Vancouver, British Columbia, Canada

Zambezi River, Mozambique

This 76 x 42km subscene, of a RADARSAT-2 Wide dual polarized (VV and VH) image was acquired February 9, 2008. The image shows flooding along the Zambezi River and catchment area due to higher-than-normal rainfall. The main river channel, as well as flood extents, are evident. Colour variation along the river(s) and flooded areas illustrate the different scattering mechanisms associated with various surface features such as: stagnant vs. flowing water, flooded vs. non-flooded vegetation, vegetation density and type etc

For example, the normal river course of the Zambezi River runs in the north-south direction. Due to the type of surface scattering, the normal river channel gives a stronger VV response and appears as blue in the colour composite image. In contrast, the open water and open flooded areas produce a weak response in both polarizations, and therefore appear black. To the west of the Zambezi River, a smaller river channel is flooded. Just north of this are areas of blue and green - which is likely low biomass, flooded vegetation. The blue-green colour is characteristic of radar scattering from the water (VV polarization) and vegetation (VH polarization).

The cross pol channel (VH) proves especially useful for detecting open water in a beam mode and position (Wide 1) that traditionally, due to its steep incidence angle, was often a poor choice for flood detection. With the advanced multi-polarizations available on RADARSAT-2, the range of incidence angles that can be readily used for flood detection has expanded.