This loss of visibility in flood detection has been quantified
in a study by Mason et al. (2010) that used a TerraSAR-X image
containing urban flooding together with contemporaneous aerial
photography for validation of the TerraSAR-X result. This employed
a SAR simulator in conjunction with a LiDAR Digital Surface Model
(DSM) to estimate regions of the image in which water would
not be visible due to shadow or layover caused by buildings and
taller vegetation. Fig. 2 shows the LiDAR DSM of the Tewkesbury
area, while Fig. 3 shows those parts of the image not visible to the
SAR due to radar shadow and layover.