Flood extent area mapping using sentinel 1 SAR image (a case study: the flood of Poledokhtar, march 1398)

Flood is one of the most widespread and common natural hazards in the world. Depending on the severity of the rains and other factors affecting the flood, it can cause severe personal and financial damage to human. In this paper, Sentinel-1 Synthetic Aperture Radar images and their application in flood spreading mapping along the Kashan River, Poledekhtar County, have been investigated. The purpose of this research is to produce a map that is extracted from the SAR images (sentinel 1), showing the extent of Kaskan river flooding in beginning of year 1398. The main data of the paper are Sentinel 1 (SAR), satellite images before (2019/03/28) and after (2019/04/03), the flood as well as Sentinel 2 satellite images. For this purpose, pre-processing and correction of different images were performed first. The Kashkan River Area was extracted using the NDWI Water Index from sentinel 2 image (2019/05/05). This image was used as a reference image. Then before and after the flood images were analyzed using Utso thresholding method and finally the flood area was extracted through image classification. SNAP and ArcGIS software were used for this purpose. Results show that in the study area, 7.99 km2 of the river banks has been submerged due to the April 1389 flooding. Also Radar image data can be used for flood surveillance because of imaging in all weather conditions, and the areas involved in flooding can be extracted from these images in the shortest possible time. It can also achieve detailed observations of 10m resolution for water extent using Sentinel-1 SAR imagery at an interval of several days (depending on latitude with a 5 or 6-day revisit and 12-day same orbit revisit time at the equator) to be used in future planning.