Enns - Aich

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Enns - Aich


Factsheet: Enns - Aich

General
Country AT
River Name Enns
Site Name Enns - Aich
River Characterisation
    River typology
    Location (Lat Lon) 47.42112, 13.816094
    Altitude mid-altitude: 200 - 800 m
    Catchment area large: > 1000 - 10000 km2
    Geology Siliceous
    National code/
    River type name
    Hydromorphological quality elements

    Biological quality elements
    Ecosystem Services
    EU Directives
    Pressures
    Measures
    Other
    Project size 0.6 km
    Approximate costs 100 000 - 1 000 000 Euros
    Synergy Flood protection, ecology, recreation
    Status Realised
    Period of realization 2003 - 2004
    Evaluation Hydromorphological and ecological changes
    Implemented by municipality Aich


    Key features of the case study

    As part of the “flood protection programme for the Upper Enns River” ecological orientated measures were implemented at the river Enns in the village Aich. Besides several technical measures like a flood protection dam the river bed was widened in two sections both as retention area and for ecological benefits. Bank stabilization structures were removed and for this reason lateral erosion increased and the development of gravel bars was initialized. A new side arm was created which offers diverse instream structures and many different habitat types.

    Site description

    The river Enns has its source in the Radstädter Tauern Mountains in the Austrian federal state of Salzburg. The Enns continues its flow across the federal states Styria and Upper Austria where it joins the Danube after 254 km. At the project site the Enns valley forms the border between the Limestone Alps in the north and the Grauwackenzone in the south. The sub-catchment size is about 800 km² and the average annual flow 21,5 m³/s. Before regulation measures took place on the river Enns this river section was influenced by two tributaries. The high bed load input of the tributaries formed alluvial cones which lead to an increasing slope downstream. The combination of increased slope and high bed load input created locally a braiding river character with gravel banks, vegetated islands and sequences of cut- and slip-off banks.

    Drivers and Pressures

    In the middle of the 19th century the regulation of the river Enns started aiming the expansion of agricultural land use and settlement areas. The river course in the Enns valley was shortened by 18%. 37 meander bends were cut off and the river was straightened. Due to drainage measures in the valley bottom many swamps fell dry. Additionally the Enns and their tributaries are used also for hydropower production.

    Global objectives

    After heavy flood events in August 2002 plans for a 100 years flood protection for the municipality of Aich were initiated. The aim was to realize an ecological orientated river compatible flood protection programme.

    Specific goals

    • 100 years flood protection for the settlement area
    • Conservation and improvement of ecological status
    • Maintenance and creation of retention areas
    • Orientation on potential river type

    Measures selection

    Success criteria

    Ecological response

    Hydromorphological response

    Monitoring before and after implementation of the project

    Socio-economic aspects

    Contact person within the organization

    Extra background information

    References


    Related Measures

    Related Pressures