RiverRiver RestorationRestoration inin UrbanUrban AreasAreas

Petra Podraza

1 for the Life of Towns 2007 Main Problems in Urban Rivers • • volume ( and peak flow condition) • technical constructed bed • poor optical appearance • low ecological quality

2 Rivers for the Life of Towns 2007 Actually measures in urban areas are often sectoral, considering only one purpose like • protection • City development • Natural protection • Recreation

=> Realized measures often are in conflict with other purposes

3 Rivers for the Life of Towns 2007 Example: Flood Protection Small flood and rain water retention basin in the city of Dortmund Advantage: • technical building preventing the houses downstream from flooding • as a water element in the Disadvantage: city • reduced water storing capacity • lake isn’t accessible (fenced to prevent children to fall into) • due to dikes, the lake isn’t visible • interrupted continuum of the river

•4 midge mass development Rivers for the Life of Towns 2007 Concept of Urban River Planing

Measures + Realization

Planning Process Clearance + Consulting Restrictions Spatial Limitation, Cost Benefit, Third Party Claim TargetsDemands + Targets + Demands Targets + Demands Water Urban Ecology Management Development Characteristics of Urban River 5 Rivers for the Life of Towns 2007 Example: Flood Protection Flood and rain water retention Water retention basin in the during rainfall city of Essen

6 Rivers for the Life of Towns 2007 Example: Impact - Flooding

Best Practice in large rivers => Measures in the river basin: • activated •reservoirs • flood retention basin

=> Local in the city • , dikes and floodwalls • high flow rescue concepts

7 Rivers for the Life of Towns 2007 Example: Impact - Flooding

Best Practice in small rivers => Measures to reduce rainwater discharge

=> Measures in the river

8 Rivers for the Life of Towns 2007 Measures to reduce rainwater discharge Example: Hoppegarten

Business Park: 100 ha Rainwater discharge up to 10 m³/s Small brook as receiving water => Large retention volume would

9 be necessaryRivers for the Life of Towns 2007 Measures to reduce rainwater discharge => Trough and Drainage System

Advantage: • Purification of the rainwater • No artificial peak flow condition in the brook • recharge • Visual integration in the business park

10 Rivers for the Life of Towns 2007 Measures to reduce rainwater discharge INNODRAIN©

11 Rivers for the Life of Towns 2007 Measures in the River => rehabilitating urban rivers by combining the demands of the citizens: - safeness (flood protection) - discharging comfort (rain water management) - liveable urban climate - nice urban scenery, recreation with the ecological demands of the aquatic fauna and flora (=> EG WFD): - liveable water quality and hydrology - continuity of the river - appropriate structures of bed and

12 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 natural morphological conditions can help to improve the aquatic environment with its biological communities.

13 Rivers for the Life of Towns 2007 Signal for Hibernation swarming

Shading

Compensatory Summer habitat upstream flight for insect adults

Leaf litter input Hatching, Emergence

Egg

14 Rivers for the Life of Towns 2007 Man-made structures replacing natural morphological conditions: Mini-

15 Rivers for the Life of Towns 2007 Man-made structures replacing natural morphological conditions: Bow-constructions at urban rivers Signal for swarming with spatial limitation

Summer habitat for insect adults Leaf litter input

Hibernation Cross-sectiom Hatching, Emergence Compensatory upstream flight

Egg deposition Shading

Top-view 16 Rivers for the Life of Towns 2007 Rehabilitated urban river Social aspects:

Optical impression

Sculpture

Access to the river granted

17 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 in flood situations

18 Rivers for the Life of Towns 2007 Rehabilitated urban river Ecological aspects:

Maximum profile

Gravel banks at the base of the walls replacing the amphibian zone

Streambedwithnatural substrates

19 Rivers for the Life of Towns 2007 Rehabilitated urban river Ecological aspects: Sealed wall instead of natural stone wall with Conclusion: The picturecavities, looks covered rather with nice, twiner and clamberers • but the rehabilitated river is not really visible for the citizen No trees to shade => eutrophication, substrates and overgrown with water plants and algae • the river does not work as pretentious aquatic habitat Wrong plant species on the banks

Wrong substrate composition, not complying with the stream type

20 Rivers for the Life of Towns 2007 Man-made structuresIt is not so easy to restore urban replacing rivers appropriately . You have to natural morphologicalconsider the human demands conditionsbut you also have to learn to look at your measures with the eyes of a fish or an aquatic ??? insect! No!

21 Rivers for the Life of Towns 2007 RiverRiver RestorationRestoration inin UrbanUrban AreasAreas

Thank you for your attention!

22 Rivers for the Life of Towns 2007