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