Inundation Impact on Croplands of 2020 Flood Event in Three Provinces of China

Floods are threatening agricultural production and causing enormous crop losses globally. In June–July 2020, the Yangtze and Huai River basins were hit again by exceptionally heavy rainfall and flooding, followed by massive inundation of croplands. However, quantitative studies on the impact of flooding on crops are still lacking. Therefore, quick and accurate mapping of flood and quantitative assessment of inundation impact on crops is vital. The main objectives of this article are to map the flooding areas and analyze the inundation impact on crops. The result of flood mapping with SAR images achieves an overall accuracy of 0.9023, which facilitates the analyses of phenological temporal change and Normalized Difference Vegetation Index (NDVI) losses of crops. It is found that the inundation resulted in a phenological lag in crops grown in the 2020 summer. The phenological lag resulted in a significant NDVI loss, especially in the earlier stage. With the extension of phenology latency, crops suffered even greater losses. Conversely, in the winter of 2020, the crops show obvious phenological advances, and compared with 2019, there was no obvious NDVI loss.