Investigation of rivers planform change in a semi-arid region of high vulnerability to climate change: A case study of Tigris River and its tributaries in Iraq

Abstract

In this paper, the planform changes of rivers in a semi-arid region, which are particularly vulnerable to the impacts of climate change, were investigated. This research provides valuable insights into the adaptation and mitigation efforts necessary for effective climate change risk management in this area. A comprehensive analysis was carried out using satellite images and GIS to investigate the changes in the planform of the Mosul-Makhool reach of the Tigris River and its Lesser Zab and Greater Zab tributaries as a case study. To date, no studies have examined the impact of dam construction and climate change on the planform changes of these rivers. A survey was conducted to analyze the channel planform from 1979 to 2021. Various channel planform features were computed, including sinuosity index, braiding index, erosion and accretion, migration rate, confluence point, and junction angle. Results demonstrated that the Tigris River has low meandering features, the Lesser Zab has moderate meandering features, and the Greater Zab has the highest sinuosity index value of 1.95, which indicates very high meandering features. The change in the sinuosity index was fairly small. Generally, the rivers tended slightly towards deposition rather than erosion. The migration rate of the meandering rivers was high, with the highest value recorded in the Tigris River and Greater Zab. The average movement rate of the Greater Zab-Tigris River confluence was 31.81 m/year, and the Lesser Zab-Tigris River confluence moved 20.2 m/year. The study results demonstrate that climate change and dam construction significantly impact the rivers' planform in semi-arid regions. This investigation holds significant importance in evaluating morphodynamic changes in river systems worldwide with great detail and accuracy using satellite data.