Erosional equivalences of levees: Steady and intermittent wave overtopping

Dean, Robert G.; Rosati, Julie Dean; Walton, Todd L.; Edge, Billy L.

doi:10.1016/j.oceaneng.2009.07.016

Cited by 50 publications

(75 citation statements)

References 2 publications

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“…It was noted that under overflow conditions whereby the shear stress exerted on the levee was comparable to the peak shear stress during overtopping events, the grass cover did fail during overtopping but did not fail during overflow. This discovery conflicts with the current theories explaining the strength of grass under wave loading and overflow [24] [25] but is in agreement with the latest design rules for the maximum allowable mean overtopping discharges of 5 l/m/s which have been set in The Netherlands [26]. …”

Section: Overflow or Overtopping Resistance Of Grasssupporting

confidence: 56%

On the importance of analyzing flood defense failures

et al. 2016

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Abstract. 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 overtopping or geotechnical failure mechanisms such as instability or internal erosion. Subsequently geotechnical failures could trigger an overflow leading for the breach to grow in size Not only the conditions relevant for these failure mechanisms are highly uncertain, also the model uncertainty in geomechanical, internal erosion models, or breach models are high compared to other structural models. Hence, there is a need for better validation and calibration of models or, in other words, better insight in model uncertainty. As scale effects typically play an important role and full-scale testing is challenging and costly, historic flood defense failures can be used to provide insights into the real failure processes and conditions. The recently initiated SAFElevee project at Delft University of Technology aims to exploit this source of information by performing back analysis of levee failures at different level of detail. Besides detailed process based analyses, the project aims to investigate spatial and temporal patterns in deformation as a function of the hydrodynamic loading using satellite radar interferometry (i.e. PS-InSAR) in order to examine its relation with levee failure mechanisms. The project aims to combine probabilistic approaches with the mechanics of the various relevant failure mechanisms to reduce model uncertainty and propose improvements to assessment and design models. This paper describes the approach of the study to levee breach analysis and the use of satellites for breach initiation analysis, both adopted within the SAFElevee project.

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Section: Overflow or Overtopping Resistance Of Grasssupporting

confidence: 56%

On the importance of analyzing flood defense failures

et al. 2016

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“…This relation is used in this study such that the bed shear stress can be used as loading parameter of the erosion model. Dean et al (2010) showed the importance of including overtopping duration and the effect of using intermittent wave overtopping for the computation of dike erosion. The method of Dean et al (2010) was extended by Hughes (2011) to accurately estimate the excess wave volume above a critical bed shear stress threshold for each overtopping wave, in which the cumulative excess work volume is the summation of the erosion contributions of the individual overtopping waves.…”

Section: Erosion Modelmentioning

confidence: 99%

“…Dean et al (2010) showed the importance of including overtopping duration and the effect of using intermittent wave overtopping for the computation of dike erosion. The method of Dean et al (2010) was extended by Hughes (2011) to accurately estimate the excess wave volume above a critical bed shear stress threshold for each overtopping wave, in which the cumulative excess work volume is the summation of the erosion contributions of the individual overtopping waves. We combined the methods of Valk (2009), Dean et al (2010) and Hughes (2011) to adapt the turf-element model presented in Hoffmans (2012) to a time-and depth-dependent erosion model.…”

Section: Erosion Modelmentioning

confidence: 99%

“…The method of Dean et al (2010) was extended by Hughes (2011) to accurately estimate the excess wave volume above a critical bed shear stress threshold for each overtopping wave, in which the cumulative excess work volume is the summation of the erosion contributions of the individual overtopping waves. We combined the methods of Valk (2009), Dean et al (2010) and Hughes (2011) to adapt the turf-element model presented in Hoffmans (2012) to a time-and depth-dependent erosion model. The erosion model is time dependent since the predicted scour depth due to an overtopping wave is based on the space-and timevarying bed shear stress using a defined time step.…”

Section: Erosion Modelmentioning

confidence: 99%

“…However, no translation towards erosion was made and the set of formulas was derived from a one-dimensional model. Dean et al (2010) developed a method in which erosion development was computed based on the time-varying characteristics of the intermittent overtopping waves. They showed the importance of time dependency in the computation of scour depths.…”

Section: Introductionmentioning

confidence: 99%

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Modelling effects of an asphalt road at a dike crest on dike cover erosion onset during wave overtopping

et al. 2018

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Structures integrated in a grass-covered dike may increase erosion development. Currently, safety assessment methods for flood defences are only applicable for a conventional grass-covered dike and the effects of structures on dike cover erosion are poorly understood. Since many dikes have a road on top, it is important to study the effect of such a road structure on erosion onset during wave overtopping. To investigate this effect, a coupled hydrodynamic-erosion model was developed. The erosion onset caused by overtopping waves was predicted by combining the time-varying bed shear stresses from the hydrodynamic model with a depth-dependent erosion model. The results show that roads on top of a dike increase the erosion of the neighbouring grass cover. This increase in erosion may have a negative impact on dike stability. Therefore, we recommend considering effects of constructions on top of dike profiles during safety assessments. Explicitly, consideration of the roughness transitions in the safety assessments of dikes is recommended.Electronic supplementary material The online version of this article (https://doi

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