Breaching of earth embankments and dams

Despite 'modern' construction and management techniques, flood embankment and embankment dam failures occur almost routinely around the world. The need to understand, predict and prevent the breaching process remains a high priority for owners and flood risk managers alike. This research provides new understanding and improved methods for predicting breach initiation and growth through earth flood embankments or dams. The improvement of breach model accuracy has made slow progress over the past 20 years, with confusion around breaching processes arising from a lack of appreciation of soil mechanics interacting with hydraulics and structural behaviour. The prediction of different breach processes requires the integration of techniques from all three disciplines. This thesis makes advances from earlier work (Mohamed, 2002) to produce a predictive breach model intended for industry application. The research develops improved approaches for flow calculation, sediment erosion and structural response for predicting breach initiation and growth and uses field data, including video footage, from the EU IMP ACT project and large scale test and case study data from collaboration with the International Dam Safety Interest Group breach modelling project. Sediment erosion equations, rather than equilibrium transport equations are used and the significance of the estimated performance of any grass cover and the influence of breach drowning recognised. The relationship between reservoir surface area and the erodibility of the embankment soil for the characteristics of the breach outflow hydrograph is also highlighted. Building from these developments, a new method to simulate breach through embankments comprised of different zones of material type and state has been developed which provides a significant step forward in our ability to simulate breach through real rather than idealised structures. This thesis demonstrates how this modelling approach can predict significantly different breach behaviour, and hence outflow hydrograph, dependent upon the embankment construction and soil state.