 489.5.
NUTS Code
Brandenburg
RBD code
DE5000
Transboundary
0
Data provider
Verena Mattheiss, ACTeon
Longitude
11.478521
Latitude
53.097326
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