Abstract
Overtopping of earthen levees can result in lee side erosion, levee failure and severe flooding consequences. Erosion takes time and early design guidance did not account for overtopping duration. The potential overtopping durations associated with hurricanes depends on the time histories of the surges and waves and are usually shorter than for riverine or coastal flooding by other storm types. With significant advancements in hurricane-induced storm surge modeling, it is appropriate to improve the levee erosion response characteristics. This paper presents the results of a blind-folded comparison of a method developed by Dean, et al (2010) to two levee locations in the New Orleans area. The levees failed in one area where the waves were larger than the second area where the levees performed well. The method applied accounts for surge and wave time histories, levee geometry and grass cover quality. Results are consistent with failure at the location of higher wave heights; however, the method also predicts failure at the location where levee function was retained. At the latter location, for good quality grass cover and a wave period of 4 s, a required levee crest elevation of 5.9 m is determined compared to an actual elevation of 5.8 m. For poor grass quality and a wave period of 8 s, the method indicates a required crest elevation of 7.4 m. The method can be applied to optimize levee design, for example, through investigating the trade offs between crest elevation and levee side slopes.
Highlights
Considerable efforts have been directed to understanding the mechanics of levee overtopping by waves, erosion limits to retain levee functionality and development of appropriate design criteria
This paper presents the results of a blind-folded application of recently developed methodology to Hurricane Katrina at two locations on the St
This paper has presented a blinded-folded comparison of required levee crest elevations for retention of levee function at two locations in the St
Summary
Considerable efforts have been directed to understanding the mechanics of levee overtopping by waves, erosion limits to retain levee functionality and development of appropriate design criteria. The results of these efforts are summarized as recommended design criteria in van der Meer (2002, hereafter referred to as the “TAW Manual”), the EuroTop Manual (2007) and the U. Design criteria for grass covered levees were based solely on the magnitude of levee overtopping and grass cover quality and did not include duration it is well known that time is required to accomplish sufficient erosion to compromise levee functionality. At one location where the levees failed, the storm surges and wave heights were significantly larger than at the second location where the levee performed well
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