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Secchia River drainage basin and (inset a) aerial photo of the levee breach occurred on January 19, 2014 near San Matteo (Modena, Italy).
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Mammal bioerosion is an emergent threat to the functionality of levees. In the present paper, the problem of assessing the failure probability of levees affected by mammal bioerosion is addressed. A fully bivariate description of peak flow discharge and flood duration is combined with a deterministic unsteady seepage flow model to obtain a suitable...
Citations
... In the literature, the explicit consideration of local heterogeneities mainly focused on the study of crack formation in dams (He et al., 2021;Savage et al., 2019) and effect of animal burrows on levee stability. The latter has been recently investigated numerically and experimentally (Balistrocchi et al., 2021;Dassanayake and Mousa, 2020;Onda and Itakura, 1997;Palladino et al., 2020;Saghaee et al., 2017;Taccari, 2015). ...
... The decrease in FS (or increase of Pf) in the damaged levee is considered a proof of concept of the risk associated with the presence of cavities, but, in some cases, the assumed failure surface may not be representative of the real conditions. In many studies, for example, Balistrocchi et al. (2021), Palladino et al. (2020), Taccari (2015), failure is assumed to occur when the phreatic line reaches the landside slope surface. This is the necessary condition for the onset of erosion at the toe or through the levee body which usually progresses more slowly than concentrated erosion. ...
This article discusses the levee failure that occurred on 6 December 2020 at Castelfranco Emilia, near Modena (Italy), showing that it cannot be explained without assuming the presence of local heterogeneities or a small cavity. The possible presence of these defects is supported by evidence derived from historical data and site observations. Fully coupled hydromechanical finite element simulations prove that the river embankment assumed without any deficiency had a sufficient level of safety for the considered event, thus it is necessary to hypothesize the presence of a local defect. The presence of a small cavity, in hydraulic communication with the river and buried at shallow depth, is assumed. This could be, for example, a new den, an old animal burrow repaired only partially, or a rotten plant root. Numerical analysis shows that the increase in water pressure within the cavity can trigger local failure of the landside slope, thus starting concentrated erosion. In highly erodible soils, this mechanism can lead very rapidly to the opening of the breach. A new analytical expression for the factor of safety of the soil wedge between the cavity and the surface is proposed. This approach is very simple and easily applicable, for example, to the assessment of levee vulnerability to animal burrows at a large scale. The results of the study are relevant for the management of water retaining structures.
... Marijnissen et al. [3] used an extensive probabilistic method to re-evaluate the multifunctional dikes in the Netherlands considering the society and economy. Balistrocchi et al. [4] discussed the advantages of the two methods, i.e., numerical simulations and fragility curves, to study the failure probability analysis of levees. He proposed a model to calculate the failure probability of a mammal bioerosion levee considering the peak flow discharge and flood duration. ...
For the risk assessment of flood defense, a comprehensive understanding of risk factors affecting dike failure is essential. Traditional risk assessment methods are mostly based on experts’ experience and focus on just one type of failure mode of flood defensive structures. The risk resources, including the analytical factors and non-analytical factors, were summarized firstly according to the general experience of dikes. The uncertainty of the resources that affect dike safety can be quantified by membership degree. Hence, a fuzzy influence diagram based on fuzzy mathematics was proposed to assess the safety of the dikes. We evaluated the multi-failure modes at the same time by a fuzzy influence diagram. Taking a dike as an example, the expected value of the dike failure was 6.25%. Furthermore, the chance of damage to this dike was “very unlikely” according to the descriptive term of the Intergovernmental Panel on Climate Change (IPCC). The evaluation result was obtained as a probabilistic value, which enabled an intuitive perception of the safety of the dikes. Therefore, we provided some reasonable suggestions for project management and regular maintenance. Since the proposed method can account for uncertainties, it is well suited for the risk assessment of dikes with obvious uncertainties.
... This paper focuses on the effect of small and medium-sized cavities, such as those burrowed by mammals, on the stability of the landside slope of levees. Recent studies investigated this issue numerically [5][6][7][8][9][10], conducting seepage analyses eventually coupled with the limit equilibrium method (LEM) to evaluate the factor of safety (FS) of the slope. ...
... Bi-dimensional seepage analyses are performed considering idealized geometries and material properties of the cavity. In many cases, e.g., [6,8,10], failure is assumed to occur when the phreatic line reaches the landside. This is the necessary condition for the onset of erosion at the toe or through the levee body. ...
Earth dams and levees often offer an attractive habitat for burrowing animals such as
porcupines, nutria, badgers, etc. However, their activity may damage the earth structure, potentially
leading to catastrophic failures. If the burrow system connects the waterside and the landside, water
flows through the pipe and it can start concentrated erosion. This paper shows that the conditions
to trigger concentrated erosion can be generated by a local instability mechanism of the landside
slope in which the soil cover between the cavity and the surface is expulsed due to increasing water
pressure. A simplified model based on the limit equilibrium method is proposed and compared with
bi-dimensional and three-dimensional finite element analyses. This mechanism can better explain
real failure cases. The results provide useful suggestions for the assessment of levee vulnerability to
animal burrows and for the management of water retaining structures
