structural approaches to managing flooding and flood...

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Structural approaches to managing flooding and flood defence management

Dr Simon McCarthy

PRS4526 Flood Risk Management 2014/2015

Learning outcomes

• An understanding of the role of flood defences in the wider FRM

• Appreciation of the range of different types of defences and their roles

• An understanding of maintenance issues and related defence conditions

• An appreciation of the importance of information system in the management process


Lecture overview

The Concepts – UK case

Structural Approaches – not engineering construction

(CIRIA guidance)

Maintenance – management approach

Seminar – condition grading and Lower Thames Scheme


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The Concepts

Flood Management infrastructure - concepts



Source – Pathway – Receptor – Consequence (S-P-R-C) Model



Risk based FRM Decisions

• Rely on Appropriate Quality S-P-R-C Data e.g.

o Gauging flows (Source)

o Asset condition/Crest Levels (Pathway)

o Land Use (Receptor)

o Damage to Property, people and the environment (Consequence)

Gauging Venice & Vicenca Italy

Defending what?


A flooded Cockermouth high street in 2009, Cumbria. Photo by: Owen

Humphreys/PA (Source: the Guardian) Aerial view residential flooding - Cockermouth, Cumbria © Environment Agency

Receptor & Consequences

Residential and businesses

People and livelihoods

Social and Economic disruption

Loss of life Flooding river in Cornwall, 2010 (Source: www.onegeology.org )

Agriculture

http://www.onegeology.org/

Electricity Gas

Water supply Wastewater

Utilities infrastructure and related services

Water supply reaches Gloucestershire after floods in

2007 ©BBC

Photo by Andy Rain/EPA (Source: The Guardian)

Waste water evaporation pits in Wyoming © Ted

Wood/ Corbis (Source: The Guardian)

Photo PA (Source: The Telegraph)

Defending what?


Schools Hospitals

Emergency

services

Other critical

infrastructure

Flooded School - Stockton-on-tees in Durham © Environment Agency

© Environment Agency

Worthing Hospital, June 2012 © Daily Mail

British Airways aircaraft takes off at a wet and rainy

Heathrow airport in London, December 2013 © Andy

Rain/EPA (Source: the Guardian)

Defending what?


Public building &

services and

Staff / personnel

Road networks Rail networks

Telecommunications

Flooding in Workington, November 2009 © Environment Agency Saltcoats in Scotland © PA (taken from www.telegraph.co.uk)

BT Tower image (Source; TimeOut London)

Defending what?


Networks

Issues of Responsibility – who owns the flood defence


“A flood defence asset is defined as an asset that would, by its failure, increase the LIKELIHOOD of flooding from (main) river or the sea to people, property and infrastructure”

Property excludes gardens but includes agricultural land and Habitats Directive Sites

Infrastructure includes Roads, Public Rights of Way and Railways

Environment Agency UK definition

How are the responsibilities defined?

Who has responsibility for non main river and surface water / ground

water / sewer flooding?

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Structural Approaches


Flood Characteristics

Occurrence of the hazard event

- Speed of onset: sudden, slow or creeping

- Frequency or return period

- Size

- History

Impact

- Area: Focused or diffuse

- Intensity

- Immediacy and duration

Is defence infrastructure appropriate or possible?


Upper Trent Systems Tamworth System

Flood Risk Management System


River

Sea and River

Sea

Weirs Culverts

Debris

screens

Channels

Embankments

Structures

Revetments

Flood gates

Barriers

Bridges

Demountables

Outfalls

Flaps

Sluice

Property

Level

Protection

Seawalls

Beaches

Groynes

Dunes

Saltmarsh

Outfalls

Defence Infrastructure Components


Flood Risk Management System

Defence Components Approaches

Flood Storage

Weirs

Culverts

Debris

screens

Embankments

Structures

Outfalls

Flaps

Sluice

Flood gates

Barriers

System

Sea Defence

Seawalls

Beaches

Groynes Weirs

Embankments

Structures

Bridges

River Defence

Approach & System

ONLY AS STRONG AS

THE WEAKEST LINK

River


Weir System Vicenca Italy

Culvert Cringle Brook

Channel Doncaster

Channel Vicenca

Italy Trash / Debris screen

Basingstoke

Sea and River


Sluice gate flood storage

area Todmorden

Embankment Millward

flood storage area

Flap Valves Northampton Embankment River Don Revetment Santos Brazil

Revetment Thames


Sea and River

Structure Wood pile

Thames

Structure brick & mastic

Northampton

Structure Steel pile

Flood Gates & Barriers


Sea and River Demontables

Brick design Vicenca


• Who is protected?

• Responsibility for building?

• Access to build in emergency?

Sea and River



Property

Level

Protection (PLP)

Doncaster

Thames

• Standards

• Flood type

• Operation

• System issues

Sea


Beach and Groyne Ferring

Sea wall Brighton

Dune system

Burnham

Outfall Santos

Brazil

Salt Marsh Salcott

Additional FRM ‘defence’ Approaches


Managed Re-Alignment

(Humber estuary)

Cambridge reed planting

Farming practices

Flood storage

Soft / green defences

Sustainable Urban Drainage (Week 22)

Dredging

Diversion channels

Pumping

Managed re-alignment

River restoration

Lode pumping station

River Restoration techniques


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Maintenance

Maintenance Approach UK


Quantify and Record

• All flood defences: Location, Type, Construction

• Their importance in the system / the system nationally

• Target condition

• Current condition

Provide a single easily accessible and definitive store for all

data on flood and coastal defences with the appropriate tools to

allow manipulation of that data in order that we can understand

flood risk better and so make better informed decisions about

managing defence assets. (Environment Agency)

BUT

If Data Quality and Consistency is poor or poor and not clearly

recognised as such then value to decision making is diminished

and even detrimental

Describe the location


Describe the defence


Channel Side 2

Inward Face 1

Inward

Face 2

Berm 1

Inward Face 3

Flood Crest



Outward

Face 1

Berm 2 0utward

Face 2 Berm 3

Outward Face 3



Flood Level

MHW

MLW

Sea Bed Channel Side 1

Channel Side 2

Inward Face 1

Berm1

Inward Face 2

Flood Crest

Outward Face 1

Berm 2

Outward Face 2

Berm 3

Outward Face 3

• Weighting factors


Full classification for any combination of defence



Grade Rating Description

1 Very Good Cosmetic defects that will have no

effect on performance

2 Good Minor defects that will not reduce the

overall performance of the asset

3 Fair Defects that could reduce performance

of the asset

4 Poor Defects that would significantly reduce

the performance of the asset. Further

investigation needed.

5 Very Poor Severe defects resulting in complete

performance failure

Describe the condition • Visual inspection. Frequency dependant on risk matrix.

• Every element of every defence

• Description and pictures for every element for consistency

• System failure not related to length or type defence

Defended Height and Design Standard


Boston UK

Burnham splash wall

Access Point

Forecasting Failure


Narrow turf embankment

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

-1.25 -0.75 -0.25 0.25 0.75

Negative freeboard [m]

Pro

ba

bilit

y o

f b

rea

ch

[-]

CG1

CG2

CG3

CG4

CG5

8m wide

Fragility Curve

Environment Agency / Defra (2009).

Describe the risk: Target Condition


HIGH e.g.

LUB A/B or

Habs Regs

sites

HIGH HIGH HIGH HIGH

MEDIUM e.g.

LUB C, or

SSSI's

LOW MEDIUM MEDIUM HIGH

LOW e.g. LUB

D/ELOW LOW LOW MEDIUM

Low-Negligible

risk to life.

Medium- Time

likely to be

available for

evacuation in

event of failure.

High- Little

warning of

flooding to

residential or

commercial

property

Very High- Little

warning of failure.

Possible loss of

life/major injury.

Sudden impact to

vulnerable groups.

e.g.

small/medium

watercourses,

defences

protecting

agricultural land,

Category D FSRs.

e.g. significant

watercourses

without raised

defences,

diversion

channels,

Category C FSRs,

etc

e.g raised

defences.

e.g. very

significant raised

defences or

category A/B FSRs.

Very significant

structures.

Imp

act

of

flo

od

ing

Analysing the Consequence of Failure of an FRM System

Potential Impact on People from System Failure

1 2 3 4

5 6 7 8

9 10 11 12

Environment Agency / Defra (2009).

Defence Record


Example UK Data Management System


Historic example of the Environment Agency

National Flood and Coastal Defence Database ( © Environment Agency)

Maintenance & Inspection


Visual impeded Northampton

Access Wick St Lawrence

Animal burrows

• Regular visual inspections

• Engineering inspections if required

• Post event inspections


Cleared? River Wye Functionality

Romsey Danes

Sea defences

Clevedon & Swanscombe Rotation

Wick St Laurence

Lock Gates Cambridge

Crest erosion Kelvedon

Maintenance & Inspection

Blockage Doncaster

Culvert Inspections


Culvert blockage West Garforth

Integrated Urban Drainage Pilot Newsletter 2007

Inception Report 2007

Maintenance vs Environment


Margin habitat Poor Margin habitat


Building in Community Ownership

Visibility

Engagement

Learning outcomes

• An understanding of the role of flood defences in the wider FRM

• Appreciation of the range of different types of defences and their roles

• An understanding of maintenance issues and related defence conditions

• An appreciation of the importance of information system in the management process


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Seminar

• Environment Agency / Defra (2009). Guidance on determining asset deterioration and the use of condition grade deterioration curves. Product Code: SCHO0509BQAT-E-P

• Environment Agency. (2008) Condition Assessment Manual (CAM). Environment Agency: Bristol.

• Ciria (2014). International Levee Handbook. http://www.ciria.org/service/ILH download

• Hall, J.M., Hockin, D.L., Ellis, J.B. (1993). Design of flood storage reservoirs. CIRIA

• Penning-Rowsell, E.C., Johnson, C., Tunstall, S., Tapsell, S., Morris, J., Chatterton, J., and Green, C. (2005) The Benefits of Flood and Coastal Risk Management: A Manual of Assessment Techniques, Middlesex University Press, London.


References

http://www.ciria.org/service/ILH download

http://www.ciria.org/service/ILH download


Slide references– Licenses Slide License/Source

5/6 a. FLOODsite (2009) Flood risk assessment and flood risk management. An introduction and guidance based on experiences and

findings of FLOODsite (an EU-funded Project. Deltares / Delft Hydraulics, Delft, the Netherlands. Publically available Report Number

T29-09-01 Ed.2, available at: http://www.floodsite.net/html/publications2.asp?documentType=1&Submit=View

b. Diagram redeveloped learning from Parker, D.J. (ed.), 2000. Floods. Volumes I and II. Routledge, London

7 Photographs by Simon McCarthy as part of the WeSenseIt project Italy.

12 Photographs by Simon McCarthy as part of the WeSenseIt project Doncaster culvert & personal picture Thames.

16 Maps adapted from teaching materials provided by and permission given to reproduce by John Chatterton

19 Photographs by Simon McCarthy as part of the WeSenseIt project: Doncaster and Vicenca

Photographs by John Chatterton private collection Cringle and Basingstoke

20 Photographs by Simon McCarthy as part of the WeSenseIt project and private collection : Don, Santos and Thames

Photographs by John Chatterton private collection Northampton, Millward and Todmorden

21 Photographs by Simon McCarthy as part of the WeSenseIt project and private collection : Northampton and Thames

Photographs by John Chatterton private collection flood gates and structure steel

22 Photograph by Simon McCarthy as part of the WeSenseIt project Italy

23 Photographs by Simon McCarthy as part of the WeSenseIt project and private collection : Doncaster and Thames

24 Photographs by Simon McCarthy as private collection : Santos and Brighton

Photographs by John Chatterton private collection Burnham and Ferring

Photograph Salt marsh creative commons Matthew Baker

25 Photographs by John Chatterton private collection flood gates and structure steel

26 http://thebritishgeographer.weebly.com/floods-and-river-management.html

29-34 Training materials created by John Chatterton and reproduced with permission. Photographs by John Chatterton private collection

http://www.floodsite.net/html/publications2.asp?documentType=1&Submit=View

http://thebritishgeographer.weebly.com/floods-and-river-management.html








Slide references– Licenses Slide License/Source

35 Photographs by John Chatterton private collection

40 Photographs by Simon McCarthy private collection

Photographs by John Chatterton private collection Northampton, St Lawrence, animal burrows



44 Photographs by Simon McCarthy as part of the WeSenseIt project: Doncaster - engagement

Visibility: Nar flood storage reservoir (Norfolk); attribution Martin Pearman. This file is licensed under the Creative Commons

Attribution-Share Alike 2.0 Generic License. Available from http://commons.wikimedia.org/wiki/File:Nar_Flood_Storage_Reservoir_-

_geograph.org.uk_-_1224129.jpg

Visibility: Richard Allaway Frankwell Flood Defences

https://www.flickr.com/photos/geographyalltheway_photos/2996432907/in/photolist-5yMv7k-5yRGY1-5yRJb3-5yRLrs-5yMuy2-

5yMsRe-5yRQi7-5yMtbp-5yMrEi-5yRPYd-5yRRnQ-5yMqGV-5yMx42-5yRQCN-icLGya-6NwBpX-ac5Ucz-iV4bsC-iV5Wnm-iV3nhz-

ezCiEo-edDJWC-bTLNag-4W9kHN-bERZjs-81ENa4-bGQxmc-8SAG5C-vgbm6-bNR1Ma-knNHpC-bCFjo7-ivZP5v-3uStBq-8JeZkw-

xaPuT-xaPuU-8JeYnE-8JbTzF-ckGs29-7KR9vw-io2c2f-apsemw-9bhWh2-dE6zvr-dE6Bvg-dEbZ9J-dEbYKh-dEbYjj-dE6AP8

20 Photographs by Simon McCarthy as part of the WeSenseIt project and private collection : Don, Santos and Thames

Photographs by John Chatterton private collection Northampton, Millward and Todmorden

21 Photographs by Simon McCarthy as part of the WeSenseIt project and private collection : Northampton and Thames

Photographs by John Chatterton private collection flood gates and structure steel

22 Photograph by Simon McCarthy as part of the WeSenseIt project Italy

23 Photographs by Simon McCarthy as part of the WeSenseIt project and private collection : Doncaster and Thames

24 Photographs by Simon McCarthy as private collection : Santos and Brighton

Photographs by John Chatterton private collection Burnham and Ferring

Photograph Salt marsh creative commons Matthew Baker

25 Photographs by John Chatterton private collection flood gates and structure steel

26 http://thebritishgeographer.weebly.com/floods-and-river-management.html

29-34 Training materials created by John Chatterton and reproduced with permission. Photographs by John Chatterton private collection

http://commons.wikimedia.org/wiki/File:Nar_Flood_Storage_Reservoir_-_geograph.org.uk_-_1224129.jpg





https://www.flickr.com/photos/geographyalltheway_photos/











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