title: Interplay between river dynamics and international borders: The Hirmand River between Iran and Afghanistan.
abstract: Fluvial dynamics in riverine borders can play an important role in political relationships between countries. Rivers move and evolve under the influence of natural processes and external drivers (e.g. land use change in river catchments). The Hirmand River is an important riverine border between Iran and Afghanistan. The present study shows the evolution and lateral shifting of the Hirmand River along the international border (25.6km) over a period of 6 decades (1955-2015). Seven data series of aerial photos, topographic maps and Landsat images were used to analyze land cover and channel changes in the study reach. The land cover has changed dramatically on both sides of the border during the last 6 decades, especially in the Afghan part. Overall, 49% of all land surface changed its cover type, especially the area of agriculture and residential land contributed to that, with an increase in surface area of about 4931ha and 561ha, respectively. On the other hand, the natural cover and water bodies decreased to 38% and 63%, respectively. The impact of these land use changes on the morphological evolution of Hirmand River was investigated in 5 sub-reaches. We found an average decrease of the active channel width of 53% during 60years and the average River Network Change Index for the whole study reach during 60years was -1.25m/year. Deposition and narrowing turned out to be the main processes occurring within the study reach. Furthermore, due to natural riverine processes the Hirmand River has moved towards Afghanistan (37m on average) and lateral shifting was found to be up to 1900m in some sections.
authors.affiliation: Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, Emam Reza Street, Noor, P.O. Box: 46417-76489, Iran. Electronic address: saleh.yousefi@modares.ac.ir.
authors.forename: Saleh
authors.initials: S
authors.lastname: Yousefi
authors.affiliation: Soil Physics and Land Management Group, Wageningen University, Droevendaalsesteeg 4, 6708PB Wageningen, Netherlands; Civil, Surveying and Environmental Engineering, The University of Newcastle, Callaghan 2308, Australia. Electronic address: saskia.keesstra@wur.nl.
authors.forename: Saskia
authors.initials: S
authors.lastname: Keesstra
authors.affiliation: Department of Natural Resources and Environmental Engineering, College of Agriculture, Shiraz University, Shiraz, Iran.
authors.forename: Hamid Reza
authors.initials: HR
authors.lastname: Pourghasemi
authors.affiliation: Department of Geosciences, University of Padova, Via Gradenigo 6, 35131 Padova, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Surian
authors.affiliation: Former MSc Student, Department of Watershed Management, Faculty of Natural Resources, Lorestan University, Khoramabad, Iran. Electronic address: s.mirzaee90@yahoo.com.
authors.forename: Somayeh
authors.initials: S
authors.lastname: Mirzaee
keywords: Channel shifting; Hirmand river; Remote sensing; River evolution; Riverine border