Unveiling hidden dynamics of river morphology: insights from the 2010 flash flood and Karun-4 dam impact in Southwestern Iran Arash Koohizadeh Dehkordi a , Milad Khastar Boroujeni b , Mohammad Reza Nikoo c,* , Nasim Sadra c , Rouhallah Fatahi Nafchi d , Hossein Samadi Boroujeni e a Department of Water Engineering, College of Agriculture, Shahrekord University, Shahrekord, Iran b Department of Water Engineering, Ferdowsi University of Mashhad, Mashhad, Iran c Department of Civil and Architectural Engineering, Sultan Qaboos University, Muscat, Oman d Department of Water Engineering, Shahrekord University, Shahrekord, Iran e University of Technology Sydney, Sydney, Australia A R T I C L E INFO This manuscript was handled by Emmanouil Anagnostou, Editor-in-Chief, with the assis- tance of Giulia Sofia, Associate Editor Keywords: Erosion and deposition Flood impacts Landsat imagery River morphology Reservoir operations ABSTRACT This research presents a novel, comprehensive analysis of the geomorphological evolution of the Bazoft River over 30 years (1985–2015), combining high-resolution satellite imagery with advanced spatial analysis tech- niques to reveal the unprecedented interplay between extreme flood events and large-scale dam construction. It highlights, for the first time in this region, how the December 2010 flash flood and the Karun-4 Dam’s impoundment revealed previously unexplored dimensions of erosion, deposition, and channel dynamics. Large bank migrations and flood-event-related asymmetric bank erosions were realized; impoundment of this dam caused ultimate variations within a radius of 21 km in geometrical status. It remarkably identifies distinct phases of instability and stabilization in the period of filling, which is important to understand sediment transport and river regulation in extreme anthropogenic intervention. The general sinuosity trends underlined the differential response of the reaches, identifying the second and third intervals as those most sensitive to hydrological and structural controls. The paper uses remote sensing to bring together temporal dynamics of extremes with spatial scales of dam-induced geomorphic modification. This would add value to the current understanding and man- agement of river systems undergoing rapid hydrological and structural alteration and contribute to the inter- national debate on the sustainable development of water resources and riverine ecosystem resilience. 1. Introduction River geomorphology science plays a significant role in effective water resource management, particularly in dam reservoir projects (Bridge, 2003; Meshkova, 2012; Wohl, 2017; Wohl, 2020; Cekrezi, 2024). River geomorphology science is required in planning, design, and maintenance because river morphology significantly influences sedi- mentation trends, erosion risk, and general ecosystem health (Gilvear, 1999; Grabowski et al., 2014; Tullos et al., 2021; Pi´egay et al., 2023). Integration of remote sensing technology and Geographic Informa- tion Systems (GIS) has proven to be a viable approach to the monitoring and analysis of geomorphological change in river systems (Grabowski et al., 2014; Tomsett and Leyland, 2019; Boothroyd et al., 2021; Vu et al., 2024). The multispectral imagery provided by Landsat, with its extensive coverage, moderate spatial resolution, and availability, proves to be especially valuable in this regard (Baki and Gan, 2012; Fisher et al., 2016). Techniques utilized in digital image processing, like auto- classification methods and pixel-based water masks, allow aquatic en- vironments to be separated from other earth features and temporal changes to be monitored (Fisher et al., 2016; Elmi, 2019; Li et al., 2022; Nagaraj and Kumar, 2024). Surface waters are distinguished using various techniques, including the use of spectral band data, supervised and unsupervised classification, and water indices (Rundquist et al., 1987; Otukei and Blaschke, 2010; Jiang et al., 2014). Among these indices, the Normalized Difference Water Index (NDWI) has been determined to possess better accuracy and effectiveness in water pixel identification (McFeeters, 1996; Zhou et al., 2017; Wang et al., 2018; Zhou et al., 2021; Al-Ali et al., 2024). Despite the effectiveness of NDWI, it also has some limitations, * Corresponding author. E-mail addresses: koohizadeh@stu.sku.ac.ir (A.K. Dehkordi), m.reza@squ.edu.om (M.R. Nikoo). Contents lists available at ScienceDirect Journal of Hydrology journal homepage: www.elsevier.com/locate/jhydrol https://doi.org/10.1016/j.jhydrol.2025.133709 Received 24 January 2025; Received in revised form 13 April 2025; Accepted 14 June 2025 Journal of Hydrology 661 (2025) 133709 Available online 26 June 2025 0022-1694/© 2025 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.