Integrated Flood Risk Analysis
and Management Methodologies
Grass Erosion on Embankments
AN OVERVIEW
Date
April 2008
Report Number
T04-08-03
Revision Number
9_1
Task Leader
HR Wallingford
FLOODsite is co-funded by the European Community
Sixth Framework Programme for European Research and Technological Development (2002-2006)
FLOODsite is an Integrated Project in the Global Change and Eco-systems Sub-Priority
Start date March 2004, duration 5 Years
Document Dissemination Level
PU
Public
PP
Restricted to other programme participants (including the Commission Services)
RE
Restricted to a group specified by the consortium (including the Commission Services)
CO
Confidential, only for members of the consortium (including the Commission Services)
Co-ordinator:
HR Wallingford, UK
Project Contract No: GOCE-CT-2004-505420
Project website:
www.floodsite.net
PU
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
DOCUMENT INFORMATION
Title
Lead Author
Contributors
Distribution
Document Reference
Erosion of Embankments - A Review of Current Knowledge
Marta Roca Collell, Mark Morris
Georg Petersen
Public
T04-08-03
DOCUMENT HISTORY
Date
04/04/08
16/3/09
Revision
1_0
9_1
Prepared by
MRC
Mark Morris
Organisation
HRW
HRW
Approved by
Notes
Initial drafting
Final edits / formatting
ACKNOWLEDGEMENT
The work described in this publication was supported by the European Community’s Sixth Framework
Programme through the grant to the budget of the Integrated Project FLOODsite, Contract GOCE-CT2004-505420.
DISCLAIMER
This document reflects only the authors’ views and not those of the European Community. This work
may rely on data from sources external to the FLOODsite project Consortium. Members of the
Consortium do not accept liability for loss or damage suffered by any third party as a result of errors
or inaccuracies in such data. The information in this document is provided “as is” and no guarantee or
warranty is given that the information is fit for any particular purpose. The user thereof uses the
information at its sole risk and neither the European Community nor any member of the FLOODsite
Consortium is liable for any use that may be made of the information.
© FLOODsite Consortium
T04-08-03_ErosionofEmbankments_v9_1.doc
ii
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
SUMMARY
This report details review work undertaken as part of FLOODsite Task 4 – Understanding and
prediction of failure modes, Activity 3 – Front and rear face erosion, Action 4 – Identification of gaps
on erosion.
Erosion of the surface protection of vegetated fluvial and coastal embankments is the first step towards
the breaching of an embankment. A detailed knowledge of the driving forces, factors and mechanisms
is necessary to understand the processes and is a key element in managing failure risks.
Past and present research on the erosion of surface vegetation has been reviewed and this report
provides a brief summary along with listings of relevant projects and research findings. Based upon
these results, gaps in knowledge were identified and research needs described.
T04-08-03_ErosionofEmbankments_v9_1.doc
iii
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
T04-08-03_ErosionofEmbankments_v9_1.doc
iv
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
CONTENTS
Document Information........................................................................................................................ii
Document History...............................................................................................................................ii
Acknowledgement ..............................................................................................................................ii
Disclaimer .........................................................................................................................................ii
Summary ........................................................................................................................................iii
Contents ......................................................................................................................................... v
1.
Introduction ........................................................................................................................... 1
1.1
General framework.................................................................................................... 1
1.2
Aims and objectives .................................................................................................. 2
1.3
Structure of this report .............................................................................................. 2
2.
Summary of existing knowledge ........................................................................................... 3
2.1
Fundamentals about erosion resistance..................................................................... 3
2.2
Current and Recent knowledge sources .................................................................... 4
2.2.1 Research Projects......................................................................................... 4
2.2.2 Reference Institutions.................................................................................. 5
2.2.3 Journal Papers.............................................................................................. 6
3.
Recommended actions and initiatives ................................................................................... 7
3.1
Determination of time to failure................................................................................ 7
3.2
Vegetation management............................................................................................ 7
3.3
Develop a wider management framework linking vegetation type, management,
soil moisture, soil fissuring and soil erodibility ........................................................ 8
3.4
Improve basic knowledge and understanding of vegetation-erosion processes........ 8
3.5
Defining failure modes and mechanisms .................................................................. 9
3.6
Experimental and field data ...................................................................................... 9
3.7
Estimation of vegetation roughness ........................................................................ 10
4.
Summary and prioritisation of recommended actions ......................................................... 11
5.
References ........................................................................................................................... 13
Appendix 1: Current Research Details ............................................................................................. 15
Tables
Table 2.1 Selected research programmes and projects showing main research topic areas............ 4
Table 4.1. Summary and prioritisation of recommended actions................................................... 11
Figures
Figure 1
General framework of vegetated embankments.............................................................. 2
T04-08-03_ErosionofEmbankments_v9_1.doc
v
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
T04-08-03_ErosionofEmbankments_v9_1.doc
vi
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
1.
1.1
Introduction
General framework
For the engineer, vegetation is a highly variable material hence calculations with vegetation will carry
a high degree of uncertainty.
The type and condition of vegetation on an embankment can have both positive and adverse effects on
embankment performance. Embankments considered within this report comprise sea, river and
reservoir flood defences.
Why is there vegetation on an embankment?
In practice it is important for an embankment to maintain integrity and stability up to (and preferably
beyond) the maximum design load conditions. To cope better with these loads, the surface layer is
typically protected by different means, including vegetation.
As well as the main goal of providing surface protection, the design of embankments may also
consider the creation of a more natural river environment and habitats and to promote recreational
areas for the surrounding population. In this role, the selection of appropriate vegetation is
fundamental.
What is the influence of vegetation?
Vegetation can have a number of effects beyond the provision of resistance to erosion. Vegetation
may affect the conveyance of the river and the performance / deterioration processes of embankments.
Erosion resistance
Vegetation increases the resistance of the embankment surface to erosion because it reduces flow
velocity and shear stresses near to the embankment soil surface. Vegetation can also provide direct
surface protection to erosion if it is long and flexible enough to lay and cover the soil surface when it
is affected by a flow. Further protection from vegetation is provided by the root mat which develops
below the bed surface of the embankment providing additional strength to the soil structure.
Conveyance
Conveyance is a quantitative measure of the discharge capacity of a watercourse. Water levels related
to a certain discharge are mainly influenced by the resistance to flow due to surface roughness. In
channel vegetation modifies the roughness surface depending on its type (flexibility, size, etc), the
season (the expected biomass and the percentage covered will vary during the year), and other factors
such as maintenance.
Deterioration
Vegetation can lead to embankment deterioration in several ways. One of the main types of
deterioration relates to changes in soil moisture. In certain soils, prolonged extraction of moisture by
plant roots can lead to desiccation and thus to cracking and seepage. Trees on an embankment can
also promote local erosion around its trunk causing narrowing of the embankment cross-section.
Ultimately, the failure of a tree and its roots could cause severe erosion of the soil. In addition, as
vegetation promotes the creation of habitats, it can also encourage burrowing within embankments by
vermin.
Management actions also affect the performance of vegetation. For example, the eventual strength of
the grass is governed by the management regime. Species that are not managed tend to have weak and
sparse roots which results in a grass layer far less resistant to erosion.
Figure 1 summarises the general framework of points highlighting how vegetation influences
embankment performance.
T04-08-03_ErosionofEmbankments_v9_1.doc
1
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
Motivations
•
•
•
•
Environmental issues
Surface protection
Recreational purposes
Spontaneously growing
Influences on
Erosion resistance
MANAGEMENT
Vegetated embankments
Conveyance
Deterioration processes
Figure 1
1.2
General framework of vegetated embankments
Aims and objectives
The objective of this review is to provide a brief overview of knowledge, and hence gaps in
knowledge, relating to erosion of embankment surface protection. The review does not repeat
literature reviews and work already done by others, but instead references these and forms a concise
overview of the current state of art, practice and, in particular, identifies where the gaps in knowledge
are and what needs to be done to address these.
1.3
Structure of this report
A summary of fundamental concepts about erosion resistance and existing research projects is
presented in Chapter 2. Recommended actions and initiatives are presented in Chapter 3 (taking into
account work done) and a suggested prioritisation of these actions is presented in Chapter 4.
Supporting material on Current Research Details may be found in Appendix 1.
T04-08-03_ErosionofEmbankments_v9_1.doc
2
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
2.
Summary of existing knowledge
This review does not repeat literature reviews and work already done but instead, references these and
forms a concise overview of the current state of the art to act as a base to identify where gaps in
knowledge exist and how these may be addressed.
A brief summary of key issues regarding erosion resistance is presented in Section 2.1. An overview
of recent and ongoing research projects is given in Section 2.2. In collating the information, outputs
from Actions 1-3 of FLOODsite Task 4 are also incorporated, along with past and present research
work undertaken in the UK, Germany, the Netherlands, the US and from EC and European national
research programmes.
2.1
Fundamentals about erosion resistance
The surface layer of an embankment needs to cope with a number of different conditions which can
occur solely or in combination with each other. Loading conditions, for which the intensity may vary
include:
• Wave breaking impacts on the exposed (seaward / river ward) front face:
• Wave run up on the front face
• Lateral flow currents along the front face
• Overtopping flows over the crest and down the rear (landward) face:
• Overflowing - when water levels rise above the crest level and flow passes continuously over the
crest
• Seepage flows through the embankment (developing into piping)
• Rapid drawdown, generating a risk from uplift pressures in the surface cover layers
In addition climatic factors have an effect on the embankment condition with, for example, rain and
sun leading to wetting and drying of the embankment, combined with frost and ice causing further
surface damage.
Erosion of an embankment occurs when bank material is displaced by the effect of these loads causing
friction, drag, lift and pressure forces. Erosion can occur on any exposed face, for example the front
face, inner toe, crest, rear face and outer toe.
The initiation and speed of erosion is controlled by the difference between loading forces and
resistance forces. Whilst the loading forces are dependent on the environmental conditions, the
resistance forces are dependent on the embankment design, its shape, type and size of materials used
and quality of work.
The erosion process generally starts when loading forces exceed the resisting forces of particles or
elements. As a first step, the resistant surface protection is attacked. Only when this fails does the
embankment itself starts to erode, which is normally a faster process than erosion of the surface
protection. Exceptions exist in the case of internal erosion where the soil matrix within the
embankment body is eroded and particles start migrating internally causing stability loss and voids,
eventually leading to piping.
The effect of repetitive loading and stress concentration around non-homogeneities in vegetation is
related with the concept of progressive collapse. It can be seen that vegetation (e.g. turf) can be
weakened by repetitive loading. Hence, discontinuous loadings as wave overtopping flow or wave
impact has the potential to generate a more critical condition than steady overflow.
T04-08-03_ErosionofEmbankments_v9_1.doc
3
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
2.2
Current and Recent knowledge sources
2.2.1 Research Projects
A considerable number of research programmes have been undertaken to improve knowledge about
breach initiation and development but only a few of these projects specifically consider the
performance of vegetation in cover layers. Some of the current or recent larger projects and
programmes are summarised in Table 2.1 below. A more detailed description of the projects and
research programmes is available through the summaries provided under Appendix 1.
Selected research programmes and projects showing main research topic areas
(x)
x
x
x
x
x
x
x
x
Laboratory tests
x
x
Large scale
models
x
x
Field data
x
x
x
x
Research approach
seepage/erosion
x
wave
overtopping
x
x
x
x
x
x
x
wave run-up
run-down
x
wave-impact
No specification
x
Failure modes/actions
General
Fluvial
x
x
PROJECT
EROGRASS
Engineering
tools…
FLOODsite
INFRAM
IPET
RIMAX
COMCOAST
Type of
vegetation
Coastal
Type of
dike
Grass
Table 2.1
x
x
x
x
x
x
x
x
x
EroGRASS (2007-2008)
EroGrass investigated risk-based design and understanding of failure modes for sea dikes and aimed to
enhance the limited information on erosion resistance of grass covered dikes and embankments. The
project comprised large-scale model tests on sea dikes with grass cover investigating the failure of
grass cover on the seaward side by wave impacts and wave run-up / run-down and failure of grass
cover on the landward side by wave overtopping. Aspects of this research was undertaken in
collaboration with research under FLOODsite Task 6 (Morris et al., 2009).
Engineering tools for safe, efficient hydraulic structures and channels (2008)
Improved methods for predicting earthen embankment erosion and failure, and development of
generalised hydraulic guidelines and tools for roller compacted concrete spillways used to protect
earthen structures from erosion and to increase discharge capacity. This will consider quantification
of the protective capabilities of vegetation.
FLOODsite Task 4 (2006-2009)
Understanding and predicting failure modes. This research collected existing information on defence
failure mechanisms and extended knowledge in a number of critical areas by reviewing current
international projects and detailed failure mode analysis on the basis of hydraulic model testing and
numerical modelling (Allsop et al., 2007).
Wave Overtopping Simulator (Infram - 2007)
A wave overtopping simulator was developed in response to the need to test wave overtopping
performance of grass covered dikes. A prototype was developed and tested by Infram as part of the
FLOODsite and ComCoast projects (van der Meer, 2006a). The simulator is placed on top of the
embankments and flow surges released to simulate wave overtopping processes. The performance of
grass and sub soil may be assessed through to destruction.
T04-08-03_ErosionofEmbankments_v9_1.doc
4
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
Studies were also undertaken into development of grass reinforcement to strengthen grass resistance to
wave overtopping (van der Meer, 2006b).
IPET - Interagency Performance Evaluation Taskforce (2005-2007)
Performance Evaluation of the New Orleans and Southeast Louisiana Hurricane Protection System.
The project comprised an intense performance evaluation of the New Orleans and Southeast Louisiana
Hurricane Protection System during Hurricane Katrina. IPET applied some of the most sophisticated
capabilities available in civil engineering to understand what happened during Katrina and why. Their
purpose was not just new knowledge, but application of that knowledge to the repair and reconstitution
of protection in New Orleans as well as improvement to engineering practice and policies. The results
of much of the IPET work are largely already in the ground, having been transferred and applied prior
to the formal completion of the project report.
• The System: What were the pre-Katrina characteristics of the hurricane protection system (HPS)
components; how did they compare to the original design intent?
• The Storm: What was the surge and wave environment created by Katrina and the forces incident
on the levees and floodwalls?
• The Performance: How did the levees and floodwalls perform, what insights can be gained for the
effective repair of the system, and what is the residual capability of the undamaged portions?
What was the performance of the interior drainage system and pump stations and their role in
flooding and dewatering of the area?
• The Consequences: What were the societal-related consequences of the flooding from Katrina to
include economic, life and safety, environmental, and historical and cultural losses?
• The Risk: What were the risk and reliability of the hurricane protection system prior to Katrina,
and what will they be following the planned repairs and improvements
RIMAX, Subject 3 Protection and Control (2005-2007)
Risk Management of Extreme Flood Events. The aim of RIMAX was to develop and implement
improved instruments of flood risk management by the integration of different disciplines and several
participants. Research focused on extreme flood events in river basins with mean events with a return
period of more than a 100 years and a highly destructive potential. Next to other tasks, Subject 3,
Protection and Control, deals with:
• Dyke safety, monitoring and dyke protection
• Management of dams and retention systems
• Management of urban infrastructure (water supply, sewage etc.) during floods
• Risk-based reliability analysis of flood defence system
COMCOAST (2004-2007)
ComCoast was a European project that developed and demonstrated innovative solutions for flood
protection in coastal areas. ComCoast created multifunctional flood management schemes with a more
gradual transition from sea to land, which benefits the wider coastal community and environment
whilst offering economically sound options. The ComCoast concept focused on coastal areas
comprising embankments. Smart grass reinforcement was extensively researched and tested with a
wave overtopping simulator on real dikes (van der Meer, 2006a, van der Meer, 2006b).
Most of these projects are based upon, or use as a reference, previous investigations which focus on
different aspects of the breaching process but not specifically vegetation (for example IMPACT, DSIG
Breach, HR Breach, EurOTop, PRODEICH, CLASH, etc.).
2.2.2 Reference Institutions
Some research institutions are considered as a reference on this topic:
• CIRIA
Is a member-based research and information organisation in the UK dedicated to
improvement in the construction industry. It has published grass performance curves relating total
exposure time to failure under a steady flow velocity (Hewlett et al., 1985). These are widely used
T04-08-03_ErosionofEmbankments_v9_1.doc
5
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
in the UK both for design and performance assessment.. It has also recently published an updated
version of the manual “Use of vegetation in civil engineering”(Coppin and Richards, 1990).
•
TAW
Technical Advisory committe for Flood Defence and its continuating platform ENW
(Expertise Network for Flood Protection) sited in The Netherlands bring together specialist in the
area of flood protection. They have published several documents about grass cover as dike
revetments (TAW, 1997, TAW, 1999). However, despite a programme of research from 1986
until at least 1996, detailed guidance on erosion resistance to overtoping and overflowing water is
missing.
•
USACE / USDA / USBR. The US Army Corps of Engineers, US Department of Agriculture and
US Bureau of Reclamation are all federal agencies that publish guidance documents to support
embankment (levee) and dam design, construction and management. The USDA (ARS-HERU at
Stillwater) has a long history of research into grass-erosion performance aimed at aiding the
construction and maintenance of small farm reservoirs.
2.2.3 Journal Papers
Many research projects promoted by Universities and Research Centres study the influence between
river hydraulics and vegetation. Their results are usually published in technical journals.
Resistance and turbulent characterization of open channel flow over vegetation has been extensively
studied. As vegetation is flexible in varying degrees, studies found in literature cover a wide range of
emergent/non-emergent and flexible/rigid vegetation. Many laboratory tests were performed to
investigate this problem. Vegetation was usually simulated with rigid wooden or steel cylinders or
rods or with plastic elements when flexibility was considered. Few experiments were performed with
real grass or turf. Work done by N.Kouwen during the 70’s and 80’s is just named as a reference. He
used dimensional analysis to create a simple model to evaluate resistance to flow depending on the
geometric and mechanical properties of submerged plants (density, elasticity) and flow conditions.
Another important topic covered by papers is the influence of vegetation in compound-channels flows.
In compound channels the momentum transfer between the main channel and the floodplain strongly
influences water levels. In natural rivers, floodplains are often home to many kinds of vegetation that
increases flow resistance. Laboratory tests considering vegetation in compound channels are also
found in literature.
Bank erosion caused by hydraulic forces acting on the bank surface has also received a lot of attention.
The most commonly observed bank erosion phenomena in nature are the failure of banks due to
geotechnical instability of the bank. The rate of bank erosion (taking into account streamline flow and
secondary currents) is linearly related to the excess near-bank velocity. An erosion coefficient is
included to account for variations in bend geometry and properties of bank material. In this case
vegetation is considered to influence bank roughness and cohesion.
However, despite this wide range of ‘associated’ research into vegetation in and around the river
channel, research that directly addresses the issue of bank vegetation preventing erosion induced by
overtopping or overflowing is very limited.
T04-08-03_ErosionofEmbankments_v9_1.doc
6
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
3.
Recommended actions and initiatives
Despite many research studies being undertaken during the past three decades, the engineering role of
vegetation in resisting erosion under various overtopping and overflowing conditions is still poorly
understood. Whilst some aspects of vegetation maintenance and management have been well
researched and documented, others aspects relating to erosion performance are understood only
qualitatively and application of knowledge is based on engineering experience and judgement.
Seven actions are recommended to help address this gap in understanding vegetation performance:
3.1
Determination of time to failure
Objective
Improve the base data and guidance for predicting the limit state failure of grass cover due to erosion
Justification
The time to damage the vegetation layer and erode through the root system to the soil below is critical
for determining the performance of grass cover as a protection measure. The curves allowing total
exposure time to failure under a steady flow velocity, presented by CIRIA 1976, are the most current
reference containing such design guidance. However, this flow-duration erosion resistance model is
based on limited data and its validity for intense, high velocity flow is uncertain. There is a need to
extend these curves to cover different dike slopes, vegetation types and to increase the intensity of the
flow load so that it is representative of the different loads. Reliability in this area can only be improved
with additional physical and prototype scale testing.
Since existing guidance on vegetation performance is limited and over 20 years old, review,
integration and analysis of more recent performance data (worldwide) might allow a quick advance in
the provision of more reliable design / performance guidance for industry.
Actions
• A detailed review of the basis of any current erosion models and a detailed review of the
availability of new field or laboratory test data (last two decades).
• Analyse combined data and / or extend data sets through large scale / prototype testing.
• Further develop and extend performance curves consistent with original CIRIA curves
3.2
Vegetation management
Objective
Review and update guidance for managing vegetated embankments to improve surface erosion
performance
Justification
The type of grass management scheme employed plays a very important role in developing a dense
and erosion resistant vegetation cover (TAW, 1997, TAW, 1999). Hence, management practice should
be optimized to strengthen erosion resistance and help limit or avoid other forms of embankment
deterioration.
As maintenance is a major cost factor during the lifetime of an embankment, such costs should also be
considered when developing and optimising management and design options. Monitoring and
inspection of surface protection layers are important actions for asset management. Research into
effective and efficient monitoring for embankments with different types of surface protection is
therefore important.
T04-08-03_ErosionofEmbankments_v9_1.doc
7
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
Actions
• Review existing knowledge regarding embankments (vegetation) management
• Collect field data demonstrating the impact of different management approaches
• Produce updated guidance for the management of vegetated embankments
• Implementation a programme for ongoing monitoring and data collection
3.3
Develop a wider management framework linking vegetation type,
management, soil moisture, soil fissuring and soil erodibility
Objective
The way in which vegetation helps or hinders embankment performance depends upon complex
interactions between vegetation type and state and soil type and state. The objective here is to clarify
those relationships in order to provide more reliable guidance on how to optimise performance from
both vegetation and soil.
Justification
The type and condition of vegetation affects its erosion resistance. This performance is closely linked
with the type of soil that the embankment is built from. In turn the condition (and erodibility) of the
soil depends upon factors such as composition (clay content), moisture content and compaction. The
condition of the outer layer of the soil is directly affected by the vegetation, both in terms of
integrating with the root mesh and moisture content. These can also directly affect fissuring within the
soil layer. In order to manage the grass-soil layer most effectively, it is important to recognise and
quantify these complex interactions so that optimal combinations of vegetation and soil type and state
may be achieved.
Actions
• Review and bring together existing knowledge on vegetation performance and management, soil
erodibility and soil fissuring. Identify common factors and develop a framework for optimising
performance
• Validation of proposed approaches is likely to require field and / or laboratory testing
• Provide industry guidance covering simultaneous management of soil type and state and
vegetation type and state
3.4
Improve basic knowledge and understanding of vegetation-erosion
processes
Objective
The improve knowledge and understanding in key process areas relating to the performance of
vegetation against erosion. Specifically, investigating root performance, response to different load
types, cumulative effects and performance on steep slopes
Justification
Improvement of vegetation as a protection measure against erosion requires improved knowledge and
understanding of specific processes. The areas that require research focus include:
Analysis of root performance - The range and distribution of root diameters and density is an
important parameter to determine resistance to erosion because it is correlated with tensile strength.
The root cohesion acts as a distributed pressure for some failure mechanisms. With increasing root
spacing there is a need to consider discrete root loading. The root area ratio also varyies during the
year hence seasonality has to be considered.
Analysis of response to different load types and slope - Lateral currents, overflow and waves are the
main loading types on vegetated surfaces, hence knowledge about these processes should be
improved, especially in relation to wave overtopping and impact, and unsteady and discontinuous
flow, for which there is even less information available and limited numerical models. Response also
T04-08-03_ErosionofEmbankments_v9_1.doc
8
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
needs to include grass behaviour under flow on flat, gently sloping and steeply sloping embankment
face.
Cumulative loading effects – The impact on vegetation performance of cumulative loading from a
combination of different loads may be more substantial than individual events. For example,
prolonged high steady water, followed by drawdown and then wave impact may result in a more rapid
failure that simply wave impact.
Actions:
Root performance:
• Review of existing knowledge leading to improved understanding and predictive models on root
performance. Potential development and justification of discrete root loading models if
appropriate.
Loading types and slope:
• Identify specific influences that load types have on surface erosion basic failure modes
• Detailed R&D to improve the accuracy of performance predictions for wave impact and
overtopping
• Assessment and improved understanding of the impact of slopes (including steep slopes) on
vegetation performance
Cumulative loading:
• Review and analysis of the potential effects of different cumulative loading
• Identification of likely correlations between loading types for a range of seasonal and storm
conditions, but also including climate change trends. Guidance on optimal management action and
measures to maintain embankment performance
3.5
Defining failure modes and mechanisms
Objectives
The objective here is to improve knowledge on vegetation failure mechanisms and provide
descriptions in a format suitable for use in reliability and system risk models.
Justification
Current descriptions for grass failure modes are limited. A majority of knowledge regarding
performance is qualitative rather than quantitative, hence not in a format suited for use in reliability or
system risk analysis. A range of factors and processes should be considered including surface erosion,
infiltration and seepage, uplift, sliding, soil dessication etc.
Actions
• Identify main factors that contribute to failure of the surface vegetation
• Analyse failure modes leading to development of limit state descriptions suitable for use in
reliability and system risk models
3.6
Experimental and field data
Objectives
Support the collection of field and / or prototype scale data on the erosion of vegetated surface
embankments to support failure mode analysis and model development.
Justification
Most types of vegetation, such as grass, cannot be easily studied at scales other than prototype, hence
large scale tests and collation of field data is needed. This may be achieved, for example, by
establishing long term monitoring sites, using redundant embankments as test sites or source material
and by performing prototype scale tests in the laboratory or with equipment such as the wave
simulator on site.
T04-08-03_ErosionofEmbankments_v9_1.doc
9
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
Actions
• Establish long term monitoring of different sites covering different vegetation type, management
procedure, loading etc. to develop reliable performance data sets
• Undertake large scale laboratory or field tests – for example using the wave overtopping simulator
– to establish specific embankment – vegetation performance curves. Consider tests covering a
range of vegetation types, condition, soil types, condition and loading types
3.7
Estimation of vegetation roughness
Objective
Improve guidance on the selection of roughness coefficients used in failure mode analysis for surface
protection
Justification
Roughness formulations that are used in flow models are designed for uniform flow conditions at
reasonable depths of flow. Erosion of grass cover typically occurs with very fast and / or pulsing
turbulent, shallow flow – conditions that are far from those used to develop normal roughness
relationships. Seasonality is another parameter that affects vegetation roughness and should also be
considered.
Actions
• Investigation into roughness coefficients under typical erosion flows (overtopping / overflowing)
leading to guidance on parameter calculation including allowance for seasonal variations.
T04-08-03_ErosionofEmbankments_v9_1.doc
10
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
4.
Summary and prioritisation of recommended actions
The actions identified in Section 3 are summarised in Table 4.1 below and assessed to provide an
indication of priority (based upon judgement) for the various actions. Actions are categorised
according to:
Nature of Initiative
Field Fieldwork
Res Research
BP Best Practice/Guidance documents
Data Investigation/Data collection
Priority of Initiative
H High
M Medium
L Low
Table 4.1. Summary and prioritisation of recommended actions
No.
1
1.1
1.2
1.3
4.1
4.2
4.3
4.4
4.5
Action
Determination of time to failure
Review of current erosion models and available data
Analyse data and extend data through testing
Develop improved performance curves (such as CIRIA 116)
and guidance
Vegetation management
Review of existing knowledge re management
Field data collection demonstrating different management
approaches
Design guidance for management of vegetated embankments
Implementation of programme for monitoring and data
collection and analysis
Framework linking vegetation type, management, soil
moisture, soil fissuring and soil erodibility
Review and develop framework linking vegetation
performance, management action, soil erodibility and soil
fissuring.
Validation of proposed approaches through field and / or
laboratory testing
Guidance covering simultaneous management of soil type
and state and vegetation type and state
Improve basic knowledge and understanding of vegetation
– erosion processes
Investigate / review root performance
Identify influence on surface erosion of various load types
Investigation into wave impact and overtopping processes
Performance of vegetation on steep slopes
Potential effects of cumulative loading
4.6
5
5.1
5.2
Cumulative loading correlations / climate change
Failure modes and mechanisms
Identification of main factors affecting failure; failure modes
Analysis of failure modes leading to limit state equations
2
2.1
2.2
2.3
2.4
3
3.1
3.2
3.3
4
T04-08-03_ErosionofEmbankments_v9_1.doc
11
Nature
Priority
Res
Res/Field
Res/BP
H
H
H
Data
BP
H
H
BP
BP
H
H
Res
H
Res / Field /
Data
BP
H
H
Res
Res
Res
Res
Res / Field /
Data
Res / Data
L
M
M
L
M
Res / Data
Res / Data
M
M
M
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
No.
6
6.1
62
7
7.1
Action
Experimental and field data
Establish long term monitoring programme
Collect large scale / prototype performance datausing, for
example, the Wave Overtopping Simulator
Estimation of vegetation roughness
Investigation of vegetation roughness coefficients under
conditions typical for embankment grass erosion
T04-08-03_ErosionofEmbankments_v9_1.doc
12
Nature
Priority
Res/Field/Data
Res/Field/Data
H
H
Field/Res/Data
L
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
5.
References
1. Allsop, N.W.H.A., Kortenhaus, A. and Morris, M.W. (2007) Failure mechanisms for flood
defence structures, FLOODsite Report T04-06-01. www.floodsite.net
2. Coppin, N.J. and Richards, I.G. (1990) Use of vegetation in civil engineering, (First Edn),
Butterworths.
3. Hewlett, H.W.M., Boorman, L.A., Bramley, M.E. and Whitehead, E. (1985) Reinforcement of
steep grassed waterways, CIRIA. CIRIA, L.
4. Morris, M.W., Kortenhaus, A. and Visser, P.J. (2009) Modelling breach initiation and growth,
FLOODsite Report T06-08-02. www.floodsite.net
5. TAW (1997) Erosion resistance of grassland as dike covering. (TAW), T. A. C. f. F. D. i. T. N.
6. TAW (1999) Grass cover as a dike revetment. (TAW), T. A. C. f. F. D.
7. van der Meer, J.W. (2006a) Development of alternative overtopping resistant sea defences,
FLOODsite Report T04-07-05; ComCoast WP3 Final Report.
8. van der Meer, J.W. (2006b) Placement of smart grass reinforcement at test sections Gronigen
Sea Dike, FLOODsite Report No. T04-07-06 / ComCoast WP3 Final Report.
T04-08-03_ErosionofEmbankments_v9_1.doc
13
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
T04-08-03_ErosionofEmbankments_v9_1.doc
14
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
Appendix 1: Current Research Details
T04-08-03_ErosionofEmbankments_v9_1.doc
15
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
T04-08-03_ErosionofEmbankments_v9_1.doc
16
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
EROGRASS
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Erosion resistance of grass covered dikes and embankments
http://www.kyst.dk/erograss
Danish Coastal Authority (DCA), Denmark
IHE Delft, Netherlands
Strathclyde University, UK
Tallinn University, Estonia
Delft Hydraulics
Delft University
EC FP6
EroGrass looks into risk-based design and understanding of failure modes of
sea dikes and aims to enhance the limited information on erosion resistance of
grass covered dikes and embankments. The project comprises large-scale
model tests on sea dikes with grass cover investigating in the failure of grass
cover on the seaward side by wave impacts and wave run-up / run-down and
failure of grass cover on the landward side by wave overtopping. In general it
looks into the improvement of understanding of grass cover behaviour.
The main objective of the HYDRALAB III project EroGRASS is to perform
large scale model tests to investigate in detail the failure of grass cover layers
due to (i) wave impact, (ii) wave run-up and run-down flow and (iii) wave
overtopping. The large scale tests at a prototype dike model will be performed
in the Large Wave Flume (GWK) of the Coastal Research Center (a joint
centre of the Universities of Hannover and Braunschweig) in Hannover
(Germany).
The crest height of the dike model will be 5.8 m above the flume bottom. The
seaward slope is 1:4 and the shoreward slope is 1:3. The dike crest will be 2 m
wide. The clay layer thickness is 0.8 m on the seaward and landward slope as
well as on the dike crest. The length of the dike model is 5 m corresponding to
the flume width. Since it is not feasible to sow grass on the clay layer and wait
for a well-established grass cover, grass mats will be peeled at the southern
wing dike of the Ribe flood defence system (Denmark). The Ribe flood
defence system is located approximately 50 km north of the German-Danish
border. Grass mats are 2.35 m long, 1.25 m wide and approximately 0.15 m
thick.
The access of the EroGRASS project to the Large Wave Flume in Hannover is
funded by the sixth EC framework programme through the Integrated
Infrastructure Initiative HYDRALAB III. The programme provides user
groups access free of charge to the facilities for their research project and
covers travel and subsistence costs. The programme is intended for short
access periods, not exceeding 3 months.
Keywords
Timeframe
Contact
Grass erosion, dikes, Grass cover layer, grass erosion, large scale tests, dike
model, HYDRALAB III, Large Wave Flume (GWK), Coastal Research Center
Hannover
April 2007 to approximately April 2008
Thorsten Piontkowitz
[email protected]
T04-08-03_ErosionofEmbankments_v9_1.doc
17
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
Engineering tools for safe, efficient hydraulic structures and channels
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Keywords
Timeframe
Contact
Improve methods of predicting earthen embankment erosion and failure
http://www.ars.usda.gov/research/projects/projects.htm?ACCN_NO=411569
USDA/HERU
United States Department of Agriculture. Agriculture Research Service
Improve methods of predicting earthen embankment erosion and failure, and
develop generalized hydraulic guidelines and tools for roller compacted
concrete spillways used to protect earthen structures from erosion and
increase discharge capacity. Improving methods of predicting earthen
embankment erosion and failure will include sub-objectives of quantification
and erosion measurement of embankment materials, quantification of
protective capabilities of vegetation, development of algorithms and
computational models that can be used by the profession to predict earthen
embankment erosion and failure causing downstream flooding. The
development of generalized hydraulic guidelines and tools for roller
compacted concrete spillways will include sub-objectives of development of
preliminary guidelines for dimensioning converging sidewalls as well as
understanding air entrainment, flow bulking and energy dissipation leading to
generalized equations for dimensioning stepped spillways, downstream
basins and rip-rap protection that will be used by the engineering profession
to design spillways.
earthen embankment erosion
2007 - 2012
Greg Hanson
[email protected]
T04-08-03_ErosionofEmbankments_v9_1.doc
18
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
FLOODsite Task 4
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Keywords
Timeframe
Contact
Publications
related to
Project
Understanding and predicting failure modes
www.floodsite.net
HR Wallingford, UK
WL | Delft, Netherlands
Leichtweiss Institut, Germany
Technische Universitaet Dresden, Germany
Institute for Hydrology and Ecology, UK
IBW, Poland
INFRAM, Netherlands
EC 6th Framework Programme
This research aims to both gather existing information on defence failure
mechanisms and to extend knowledge in a number of critical areas by reviewing
current international projects and detailed failure mode analysis on the basis of
hydraulic model testing and numerical modelling of the most relevant failure
modes. Outcomes comprise
Erosion, Failure, Embankment, Initiation, Surface Cover
2006-2009
Mark Morris
[email protected]
Husrin S. (2007) Laboratory experiments on the erosion of clay revetment of
sea dike due to breaking wave impacts , IHE, Delft, The Netherlands (M4.4)
Stanczak G. (2006) Laboratory tests on the erosion of clay revetment of sea dike
with and without a grass cover induced by breaking wave impact, LWI report
935, LWI - TU Braunschweig, Braunschweig, Germany (contribution to M4.3)
Allsop W. Kortenhaus A. Morris M. et al. (2007) Failure Mechanisms for Flood
Defence Structures, FLOODsite report T04-06-01
Doorn N. (2007) Understanding and Predicting Failure Modes: Failure Modes
for Revetments T04-07-03
van der Meer J. (2007) ComCoast work package 3: Development of alternative
overtopping resistant sea defences T04-07-05
Danuta L. (2007) Air trapping phenomenon and cracking - model tests on flood
embankment T04-07-10
T04-08-03_ErosionofEmbankments_v9_1.doc
19
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
Wave overtopping simulator (Infram)
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Wave overtopping simulator tests a reinforced grass layer on a seadike
http://www.infram.nl/infotype/webpage/view.asp?objectID=227
Infram, Netherlands
Royal Haskoning, Netherlands
Dutch Ministry of Transport, Public Works and Water Management
In May 2007 the Ministry of Transport, Public Works and Water
Management will use a wave overtopping simulator to test a traditional dike
section with grass and a dike section reinforced with a geotextiel that is
placed beneath the grass layer. In order to make the crest and the inner slope
of the dike resistant to wave overtopping, a consortium of Royal Haskoning
and Infram came up with the idea to reinforece the grass (Smart Grass
Reinforcement). The tests will be taking place in Delfzijl, where on May
2006 the test sections have been made.
Infram came up with the idea of the wave overtopping simulator. Then a
prototype was developed and tested by Infram, together with four students
Civil Engineering. Last june 23th the prototype was demonstrated at the test
location of the constructor, "Nijholt Staal & Machinebouw" in Heerenveen.
The prototype is a full cross-section of the wave overtopping simulator, but
only 1 m wide, the actual wave overtopping-simulator will be 4 m wide! It
can be loaded then with 14.000 litres of water. The simulator will be placed
above the dike crest and can simulate the waves overtopping the dike crest.
The target of this project is to determine if it is possible to protected dikes
against wave overtopping. This means that the crest and the inner slope of the
dike must be able to resist wave overtopping at extreme storm conditions. In
the future the wave overtopping simulator will be used to determine how long
regular grass on a dike can resist overtopping seawater
Keywords
Timeframe
Contact
Publications
related to
Project
Overtopping erosion
2007
Van der Meer JW. Bernardini P. Snijders W. Regeling HJ. (2006) The wave
overtopping simulator
De Rouck J. van der Meer JW. Allsop NWH. Franco L. Verhaeghe H. (2002)
Wave overtopping at coastal structures: development of a database towards
up-graded prediction methods
T04-08-03_ErosionofEmbankments_v9_1.doc
20
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
IPET - Interagency Performance Evaluation Taskforce
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Keywords
Timeframe
Contact
Performance Evaluation of the New Orleans and Southeast Louisiana Hurricane
Protection System
https://ipet.wes.army.mil/
Interagency Performance Evaluation Task Force
U.S. Army Corps of Engineers
The project comprises an intense performance evaluation of the New Orleans
and Southeast Louisiana Hurricane Protection System during Hurricane
Katrina. IPET applied some of the most sophisticated capabilities available in
civil engineering to understand what happened during Katrina and why. Their
purpose was not just new knowledge, but application of that knowledge to the
repair and reconstitution of protection in New Orleans as well as improvement
to engineering practice and policies. The results of much of the IPET work are
largely already in the ground, having been transferred and applied prior to the
formal completion of this report.
• The System: What were the pre-Katrina characteristics of the hurricane
protection system (HPS) components; how did they compare to the original
design intent?
• The Storm: What was the surge and wave environment created by Katrina
and the forces incident on the levees and floodwalls?
• The Performance: How did the levees and floodwalls perform, what insights
can be gained for the effective repair of the system, and what is the residual
capability of the undamaged portions? What was the performance of the
interior drainage system and pump stations and their role in flooding and
unwatering of the area?
• The Consequences: What were the societal-related consequences of the
flooding from Katrina to include economic, life and safety, environmental,
and historical and cultural losses?
• The Risk: What were the risk and reliability of the hurricane protection
system prior to Katrina, and what will they be following the planned repairs
and improvements (Dec. 2007)
performance evaluation, dike failure
2005-2007
Wayne Stroupe
[email protected]
T04-08-03_ErosionofEmbankments_v9_1.doc
21
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
RIMAX, Subject 3 Protection and Control
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Keywords
Timeframe
Contact
Risk Management of Extreme Flood Events
www.rimax-hochwasser.de/400.html?&L=1
GeoForschungsZentrum Potsdam (GFZ), Germany
Center for Disaster Management and Risk Reduction Technologies (CEDIM),
Germany
German Federal Ministry of Education and Research (BMBF)
The aim of RIMAX is to develop and implement improved instruments of flood
risk management by the integration of different disciplines and several
participants. It focuses on extreme flood events in river basins with mean
events with a return period of more than a 100 years and a highly destructive
potential. Next to other tasks, Subject 3, Protection and Control, deals with:
• Dyke safety, monitoring and dyke protection
• Management of dams and retention systems
• Management of urban infrastructure (water supply, sewage etc.) during
floods
• Risk-based reliability analysis of flood defence system
Extreme Flood, Risk Management, Dike safety
01/2005 – 12/2007
Bruno Merz
[email protected]
T04-08-03_ErosionofEmbankments_v9_1.doc
22
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
COMCOAST
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Keywords
Timeframe
Contact
Multifunctional flood management schemes on coastal areas comprising
embankments
http://www.comcoast.org
Rijkswaterstaat, the Netherlands (Lead Partner)
Province of Zeeland, the Netherlands
Province of Groningen, the Netherlands
University of Oldenburg, Germany
Environment Agency, United Kingdom
Waterways & Seacanal NV, department 'Zeeschelde', Belgium
Danish Coastal authority, Denmark
Community of Hulst, the Netherlands
Waterboard Zeeuwse Eilanden, the Netherlands
Waterboard Zeeuws Vlaanderen, the Netherlands
EC Interreg North Sea Programme IIIB
ComCoast was a European project that developed and demonstrated innovative
solutions for flood protection in coastal areas. ComCoast created multifunctional
flood management schemes with a more gradual transition from sea to land,
which benefits the wider coastal community and environment whilst offering
economically sound options. The ComCoast concept focused on coastal areas
comprising embankments. Smart grass reinforcement was extensively researched
and tested with a wave overtopping simulator on real dikes.
grass reinforced embankments
2004-2007
Frans Hamer
[email protected]
T04-08-03_ErosionofEmbankments_v9_1.doc
23
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
IMPACT
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Keywords
Timeframe
Contact
Publications
related to Project
Investigation of Extreme Flood Processes and Uncertainty
http://www.impact-project.net
HR Wallingford, UK
Universität Der Bundeswehr Munchen, Germany
Université Catholique de Louvain, Belgium
CEMAGREF, France
Università di Trento, Italy
University of Zaragoza, Spain
CESI, Italy
SWECO Gröner AS, Norway
Instituto Superior Technico, Portugal
Geo Group, Czech Republic
H-EURAqua, Hungary
EC FP5
Research into extreme flood processes covering breach formation, flood
propagation, sediment movement and modelling uncertainty. In addition,
investigation of the use of geophysics for the rapid integrity assessment of
embankments. Specific objectives are to advance scientific knowledge and
understanding, and develop predictive modelling tools in four key areas.
Specifically, WP2, Investigation of breach formation processes includes
understanding the formation processes, prediction of breach formation rate (and
hence flood hydrograph) and prediction of breach location. Research combines
field modelling (controlled failure of 6m high embankments) with laboratory
modelling (failure of 0.6m high embankments) and numerical model
development (comparison of breach model performance worldwide).
Breach formation, Dam-break, Emergency management, Erosion, Flood
management, Flood propagation, Flood risk management, Modelling, Models,
Morphology, Sediments
2001-2004
Mark Morris
[email protected]
Mohamed MAA. Samuels PG. Morris MW. Ghataora GS. (2002) Improving the
Accuracy of prediction of breach formation through dam and flood emankments,
Journal/Event/Publication: Flow 2002 Conference
Broich K. (2002) Determination of initial conditions for dam erosion due to
overtopping and possible integration into a probabilistic design concept,
Journal/Event/Publication: Wallingford, Proc. Of 2nd IMPACT Wprkshop,
Wallingford, UK, 16/17 May 2002
Broich K. (2002) Simulation of the IMPACT Dam-break experiments using
different calculation methods, Journal/Event/Publication: Proc of 2nd IMPACT
Workshop, Mo I Rana, Norway, 12/13 Sep 2002
Broich K. (2003) Verfahren zur hydraulischen Berechnung voon Damm- und
Deichbruchen, Journal/Event/Publication: Proceeding of national Symposium on
“Sicherung von Dammen und Deichen – Handbuch fur Theorie uns Praxis. Ed
R.A Hermann and J. Jensen, ISBM 3-936533-09-1, Universitat Siegen 7.2
Broich K. (2003) Sediment transport in breach formation process,
Journal/Event/Publication: Proc. Of 4th IMPACT Workshop, UCL Louvain-laNeuve, 6/7.11.2003
T04-08-03_ErosionofEmbankments_v9_1.doc
24
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
Dam Safety Interest Group (DSIG) Breach Modelling Project
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Keywords
Timeframe
Contact
Breach model benchmark testing
www.ceatech.ca/DSIG.php
Dam owners from Canada, United States, Australia, Sweden, France, United
Kingdom and Germany
DSIG are undertaking a programme of research to
• review and identify top performing / top potential breach prediction models
• review and collate field and laboratory data for model validation
• perform objective breach model benchmark tests
Benchmark tests, Breach formation, Dam-break, Embankments, Erosion,
Modelling
2005 – 2007 - - - > 2009 - - - > ?
Mr. Constantine G. Tjoumas / [email protected]
T04-08-03_ErosionofEmbankments_v9_1.doc
25
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
HR BREACH
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Keywords
Timeframe
Contact
Breach modelling
http://www.hrwallingford.co.uk/Corporate%20literature/
NA028%200709%20MWM%20Breach%20modelling.pdf
HR Wallingford
HR Wallingford
HR Wallingford instigated a programme of research and development to produce
a numerical model for prediction of breach formation through embankment dams
and linear flood defences. This in-house project was initiated in 1998 (following
the CADAM project) and has resulted in the production of a prototype model
(HR BREACH). This model integrates hydraulics and soil mechanics theory and
continues to be developed through the IMPACT project and other related studies.
The longer-term plan for the HR BREACH model is to incorporate the model
into existing flow models (1D / 2D) to provide an interactive flood risk
management tool. In the meantime, use of the model on flood management
projects is possible on a case by case basis.
Embankment erosion, Breach modelling
1998-2009
Mark Morris
[email protected]
T04-08-03_ErosionofEmbankments_v9_1.doc
26
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
EurOtop
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Keywords
Timeframe
Contact
Wave Overtopping of Sea Defences
and Related Structures - Assessment
Manual
http://www.overtopping-manual.com
HR Wallingford, UK
Infram, Netherlands
LWI, Germany
BAW, Germany
University of Edinburgh, UK
Environment Agency, UK
German Coastal Engineering Research Council (KFKI)
Rijkswaterstaat, Netherlands Expertise Network on Flood Protection
The new "European Overtopping Manual" presents the latest techniques and
approved methods for establishing overtopping hazards and flooding for an
extensive range of structure types. It is relevant to shoreline and coastal
engineers, most of whom have used the predecessor manuals, "Overtopping of
Seawalls: Design and Assessment Manual" (R&D Technical Report W178,
1999), the Dutch "Technical Report: Wave run-up and wave overtopping at
dikes" (TAW, 2002 English edition), and the German Die Küste (EAK, 2002).
dike failure, overtopping
2007
Dr. Tim Pullen
[email protected]
T04-08-03_ErosionofEmbankments_v9_1.doc
27
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
PRODEICH
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Keywords
Timeframe
Contact
Publications
related to Project
Probabilistic design method for sea defences
http://www.lwi.tu-bs.de/hyku/deutsch/projekte/prodeich.html
Leichtweiß-Institut für Wasserbau (LWI), Germany
Institut für Grundbau und Bodenmechanik, Uni Essen, Germany
BMBF
Within the framework of future coastal protection strategies, probabilistic
methods will play an important role for determination of failure probability of
coastal defence structures. They are the basis for risk analysis of flood- and
coastal defence (FCD) systems including all integrated FCD elements like dikes,
dunes, seawalls, etc. as well as special structures and allow for the quantitative
assessment of the consequences in a case of failure. The research aims to
develop a probabilistic design method for sea dikes under consideration of the
most important failure modes on the basis of existing deterministic approaches.
It will allow the design engineer to derive a quantitative prediction of the safety
and reliability of a dike for a given timeframe. This prediction will be suitable
for design purposes as well as for safety assessments of existing dikes.
Breach formation, Embankments, Failure mechanisms, Flood defence structure,
Probabilistic design, Sea dike, Failure analysis, Fault tree, Probabilistic design,
Damage analysis, Stability, Failure modes, Failure probability
2000 - 2002
Prof. Dr.-Ing. Hocine Oumeraci
[email protected]
Kortenhaus A. Oumeraci H. (2002) Probalilistische Bemessungsmethoden für
Seedeiche (ProDeich). LWI Bericht, 877 KFKI Signatur: E 34 942 Lit.
Kortenhaus A. Oumeraci H. Weissmann R. Richwien W. (2002) Failure mode
and fault tree analysis for sea and estuary dikes. Proc. 28th ICCE, Cardiff, KFKI
Signatur: E 34 930
T04-08-03_ErosionofEmbankments_v9_1.doc
28
April 2008
FLOODsite Project Report
Contract No:GOCE-CT-2004-505420
CLASH
Research Topic
Website
Contractor /
Participants
Funder / Client
Description
Keywords
Timeframe
Contact
Crest Level Assessment of Coastal Structures by full scale monitoring, neural
network prediction and Hazard analysis on permissible wave overtopping.
www.clash-eu.org
Ugent, Department of Roads, Bridges and Coastal Engineering, Belgium
FCCD, Ministry of the Flemish Community, Belgium
FCFH, Ministry of the Flemish Community, Belgium
LWI, Department of Hydromechanics and Coastal Engineering, Germany
Aalborg University, Department of Civil Engineering, Denmark
Universidad Politécnica de Valencia. Departamento de Transportes, Spain
MODIMAR, Italy
DH, WL/Delft Hydraulics, Netherlands
INFRAM, Netherlands
RIKZ, Netherlands
Manchester Metropolitan University. Centre for Mathematical modelling and
flow analysis, UK
University of Edinburgh, UK
HRWallingford, UK
EC – Fifth Framework Programme
It has been proven that wave run-up is underestimated by small scale model tests
due to scale effects. Therefore, there is a strong suspicion that wave overtopping
will be underpredicted too. Full scale measurements on wave overtopping will be
carried out at four sites. One site will concentrate on the effect of long waves on
shallow water. Full scale measurement results are simulated by small scale and
numerical modelling to quantify and to explain suspected scale effects. As no
generic prediction method for crest level assessment exists, this project will
create one. All existing data on wave overtopping will be collected and
supplemented with the full scale data and the "white spot" data gathered in this
project. Information on permissible levels of wave overtopping is poor and
vague. A hazard analysis (including socio-economic effects) will give a sound
answer to the question of safety of pedestrians, vehicles, buildings, etc.
overtopping, full scale measurements
2002-2004
Prof. Dr. ir. Julien De Rouck, [email protected]
T04-08-03_ErosionofEmbankments_v9_1.doc
29
April 2008