Urban river restoration

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    1 Rivers for the Life of Towns 2007

    RiverRiver

    RestorationRestorationinin

    Urban AreasUrban Areas

    Petra

    Podraza

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    2 Rivers for the Life of Towns 2007

    Main Problems in Urban Rivers

    water quality

    discharge volume (floods and peak flow condition)

    technical constructed river bed

    poor optical appearance

    low ecological quality

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    3 Rivers for the Life of Towns 2007

    Actually measures in urban areas are oftensectoral, considering only one purpose like

    Flood protection City development

    Natural protection

    Recreation

    => Realized measures often are in conflict with other

    purposes

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    4/224 Rivers for the Life of Towns 2007

    Example: Flood Protection

    Small flood and rain waterretention basin in the city of

    Dortmund

    Advantage: technical building preventing

    the houses downstream from

    flooding lake as a water element in the

    cityDisadvantage:

    reduced water storing capacity

    lake isnt accessible (fenced to prevent children to fall into)

    due to dikes, the lake isnt visible

    interrupted continuum of the river

    midge mass development

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    5/225 Rivers for the Life of Towns 2007

    Characteristics of Urban River

    Water

    Management

    Urban

    Development

    Ecology

    Targets+Dem

    ands

    Targets

    +Dem

    ands

    Targets+Dem

    ands

    Planning Process

    RestrictionsSpatial Limitation, Cost Benefit, Third Party Claim

    Measures + Realization

    Clearance +Consulting

    Concept of Urban River Planing

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    Example: Flood Protection

    Flood andrain water

    retention

    basin in thecity of

    Essen

    Water retentionduring rainfall

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    7/227 Rivers for the Life of Towns 2007

    Example: Impact - Flooding

    Best Practice in large rivers

    => Measures in the river basin: activated floodplains

    reservoirs

    flood retention basin

    => Local in the city dams, dikes and floodwalls

    high flow rescue concepts

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    8/228 Rivers for the Life of Towns 2007

    Example: Impact - Flooding

    Best Practice in small rivers

    => Measures to reduce rainwater discharge

    => Measures in the river

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    9/229 Rivers for the Life of Towns 2007

    Measures to reduce rainwater dischargeExample: Hoppegarten

    Small brook as receiving water=> Large retention volume would

    be necessary

    Business Park: 100 ha

    Rainwater discharge up to 10 m/s

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    Measures to reduce rainwater discharge=> Infiltration Trough and Drainage System

    Advantage:

    Purification of the rainwater

    No artificial peak flow condition in the brook

    Groundwater recharge

    Visual integration in the business park

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    Measures to reduce rainwater dischargeINNODRAIN

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    Measures in the River

    => rehabilitating urban rivers by combining thedemands of the citizens:

    - appropriate structures of stream bed and riparian zone

    - continuity of the river

    - liveable water quality and hydrology

    - nice urban scenery, recreation

    - liveable urban climate

    - discharging comfort (rain water management)

    with

    the ecological demands of the aquatic fauna and flora

    (=> EG WFD):

    - safeness (flood protection)

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    13 Rivers for the Life of Towns 2007

    But:

    spatial limitations inhibit rivers to be restored to

    natural conditions

    the knowledge on morphological minimum

    requirements of the aquatic community to reach GES

    or GEP is rather poor.

    Designing structures which are able to replace naturalmorphological conditions can help to improve the

    aquatic environment with its biological communities.

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    14 Rivers for the Life of Towns 2007

    Signal forswarming

    Shading

    Leaf litter

    input

    Compensatoryupstream flightSummer habitat

    for insect adults

    Hibernation

    Hatching,

    Emergence

    Eggdeposition

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    15 Rivers for the Life of Towns 2007

    Man-made structures

    replacing natural

    morphological conditions:

    Mini-floodplain

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    16 Rivers for the Life of Towns 2007

    Cross-sectiom

    Top-view

    Signal for swarming

    Shading

    Leaf litter

    input

    Compensatory

    upstream flight

    Summer habitat

    for insect adults

    Hibernation

    Hatching,

    Emergence

    Egg deposition

    Man-made structures replacing

    natural morphological conditions:

    Bow-constructions at urban riverswith spatial limitation

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    17 Rivers for the Life of Towns 2007

    Rehabilitated urban river

    Social aspects:

    Sculpture

    Optical impression

    Access to the river granted

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    18 Rivers for the Life of Towns 2007

    Rehabilitated urban river

    Social aspects:

    Parking place instead of

    pedestrian zone with view

    points

    Access to the river without

    plattform, dangerous inflood situations

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    19 Rivers for the Life of Towns 2007

    Rehabilitated urban river

    Ecological aspects:

    Gravel banks at the base of

    the walls replacing the

    amphibian zone

    Maximum profile

    Stream bed with natural

    substrates

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    20 Rivers for the Life of Towns 2007

    Rehabilitated urban river

    Ecological aspects:Sealed wall instead of

    natural stone wall with

    cavities, covered with twinerand clamberers

    Wrong substrate composition,

    not complying with the streamtype

    No trees to shade =>

    eutrophication, substrates

    overgrown with water plants

    and algae

    Wrong plant species on thebanks

    Conclusion: The picture looks rather nice,

    but the rehabilitated river is not really visible

    for the citizen

    and

    the river does not work as pretentious

    aquatic habitat

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    21 Rivers for the Life of Towns 2007

    Man-made

    structuresreplacing

    natural

    morphologicalconditions

    ???

    No!

    It is not so easy to restore urbanrivers appropriately . You have to

    consider the human demandsbut you also have to learn to

    look at your measures with the

    eyes of a fish or an aquatic

    insect!

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    22 Rivers for the Life of Towns 2007

    RiverRiverRestorationRestoration

    inin

    Urban AreasUrban Areas

    Thank you

    for your

    attention!