River Restoration in Urban Areas. Petra Podraza

Transcription

1 River Restoration in Urban Areas Petra Podraza 1 Rivers for the Life of Towns 2007

2 Main Problems in Urban Rivers water quality discharge volume (floods and peak flow condition) technical constructed river bed poor optical appearance low ecological quality 2 Rivers for the Life of Towns 2007

3 Actually measures in urban areas are often sectoral, considering only one purpose like Flood protection City development Natural protection Recreation => Realized measures often are in conflict with other purposes 3 Rivers for the Life of Towns 2007

4 Example: Flood Protection Small flood and rain water retention basin in the city of Dortmund Advantage: technical building preventing the houses downstream from flooding lake 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 midge mass development 4 Rivers for the Life of Towns 2007

5 Concept of Urban River Planing Measures + Realization Planning Process Clearance + Consulting Restrictions Spatial Limitation, Cost Benefit, Third Party Claim Targets + Demands Water Management Targets + Demands Urban Development Ecology Characteristics of Urban River 5 Rivers for the Life of Towns 2007 Targets + Demands

6 Example: Flood Protection Water retention during rainfall Flood and rain water retention basin in the city of Essen 6 Rivers for the Life of Towns 2007

7 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 7 Rivers for the Life of Towns 2007

8 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

9 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 be necessary 9 Rivers for the Life of Towns 2007

10 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 10 Rivers for the Life of Towns 2007

11 Measures to reduce rainwater discharge INNODRAIN 11 Rivers for the Life of Towns 2007

12 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 stream bed and riparian zone 12 Rivers for the Life of Towns 2007

13 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

14 Hibernation Signal for swarming Shading Summer habitat for insect adults Compensatory upstream flight Hatching, Emergence Leaf litter input Egg deposition 14 Rivers for the Life of Towns 2007

15 Man-made structures replacing natural morphological conditions: Mini-floodplain 15 Rivers for the Life of Towns 2007

16 Man-made structures replacing natural morphological conditions: Bow-constructions at urban rivers with spatial limitation Signal for swarming Leaf litter input Summer habitat for insect adults Cross-sectiom Compensatory upstream flight Hatching, Emergence Hibernation Shading Egg deposition Top-view 16 Rivers for the Life of Towns 2007

17 Rehabilitated urban river Social aspects: Optical impression Sculpture Access to the river granted 17 Rivers for the Life of Towns 2007

18 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

19 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

20 Rehabilitated urban river Ecological aspects: Sealed wall instead of natural stone wall with cavities, covered with twiner and clamberers Conclusion: The picture looks rather nice, but the rehabilitated river is not really visible for the citizen and No trees to shade => eutrophication, substrates 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

21 Man-made structures replacing natural morphological conditions??? It is not so easy to restore urban rivers appropriately. You have to consider the human demands but 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

22 River Restoration in Urban Areas Thank you for your attention! 22 Rivers for the Life of Towns 2007