Case study:Lebendige Alster

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Location: 53° 32' 56.16" N, 9° 59' 8.24" E

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Project overview

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Status	In progress
Project web site
Themes	Habitat and biodiversity, Hydromorphology, Urban
Country	Germany
Main contact forename	Wolfram
Main contact surname	Hammer
Main contact user ID
Contact organisation
Contact organisation web site	http://https://www.lebendigealster.de
Partner organisations
Parent multi-site project
This is a parent project encompassing the following projects	No

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Project summary

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The Alster river is 56-kilometer-long, originates near the community of Henstedt and ends with its estuary into the river Elbe in Hamburg. The best-known part of the Alster is the Alster Lake, which is formed in the inner-city area of Hamburg by the Inner and Outer Alster. Since 2011, the cooperation project “Lebendige Alster” works to improve the ecological condition of the Alster, with its various, sometimes rare, habitats, and to raise awareness of nature conservation. Like many other rivers the impact of urban development is evident in e.g. biodiversity and hydromorphology. Some of these manmade impassable constructions can already be overcome. Due to newly built fish ladders migratory fish can return to the Alster, but then end up in the poorly structured and not very natural area of the canal (Fleet). The absence of natural vegetation confronts many water organisms with difficult living conditions. Here numerous innovative measures to create new living spaces have already been implemented in the canals and the project aims to add more. During the day, the water in the Alsterfleet is dammed and drained at night, creating strong currents. For this purpose, a “current cocoon” has already been inserted into the canal to create sheltered zones during strong currents. An old typical cargo ship (Grüne Schute) was also rebuilt into a vegetation rich area, where fish and insects can access the Schute through recesses in the ship's side and in the floor. The roots of willow and alder, reeds and aquatic plants offer protection, are hiding places and sources of food. Besides offering positive effects to the surrounding vegetation, the Grüne Schute is also used as an educational venue to allow schoolchildren, citizens and other interested parties to participate in the project and to provide environmental education.

Outside of urban Hamburg, numerous habitat types which have become rare were designed in the first part of the project. A shortage of dead wood, as a result of regular removal, was counteracted with controlled tolerance of deadwood accumulations. Introduction of mobile deadwood as well as installation of individual trees including crowns resulted in improved hydromorphology. The gravel-gap system of the riverbed as an important habitat was supported with the removal of sand, installation of gravel depots on undercut slope areas, narrowing of waters with gravel made flow deflectors.

In addition to the near-natural development of the Alster waters, there are also improvements in local recreation and environmental education.

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Catchment and subcatchment Select a catchment/subcatchment Site Edit site Name WFD water body codes DEHH_al_05/15/16 WFD (national) typology WFD water body name Alster Pre-project morphology Reference morphology Desired post project morphology Heavily modified water body Yes National/international site designation Local/regional site designations Protected species present Yes Invasive species present Yes Species of interest Dominant hydrology Dominant substrate River corridor land use Average bankfull channel width category Average bankfull channel width (m) Average bankfull channel depth category Average bankfull channel depth (m) Mean discharge category Mean annual discharge (m3/s) Average channel gradient category Average channel gradient Average unit stream power (W/m2) Project background Edit project background Reach length directly affected (m) Project started Works started Works completed Project completed Total cost category Total cost (k€) Benefit to cost ratio Funding sources Cost for project phases Phase cost category cost exact (k€) Lead organisation Contact forename Contact surname Investigation and design Stakeholder engagement and communication Works and works supervision Post-project management and maintenance Monitoring Reasons for river restoration Edit reasons for restoration Mitigation of a pressure Hydromorphology Biology Physico-chemical Other reasons for the project Measures Edit Measures Structural measures Bank/bed modifications Floodplain / River corridor Planform / Channel pattern Other Non-structural measures Management interventions Social measures (incl. engagement) Other Monitoring Hydromorphological quality elements Edit Hydromorphological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Biological quality elements Edit biological quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Physico-chemical quality elements Edit Physico-chemical quality elements Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Any other monitoring, e.g. social, economic Edit Other responses Element When monitored Type of monitoring Control site used Result Before measures After measures Qualitative Quantitative Monitoring documents Upload monitoring documents Additional documents and videos Upload additional documents Additional links and references Edit links and references Link Description Supplementary Information Edit Supplementary Information