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Flood risk assessment and management often requires the prediction of potential breaching of a flood defence embankment or dam in order to either assess potential impacts or provide information to assist emergency planning, evacuation, repair strategies and improve alternative future design strategies. There are many different aspects of the overall breaching process, which are more, or less, relevant to the wide range of potential end users of such information. Consequently, the prediction of breach growth is an area where research has been undertaken for many decades in an attempt to provide more reliable models and predictions. However, despite many initiatives providing observations and recommendations as to processes observed and how research might progress, more detailed literature searches will often uncover conclusions and observations noted a decade or two or three earlier that are similar to those being made today. In particular, observations relating to material type, state (such as water content and compaction) and properties are relevant here. This prompts the obvious question as to why our ability to predict breach initiation and growth has not progressed further over this period. Why are so many studies identifying similar issues and, in effect, 'reinventing the wheel'? With a programme of research into breach initiation and growth under the EC FLOODsite Project and continued pressure to improve tools and techniques following events such as those seen at New Orleans in August 2005, this paper considers this question of apparent slow progress and offers some suggestions as to why this may have occurred and what direction might prove more effective in the future.

Predicting how a flood defence structure, such as a river or coastal embankment, behaves under varying load conditions is an essential part of undertaking a flood risk assessment. This understanding directly influences the prediction of rate and volume of any flood water that may cross over or through the flood defence structure and impact on the protected area behind. A range of research and model development has been undertaken through Task 6 of the FLOODsite project, building upon earlier work under the IMPACT project and linking with ongoing international initiatives such as the Dam Safety Interest Group breach modelling project. This paper outlines the innovative research undertaken by three organisations within FLOODsite investigating wave induced breach initiation, the influence of soil state and cracking on initiation and improved simulation of the breach initiation and growth stages to support flood risk analyses.

The future management of flood risk will not come from a single technical solution or policy but from a range of responses which are tuned to the specific circumstances at a local or regional scale, taking account of national governance structures and public attitudes towards flood risks. This diversity of approach is recognised by the embodiment of the subsidiarity principle in the European Directive on the assessment and management of flood risks. This paper covers some of the main areas of innovation achieved within the European funded research project FLOODsite. These innovations will facilitate the implementation of the European Directive actions of flood risk assessments, risk mapping and the preparation of flood risk management plans. FLOODsite does not propose a single integrated methodology for flood risk management; rather it provides a set of linked methods which support integrated flood risk management. We also compare FLOODsite against the ambitions set for the EC Sixth Framework Programme Integrated Projects.Chp_049.indd 433 9/6/2008 7:39:02 PM

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Risk analysis models of fluvial and coastal flood systems have been in use for over a decade. They have been applied to support a wide range of flood risk management decisions, including long term strategic planning and shorter term asset management. Models that are currently applied in practice make a number of simplifying assumptions. The development of a new model that offers a major improvement over these methods is described. The new model incorporates: a unique dynamic 2D inundation model that captures sub-mesh element topography (RFSM EDA); a new computationally efficient model of embankment breach growth (AREBA) and extends the range of consequences considered to include the loss of life. The model has been applied on a pilot site to demonstrate its capabilities. A flood system risk analysis model with dynamic sub-element 2D inundation model, dynamic breach growth and life-loss

Executive summaryEarthen embankments that are categorised as large (15m or greater in height) number in the tens of thousands globally. Embankment dam risk assessment is a vital measure that has been adopted throughout the industry to assess the potential impact that catastrophic dam failures can carry. A critical part of this assessment is the prediction of the breach process, which will determine the reservoir outflow hydrograph. This is crucial for the following stage of flood routing, which aids in flood risk assessment, evacuation planning and land-use planning.This report provides details of the breach prediction methods available to users, ranging from simple parametric equations to complex multi-dimensional erosion models. These are commonly divided into three categories; parametric models, semi-physically based models and physically based models.

In order to undertake a flood risk analysis, the performance of different flood defence structures under varying load conditions needs to be represented. This paper reports on work undertaken through the FLOODsite Project (Task 4) in bringing together available information on failure modes for a number of representative flood defence structure types, to support the development and implementation of system wide models for flood risk assessment. The work comprised a review of structures and failure modes which have occurred in the past, and an investigation of limit state equations and associated uncertainties for both the models and the input parameters. Summaries of all failure modes were combined to create a single reference document; it is hoped that this will be maintained and updated into the future as knowledge on different failure mechanisms evolves. Additional research into selected failure modes and embankment processes was also undertaken and is summarised in this paper, including recommendations as to areas where future research should be focussed.