The usefulness of different RADARSAT beam modes in the assessment of oil lakes and polluted surfaces in the Greater Burgan oil field, Kuwait

An infamous catastrophe imposed on Kuwait's desert environment during the 1990-91 Arabian Gulf War was the formation of oil lakes and oil-contaminated suifaces. Approximately 96% of the oil from the lakes was recovered and exported; however, the remaining one million barrels of unrecoverable oil is stuck to the bottom of the oil lakebeds. The need to continuously monitor the oil lakes and polluted surfaces is obvious as they might be part of Kuwait's desert for a long time and pose several hazards to the environment. This paper evaluates the usefulness of RADARSAT SAR beam modes and resolutions in distinguishing between the oil lakes and the various contaminated surfaces at the Greater Burgan oil field. In the flat eolian desert environment, the predominant factor modulating the radar signal is the nature of the soil surface, i.e., disturbed versus undisturbed sand sheet, and the distribution of scrubs. RADARSAT fine beam mode images faithfully mapped various surfaces such as oil lakes, tarmats, partially covered oil lakes, reclaimed oil lakes, contaminated suifaces, and disturbed surfaces from cleanup activities. These span low signals, intermediate gray tones and bright areas. Oil lakes with very weak backscattering appear as near circular or rectangular features in the radar images. 'The three RADARSAT standard beam mode images (SI, S4, and S7) acquired within a period of 14 days in November 1996 were quite similar, with only subtle differences. The S4 image, however, was most sensitive to surface roughness variations and vegetation distribution. The change detection image between RADARSAT standard beam mode low incidence image (S1) and any of the high incidence images (S4 and S7) essentially mapped the difference between the fenced/protected oil field area with more disturbed surface and vegetation, and unprotected areas that are subject to overgrazing and land degradation.