Comparison and prioritization of flooding in Nekarood sub-basins using morphometric method in GIS

 Floods are one of the most catastrophic and dangerous natural hazards because they are sudden and unpredictable and lead to the destruction of infrastructure, and a threat to human life and property. Identifying areas with high flood potential is one of the most important tasks in flood control and reducing the damage caused by it. Floods are one of the most serious natural hazards that pose serious threats to residential areas and also pose financial and human risks. Floods rank first in terms of damage caused by earthquakes, volcanoes, and landslides. Cited. Floods can occur not only in the plains but also in mountainous environments. Flood analysis and its relationship to explanatory variables can help water managers identify the most effective variable in floods. Communities, countries, and pcontinents have suffered severe human losses and economic costs due to the increasing severity and frequency of these natural disasters). In the world due to the increase of these natural disasters, human death in the coming period is probably doubled. Floods are one of the most serious natural hazards that pose a serious threat to residential areas. Climate change and the steady increase in urbanization that occurs with increasing population, followed by an increase in man-made structures, ultimately reduce permeability and possibly further increase the risk of floods and the potential for socio-economic damage. Confirming the growing risks and increasing frequency of flood events, a paradigm shift in flood risk management is observed in many countries, such as Europe. Flood management and mitigation require comprehensive perspectives that take into account a diverse set of flood risk management measures, including active stakeholder engagement, communication, and awareness raising. The present study was conducted in the Neka Rud watershed in Mazandaran province. The use of geographical systems can identify flood-sensitive areas with high accuracy in the shortest time using information layers. This watershed is one of the most important watersheds in the province and its study is of great importance in terms of flood risks due to its high rainfall. Enjoys. The overall purpose of this study is to prioritize sub-basins concerning flooding based on morphological analysis and also to use GIS software as an efficient and cost-effective tool. In this study, the morphometric study of the watershed was investigated and flood sub-basins were identified. The purpose of this study is to identify areas with high flood potential in the Neka River watershed of Mazandaran province to prevent the risks of this natural disaster and prevent financial and human damage.

 Seventeen Morphometric parameters were determined to describe the watershed and prioritize the sub-basins of the Neka watershed according to the sensitivity to sudden floods. The basic parameters were measured directly from the DEM using GIS techniques and include basin area, basin length, environment, number of streams, and flow lengths for each flow rating. In this study, very important morphometric parameters were quantitatively selected and used for this analysis. These parameters are directly or inversely related to runoff hazards, peak discharge, and soil erosion. These parameters were divided into three parts: linear, uneven, and surface. Finally, sub-basins were prioritized using this method. To assess the morphology of the watershed, a digital elevation map (DEM) with a resolution of 12.5 m was loaded. Morphological parameters are directly or inversely related to the outbreak. After morphological ranking, the values of each sub-basin were collected to classify and determine their susceptibility to flash floods. The values of the sum of morphometric parameters summarized from 0 for the lowest rank value and 1 for the highest rank value to obtain the flood sensitivity index for each sub-basin were normalized and finally evaluated. Clear changes are observed in the basic parameters of watersheds such as area, environment, and length of the basin. These basin parameters are a very remarkable hydrological feature. The watershed area varies from 484.37 square kilometers under the N1 basin to 48.18 km2 under the N8 basin. The environment can also be used as an indicator of the shape and size of the watershed. According to the obtained results, there is a high correlation between the area and the watershed environment.

The Neka Basin was divided into 12 sub-basins using the Hydrology Toolbox from ArcGIS. According to the obtained results, it was found that sub-basins N8 and N9 have a high priority for flooding. The results show that these two sub-basins are very prone to flooding. Also, sub-basins N11 and N12 have a much lower risk of flooding. The total number of 12 sub-basin flows for the watershed is 366681 and for the first time, it constitutes 52% of the total watershed flows. Geometric values for 12 watersheds are shown in the form of a graph and a straight line, where the log values of the flow number are plotted on a graph.

Because there are insufficient historical climatic and hydrological records for hydrological modeling, morphometric analysis has been used to assess sub-watershed susceptibility to flooding. The results and analysis obtained in the present study have several fields for practical application and future development. Morphometric analysis of the Neka basin has shown that the watershed is a six-stage drainage system that is very sensitive to flooding. According to the results, sub-basins N8 and N9 have a high risk of flooding. In contrast, the N12 sub-basin has a much lower rate of flooding. The study of the basin showed that the reason for the low flooding below the N12 basin is the shape of the basin and the amount of slope, which has an elongated shape and the area is almost flat in terms of unevenness, which reduces the risk of floods. This study showed that the protection of the region against sudden floods should be the main priority of the competent authorities to protect human lives and agricultural farms and ultimately prevent flood disasters. In this study, it was proved that integration and morphological analysis with GIS can provide a significant tool for understanding the characteristics of watershed sub-basins related to flood management.