An alternative process-based approach to predicting the response of water-saturated porous media to harmonic hydrodynamic loads

Methods have been developed to predict how hydrodynamic loads acting on nearly saturated porous media are transmitted to the subsoil. In line with the effective stress principle of Terzaghi, these methods apply the boundary conditions that the effective stresses at the surface of a porous medium are zero, and that the pore water pressures...

An analytical process-based approach to predicting breach width in levees constructed from dilatant soils

An accurate prediction of the breach widening rate after the onset of a levee failure is essential for flood risk assessments. Current state-of-the-art analytical breach growth relations are empirical in nature. The large variety in loading conditions, levee design, and levee construction material, combined with the limited amount of accurate...

Detachment of dilatant soil due to high hydraulic shear stresses explained

When soil surfaces are exposed to high shear stresses induced by high-velocity water flows, they erode. Erosion consists of the detachment, entrainment and transport of soil particles. When exposed to high shear stresses the process of soil detachment is no longer given by the pick-up of individual particles but by the continuous shear failure...

Verification of a Predictive Formula for Critical Shear Stress with Large Scale Levee Erosion Experiment

Apart from the soil erodibility parameter, the critical shear stress is the most important parameter in predicting erosion rates. On the basis of experiments several empirical formulas have already been de-veloped which relate the critical shear stress to soil properties. Based on these findings and supported by new large scale experiments, a...

Relating grass failure on the landside slope to wave overtopping induced excess normal stresses

A high quality safety assessment of levee systems requires a good prediction of when the grass cover of levees fail. Current methods relate the onset of failure to the peak in momentum or energy of the flow, instead of the peak in momentum transfer or energy transfer to the grass cover. The critical velocity necessary in the current methods...

Towards an International Levee Performance Database (ILPD) and Its Use for Macro-Scale Analysis of Levee Breaches and Failures

Understanding levee failures can be significantly improved by analysing historical failures, experiments and performance observations. Individual efforts have been undertaken to document flood defence failures but no systematically gathered large scale, open access dataset is currently available for thorough scientific research. Here, we...

Preliminary Results of the Safelevee Project

Comparing soil erodibility predictions against the fundamental understanding of erosion

In breaching of levees, sediment erosion is induced by high flow velocities. Due to the often continuously acceler-ating flow, no equilibrium transport conditions are reached. The erosion rate is often described by the erosion equation which linearly relates the erosion rate to the excess shear stress by means of a soil erodibility coefficient....

Evaluating the Impact of the Covariance of the Friction and Potential Gradient on Describing the Infiltration Process

During infiltration of water in soil, menisci form at the interface of water, grains, and air in the pores, inducing suction due to surface tension. Due to the random distribution of interconnected pores of different sizes, characteristic of porous media, differences in suction and friction inside pores give a diffusing infiltration front. The...

Detection and Analysis of Weak Spots in Levees Based on Satellite Radar Interferometry

Comparing overflow and wave-overtopping induced breach initiation mechanisms in an embankment breach experiment

As part of the SAFElevee project Delft University of Technology collabored with Flanders Hydraulics Research, and Infram B.V. in the preperation and execution of a full scale embankment breach experiment in November 2015. This breach experiment was performed on an 3.5m high embankment with a sand core and clay outer layer situated along the...

Distributions for wave overtopping parameters for stress strength analyses on flood embankments

A process based assessment of the probability of failure of a flood embankment, as well as an assessment of the consequences of failure of an embankment require insights into the stresses on the landside slope of an embankment. These assessments are hindered by the empirical nature of the wave overtopping parameters. Failure initiation is often...

On the importance of analyzing flood defense failures

Flood defense failures are rare events but when they do occur lead to significant amounts of damage. The defenses are usually designed for rather low-frequency hydraulic loading and as such typically at least high enough to prevent overflow. When they fail, flood defenses like levees built with modern design codes usually either fail due to wave...

Unveiling the consequences of your breach growth model choice

Within the frame work of the realisation of the ‘Sigmaplan’ for the river Schelde in Flanders (Belgium), a large-scale dike breaching experiment following overflow was held at Lillo (Antwerp) in 2012. The outcomes of the breach test serve to unveil the impact of a chosen breach growth model, to set application limits, to come up with guidelines...

Morphological changes along a dike landside slope sampled by 4D high resolution terrestrial laser scanning

Emergence of light detection and ranging (LiDAR) technology provides new tools for geomorphologic studies improving spatial and temporal resolution of data sampling hydrogeological instability phenomena. Specifically, terrestrial laser scanning (TLS) collects high resolution 3D point clouds allowing more accurate monitoring of erosion rates...

A SWOT analysis of hydrodynamic models with respect to simulating breaching

Deriving the bed shear stresses from hydrodynamic models in breach models is challenging due to the continuous changing hydraulic head over the breach in combination with horizontal and vertical flow contractions, and the continuous rapidly changing breach geometry. Three stages can be distinguished in breach flows. Stage 1 initiates when the...