(1) technical description: It is proposed to study storm surge deposits of Hurricane Rita in Louisiana coastal marshes to help answer two questions of significant societal importance: how significant to long-term coastal marsh sedimentation are episodic, but large inputs of sediment from hurricane storm surges? and, are storm surge deposits distinguishable from tsunami deposits in coastal marshes? To address the first question it is proposed to sample and characterize the storm surge deposits within weeks of deposition, while the sediments will be at the surface of the marsh, clearly identifiable and relatively undisturbed by erosion and bioturbation. The same deposits will resurveyed after 1.5 years to determine how much of the deposit is incorporated into the marsh and contributes to long-term marsh sedimentation. The significance of this contribution will be determined by comparing the storm surge sedimentation to long-term average sedimentation rates of the underlying marsh gained from cesium-137 dating. The second question will be addressed by determining if internal sedimentary structures within the storm surge deposits support the hypothesis that tsunami deposits can be identified by internal evidence of multiple pulses of sediment-laden water, consistent with a tsunami wave train. Such structures are common in tsunami deposits, but are apparently absent in storm surge deposits.
(2) nontechnical description: Hurricane-derived storm surge sedimentation may be an important, but poorly understood mechanism of coastal marsh growth. Data from this study will improve our understanding of this mechanism and our ability to accurately and realistically predict marsh growth. Better understanding of marsh sedimentation will be important for studies of the fate of coastal marshes vulnerable to sea level rise caused by global warming. Better understanding of the potential impact of storm surge deposits on long-term marsh sedimentation will result in more reliable and realistic predictions of long-term marsh growth. This predictive capability will be important for the effective protection and management of these ecologically and commercially important habitats. Reliable identification of tsunami deposits is required for effective estimation of earthquake recurrence intervals and for tsunami hazard mitigation research. This project will also serve to integrate research and education, because a graduate research assistant will participate in fieldwork and laboratory work and will use the project as the basis for a master's thesis. The results of this project will be broadly disseminated to enhance scientific and technical understanding in a variety of ways, reaching scientific researchers, policy-makers and the public-at-large. It is anticipated that this project will result in several conference presentations and peer-reviewed journal articles.
