Geomorphological evolution along international riverine borders: The flow of the Aras River through Iran, Azerbaijan, and Armenia

Abstract

International rivers are one of the most politicized natural resources. Their dynamism, whether driven by the influence of natural processes or artificial drivers, can generate political issues between countries where de river is the common boundary. The present study has tried to discern the role of international riverine borders as a limiting factor of their dynamics from a geomorphological point of view. In this context, the main objective of this research is to assess how land cover in the floodplain has been affected by river dynamics along a border by analysing a 160-km-long reach of the Aras River, which is the natural frontier between Iran, Azerbaijan, and Armenia, over the last 35 years (i.e., 1984-2019). Landsat images from 1984 to 2019 have been used to assess land cover changes in a floodplain buffer using Support Vector Machine algorithms and geomorphological changes through indexes such as the River Network Change Index, Channel Mobility Index, Sinuosity index, and Bank retreat index. The results show that active channel has mainly experienced a narrowing process during the study period, with a narrowing rate of 2.05 m/year. In addition, the average value of the River Network Channel Index (-2.45 m/year) reveals that lateral deposition and narrowing were the main processes occurring within the study reach. Channel displacement toward the non-Iranian part was more prominent, being around 27 m on average along the whole study reach which may cause new problems and conflicts that conditions the border situation. In the whole study period, the succession category showed a higher rate of increase in comparison with rejuvenation. Stabilization of surfaces prevailed, with most of the area maintaining the same type during the study period. Regarding land cover types, artificialization appears to be the most prominent transition that express the Aras River, and specifically the floodplain buffer zone, has been strongly affected by human pressure, with farmland activities, urbanization, and damming being the most important types. The key to this habitat degradation comes from the management with irrigation purposes of large reservoirs that directly or indirectly would cause most of the changes detected.

Keywords: Geomorphological changes; Land cover; Riverine border; SVM; Satellite images.