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Natural Flood Management
Ann Skinner FCIEEM, C Env, C Ecol and Chris Uttley, Stroud District Council
CIEEM lunch time webinar, February 24th 2017
Working with natural processes to manage flood risk, benefit people and wildlife
Natural flood management
Floodplain connected with
channel/sea with high degree of freedom
Floodplain connected with
channel/sea with high degree of control
Floodplain disconnected from channel/sea, except
in exceptional circumstances
Natural floodplain/coastal
zone (minimal intervention)
Managed re-alignment, upland grip blocking, re-
meandering
Wet washlands, balancing ponds, regulated tidal
exchange, swales
Green roofs, permeable paving
Flood walls, pump drainage, dry
washlands
Natural flood risk management
Soft engineering/
restoration
Mitigated hard engineering
Hard engineering
Heavily
m odified r iver
or c oa s tline
(Semi) natural
r iver or
c oa s tline
- Natural Processes +
Ad
ap
ted fro
m R
SP
B
…taking action to manage flood and coastal erosion risk by protecting,
restoring and emulating the natural regulating function of catchments,
rivers, floodplains and coasts
Woodland & gully planting
Blue-green infrastructure (eg SUDS) in urban areas
Remove redundant in-stream structures
Two-staged channels
Large woody material dams
Sand dunes & shingle
beaches as natural
defences
Upland grip blocking & reduced
stocking densities Shelter belts and
hedgerows
River & floodplain
restoration Floodwater storage in
wetlands/washlands
Sand engines
Changes in land
use/management - arable
reversion, buffer strips,
rural sustainable drainage
& cover crops
Water level
management
Setting back flood
embankments
Managed realignment of coastal
defences & salt marsh creation
Examples of natural flood management
The natural flood management journey
• PAG1 2001
• Floods Directive 2007
• Pitt Review 2008
• Defra multi-objective pilot projects
• Flood Risk Regulations 2009
• Flood & Water Management Act 2010
• National FCERM Strategy for England 2011
• EU Natural Water Retention Measures 2014
• EA position statement 2015
Alkborough Flats, Humber Estuary
Barriers identified by stakeholders
Washing topsoil down the drain – January 2014
Absorption
Run-off
Pickering – slowing the flow
Pickering
Large woody material
Floodplain planting
Buffer strips
Upland grip
blocking
What else do we want? Floodplain meadows!
KILLER FACT: floodplain meadows store/process sediment-bound P & N, converting excess nutrients into an agriculturally valuable crop that supports pollinating insects
Steart natural flood management scheme
• 250 hectares of new intertidal and wetland habitat
• Contributes to the protection of 100,000 properties
• Value of property protected - £5 billion
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
Wave
energ
y
Saltmarsh width
Developing the Evidence Base
Evidence
Directory
Opportunity
Maps
Catchment &
Coastal Labs
Beavers!
• 2.8 ha fenced site in N. Devon
• 2 beavers introduced 2011, now 5
• Dramatically changed site from small
first order tributary running through
wet woodland, to a diverse mosaic
wetland environment
~ Darling, so how many
properties are we protecting
from flooding?
Chris Uttley
Project Officer
Stroud Rural Sustainable Drainage Project.
Three years of practical Natural Flood Management in the Stroud Valleys
Data, Desk & field work
OS Map
Surface water flood maps
Aerial photo
Geology
Alot of walking and ground-truthing
Stroud Frome (Upper catchment = 200km2)
How does NFM work?
3 primary mechanisms: 1. Increasing Roughness (Physically
impeding flow in channel, diverting onto flood plain)
2. Attenuating flows (insoils, channel, floodplain)
3. Infiltrating flows (tree planting, soakaways, spreads)
What is the Stroud model of Natural Flood Management?
Large number of small
interventions dispersed around
catchment, low risk, low
Cost!
La
UNCLASSIFIE
D
UNCLASSIFIE
D
What have we built and done?
280+ Interventions (170 Large Woody Debris leaky dams in 4 tributaries)
21% of the Stroud Frome catchment discharges through NFM features.
What will this achieve for environment?
1. Slow down the peak flood flows
travelling down the valleys
2. Slow down transportation of sediment and soil.
3. Provide habitat diversity
4. Restored natural stream processes
5. Increased infiltration to groundwater
Lessons Learned from Stroud
1. Keep it local & community lead 2. Build capacity in landowners, local contractors &
volunteer groups 3. Build small and many rather than few and large. 4. Start as upstream as possible 5. Don’t wait for perfect data before building. Focus on
low risk, certain wins to gain confidence. 6. Don’t focus on volumes, heights and measurements.
Where can I find more information?
• EU Natural water retention measures http://nwrm.eu/
• SEPAs natural flood management handbook https://www.sepa.org.uk/media/163560/sepa-natural-flood-management-handbook1.pdf
• Environment Agency https://www.gov.uk/government/publications/working-with-natural-processes-to-reduce-flood-risk-a-research-and-development-framework
• River Restoration Centre http://www.therrc.co.uk/Workshops/RRC/2014_A_NFM/NFM_SR1.pdf
• Stroud District Council
• https://www.stroud.gov.uk/rsudsfilm
• https://www.stroud.gov.uk/nfmtechnicalfilm