All-weather operation and high-resolution data are among the most important elements in remote sensing observations in coastal lagoon regions. Remote sensing from an aircraft platform has flexibility in observation timing and in the selection of observation areas. Multi-parameter and high-resolution Pi-SAR observations were conducted from 2001 to 2003 to obtain the basic characteristics of Normalized Radar Cross-section(NRCS)and SAR images over Lakes Shinji and Nakaumi to study the usefulness of such airborne SAR observations for coastal lagoon areas. X-band NRCSs obtained from the three observations show that NRCS values and the wind-speed dependence are similar to those obtained in experiments over the ocean, indicating that X-band SAR can be used for high-resolution wind speed mapping. Frequency and polarization dependences of NRCS in clean and signature areas were also analyzed. This indicated that the depression of NRCS at some signatures have a clear frequency dependence, while others do not. This finding suggests that multi-frequency SAR could be used to classify signatures.