Fig. 4 shows the changes of polarimetric parameters in farmlands.
Damaged farmlands are further divided into two groups, F1 (Fig. 4(a))
and F2 (Fig. 4(b)), based on a difference in scattering characteristics.
For the first case (F1), tsunami-induced changes in scattering mechanism
can be characterized by the decrease of surface and volume
scattering powers, which actually represent the typical scattering characteristics
of inundated fields. A decrease in anisotropy indicates the reduction
of minor scattering processes after flooding. It should be noted
that the PALSAR dataset was acquired about one month after the disaster.
Flooded seawater had receded in this case and remaining sediments
or debris could have caused the SAR signal backscattering. The second
site (F2) is located further inland, and it can be assumed that less debris
was deposited there during tsunami flooding than at F1. Contrary to
those at F1, the changes in scattering mechanism at F2 can be characterized
by an increase of the surface scattering component and a decrease
of the scattering randomness, as shown in Fig. 4(b).