Flood polygons

This polygon (translucent blue with a blue border) is drawn by the analysts recording the flood event. It is meant to include all the areas reported as affected, by official source or the media. It does not represent the area actually under water.

Microwave flood detection

Flooded area, as detected in microwaves by the Global Flood Detection System of the JRC, based on NASA TRMM/GPM observations. This system has a rather low resolution (of 5-10km) but is not affected by clouds.
For more details, see http://www.unisdr.org/files/9622_LBNA23303ENC002.pdf.
The areas with a flood signal along the coast are an artefact of the system and should not be considered.

Optical Flood detection

Flooded area as detected in optical wavelengths by NASA/MODIS, known as "MODIS Flood Product". Data are made available by NASA GSFC Flood Mapping Project, http://oas.gsfc.nasa.gov/floodmap/index.html. Resolution of 250m, heavily affected by cloud cover.