Industry Research into Dam and Levee Breach Erosion Through Coarser Grained Materials

Predicting breach erosion processes is essential for the effective risk management of both dams and levees. In recent years, a variety of research efforts have improved our knowledge of erosion processes, and in particular validation of the work on headcut erosion through cohesive soils performed at USDA-HERU. A similar level of analysis and validation is required for coarser grained and mixed materials to provide a clearer overview of when breach erosion processes change from headcut through surface erosion to slumping of rockfill. Since the release of flood water through a breached dam or levee depends both upon the rate of soil particle erosion and the macro erosion process (i.e. whether headcut or surface erosion or some other process occurs) it is important to ensure that conditions for these macro and micro erosion processes are understood in relation to different soil types and conditions, and that any breach prediction models correctly reflect these processes. This paper presents an update on progress with a programme of research being implemented by EDF which investigates (i) how macro erosion processes change in relation to soil type and state, (ii) the validity of soil erosion relationships used for coarser and mixed grained erosion and (iii) the performance of breach models in predicting the breaching processes. This research combines laboratory testing at UPM (~1m scale tests), and potentially also at CNR (~2m scale tests), with large scale field tests (2-4m high) to be undertaken at a new test facility being constructed in the River Ebro catchment in Spain near Zaragoza. The work also combines breach model performance validation through a programme of international collaboration and aligns with research into soil erosion currently underway in the USA by the Army Corps of Engineers (ERDC, Vicksburg) and the Bureau of Reclamation (Denver).