Joint VIIRS-ABI Floodwater Fraction Map Products:

Daily:

The floodwater fraction percentage (1-100%) indicates the coverage of the pixel (~375m spatial resolution) that contains water. Higher percentages indicate more water and thus flooding.

Five-Day Composite:

This is a composite flood extent that saves the max water fraction percentages over a moving window of 5 days to improve obscuration due to cloud cover. For example, if a pixel is covered in clouds 4 out of the 5 days, the one day that it was visible will be the value that saves to this final max-merged flood extent. Values are made binary so that red = detected flooding and everything else is null. The threshold used for this product to indicate flooding is 40% floodwater fraction, meaning that if a pixel was more than 40% covered in water at any time over the 5-day moving window, it is classified as flooded. 

Credit:

NOAA JPSS Program Office

George Mason University

Space Science and Engineering Center at the University of Wisconsin-Madison

Get more information:

NOAA Global Flood Product Quick Guide

Near Real Time Flood Detection Using VIIRS Imagery