The success of experimental studies to investigate hydraulics of dam breaching requires an adequate specification of geotechnical parameters and control over its realization in field or in laboratory conditions. Although this is known, there are few studies specifically addressed to formulate and discuss the requirements for comparable laboratory hydraulic tests to study embankment failure by overtopping. This study addresses this research gap specifically for homogeneous earthfill dams. It is aimed at proposing and discussing a set of core procedures and monitoring techniques to be observed in studies of dam breaching by overtopping. A first procedural step involves the theoretical discussion of similarities between model and prototype erodibility. Further steps involve observations of breached model dams under controlled hydraulic and geotechnical conditions. Requirements for comparability of hydraulic laboratory practice are described and discussed, and it is argued that the key geotechnical parameters of control are the soil composition (more specifically, the fraction of fine material) and the compaction conditions (relative compaction and water content). To attain similarity conditions in what concerns model dam erodibility, whose failure modes should include headcuts and undercutting, a range of reference values for the geotechnical control parameters is suggested and construction/compaction methods are discussed.

The quantification of the breach hydrograph of an overtopped earth dam remains a challenge, even in controlled laboratory conditions. In this work, the breach hydrograph is calculated as the product of the velocity normal to a breach cross section and the estimated area of that cross section. Although theoretically simple, because it is based on the very definition of discharge, this direct approach is an absolute novelty in dam-breach studies. To illustrate the application of the method, a laboratory model of an earth dam, built with cohesive sediments, was closely monitored. Competent velocities were estimated from surface velocity maps measured with large-scale particle image velocimetry (LSPIV). The breach area was estimated by analyzing images of the traces of a laser sheet on the free surface and the breach bottom. The direct breach hydrograph was compared with an estimate based on the mass balance in the reservoir and with the discharge obtained through a rating curve of a downstream spillway. The novel method was shown to reproduce the main expected features of the breach hydrograph. The potential to provide estimates free from experimental artifacts caused by improper description of inertial effects is underlined. The advantages and the difficulties inherent to the method are discussed.

The present work addresses the influence of internal drainage systems on failure by overtopping of earth dams. It is based on data collected in six homogeneous dam breach laboratory experiments. Different drainage systems were tested: (a) toe drain only and (b) complete internal drainage system—chimney filter, horizontal blanket and toe drain. The tests were performed with the same embankment body material, reservoir dimensions and inflow conditions but different relative compactions. We analyze the breach hydrograph and the stages of dam breaching. The failure of dams with complete and fully functional drainage systems exhibits marked differences, the most conspicuous of all being the longer duration of the initial erosion stage. This is accompanied by a lower increase rate of its breach discharge. We argue that this is the combined result of the upstream migration of the locus of hydraulic control and of a higher resistance to erosion of the downstream shell, kept unsaturated by the drainage system. Hydraulic control moves upstream, to a less morphologically active cross‐section, as a result of channel deepening once the chimney drain is uncovered and eroded. Once the erosion merges with the cavity where the chimney filter was, marking the end of the initial erosion stage, the rate of erosion increases and becomes comparable to that of dams with toe drain only. Our argument about the longer duration of the initial stage is not applicable to latter stages—the total time before full collapse is not necessarily increased.

Embankment structures in civil engineering, such as earth dams and fluvial dikes, have a crucial role in society. These structures, often used for water storage and mining tailing containment, are cost-effective due to their reliance on locally sourced materials. While the failure of concrete structures is not so frequent but often lead to severe consequences, embankment structures, particularly fluvial dikes, are more prone to breach and the consequences vary from mild to catastrophic, depending on the proximity to human populations. Worldwide, some fluvial dike failures have resulted in catastrophic outcomes for human lives, the local economy and the environment. This paper aims to develop a methodology to calculate in situ breach outflow hydrographs, resorting to real-time, non-intrusive and friendly access technology. The goal is to provide a practical platform for developing and testing integrated systems applicable to prototype failure cases. An accurate, real-time hydrograph estimation capacity improves risk assessment. The proposed methodology deploys, in a medium-scale experimental facility, common technology and data processing techniques to characterize the evolution of a fluvial dike failure. The morphodynamic and hydrodynamic components influencing the in situ breach outflow hydrograph are assessed by characterizing, in real-time, the breach morphology at the surface and underwater, the surface velocity maps and the corresponding cartesian coordinates.