Abstract
Flood detection and monitoring is increasingly important, especially on remote areas such as African tropical river basins, where ground investigations are difficult. We present an experiment aimed at integrating multi-temporal and multi-source data from the Sentinel-1 and ALOS 2 synthetic aperture radar (SAR) sensors, operating in C band, VV polarization, and L band, HH and HV polarizations, respectively. Information from the globally available CORINE land cover dataset, derived over Africa from the Proba V satellite, and available publicly at the resolution of 100 m, is also exploited. Integrated multi-frequency, multi-temporal, and multi-polarizations analysis allows highlighting different drying dynamics for floodwater over various land cover classes, such as herbaceous vegetation, wetlands, and forests. They also enable detection of different scattering mechanisms, such as double bounce interaction of vegetation stems and trunks with underlying floodwater, giving precious information about the distribution of flooded areas among the different ground cover types present on the site. The approach is validated through visual analysis from Google EarthTM imagery. This kind of integrated analysis, exploiting multi-source remote sensing to partially make up for the unavailability of reliable ground truth, is expected to assume increasing importance as constellations of satellites, observing the Earth in different electromagnetic radiation bands, will be available.
Highlights
Satellite remote sensing plays an important role in the observation of flood events [1,2,3].Synthetic aperture radar (SAR) imagery is useful for water extent detection [4,5,6], thanks to its all-weather, day/night imaging capabilities
Flood monitoring on thickly vegetated, remote areas is important for damage assessment, as well as for studying the response and evolution of inundation phenomena in tropical countries
We show an experiment on the integration of multi-temporal, multi-sensor, and multi-polarization SAR data with CORINE land cover information to infer consistent information about a flood phenomenon occurred in early 2015 on the African Shire River basin, in Mozambique
Summary
Satellite remote sensing plays an important role in the observation of flood events [1,2,3].Synthetic aperture radar (SAR) imagery is useful for water extent detection [4,5,6], thanks to its all-weather, day/night imaging capabilities. A further advantage of SAR sensors is the possibility of better recognizing floodwater in different ground conditions, thanks to their insensitivity to confusing factors such as water color, and the high sensitivity of the microwave radiation to water surfaces. The latter determines the appearance of open, calm water as dark in a SAR image; SAR often permits detecting water beneath vegetation, thanks to the capacity of microwaves to penetrate below the vegetation canopy.
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