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Management, Operations, and Maintenance
Published in Robert H. Kadlec, Treatment Marshes for Runoff and Polishing, 2019
Berms and levees require inspection and maintenance. Routine activities include mowing, and pothole repair on drivable levees. Bank erosion is a common problem for small urban systems. Erickson et al. (2010) report that 11% of urban systems surveyed in Minnesota and Wisconsin required berm maintenance. A primary concern for urban systems is berm leakage. As noted in U.S. EPA (2009), leaks through embankments or wetland bottoms are often difficult to locate. They also observe that if the permanent pool becomes low during or immediately following construction, it can be a sign of poorly compacted berms.
Floods as Unnatural Disasters
Published in Kathleen A. Miller, Alan F. Hamlet, Douglas S. Kenney, Kelly T. Redmond, Water Policy and Planning, 2017
Sandra B. Zellmer, Christine A. Klein
Second, levees will fail. As one engineer explains, there are two kinds of levees: “Those that have failed and those that will fail!” (Martinsdale and Osman 2007). In fact, levees are designed to fail under some circumstances. In engineer-speak, this is dubbed residual risk. The typical 100-year levee is engineered to hold back the level of flooding that has at least a 1% chance of occurring each year (which translates into a 26% chance of flooding over the life of a 30-year mortgage). Beyond that, all bets are off. The American Society of Civil Engineers (ASCE) warns that no levee is flood-proof: Levees reduce the risk of flooding. But no levee system can eliminate all flood risk. A levee is generally designed to control a certain amount of floodwater. If a larger flood occurs, floodwaters will flow over the levee. Flooding also can damage levees, allowing floodwaters to flow through an opening, or breach. (ASCE 2010, p. 2)
Case Study 10: Living with Water, and the Role of Technological Culture
Published in Jenn Stroud Rossmann, Clive L. Dym, Lori Bassman, Introduction to Engineering Mechanics, 2015
Jenn Stroud Rossmann, Clive L. Dym, Lori Bassman
Levees may fail due to gradual erosion or sudden rupture, allowing water to flood the surrounding land. When the water level is higher than the levee, sometimes referred to as “overtopping,” this will also cause flooding, but is less disastrous as it generally does not damage the levee itself.
Decision support system for managing flooding risk induced by levee breaches
Published in International Journal of River Basin Management, 2022
Lorenzo Scopetani, Simona Francalanci, Enio Paris, Leonardo Faggioli, Jacopo Guerrini
Under the EU Floods Directive (CE, 60/2007, n.d.), the creation of risk and hazard maps is essential in river risk management. Levees play a major role in reducing flooding areas, but it is important to note that they are usually considered as non-collapsing structures, underestimating the potential flooding in case of levee failure or breach (Barbetta et al., 2017 Mazzoleni et al., 2014; Solari et al., 2014;). Moreover, some embankment systems were built many centuries ago (Tourment et al., 2018), and because of significant changes in land development and environmental conditions, they may no longer be able to withstand the load. For this reason, it is crucial to analyse the stability of these earthen structures and consider their possible collapse with the consequences they may generate (Colman et al., 2016).
The levee effect along the Jamuna River in Bangladesh
Published in Water International, 2019
Md Ruknul Ferdous, Anna Wesselink, Luigia Brandimarte, Giuliano Di Baldassarre, Md Mizanur Rahman
In 1945, Gilbert F. White wrote that ‘floods are acts of God, but flood losses are largely acts of man. Human encroachment upon the floodplains of river accounts for the high annual toll of flood losses’ (White, 1945, p. 2). Following this observation, White postulated the existence of a ‘levee effect’ in flood risk management and presented evidence for this effect in the United States. ‘Levee’ is a universal term for embankments (man-made or natural) that prevent floodwater flowing from a river to the surrounding areas; dikes are the man-made levees. In this article we will use ‘levee’, since White’s hypothesis and subsequent research used this term. The levee effect is when the construction of levees to protect property from flooding induces property owners to invest more in their property, multiplying the risk should the levee breach or be overtopped. Of course, investment in property or economic capital may be exactly why the levee was constructed in the first place. With risk being defined as the product of the probability of events (here: flooding) occurring and the likelihood caused by damage of such events (Di Baldassarre, Castellarin, Montanari, & Brath, 2009; van Manen & Brinkhuis, 2005), the levee effect implies the paradoxical result that the construction of a levee can increase rather than reduce risk: while the frequency of flooding is reduced, the potential damage is magnified. Whether the risk indeed increases when a levee is constructed depends on the relative magnitude of the two factors, which will be different in different places and at different times (Tanoue, Hirabayashi, & Ikeuchi, 2016).
Probabilistic seismic analyses of earthen levees with finite element modeling
Published in Marine Georesources & Geotechnology, 2023
Liang Zhang, Weiwei Zhan, Lei Wang
This section uses a case study of an existing earthen levee to demonstrate the probabilistic seismic assessment framework. The studied levee is adapted from a real levee built in 1990s for flood protection, which runs along a parking lot holding back a substantial area including wetlands. The earthen levee is built on top of a permanent soil foundation and composed of three types of geotechnical materials (i.e. embankment soil, rockfill zone, and No. 57 stone). The representative cross section of the levee is shown in Figure 1. The widths of the levee base and crown are 16.4 m and 0.3 m, respectively. The height of the levee is 3.35 m, and both sides of the levee have a slope ratio of 2:1 (horizontal to vertical). The rockfill zone has a base width of 6.7 m and a height of 2.1 m. The water level is 2.1 m above the ground level, which corresponds to a flood hazard of a 100-year returning period. The groundwater table of the downstream side is 0.6 m below the ground level according to subsurface exploration results. A total of eight borings were drilled at the crown and toe of representative levee sections to estimated depths of 6 to 9 m. Nine undisturbed soil samples (Shelby tube samples) were obtained, and disturbed soil samples (split-spoon samples) were taken at regular intervals. Twenty-four sieve analysis and Atterberg limits tests were performed for selected disturbed soil samples. Two direct shear tests and one consolidation test were performed for selected undisturbed soil samples. The results from field exploration and laboratory testing are used to estimate the strength parameters of soils and the geotechnical parameters for each layer of the earthen levee used in the analysis are listed in Table 1.