Flood risk Monitoring of June 1402 in Zanjan province using Sentinel-1 images

Studies in this field have been carried out by researchers with different methods such as the use of Sentinel 1 and Sentinel 2 satellite gauges and it has been proven that flood monitoring with the help of remote sensing is a suitable tool for the quick direction of the flooded area. It is used in the early management of natural disasters, especially floods. The purpose of this study is to prepare a map of the extent of water caused by the flood of June Zanjan 1402 with the help of Sentinel 1 images. This map can be used in the management and planning of land users in flood plains, raising the level of awareness and warning people about flood spots. In the region, the development of flood risk reduction plans, the preparation of comprehensive flood risk management plans, and the preparation of guidelines for dealing with and resilience to critical conditions are contracted.

The research method was carried out in steps: in the first step it was collected with the help of Sentinel-1, then in the second step: SAR data were pre-processed. The third step: the images were post-processed in the ENVI environment, with the help of the tree algorithm, and in the last step: the images were converted into vector files.

Examining the changes in flooding after seven days of flooding in the region shows that the highest water level in the northern regions of the province is in the vicinity of the main and sub-rivers of the Qezal-Ozen watershed, especially in Tarem city. It was land with 312/067192, after which more number of polygons were seen in the north of Zanjan city in the area of Qezl-Ozen aquifer basin, Lower Zanjanrud, Pare, Ghani-Biglo, higher aquifer with the area of 150/713193, which these aquifers has taken more It has occurred under the impact of tectonics in the region around Qezl-Ozen river. Most of the flood water was seen in Mahenshan, in the northern part of Mahenshan city, in Mahenshan and Uriad divisions with 375 polygons and the extent of flood water was 26/618086. In Ijroud city in Zarin Abad, in the direction of the Ijroud river, most of the flood water was in the direction of the Ijroud river with the extent of 21/06405 and with flooding of 24 polygon centers, in Abhar city, the water is from the flood in Soltanieh center in Zangan. The river (one of the branches of the Qezal Ozen River) with an area of 96 lands was seen as a face with 547 flood polygons around the river.

In the flood of June 1402 in Zanjan province, the height of the area was a key factor in controlling the direction of the flood and the persistence of water on the ground (5-b). The amount of flood water receding at altitudes less than 500 meters was very low compared to higher altitudes, in such a way that water retention was not seen at altitudes above 1000 meters, in the high places of Zanjan such as parts of Tarem, Zanjan and Mahenshan after Atmospheric precipitation had started to flow faster from the low-lying and flat areas, so that after seven days of the flood, water retention was not seen in these heights. While at altitudes of less than 500 meters, which mainly included the low altitude areas of the Qezl-Ozen catchment and its main and tributary rivers, most of the runoff was collected in the topographic holes of Tarem and Zanjan, in these low-lying areas. The region caused widespread flooding and flooding even in the population centers of these regions.

It was processed and classified into three classes and analyzed, and it was found that the largest amount of flood that entered Zanjan province was from the north of the province, especially Tarem city. Also, the study of the height factor in the flooding of the region showed that the heights of less than 500 meters, which mainly included the sub-basins of Qezl-Ozen and the rivers around it, had a high potential for flooding. Flooding also showed that the grassland vegetation has increased the flood potential of these areas due to insufficient permeability of rainfall in these areas.