Extended Abstract
Introduction
Understanding the behavior of flood events, especially with regard to agricultural uses, riverbank erosion, and land loss, and the lack of accurate information about the successive changes in the river bed and course in the coming years, has made the use of forecasting systems essential. There are 24 border rivers in Iran, the most important and longest of which is the Aras. The Aras River, which originates in Turkey, forms about 486 kilometers of Iran's water border with Azerbaijan and Armenia. The total length of the river is about 1072km and its drainage basin is 10,320km2. The annual flooding of this river causes destruction and erosion of the riverbed and instability of the river banks. Due to the slope of the river and the seasonal floods of the Aras in the months of April, May, and sometimes June, the river's flow can reach more than 1,800m3/s, causing a risk of severe soil erosion. In issues related to water boundary modification, long-term management is needed to prevent erosion and destruction of riverside lands and protect against floods. The aim of this research is to locate critical flood points in the Middle Aras watershed and predict them through integrated remote sensing methods with automatic cell models and Markov chains.
Materials and Methods
In the implementation of this study, maps of changes in the position of the Middle Aras River channel were prepared using TM, ETM+, and Sentinel1 sensor images in three time periods of 2000, 2010, and 2023. After making corrections, the images were classified using the supervised classification method in ArcGis software, and a land use map and river channel morphology were prepared. A three-kilometer buffer was used to draw a flood location map in the southern part of the river. Zoning of agricultural uses, river channels, residential and industrial areas were considered in the maps. After validating the maps and revealing the changes in the two periods of 2000 and 2010, the Kappa coefficient and matrix were determined. Then, the inter-map error matrix resulting from modeling by this method was evaluated with 2023 images along with field visits. After that, to determine the predicted ranges for changes in river morphology and environment, the 2023 baseline map was fitted with the model output. In addition to the river channel, three units of mountain-plain, agricultural land, and residential-industrial areas were processed. Finally, changes in the morphology of the river flow path for the 2030 horizon, forecasting the potential changes, and a land use hazard zoning map were prepared.
Results and Discussion
River changes in the 2030 horizon compared to 2023 showed that the Aras River has faced significant changes in part of its path and bed, respectively, about 1,800 hectares will be added to the river channel area, and this could cause significant economic losses. The results showed that the area of river land use units within a buffer zone of 3000 meters from the northern and southern banks of the river in terms of mountains and plains will decrease from 119354 hectares in 2000 to about 96000 hectares by 2030. The river channel was more waterlogged in 2010 than in 2023 and 2000. The area of rangelands in the mountain and plain land use areas was greater in 2000 than in the other two periods. The evaluation of the 2023 land use map showed that the overall accuracy of land use extraction was about 93%, with a Kappa coefficient of 0.95. In contrast, agricultural lands on the southern bank will increase from 7346 hectares to more than 22000 hectares. One of the reasons for the increase in agricultural land use in 2023 compared to 2010 was the decrease in channel width in 2023, which caused some of the riverside or floodplain lands to become drained and joined agricultural lands.
Conclusion
The Aras River, as one of the main surface water sources in the northwest of the country, plays a decisive role in the sustainability of agriculture and natural resources in the region. This region is considered one of the important hubs of agricultural and livestock production in Iran, and the productivity of irrigated lands is directly dependent on the water flow of this river. For this reason, planning for the management and protection of the Aras River and examining the process of morphological changes and bed displacement is of utmost importance, because any reduction in water level, lateral erosion, or deviation of the course can directly reduce agricultural production, limit secondary cultivation, and ultimately threaten the food and economic security of the region. The outputs of this project provided a comprehensive map of river morphology and the growth and decline of agricultural and natural resource uses in the sensitive channel area. The results of this research can provide a suitable perspective from the point of view of watershed management measures and the behavior of rivers in the country's border area, which can determine the most suitable residential areas, floodplains for agricultural fields, natural resources, and river facilities for the country's future planning in the field of Border Rivers. |
