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This Reprint centers on river engineering-a key hydraulic engineering field integrating hydrology, hydraulics, and geomorphology-featuring 14 articles grouped into three core categories to advance understanding of river systems and management.

• Category A ("Hydraulic geometry, bed roughness and sediment particle size") explores a river's physical characteristics, including channel complexity (Sarker et al.), discharge-related hydraulic relationships (Qin et al.), drain maintenance (Gabr et al.), flood impacts on riparian plants (Yi et al.), Manning's roughness calculation (Takata et al.), and sediment particle size estimation (Dehkordi et al.).
• Category B ("Hydraulic structures") addresses the design and performance of river-interacting structures, covering scour at control structures (Cabarello et al.), pier scour reduction (Zhang et al.), dike foundation erosion (Girolami et al.), geotube groin sediment dynamics (Tu et al.), intake inefficiencies (Chenari et al.), and submerged weir water-level effects (Zhang et al.).
• Category C ("Water quality recovery") focuses on quality enhancement strategies, with studies on numerical modeling for Peru's Lurin River (Mori-Sánchez et al.) and sediment/phosphorus load quantification (MacKenzie et al.).

Collectively, these studies offer actionable insights into river behavior, structure performance, and water quality management, serving as a valuable resource for hydraulic engineering researchers, engineers, and practitioners.