Mapping Oil in Marshes and Its Implications

Science Center Objects

Remote sensing helps USGS scientists detect and map surface oil in coastal environments.

 

PolSAR image coverage of the Gulf coast on 23-24
A remote sensing optical view of the 2010 Deepwater Horizon oil spill. PolSAR image coverage of the Gulf coast on 23-24 June 2010

The Science Issue and Relevance: Remote sensing detection and mapping of surface oil in deep and coastal open water environments has been and continues to be a high profile research focus. More recently, remote sensing research has recognized the need to detect and track oil pollution into the coastal embayments and tidal channels that define the coastal landscape. That recent focus recognizes and accounts for the juxtaposition of the high concentration of the world’s population and support facilities, the high occurrence of known oil reserves, and the fragility of the critical coastal wetlands that contain critical habitats and nurseries necessary for the sustainability of the coastal resource. The ability to detect and track oil intrusion into coastal land and water environments is necessary to maintain the viability of the coastal resource.

Methodology for Addressing the Issue: During the early stages of the 2010 Deepwater Horizon (DWH) spill, NASA and USGS conceived, planned, and implemented remote sensing based strategies to provide rapid response mapping of the oil spread in the Gulf of Mexico waters and to explore DWH oil mapping in tidally connected coastal inland waters and wetlands. To carryout those mapping efforts, NASA and USGS collected both aircraft-based hyperspectral imaging (HSI) and polarimetric synthetic aperture radar (PolSAR) within the open Gulf, but centered on the DWH spill and along the Gulf coast capturing inland embayments, tidal channels, and coastal vegetation. The mapping focus of the Remote Sensing Applied Research (RSAR) at WARC was to determine the capability of PolSAR to detect oil intrusion into the coastal wetlands. The RSAR efforts focused on the Barataria Bay lying just to the west and in the landward end of the Mississippi River Delta. Two RSAR led studies have shown PolSAR offers a unique perspective of marsh stability not offered by other remote sensing instruments. That perspective captures the marsh architecture, providing a new monitoring technology for mapping the status and tracking the trends of the marsh not directly obtainable from optical sources. RSAR research is determining if post-DWH changes in marsh architecture are possibly linked to oil contamination and if the mapping capabilities of the HIS and PolSAR can be fused to provide more powerful detector of abnormal change and its cause.

Future Steps: Initial results of the RSAR investigation found PolSAR detected shoreline oiling observed by ground crews as well as detected changes within the more interior marshes where observations were lacking. A subsequent RSAR study found that DWH oil had penetrated into the interior marshes and suggested a broad alignment between oil intrusions and the earlier PolSAR observed changes. Although the direct connection between the PolSAR detected changes and the occurrence of oil in the interior marshes is not confirmed, the USGS and NASA studies confirmed the critical capability of PolSAR remote sensing mapping to provide day and night rapid response mapping nearly unimpeded by inclement weather. The next step continues USGS and NASA cooperative efforts to track changes in the coastal wetland and determine if these changes are related to the DWH oil spill.