Hurricane Sandy Surge and Marsh Dieback in the New Jersey Coastal Zone Completed

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The Science Issue and Relevance: Detection of storm surge impacts on coastal marshes requires regional or broader mapping of surge flooding above and below the wetland canopy and estimation of abnormal change in wetland condition. Accomplishing these objectives will provide not only the basis for assessing Hurricane Sandy impacts to the NJ coastal wetlands, but also a framework for monitoring wetland resilience and inundation patterns in general for protecting floodplain ecosystems, mitigating flood hazards, sustaining biodiversity, and land-use planning.

Methodology for Addressing the Issue: Our approach and expectations for this study were drawn from past mapping accomplishments in the northern Gulf of Mexico that fused radar and optical image data to map surge extent, surge duration or persistence, and response of the coastal marsh to the prolonged elevated salinity from surge flooding. This study combined a radar-based time series of Hurricane Sandy surge and estimated persistence with optical sensor-based marsh condition change to assess potential causal linkage of surge persistence and marsh condition change. TerraSAR-X and COSMO-SkyMed radar images collected after Hurricane Sandy were processed to map surge along the 209 km New Jersey Atlantic Ocean coast. Surge persisted for 12 hours past landfall in marshes from Great Bay to Great Egg Harbor Bay, and up to 59 hours after landfall in many back-barrier lagoon marshes. Marsh condition change (i.e., loss of green marsh vegetation) was assessed from optical satellite images (Satellite Pour l’Observation de la Terre [SPOT] and Moderate Resolution Imaging Spectroradiometer [MODIS]) collected before and after Hurricane Sandy. Overall agreement in the SPOT and MODIS condition maps allowed assessment of a possible link between surge persistence and marsh condition change to be based on the high spatial resolution SPOT and radar image data. There was widespread agreement in the pattern of high-surge persistence and high change of marsh condition in the back-barrier lagoon marshes. Overall, the independent calculation of satellite-based flood surge persistence and marsh condition change from before to after the surge enabled detection of distinct and contiguous surge-related impacts patterns particularly extensive in back-barrier marshes surrounding Great Bay just to the right of the Hurricane Sandy landfall track.

Future Steps:

• Develop a remote sensing (RS) indicator of marsh canopy structure. The ability to map canopy structure will provide a measure to differentiate marsh types and condition, track subtle changes before irreparable and nonreversible change has taken place.
• Emergency Response, Sustainable Management, Carbon Indexing: Utilizing coordinated ground, LiDAR, and radar collections, as well as taking advantage of our developed ground-based measurement of marsh and forest canopy structure, to develop the first operational RS canopy structure mapping system.

Additional Publications:

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1. Ramsey III, E., Y. Suzuoki, A. Rangoonwala, and T., Bannister , 2013. Coastal Inundation Monitoring with C-band and L-band Satellite Data. J. American Water Res. Ass. 49(6), 239–1260.
2. Suzuoki, Y., A. Rangoonwala, and E. Ramsey III, 2011.  Monitoring coastal inundation with Synthetic Aperture Radar satellite data: U.S. Geological Survey Open-File Report 2011–1208, 46 p. < http://pubs.usgs.gov/of/2011/1208/&gt;
3. Ramsey III, E., D. Werle, Z. Lu, A.Rangoonwala, and Y. Suzuoki, 2009.  A Case of Timely Satellite Image Acquisitions in Support of Coastal Emergency Environmental Response Management.  J. Coastal Res. 25(5), 1168-1172.