*4.1. Sentinel-1A Backscatter Analysis for Lodging Detection*

The first instances of lodging were observed in the fields on 11 August 2020 due to the windstorm on 10 August 2020. Because of the temporal frequency of Sentinel-1, lodging assessment was done on acquisitions after the lodging event. As seen in the ratio images (Figures 5 and 6), the VH polarization's backscatter (σVH) increased between the pre-lodging image and the post-lodging image. We predict the increase in value of σVH is based on two conditions:

(1) The first condition is due to volume scattering from the crops. In a healthy crop, the orientation of the crop canopy is erect. When crop lodging occurs, the orientation of the canopy elements changes, the ears and the stems bend downwards and incline against each other. Since σVH is sensitive to structural changes, when lodging occurs, the volume scattering increases.

(2) The second condition is due to the high sensitivity between the interaction of vegetation and soil (double bounce effect). When a field is lodged, the vegetation-soil double scattering increases and the σVH increases as well.

The approach for the mapping of lodging as detailed in Section 3 captures the increase in backscatter as a result of the lodging event. When the lodging is severe, condition 1 and condition 2 hold and changes in σVH are very high but when lodging is moderate, condition 1 holds and changes in σVH are moderate. The reader should note that both severe and moderate lodging are very detrimental and they will lead to yield loss. In this study, ratio images in *XRis* were classified into three classes. The first class, which depicts no change, comprises mostly of urban areas, healthy crops, and standing water. The second class, which depicts moderate change, contains moderately lodged fields while the third class, which depicts severe change, contains severely lodged fields (Figures 7 and 8). After classification of the lodging areas, we then quantified the amount of corn and soybean that were moderately and severely lodged (Table 2) using the CDL map.

**Figure 7.** Lodging maps generated between (**a**) 29 July 2020 and 22 August 2020; (**b**) 3 August 2020 and 15 August 2020; (**c**) 4 August 2020 and 16 August 2020.

**Figure 8.** Spatial mosaic of all lodging maps in Figure 7a–c.


**Table 2.** Amount of lodged corn and soybean per unit area.
