Increased artificiality trend driven by an inter-basin water transfer on the Zayandeh-rud River floodplain in Iran

Abstract

The objective is to evaluate the effects of inter-basin water transfers on land use changes in the floodplain buffer area and the geomorphological evolution of a fluvial system on the receiving basin. Remote sensing techniques and machine learning algorithms have been combined with geomorphological indices for this purpose in the Zayandeh-rud Basin located in central Iran, to assess the trajectory of change over the last 50 years (from 1969 to 2020). This basin extremely experienced water crises due to artificialization events which made government transferring water from surplus basin. The outcomes of the present research express a reduction process in the area of the active channel throughout the study period, with an average narrowing rate of 0.92 m per year, i.e., a total reduction of 49.3%. Based on geomorphological indexes, Bank Retreat and River Network Channel Index, the highest sedimentation and narrowing trend was found for the period 1984-1997, while in the most recent period, from 2009 to 2020, a reverted tendency is observed which indicates higher erosion rates. Additionally, the area of natural cover, water bodies, and absence of farming classes have reduced surfaces in the floodplain to the benefit of urbanisation and agriculture. The stationarity conditions of the floodplain cover predominate followed by degradation or artificialisation processes. Given the current perspective of increasing the availability of water in the basin, an integrated planning that aims to consider environmental, socio-political, and economical elements of the system would be advantageous and needed to break the environmental degradation of this fluvial system.