C imate t C h C ange g a nd d t he F u F ture o f U ban D r D ainage g i n t he U K D vid i B a B lm l fo f r o th t, h

Transcription

1 Climate Change and the Future of Urban Drainage in the UK David Balmforth, Technical Director, MWH David Balmforth, MWH

2 2007: the wettest summer on record Long period of wet weather during the summer months Overlaid by periods of intense rainfall Very high localised run-off Three events > 1 in 100yrs

3 Major urban inundation

4 Some of the flooding was no surprise

5 Key infrastructure affected

6 Lessons learnt Water flows downhill It accumulates in low spots Drainage and sewerage systems overwhelmed early in the storm Most of the flood water is conveyed above ground Roads and paths are not designed to act as flood channels No space for water to be conveyed or stored Flooding is indiscriminate Buildings are not designed to withstand floods The flooding came as a surprise but it shouldn t have!

7 The Potential Impact of Climate Change Rainfall intensities could increase by up to 40% by 2080

8 The Potential Impact of Climate Change properties assessed + 40% rain + 130% properties affected + 200% flood damage + 40% flow + 100% flood volume

9 The Potential I mpact of Climate Change Average annual damage for all of the UK ( billion) assuming flood-management approach and expenditure remain unchanged - present day and 2080s 30 billions Intra-urban Fluvial and coastal 5 0 Present day World Markets National Enterprise Local Ownership Global Sustainability

10 The Consequence of Traditional Solutions Solution costs rise 4x to 8x

11 Understanding the Needs Glasgow m 3 watercourse overspill 1200 m 3 urban overland flow 800 m 3 public sewerage system

12 I n t e g r a t e d M o d e llin g

13 Integrated Measures Source Maximise capacity of the drainage system Pathway Improve resilience Limit flows entering drainage systems Manage flows above ground Receptor

14 Limiting the flows entering drainage systems Retrofit Infiltration Basin Source control and bio- retention

15 Limiting the flows entering drainage systems Keeping surface water on the surface Storage basin and wetland

16 Maximising drainage capacity Disruption Tackling flooding hot-spots

17 M a n a g in g flow a b ove g rou n d New development with flood pathways and storage areas identified Temporary Storage Groups of housing (clusters) Direction of minor system flow Direction of major system flow Overland flow from outside of area Road layout Minor system storage

18 Designing flood paths and sacrificial storage Road acting as flood channel spilling to woodland

19 Protect Critical Infrastructure Temporary flood defence

20 Flood R e sist a n t D e sig n Tilting flood dam Homes on stilts Retro-fit flood gate

21 Flood Resilient Materials Changing the Building Regulations

22 Colla b ora t ion Be t w e e n St a k e h old e rs Sharing data and knowledge Developing common approaches Delivering integrated solutions Building capacity and capability

23 Integration across the professions This is the way we always did our drainage planning

24 Integration across the professions Then one day we looked around

25 Integration across the professions From then on we played happily together...

26 Conclusions Conventional solutions are unsustainable Shift from defence to resilience Recognise the complexity of the urban flooding Use integrated models to understand what needs to be done Structure interventions: source/pathway/receptor Ensure stakeholders are properly engaged

27 Climate Change and the Future of Urban Drainage in the UK David Balmforth, Technical Director, MWH David Balmforth, MWH