Hannover, Germany
City population: 514110
Duration: 2000 – 2010
Implementation status: Completed
Scale: Meso-scale: Regional, metropolitan and urban level
Project area: unknown
Type of area: Other
Last updated: October 2021

The renaturalization of the water canal Hirtenbach project was part of the larger city-wide initiative that aimed at the naturalization of different parts of the city's drainage system including small trenches and streams. The initiative aimed to decrease the risk of floods, improve the water quality, protect the local flora and fauna from the pollution, as well as provide for an additional recreational area for the citizens. (Reference 1) In 2000, natural remodelling or the creation of near-natural structures began in sections. A 20, 000 m3 retention basin was also built. These actions improved flood protection and ecology of the area, and it provided local recreation opportunities. However, a study conducted in 2014 revealed that the restoration measures brought positive changes, but it was not enough to achieve a “good water status” defined by the European Water Framework Directive. Intensive care from silting and lush plant growth, wide margins, and the reduction of nutrients coming from the drainage and agriculture, need to be addressed. (Reference 2) A new landscape is expected to be created when the alder trees grow. Waterbirds and waders, as well as insects like dragonflies, bees, butterflies and crickets, have been observed in the area (Reference 3). The large drainage system of the city of Hannover includes many small trenches and streams with a total length of 152 kilometres. The intervention in Hirtenbach involved renaturalization worked on the total length of approximately 10,5 km (of which 3,3 km in the urban area). (Reference 2)

Overview

Nature-based solution

  • Grey infrastructure featuring greens
  • Blue infrastructure
  • Riverbank/Lakeside greens
  • Rivers/streams/canals/estuaries
  • Green areas for water management
  • Sustainable urban drainage systems

Key challenges

  • Climate action for adaptation, resilience and mitigation (SDG 13)
  • Climate change adaptation
  • Water management (SDG 6)
  • Flood protection
  • Stormwater and rainfall management and storage
  • Improvements to water quality
  • Green space, habitats and biodiversity (SDG 15)
  • Habitat and biodiversity restoration
  • Habitat and biodiversity conservation
  • Green space creation and/or management
  • Regeneration, land-use and urban development
  • Promote natural styles of landscape design for urban development
  • Social justice, cohesion and equity (SDG 10)
  • Social interaction
  • Health and well-being (SDG 3)
  • Creation of opportunities for recreation

Focus

Creation of new green areas, Creation of semi-natural blue areas, Maintenance and management of urban nature existing green areas, Ecological restoration of degraded ecosystems, Monitoring and maintenance of habitats and/or biodiversity, Management and improved protection of rivers and other blue areas

Project objectives

Goals of the intervention: 1) Purification of water; 2) Renaturalization of the water channel and shore; 3) Protection of fauna and flora from pollution originating from the water and minimizing the negative adverse effects of pollution; 4) Improving the flood protection of the city (Reference 1)

Implementation activities

-Increasing the self-cleaning power of the water canal by the establishment of structurally rich water profiles through the creation of suitable rainwater retention basin and near-natural structures. -Planting of trees; -Demolition of bank and embankment protection; -Installation and greening of edge strips; -Establishment of water maintenance plans for care and development while respecting the maintenance of a proper drain system; -Continuous scientific studies of water quality (monitoring) (Reference 1,2)

Climate-focused activities

Climate change adaptation:

  • Implement sustainable urban drainage infrastructure (e.g. to make space for water)
  • Renaturalization of rivers and other water bodies

Biodiversity conservation or restoration-focused activities

Biodiversity conservation:

  • Protect and enhance urban habitats
  • Preserve and strengthen existing habitats and ecosystems
  • Promote environmentally-sound development in and around protected areas
  • Create new habitats
  • Reduce negative impacts and avoid the alteration/damage of ecosystem
  • Protect species
  • Undertake specific measures to protect species
  • Means for conservation governance
  • Manage biological resources for conservation and sustainable use
  • Create and use scientific knowledge for conservation

Biodiversity restoration:

  • Rehabilitate and restore damaged or destroyed ecosystems

Main beneficiaries

  • Citizens or community groups

Governance

Management set-up

  • Government-led

Type of initiating organisation

  • Local government/municipality

Participatory approaches/ community involvement

  • Unknown

Details on the roles of the organisations involved in the project

The project was designed and implemented by the city of Hannover.

Project implemented in response to ...

... an EU policy or strategy? Yes (The European Water Framework Directive, which regulates the protection of surface waters and groundwater, sets out the targets for the reduction of pollution and the achievement of good ecologic conditions.(Reference 2))
... a national policy or strategy? Unknown
... a local policy or strategy? Yes (The project is a part of a larger long-term city initiative that aims at the renaturalization of the streams and canals (Gewässerrenaturierung) that are part of the city's drainage system. (Reference 1))

Financing

Total cost

Unknown

Source(s) of funding

  • Public local authority budget

Type of funding

  • Earmarked public budget

Non-financial contribution

Unknown

Impacts and Monitoring

Environmental impacts

  • Water management and blue areas
  • Improved water quality
  • Increased protection against flooding
  • Improved stormwater management
  • Green space and habitat
  • Increased green space area
  • Increased conservation or restoration of ecosystems
  • Reduced biodiversity loss
  • Increased number of species present

Economic impacts

  • Unknown

Socio-cultural impacts

  • Social justice and cohesion
  • Improved liveability
  • Improved access to urban green space
  • Increased opportunities for social interaction
  • Health and wellbeing
  • Gain in activities for recreation and exercise

Type of reported impacts

Achieved impacts

Presence of formal monitoring system

Yes

Presence of indicators used in reporting

Yes

Presence of monitoring/ evaluation reports

No evidence in public records

Availability of a web-based monitoring tool

No evidence in public records

References

1. Source link. (no date). 'Renaturalization of water' ('Gewässerrenaturierung'). Available at:
Source link. Accessed 15 July 2020.
2. Source link. (2016). 'The Hirtenbach' (See attachment)
3. Source link. (no date). Hirtenbach. Available at: Source link. Accessed 15 July 2020.