Floodplain restoration to improve green infrastructures and address multiple management objectives in an urban context: the case study of the Lobau

Transcription

1 Floodplain restoration to improve green infrastructures and address multiple management objectives in an urban context: the case study of the Lobau Hein T. 1,2, Baumgartner C. 3, Bondar-Kunze E. 1,2, Funk A. 1,2, Preiner S., Reckendorfer W. 1,2, Sanon S. 4, Weigelhofer G. 1,2 1 BOKU Vienna, Institute of Hydrobiology and Aquatic Ecosystem Management 2 WasserCluster Lunz GmbH, Inter-University Centre for Aquat. Ecosystem Res. 3 Nationalpark Donau-Auen GmbH 4 UNESCO-IHE Institute for Water Education ECRR conference, Vienna, September 2013

2 Urban floodplain Lobau Lobau Vienna Size: 1,039 ha (280 ha Lower Lobau area) Length: 10 km in total, Connectivity: only at downstream end

3 Important role of floodplains in urban context Important large green infrastructures Connecting important corridors and protect areas at larger scales Islands of extremely rare habitats in urban context High value for society in terms of e.g. recreation

4 Major challenges and constraints Land use change urbanization River regulation navigation and flood protection Changes at catchment scale: nutrients, sediment transport, invasive species Multiple uses

5 Uses and Conflicts Decrease of aquatic and semi-aquatic habitats still high biodiversity and internat. designation (UNESCO MaB, RAMSAR, Natura2000, NP) Improvement of flood protection Rebelo et al Important drinking water supply for Vienna (max. 25% of total amount can be provided) Pressure by recreation currently more than 600,000 visitors / a with increasing tendency

6 Questions and approach What sectors benefit from ecological restoration? For which options the highest trade-offs can be identified and what are compromise solutions? Approach: Define management sectors, options addressing key problems, include stakeholder preferences, use MCDA software (mdss5)

7 Map of measures 0.5m3/ s Dotation Point 0.5m3/ s Flood Levee 14000m3/s Flood Levee 12000m3/s Schönauer Schlitz back-flow flooding point (open) Hein et al., (2008)

8 Preferred option 1.5m3/s Option 1B Enlarge downstream opening Surface water connection to Danube QMW = 125 m³ / s Sanon 2011

9 Data: management criteria 75 Indicators Sanon et al /16/2013

10 Results: Impact on the Management criteria Trade-off between the criteria that scored high under increased hydraulic connectivity and potential drinking water production Sanon et al. 2012

11 Results: Quantified Trade-Offs Non-dominated options formed the trade-off curve between two criteria Trade-offs were quantified as the shortest distance to the theoretical ideal solution Options that provided this shortest distance are bolded out Stakeholder weights came to same result 11

12 Conclusions Current status was not preferred by any sector Realistic measures identified to improve ecological conditions Ecological restoration beneficial for other sectors as well Uses including fishery, recreation and even agriculture was possible under increased hydraulic connectivity For higher connectivity options, additional measures to secure drinking water production recommended Case study shows importance of floodplain restoration to provide multiple use green infrastructure 12

13 Acknowledgments Austrian Science Fund (grant: P11720 bio, P19907, P22978), ProVision ( /05), bmwf, BMLFUW, bmvit, EU FP7, Life Via Donau, Government of Lower Austria, Vienna MA22, MA31, MA45, MA49, OEN, IAD and Nationalpark Donau-Auen THANK YOU!

14 Results: Most Preferred Options Borda Group Compromise: Based on SAW Rankings: OPEN2 with Drinking Water Production This option was preferred by the majority of management sectors Based on TOPSIS Rankings: OPEN1B with Fishery This hydraulic option provided the shortest distance to the ideal solution OPEN2 with Drinking Water also scored close to the OPEN1B with Fishery

15 Isolation Data: 31 management options 6 hydraulic options for 5 use-scenarios including the Current DAMMED UP Status Ecological Development OPEN1A OPEN1B_SILTATI ON OPEN1B OPEN2_SILTATIO N OPEN2 Drinking Water Production Recreation Agriculture Fishery Full re-connection

16 Data: Management Sectors and Their Preferences OPEN1A Dammed Up OPEN1B with Siltation OPEN1B OPEN2 Current Status OPEN2 with Siltation

17 Loss of aquatic habitats klein groß small large Aquatic Aquatische & semi-aquatic und semiaquatische areas rel. to Flächen 1938 rel. zu (%) 1938 (%) Key driver river regulation 17