Flash floods induced by heavy rainfall occur frequently in China, which cause severe damages or even casualties every year. Flash floods generally occur in small catchments, and therefore were poorly documented. A Database including 963 flash flood events in China is compiled and studied in this study. Analytical results (a) indicate flash flood condition in China; (b) shed light on the spatial-temporal distribution of flash flood under heavy rainfall and (c) detect the characteristics of the 2016 flash flood. In 2016, the deaths due to flash floods were severe and concentrated, accounting for about half of the elderly and children. Hebei and Fujian provinces were most affected by flash floods. The disasters mainly occurred in July and the major types were river floods. Despite the frequent torrential rains, inadequate monitoring and early warning systems made the flash flooding condition even worse in 2016.

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Remote sensing image with characteristics of multiple gray level, more informative, fuzzy boundary, complex target structure and so on, there is no completely reliable model to guide the remote sensing image segmentation. In response to these issues, the article presents a remote sensing image sequence segmentation method based on improved FCM (fuzzy c-means) algorithm. The color space selects the lower relevance of HSI (hue, saturation, intensity) and adopts standard covariance matrix-the Mahalanobis distance formula, which is more suitable for the use of remote sensing image. It can solve the initial centers selection problems of fuzzy C-means clustering algorithm by the use of ECM. By using the partition of S component, it can divide the image into high S regions and low S regions. We can do FCM segmentation respectively with H component and I component of these two parts. The segmentation results can be achieved after the merger. The program experimental result shows that this method will enable FCM to converge to global optimal solution with less iteration, and has good stability and robustness. It has good effect on improving the accuracy of threshold segmentation and efficiency for remote sensing images, which can be used for content-based remote sensing image retrieval systems.

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