Comparing the potential of multispectral and hyperspectral data for 1 monitoring oil spill impact

45 Oil spills from offshore drilling and coastal refineries often cause degradation of coastal wetlands that can 46 take a long time to recover. Early oil detection may prevent losses and speed up recovery if monitoring of 47 the initial oil extent, oil impact, and recovery are in place. Satellite imagery data can provide a cost48 effective alternative to expensive airborne imagery or labor intensive field campaigns for monitoring 49 effects of oil spills on wetlands. However, these satellite data may be restricted in their ability to detect 50 and map ecosystem recovery post-spill given their spectral measurement properties and temporal 51 frequency. In this study, we assessed whether spatial and spectral resolution, and other sensor 52 characteristics influence the ability to detect and map vegetation stress and die-off due to oil. We 53 compared how well three satellite multispectral sensors: WorldView2, RapidEye and Landsat EMT+, 54 match the ability of the airborne hyperspectral AVIRIS sensor to map oil-induced vegetation stress, 55 recovery, and die-off after the DeepWater Horizon oil spill in the Gulf of Mexico in 2010. 56 We found that finer spatial resolution (3.5m) provided better delineation of the oil-impacted wetlands and 57 better detection of vegetation stress along oiled shorelines in saltmarsh wetland ecosystems. As spatial 58 resolution become coarser (3.5m to 30m) the ability to accurately detect and map stressed vegetation 59 decreased. Spectral resolution did improve the detection and mapping of oil-impacted wetlands but less 60 strongly than spatial resolution, suggesting that broad-band data may be sufficient to detect and map oil61 impacted wetlands. AVIRIS narrow-band data performs better detecting vegetation stress, followed by 62 WorldView2, RapidEye and then Landsat 15m (pan sharpened) data. Higher quality sensor optics and 63 higher signal-to-noise ratio (SNR) may also improve detection and mapping of oil-impacted wetlands; we 64 found that resampled coarser resolution AVIRIS data with higher SNR performed better than either of the 65 three satellite sensors. The ability to acquire imagery during certain times (midday, low tide, etc.) or a 66 certain date is also important in these tidal wetlands; WorldView2 imagery captured at high-tide detected 67 a narrower band of shoreline affected by oil likely because some of the impacted wetland was below the 68 tideline. These results suggest that while multispectral data may be sufficient for detecting the extent of 69 oil-impacted wetlands, high spectral and spatial resolution, high-quality sensor characteristics, and the 70 ability to control time of image acquisition may improve assessment and monitoring of vegetation stress 71 and recovery post oil spills. 72 73 Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 25 January 2018 doi:10.20944/preprints201801.0233.v1