Mapping oil in a coastal marsh with polarimetric synthetic aperture radar

Abstract

Our research focused on the effectiveness of high spatial resolution and fully polarimetric L-band SAR (NASA Uninhabited Aerial Vehicle SAR [UAVSAR]) for mapping oil in wetlands, specifically during the Macondo-1 oil spill and its impacts within Barataria Bay in eastern coastal Louisiana. Oil detection relied on PolSAR decomposition and subsequent classifications of the pre-spill (2009) and post-spill (2010) single look complex (SLC) scenes and numerous site observations. Results found that observed shoreline marsh structural damage accompanied by oil occurrence were evident as anomalous features on post-spill but not on the pre-spill SLC flight line data and that these nearshore features were reflected as a change in dominant scatter in Freeman-Durden (FD) and Cloude-Pottier (CP) decompositions and Wishart classifications seeded with the FD and CP classes. Pre- and post-spill SLC data and all decompositions and classifications also revealed a class of interior marshes within the central core of the study region that was associated with a transform of dominant scatter mechanism. The change of dominant scatter is associated with a preponderance of evidence that supports the penetration of oil-polluted waters into interior marshes. Contrary to documented nearshore impacts, however, the lack of contemporaneous observational data and possible shallow flooding in the pre-spill marsh prevent absolute determination of whether UAVSAR detected oil occurrences in the interior marshes.