Dyke relocation on the river Elbe near Lenzen, Germany

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.

The in-depth description of the case study:

cs-de-01-elbe-final_version.pdf

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:

Data provider:

Verena Mattheiss, ACTeon

Source(s):

Auenschutz - Hochwasserschutz - Wasserkraftnutzung. Beispiele für eine ökologisch vorbildliche Praxis

Die Deichrückverlegung bei Lenzen an der Elbe

Naturschutzgroßprojekt Lenzener Elbtalaue

Hochwasser: Rückverlegung des Deichs bewährt sich

Die Deichrückverlegung bei Lenzen an der Elbe

Landwirtschaftliche und touristische Nutzungsänderungen im Naturschutzgroßprojekt "Lenzener Elbtalaue" (2005 - 2009) Sozio-ökonomische Evaluierung (I)

Sozio-ökonomische Betroffenheit der Landwirtschaft durch Deichrückverlegung im Bereich der brandenburgischen Mittelelbe unter Berücksichtigung betrieblicher Anpassungsmöglichkeiten

Floodplains in Germany "Synergies with nature conservation, WFD and flood protection"

NWRM(s) implemented in the case study:

Floodplain restoration and management

Forest riparian buffers

Meadows and pastures

Channels and rills

Longitude:

11.478521

Latitude:

53.097326

Site information

Climate zone:

cool temperate dry

Mean annual rainfall:

300 - 600 mm

Mean rainfall unit:

mm/year

Average temperature:

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.

Monitoring maintenance

Monitoring impacts effects:

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.

Biophysical impacts

Retained water:

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:

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.

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

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:

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):

Type	Role	Comments
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.
Successful coordination between authorities
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.
Communication activities
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.

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:

Type	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:

Type	Role	Comments
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.
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.

Financing share:

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.

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.

Information on Economic costs other annual:

Hunting rights have been limited in the area.

Ecosystem improved biodiversity:

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:

Information on Ecosystem provisioning services:

Agricultural activities have been abandoned. No information on other potential provisioning services.

Ecosystem impact climate regulation:

No information available

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

Policy, general governance and design targets

Policy description:

The project was implemented mainly to reduce the flood risk, but also to restore alluvial forests in the area.

Policy pressure:

Policy requirement directive:

Policy impact:

Policy wider plan:

Policy area:

Policy target:

Target purpose
Runoff control
Peak-flow reduction
Pollutants Removal
Improved Biodiversity

Design & implementations

Application scale:

River Basin

Installation date:

2011

Age:

Performance timescale:

Immediate

Area (ha):

1031

Area subject to Land use change or Management/Practice change (ha):

420

Size:

420

Size unit:

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:

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:

Design contractual arrangement:

Design consultation activity:

Activity stage	Name	Key issues	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:

Design authority:

Authority type	Role	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.

Last updated: 18 Jun 2015 | Top

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Dyke relocation on the river Elbe near Lenzen, Germany

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