Reducing the Risk of Embankment Failure Under Extreme Conditions Mark Morris HR Wallingford IMPACT Project Workshop Wallingford, 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 Workshop IMPACT Workshop Initial Consultation Review Secondary consultation Review Literature and Project Review Conceptual Framework Draft findings Additional Consultation & Review via IMPACT Project R&D, Partners & Contacts Review Further 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: