The empirically derived ERS scatterometer model CMOD4 is used to examine the relationship between radar backscatter measured by synthetic aperture radar (SAR) and wind speed in shallow waters. It is demonstrated that the model can be used to obtain accurate mean wind speed information from ERS SAR, using meteorological synoptic charts to provide wind direction; this approach could enable submesoscale wind variations to be monitored. Results from the wind speed analysis were used to investigate the small-scale (<200 m) variability of the surface roughness detectable by SAR, the aim being to characterize the effects of parameters additional to the mean wind speed which contribute to the modulations of the backscatter signal. It is shown that the natural small-scale fluctuation of the SAR-derived mean wind field barely exceeds the radiometric noise limitations of the instrument. Where the small-scale variability of the calculated apparent wind speed was above this level, the cause could be linked to dynamic oceanographic parameters. ¿ 2000 American Geophysical Union