743
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
1
Computer Simulation of Levee’s Erosion and Overtopping
Simulation numérique de l'érosion et de la surverse de digues
Kamalzare M., Zimmie T.F.
Civil & Environmental Engineering department, Rensselaer Polytechnic Institute, Troy, NY, USA
Han T.S., McMullan M., Cutler B.
Computer Science department, Rensselaer Polytechnic Institute, Troy, NY, USA
Franklin W.R.
Electrical Engineering department, Rensselaer Polytechnic Institute, Troy, NY, USA
ABSTRACT: Improved computer models of erosion have been developed, considering soil hydraulic conductivity. The models deal
with erosion of levees, dams and embankments due to overtopping. The simulations trace the formation of rills and gullies, beginning
with initial overtopping and continuing to final breaching. Physical models performed at “1-
g
” and high “
g
” using a geotechnical
centrifuge have been used to calibrate the models. Previous models did not consider soil hydraulic conductivity, and although results
were quite good for the formation of rills and gullies and sediment quantities, breach times were underestimated. Essentially the water
flow was treated as if passing over a solid surface, not entering the soil, and the total water flow was available for erosion. Thus,
breach times were underestimated. Soil erodibility parameters had to be adjusted to achieve good agreement with breach times. The
new models developed consider soil hydraulic conductivity, and produce good agreement with the performance of the physical
modeling.
RÉSUMÉ : Des modèles numériques améliorés de l'érosion ont été développés, qui prennent en compte de la conductivité hydraulique
du sol. Les modèles traitent de l'érosion des digues, des barrages et des remblais par surverse. Les simulations permettent de suivre la
formation de rigoles et de ravines, s’initiant avec la surverse et se poursuivant par la brèche finale. Les modèles physiques "1-g" et "g"
à l'aide d'une centrifugeuse géotechnique ont été utilisés pour étalonner les modèles. Les modèles précédents ne considéraient pas la
conductivité hydraulique du sol, et même si les résultats étaient assez bons pour la formation des rigoles et de ravines et des quantités
de sédiments, les temps ont été sous-estimés pour la formation de la brèche. En particulier, le débit de l'eau a été traité comme s'il
s’écoulait sur une surface solide, ne pénétrant pas dans le sol, et donc le débit total d'eau était disponible pour l'érosion. Ainsi, les
temps pour la brèche ont été sous-estimés. Les paramètres d'érodabilité du sol ont dû être ajustés afin de parvenir à un bon accord
entre le temps de formation de la brèche. Les nouveaux modèles développés considèrent la conductivité hydraulique du sol, et les
résultats sont en bon accord avec les résultats de la modélisation physique.
KEYWORDS: Erosion, Levees, Computer Simulations, Physical Modeling.
1 INTRODUCTION
Levee failures often occur due to overtopping and seepage,
which creates erosive processes, portending to the breaching of
the levee and catastrophic damage on the adjacent flood plain.
Planning for such emergencies for levee or dam breaches
requires reliable predictions, especially on complex
terrain. Griffis (2007) addressed the overall design of the
engineering works, discussing the natural and engineered flood-
protection structures and strategy for major hurricanes
concerning New Orleans. His evaluation assessed the
improvements necessary to protect from the damaging effects of
water. After analyzing the failures of the natural system and of
the levees, floodwalls, pumping stations, and the absence of
flood gates on the canals, he concluded that the “design storm”
specified by congressionally authorized projects deserved
reconsideration, and that engineering design reviews should be
reorganized and implemented. In order to make such
improvements the properties of soil, especially the erodibility of
it, had to be evaluated. Wan and Fell (2004) describe the
development of two erosion rate tests, the Hole Erosion Test
(HET) and Soil Erosion Test (SET), which measure soil
erodibility. Using an Erosion Function Apparatus (EFA), Briaud
et al. (2008) investigated the erodibility of several different
types of soil, classifying the soils by erodibility based on degree
of compaction, erosion rate, water velocity and hydraulic shear
stress. Xu and Zhang (2009) found that in addition to soil type,
the degree of compaction affects erosion resistance, increasing
with compaction effort, particularly with fine soils.
Post Hurricane Katrina field surveys showed that rolled,
compacted clay filled levees performed well with minor erosion
occurring when overtopped, whereas hydraulic filled levees
with silt and sand performed poorly. Clayey material often
required long haul distances that slowed construction progress,
thus nearby granular material was often used instead (Sills et al.,
2008).
As computer capabilities progress in representing hurricane
induced storm surges, a need arises to improve understanding of
the overtopping erosion potential and to provide associated
guidance for more rational design parallels. Dean et al. (2010)
and Holmes et al. (2011) presented a three-dimensional smooth
particle hydrodynamics (SPH) simulator for modeling grain
scale fluid flow in porous media. The versatility of the SPH
method has driven its use in increasingly complex areas of flow
analysis, including the characterization of flow through
permeable rock for both groundwater and petroleum reservoir
research. SPH provides the means to model complex multi-
phase flows through such media; however, acceptance of the
methodology has been hampered by the apparent lack of actual
verification within the literature, particularly in the three-
dimensional case. The accuracy of results for low Reynolds
number flows is highly dependent on the implementation of no-
slip boundary conditions. They also presented a new, robust and
numerically efficient, method for implementing such boundaries
in SPH. Simulation results for friction coefficient and
permeability were shown to agree well with the available
