Flood Monitoring in Weifang City, Shandong Province based on Sentinel-1A SAR

Flood disasters pose numerous hazards which seriously endanger human life and property. Therefore, flood monitoring is essential. In August 2018, an unusual precipitation occurred in Weifang City, Shandong Province, China, causing severe flooding. By making full use of polarization information from Sentinel-1A SAR data before and during the disaster in Weifang City, we were able to employ the Doublet, Otsu and Region Growing methods towards VV and VH images to extract the water body information. To improve the accuracy of water body identification we took the intersection processing of VV and VH images before and during disaster respectively. Then we monitored the submerged area by taking overlay analysis of the results of before and during flood. The comparison analysis between these three methods and the InSAR result show that the Doublet method has the largest difference with the InSAR result and has the lowest recall and precision rate. The Otsu and Region Growing methods are equivalent, but the Otsu had a higher recall rate while the Region Growing method had a higher precision. The area of flood inundation in Weifang City based on the Otsu method is about 1892.7km², while the area of flood inundation according to the Region Growing method is about 1576.6km².