Use of ENVISAT ASAR Global Monitoring Mode to complement optical data in the mapping of rapid broad-scale flooding in Pakistan

O'Grady, D., Leblanc, M., and Gillieson, D. (2011) Use of ENVISAT ASAR Global Monitoring Mode to complement optical data in the mapping of rapid broad-scale flooding in Pakistan. Hydrology and Earth System Sciences, 15 (11). pp. 3475-3494.

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Abstract

Envisat ASAR Global Monitoring Mode (GM) data are used to produce maps of the extent of the flooding in Pakistan which are made available to the rapid response effort within 24 h of acquisition. The high temporal frequency and independence of the data from cloud-free skies makes GM data a viable tool for mapping flood waters during those periods where optical satellite data are unavailable, which may be crucial to rapid response disaster planning, where thousands of lives are affected. Image differencing techniques are used, with pre-flood baseline image backscatter values being deducted from target values to eliminate regions with a permanent flood-like radar response due to volume scattering and attenuation, and to highlight the low response caused by specular reflection by open flood water. The effect of local incidence angle on the received signal is mitigated by ensuring that the deducted image is acquired from the same orbit track as the target image. Poor separability of the water class with land in areas beyond the river channels is tackled using a region-growing algorithm which seeks threshold-conformance from seed pixels at the center of the river channels. The resultant mapped extents are tested against MODIS SWIR data where available, with encouraging results.

Item ID: 19741
Item Type: Article (Refereed Research - C1)
Keywords: remote sensing, ASAR, global monitoring mode, flooding, radar, C-Band, Pakistan
Additional Information:

© Author(s) 2011. CC Attribution 3.0 License.

ISSN: 1607-7938
Date Deposited: 21 Feb 2012 06:30
FoR Codes: 04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040608 Surfacewater Hydrology @ 20%
04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040604 Natural Hazards @ 10%
09 ENGINEERING > 0909 Geomatic Engineering > 090905 Photogrammetry and Remote Sensing @ 70%
SEO Codes: 96 ENVIRONMENT > 9610 Natural Hazards > 961005 Natural Hazards in Fresh, Ground and Surface Water Environments @ 20%
97 EXPANDING KNOWLEDGE > 970105 Expanding Knowledge in the Environmental Sciences @ 80%
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