We have developed spotlight mode SAR called Live SAR for flood area surveillance. Live SAR has many feature for flexible measurement. The radar system is enough light to mount on small plane, and is able to take an image of various area with an antenna on a gimbal. Live SAR can control by an easy user interface software, and can automatically outputs very high-resolution image (0.1 m) within few tens of seconds. Live SAR has been tested both on ground and helicopter in Fukuoka and Utsunomiya area which include river and sea water, and could successfully generate high resolution image. It is confirmed that the water area looks dark due to a low radar cross section. We could take some such an image to estimate the water area and water volume. As well as fixed target image, moving target has been also detected. This feature will become very important to detect the water flow direction and people refuge.