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USGS Mendenhall Postdoctoral  Research Fellowship Program

14-44. Understanding estuarine geomorphic change under hurricane forcing: role of sediment composition, aquatic vegetation, and hydrodynamics

Estuarine geomorphology governs ecological function in several ways. Light availability to desirable aquatic vegetation (e.g. seagrass) is limited by water clarity and total water depth; stability of salt marshes is dependent on sediment supply and geomorphic evolution. In this context, back-barrier estuaries have not been widely studied as often as coastal-plain estuaries, due to a lack of basic data and relatively infrequent forcing events. Modeling geomorphic change in estuaries has typically been on decadal timescales (Ganju et al., 2009) due to the difficulty of collecting data on shorter timescales and a lack of knowledge of storm effects on estuaries. Submerged aquatic vegetation is common in shallow back-barrier estuaries and is likely a major component of the geomorphic framework. Integration of aquatic vegetation into hydrodynamic and sediment transport models has typically been accomplished by modifying bed roughness (Chen et al., 2007) instead of more physically consistent approaches (e.g. extracting momentum from the flow field; Roc et al., 2013).

Barnegat Bay, New Jersey, is a typical example of an Atlantic coast, shallow, back-barrier estuary: it is benthic-dominated, poorly flushed, and an important ecological habitat. In October 2012, Hurricane Sandy made landfall near Barnegat Bay, New Jersey, presenting an opportunity to understand the nature of geomorphic change within the estuary over a very short period of time. Ongoing studies in Barnegat Bay enabled the rapid collection of topo-bathymetric LiDAR data from before and after the storm. Pre-storm surveys also characterized the bottom substrate as well as the stratigraphy. To date there has been no comprehensive data collection of this type in an estuary. This offers a rare opportunity to test the skill of sediment transport models to simulate storm impacts on estuarine systems and to characterize the geomorphic event-response of the estuary. On the Atlantic coast, several areas are characterized by shallow back-barrier estuaries with extensive seagrass communities (Great South Bay, Barnegat Bay, Chincoteague Bay, Indian River Lagoon), which may be subjected to tropical forcing of increasing intensity or frequency in the future. Therefore, an understanding of the estuarine geomorphic response of Barnegat Bay to Hurricane Sandy would not only further our understanding of estuarine processes and geomorphic evolution but would also be directly applicable to other estuarine systems.

This Mendenhall Research Opportunity will allow a strong scientist with a background in coastal processes to improve the capability for evaluating estuarine geomorphic change in response to storm events, through testing and application of an existing hydrodynamic-sediment transport model of Barnegat Bay. Specific questions may include:

Model development may involve the incorporation of seagrass as a momentum sink in the existing COAWST modeling framework (Warner et al., 2010). Bottom characterization data collected by the USGS can be used to specify bottom sediment type and stratigraphy. The incumbent will determine how to apply the model: whether in an idealized context (representative conditions) or with a fully explicit hindcasting simulation. Depending on the applicant’s expertise, further work on the role of seagrass either geomorphically or ecologically could be explored with the modeling system. This type of bio-geomorphic model application and assessment is highly innovative and lacking in the peer-reviewed literature.

REFERENCES.

Chen, S. N., Sanford, L. P., Koch, E. W., Shi, F., and North, E. W., 2007. A nearshore model to investigate the effects of seagrass bed geometry on wave attenuation and suspended sediment transport. Estuaries and Coasts, 30, 296-31.

Ganju, N. K., Schoellhamer, D. H., and Jaffe, B. E., 2009. Hindcasting of decadal-timescale estuarine bathymetric change with a tidal-timescale model. Journal of Geophysical Research, 114(F4), F04019.

Roc, T., Conley, D. C., and Greaves, D., 2013. Methodology for tidal turbine representation in ocean circulation model. Renewable Energy, 51, 448-464.

Warner, J. C., Armstrong, B., He, R., and Zambon, J. B., 2010. Development of a Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) Modeling System.Ocean modelling, 35(3), 230-244.

Proposed Duty Station: Woods Hole, MA

Areas of Ph.D.: Coastal engineering, physical oceanography, coastal geology or related fields (candidates holding a Ph.D. in other disciplines but with knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications: Applicants must meet one of the following qualifications - Research Oceanographer, Research Hydrologist, Research Geologist, Research Geophysicist, Computer Scientist.

(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant’s background, education, and research proposal. The final classification of theposition will be made by the Human Resources specialist).

Research Advisors: Neil Ganju, (508) 457-2252, nganju@usgs.gov; Jennifer Miselis, (727) 803-8747 x3088, jmiselis@usgs.gov; Robert S. Nicholson, (609) 771-3925, rnichol@usgs.gov.

Human Resources Office Contact: Junell Norris, (303) 236-9557, jlnorris@usgs.gov.


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U.S. Department of the Interior, U.S. Geological Survey
URL: http://geology.usgs.gov/postdoc/opps/2014/14-44 Ganju.htm
Direct inquiries to Rama K. Kotra at rkotra@usgs.gov
Maintained by: Mendenhall Research Fellowship Program Web Team
Last modified: 17:58:09 Tue 23 Jul 2013
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