Natural Flood Management: Examples

Jenny Mant

Current Situation

• 15th May the EC science for environment policy announced:

Extreme and catastrophic floods in Europe, such as those seen in 2013, currently occur approximately once every 16 years, but this may increase to once every 10 years by 2050 …….. suggests that annual average economic losses caused by extreme floods could reach almost five times higher than 2013 values. (estimated at 23.5b euros/yr across Europe).

• Need to working with natural process and build in resilience to climate change

River Isar, Munich ‘The plan’

• Flood control via set back

• Ecology and fish passage

• Recreation and increased access

• Cost 35m Euros

• Completed 2011 (10 years)

• State funding with public consultation

The History

• 1995-2000, working group ‘Isar-Alliance’ with public input into the design

• 2000-2011, 7 sections: one completed every 12 months with total of 8km

-Contaminated sites and removal of debris from WWII (7m Euros)

-Flood protection, public beach, bank re-grading, weir removal, riparian planting and installing water quality improvement systems (28m Euros)

Ritobacken Brook, Sipoo, Finland • Address flood risk and maintenance issues

(both poor drainage and unstable banks)

• Create a 2 stage channel (800m) by evacuating flood terrace so increase flood capacity

• Cost 15,000 Euros

• Date 2010

• Delivered through the regional environmental authority with a consultant and the Aalto university

River Vidǻ, Tønder, Denmark

• Flood risk in urban centre, fish passage (2 m high weir) with need to maintain cultural heritage at site (subsidence at millpond)

• Funded by EU Life+ ( restoring habitat for Houting)

• Cost 1.37M Euros

• Partners – Danish Nature Agency and the local authority

Key Points

• Millpond and river separated (sheet piling, broad crest weir)

• Floodbanks set back

• Sluice gates and fish ladder removed

• Gravel riffles and resting area backwaters incorporated along with otter pass

• New access point for rowing club

• 700m wetlands for wider nature corridor

River Valency, Boscastle • 300m and completed in 2007

• Cost part of whole scheme

• Reduce flood risk whilst still enabling natural processes to operate and to provide an aesthetic outcome

Function and landscape

Craigie Burn (flood prevention) or ecological deterioration?

• Enhance habitat

• Urban aesthetics

• Low flows

Milton Keynes Floodplain Forest

• Gravel extraction (Hanson aggregates)

• 50 ha (approx 2000m)

• Cost 1.2m Euros

• Other partners: Council, Parks Trust, Scott Wilson

• Area suffers from poor water quality, biodiversity, landscape and flood risk

Key Elements

• Lower the floodplain by 1.27m

• Provide 460,000 cubic meters of flood storage

• Carry out a phased approach

• Started in 1994 (proposal) and contractors still on site.

• There has been significant consultation and a residents committee set up.

How do we see our Riverscapes today?

•For wildlife benefit •For community benefit •For flood risk

Multiple benefits: society & funders

R. Quaggy -hydraulic efficiency Return of form and function

Ecology and biodiversity and access to wildlife Teaching and education

Public use and safety

• 89% park improvement

• 56% less anti-social behaviour

Natural flood storage