reducing the risk of embankment failure under extreme conditions mark morris hr wallingford impact...
TRANSCRIPT
Reducing the Risk of Embankment Failure Under
Extreme Conditions
Mark MorrisHR Wallingford
IMPACT Project WorkshopWallingford, 17 May 2002
Overview
• Project objectives
• The need for this project
• Scope of work
• Programme of work
• Interaction with other initiatives
• Example issues
• Key points
How does this project contribute?
Earlier presentations showing approach to flood risk management in the UK
Tiered approach:
High Level Strategy
Intermediate Level ‘Planning’
Detailed Level ‘Doing’
EA / DEFRA Approach
Interaction with other initiatives
Embankments
(Fragility curves)
Supporting actions (training, dissemination, R&D etc.
The need for this project
Reducing the risk of embankment failure...
• Over 35,000km of flood defence embankments in England and Wales
Embankments can become less effective or may have performed less effectively:
– greater loading than designed / managed to withstand
– changes to required SoS or function
– deterioration from intended condition (as constructed or maintained)
– lack of relevant data upon which to design or manage
• Particularly relevant wrt loading under climate change
The need for this project
Reducing the risk of embankment failure...
The need for improved guidance on design & management of embankments confirmed via range of sources including:
• discussion with practitioners & researchers
• examination of science base
• examination of current practice
and through DEFRA / EA R&D programme via
• CAs in fluvial, coastal defences and O&M
• Observations from the Autumn floods (2000)
Scope of work
Reducing the risk of embankment failure...
What are the Key Goals?
Aim: To develop a systematic approach to the design & management of flood embankments
Purpose: To gain a significant improvement in the competence of defences and their
performance (benefit cost)
Process: A risk based framework for their design, inspection and maintenance (relating to potential mechanisms and consequences of failure)
Scope of work
Reducing the risk of embankment failure...
Specific specific objectives include:
– Issues affecting embankment integrity
– Current good practice
– Review of relevant science, engineering, technology base
– review of DEFRA, EA, European R&D projects
– review with practitioners / researchers to assess potential future advances
– specific issues driving future embankment related R&D
– identification of potential needs, initiatives, outputs leading to a list of priority projects
– guidance on current best practice
Scope of work
Reducing the risk of embankment failure...
Deliverables:
• A risk based framework for their design, inspection and maintenance (relating to potential mechanisms and consequences of failure)
• Review of the science base (literature / project review)
• Review of current practice (best practice)
• Prioritised future programme for DEFRA / EA R&D (including project specs, priority areas, quick start opportunities)
• Mid review workshop
Programme of work
Reducing the risk of embankment failure...
Jan 2002
Jul /Sep 2002
Oct 2002
Project WorkshopIMPACTWorkshop
Initial Consultation Review
Secondary consultation Review
Literature andProjectReview
Conceptual FrameworkDraft findings
Additional Consultation & Review via
IMPACT Project R&D,
Partners & Contacts
ReviewFurther specific consultation
Final recommendations:Practice / training / dissemination,R&D programme etc.
Continued review
(IMPACT) and
consistency with R&D Findings
Interaction with other initiatives
Reducing the risk of embankment failure...
• DEFRA / EA initiatives
– Risk, Performance, RASP, MDSF etc.
• European / International initiatives
– e.g. IMPACT
– e.g. Dutch, German, Belgian, US + experience
• Research networks
– e.g. UK Coastal zone networks
EA / DEFRA Approach
Interaction with other initiatives
Embankments
(Fragility curves)
Supporting actions (training, dissemination, R&D etc.
The challenge
Wide ranging issues...
The project requires assessment and pulling together a very broad range of issues covering:
• Types of embankment
• Issues relating to construction, design, maintenance, operation, performance, failure, emergency response….
• Drawing on experience from across disciplines
– design, O&M, etc.
– hydraulics, soil mechanics, structures
The challenge
Some example issues...
• What is best practice for vegetation management to ensure best performance?
• What performance is required?
• What design standards should be followed?
• What material specification should be used for new embankments?
• How will my breached embankment respond during the next high tide?
– How quickly will it grow?
– How should I repair this breach
The challenge
Some example issues...
• How can I assess the integrity of X000km of flood embankment? Can I focus efforts?
• How can I monitor the condition of my embankments?
• Can I raise my embankment without undue settlement? What allowance should be made?
• How can I protect my embankment against erosion?
– How far back should I set my embankment from a meandering river channel?
• How do I prevent 3rd party impacts on ‘system’ performance when defences are in mixed ownership?
The challenge
Some example issues...
• When is seepage through my embankment a problem?
• What impact will climate change have on my embankment?
• How will my embankment perform under increasing loading?
• What overtopping can my embankment withstand before failure? What should it be designed to withstand? How will this be affected by vegetation, animal burrows, wind and wave action?
The challenge
Some example issues...
• Where in my X000km of embankment will my defence system fail?
• Where should I focus my limited resources?
• What balance should I make between capital works and maintenance works?
etc etc etc!
Some Key Points...
Reducing the risk of embankment failure...
• Project focuses on embankment:
– ‘Issues’ in all stages (design, O&M, performance etc.)
– Supporting needs / R&D
– Prioritised actions - from training & dissemination through to specific R&D
• Not undertaking specific R&D, but identifying, prioritising & developing specs for such work (supporting a risk based approach)
• Welcome feedback on perceived needs / issues (see questionnaire)
• Workshop will be held in July / Sept
Mark Morris: [email protected]