Identifier

etd-11152012-174353

Degree

Master of Science (MS)

Department

Civil and Environmental Engineering

Document Type

Thesis

Abstract

Breakwaters have been constructed in many areas along Louisiana’s coastline to protect the shoreline from wave energy and erosion. During normal conditions, these breakwaters can typically be analyzed using traditional empirical methods for emergent breakwaters. However, Louisiana’s coastline is under constant threat from tropical storms and hurricanes, during which breakwaters can frequently become overtopped or submerged systems. Recent studies show that the type of shoreline response to a breakwater system may vary depending on the crest height of the breakwater in relation to the mean water level. Though emergent breakwaters typically induce sediment accretion along the shoreline, studies using laboratory and numerical models indicate that overtopped or submerged breakwaters may increase erosion of the shoreline. This variation of the hydrodynamic patterns and shoreline response is of particular interest for breakwaters along shorelines that can be impacted by hurricanes and other events that trigger large variances in water level, as the breakwaters may periodically shift between emergent and submerged states. The Holly Beach Breakwater System has been constructed to protect a vital piece coastline in southwestern Louisiana. These breakwaters are typically emergent, but can frequently be inundated by surge events and become submerged, and therefore may not always perform as intended. This study uses topographic survey data, aerial photography, and wave and surge information associated with Hurricanes Rita and Ike to identify the sediment transport patterns generated by emergent breakwaters impacted by storm surge and waves. The results of this study show that during a storm event the sediment transport patterns within the breakwater system are very different from those of an emergent system and vary with the geometry of the breakwater system. During Hurricanes Rita (2005) and Ike (2008), breakwaters near the shoreline exhibited extreme erosion and very little accretion, while breakwaters farther from the shoreline showed more accretion which, in some cases, offset the erosion of the beach. Erosion to accretion ratios for segments of breakwaters near the shore were 20 to 50 times higher breakwaters farther from shore. The cause of these erosion patterns is investigated based on the hydrodynamic conditions of Hurricanes Rita and Ike.

Date

2012

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Chen, Q. Jim

DOI

10.31390/gradschool_theses.2184

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