The environmental satellites NOAA-2 and ERTS-1 observed flooding in United States' rivers such as the Mississippi during 1973. Combination of NOAA-2 observation frequency and the ERTS-1 resolution provides an adequate satellite system for monitoring floods. Several polar-orbiting satellites of the ERTs type could view flooded areas at a reasonably high resolution Earth-synchronous satellite would further enhance flood mapping by providing observations whenever clouds are absent.