Sediment deposited during hurricanes is a little-studied but potentially important contributor to long-term coastal marsh aggradation. Studies of modern hurricane storm surge deposits are needed to quantify the impact of hurricanes on long-term marsh sedimentation rates, and to inform interpretations of prehistoric hurricane deposits. This Rapid Response project will make use of recent storm surge deposits associated with Hurricane Isaac, a Category 1 storm that impacted the U.S. Gulf Coast in August 2012. Sampling transects will be established at sites of storm surge sedimentation that vary in distance from the hurricane landfall location. Excavation pits along transects will be stratigraphically described and sampled to determine the magnitude, distribution, and characteristics of the storm surge deposits. To place the deposits in the context of long-term marsh sedimentation rates, underlying sediments will be dated in increments using Cesium-137. Transects will be revisited after a year to characterize the incorporation of the deposits into the marsh. The project will build upon related NSF-funded studies recently conducted by the principal investigator.
Results of this research will aid interpretations of hurricane deposits in the sedimentary record, which contribute significantly to assessments of hurricane recurrence intervals, long-term trends in hurricane activity, and associated risk to coastal inhabitants. The potential involvement of a graduate student will include training in sampling and analysis, presentation and publication of results, and incorporation of the research into a Master?s thesis.
, to determine if the storm surge deposits were preserved in marshes and to measure the contribution of Hurricane Isaac to long-term sedimentation in coastal marshes. Fieldwork was conducted at Grand Isle State Park, Venice, Boothville, Buras and Shell Beach, Louisiana, at Waveland, Graveline Bayou and Ocean Springs, Mississippi, and at Gulf Shores and Bon Secour Bay, Alabama. The initial fieldwork revealed that storm surge deposition was much smaller and less widespread than anticipated. Many sites had no discernable sedimentation and other sites had only a thin veneer of mostly organic debris and mud extending only a few meters inland. Consequently, plans to revisit sites to assess deposit preservation and to use cesium-137 dating to assess contribution of deposits to long-term marsh sedimentation had to be abandoned. Significant storm surges were experienced during the hurricane (3+ meters); these findings suggest that other factors, probably sediment sources and wind speed, are major controls on storm surge sedimentation. The results from this study will become part of a larger database of hurricane storm surge sedimentation (sedimentation from a Category 1 hurricane). This database will be useful for calibrating models of storm surge sedimentation resulting from hurricanes of different intensities. Because plans to revisit sites were abandoned, there were significant savings in the project budget.
