The wave overtopping load on landward slopes of grass-covered flood defences: Deriving practical formulations using a numerical model

Bergeijk, Vera M. van; Warmink, Jord Jurriaan; Hulscher, Suzanne J.M.H.

doi:10.1016/j.coastaleng.2021.104047

Cited by 9 publications

(5 citation statements)

References 27 publications

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“…These hydrodynamic loads are important for two types of dike failure: erosion of the dike cover and the block stability. The output of the numerical model can be used to determine the hydraulic load resulting in dike cover erosion [39]. Existing erosion models require hydraulic variables such as the flow velocity [4,40], the shear stress [3], or the normal stress [10], which can be calculated using this new numerical model.…”

Section: Applicationmentioning

confidence: 99%

Hydrodynamic Modelling of Wave Overtopping over a Block-Covered Flood Defence

Barendse

Bergeijk

Chen

et al. 2022

JMSE

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Wave overtopping can cause erosion on the landward slope due to high flow velocities and turbulence that cause high stresses on the cover. Innovative block revetments such as Grassblocks protect the subsoil of the dike against erosion. The blocks are permeable, which reduces the flow velocity and the pressures along the landward slope. The performance of these blocks is assessed in physical tests, which provides insights into the stability of the blocks. However, such experiments are expensive and accurate measurements are difficult due to highly turbulent conditions. Therefore, the goal of this study is to determine the hydrodynamic conditions at the dike cover caused by the wave run-up on the seaward slope and by the overtopping flow over the crest and landward slope. The geometry and wave conditions from the physical test at the Deltares Delta flume are implemented in an OpenFOAM® numerical model. Using the porousWaveFoam solver, a porous layer on the crest and landward slope is implemented, where the flow resistance of this porous layer largely depends on the resistance coefficients α [-] and β [-]. The numerical model is calibrated based on resistance coefficients as introduced earlier in the literature, which showed that the resistance coefficients of α=500 and β=2.0 performed best for the peak flow velocities and the peak pressures. The numerical model is evaluated by using these resistance coefficients in other time series of the physical tests. The evaluated model is then used to determine the hydrodynamic conditions on the landward slope, which showed that the pressure was the most influential hydrodynamic condition at the time of failure. Finally, the model showed that a porosity of n=0.6 and the porous layer thickness η=36 mm reduced the peak pressure the most.

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Section: Applicationmentioning

confidence: 99%

Hydrodynamic Modelling of Wave Overtopping over a Block-Covered Flood Defence

Barendse

Bergeijk

Chen

et al. 2022

JMSE

Self Cite

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“…The turbulence is solved using a k-ω SST turbulence model and a Nikuradse roughness height of 8 mm was used to include the roughness of the grass cover. A full description of the model and the model validation can be found in Van Bergeijk et al (2020) and Van Bergeijk et al (2022).…”

Section: Numerical Model Set-upmentioning

confidence: 99%

“…The coefficients have the dimensions 75.8 kg/m 17/5 , 156 N/m 2 , 6.21 m 1/5 and 0.75 m. The negative offset is the result of the required conditions for flow separation expressed as a combination of the landward slope steepness and the overtopping volume. These conditions were derived by Van Bergeijk et al (2022) and indicate that a minimum overtopping volume of 5 m 3 /m is required for a steepness of 1:3, while flow separation already occurs for a volume of 0.75 m 3 /m for a steepness of 1:1. The reattachment location depends on the overtopping volume.…”

Section: The Effect Of Slope Changesmentioning

confidence: 99%

The Effect Of Geometrical Transitions On The Wave Overtopping Load

Bergeijk¹,

Warmink²,

Hulscher³

2022

Proceedings of the 39th IAHR World Congress

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Erosion by overtopping waves can lead to failure of grass-covered earthen flood defences. Previous studies have indicated that cover failure starts at changes in material or geometry defined as transitions. In this study, the overtopping flow at geometrical transitions is modelled and their effect on the hydraulic load is quantified. A numerical model is developed in the OpenFOAM software and simulates the overtopping flow over the crest and the landward slope of a grass-covered flood defense. Two types of geometrical transitions were studied: slope changes and height differences. These transitions are representative for the landward crest line, the landward toe, erosion holes on the slope and a road on the crest. New relations are developed for the maximum shear stress and the maximum normal stress as result of the geometrical transitions using design parameters such as the geometry and the overtopping volume. These relations can be used in existing calculation methods to include the effects of geometrical transitions on the hydraulic load for the design and the safety assessment of flood defences.

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“…The analytical impact model works well to predict the impact location as the result of a height transitions with a vertical drop. The impact locations predicted with the analytical impact model were compared to the numerical model results and could be further validated using overtopping field tests (Van Bergeijk et al, 2021c). The impact location is calculated as a point in the analytical impact model because it is based on the trajectory of a projectile.…”

Section: Impact Forces At Height Transitionsmentioning

confidence: 99%

“…Another application of the numerical model is the design of wave overtopping tests, for example, overtopping field tests on grass-covered dikes (Van Bergeijk et al, 2021c). The expected load during the experiments can be computed using the measured cross-dike profiles in the numerical model.…”

Section: Application Of the Numerical Modelmentioning

confidence: 99%

Over the dike top: modelling the hydraulic load of overtopping waves including transitions for dike cover erosion

Bergeijk¹

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Samenvatting 1 Introduction 2 An analytical model of wave overtopping flow velocities on dike crests and landward slopes 3 Modelling the wave overtopping flow over the crest and the landward slope of grass-covered flood defences. 4 The wave overtopping load on landward slopes of grasscovered flood defences: deriving practical formulations using a numerical model. 5 The effects of transitions in cover type and height on the wave overtopping load on grass-covered flood defences 6 The cross-dike failure probability by wave overtopping over grass-covered and damaged dikes 7 Discussion 8 Conclusions and recommendations List of References

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The wave overtopping load on landward slopes of grass-covered flood defences: Deriving practical formulations using a numerical model

Cited by 9 publications

References 27 publications

Hydrodynamic Modelling of Wave Overtopping over a Block-Covered Flood Defence

Hydrodynamic Modelling of Wave Overtopping over a Block-Covered Flood Defence

The Effect Of Geometrical Transitions On The Wave Overtopping Load

Over the dike top: modelling the hydraulic load of overtopping waves including transitions for dike cover erosion

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