Regional flood mapping from space

The Earth Resources Technology Satellite (ERTS 1), launched on July 23, 1972, has been used to monitor the extent of inundation of regional floods with varying recurrence intervals. The inundated areas exhibit sharply reduced near-infrared reflectances caused by standing surface water, excessive soil moisture, and stressed vegetation, which persist up to 10–12 days after the flood peak. The amount of area affected by flooding over regions encompassing many thousands of square kilometers can be mapped definitively at 1:250,000 scale from ERTS 1 imagery in times much shorter than those required by ground-based or aircraft surveys. The ERTS 1 imagery also permits easy extension of flood mapping to areas not normally covered by more familiar survey methods. In addition to the detection of flood events, ERTS 1 can be used to map flood susceptibility indicators on the floodplain for purposes of delineating flood-prone areas.