AVHRR data from Meteorological Satellites have potential in flood moni-toring due to the high time resolution and low cost.Unfortunately

AVHRR

whichis a kind of visible-infrared sensor

cannot detect land surface through cloud

andcloud- free image is quite rare during flood period due to the bad weather

so cloudcontamination is one of the main obstacles in flood monitoring using AVHRR data. Based on the spectral characteristics of groundcovers and the principle of satelliteobservation

this paper puts forward a simple but effective method for water iden-tification using AVHRR data

which is the ratio band of channel 2 by channel 1. By using this method

waterbody can be identified not only in cloud- free areas

butalso under semitransparent cloud and in cloud shadow.This method was used suc-cessfully in the 1 991 flood disaster in Huaihe river basin.