Analyzing Temporal Morphometric Changes in River Nile's Forced Bends via RS/GIS Methods: A Case Study of the Damietta Branch in Egypt

River Nile, among the world's longest rivers, features the crucial Damietta branch in Egypt, serving as a vital irrigation source and navigation pathway from Cairo to the Mediterranean Sea. Post the Aswan High Dam's construction, significant morphological shifts occurred in this branch, particularly impacting sedimentation and erosive patterns, notably at river bends. This study investigates the long-term morphometric evolution of six forced bends along the Damietta branch of the Nile River from 1987 to 2015 using remote sensing (RS) and geographic information system (GIS) techniques. Three image classification methods—onscreen digitizing, maximum likelihood classification, and histogram thresholding—were compared for shoreline delineation accuracy, with onscreen digitizing demonstrating superior performance, validated by a low relative error of 0.42% against field data. Morphological analysis revealed a consistent pattern of outer-bank erosion and inner-bank sedimentation, strongly influenced by secondary flow currents and local hydraulic structures. Among all sites, Taranish Al-Bahr exhibited the most significant erosion and sedimentation activity, while Bana Abu-Sir showed the highest surface water area with minimal morphodynamic change, indicating geomorphological stability. All bends were classified as meanders based on sinuosity index (SI) values exceeding 1.5, with less than 0.5% deviation from previously published data. The temporal increase in surface water areas and spatial variability in sediment dynamics underscore the need for site-specific management strategies to ensure sustainable riverbank development and hazard mitigation.