We performed a Ground Based SAR (GB-SAR) and PiSAR simultaneous experiment over a flood test site. In this site, one prefab was constructed in a baseball field of a Nihon University in Chiba, Japan. The PiSAR observations were done for three days with different soil moisture condition of -25%, ̃50%, and 100%. Some GB-SAR experiments have been also done in two of three days and the scattering process are examined. Preliminary experiment with GB-SAR showed that Lband δ0 from a double scattering of ground-wall is increased for a few dB, when a reflectivity of the ground is assumed to be 1. These increase are also confirmed in the test site for both PiSAR and GB-SAR. Furthermore, high resolution GB-SAR images show double and single bounce scattering from a metal bar behind the wooden board of the prefab. We conclude that Lband SAR has a enough ability to detect a flooding area in urban site.