Manning's roughness coefficient (n) is crucial for reliable hydraulic analysis of natural and artificial open channels. This paper presents a state-of-the-art work on principles of flow resistance mechanisms of natural channels and n estimation approaches. Furthermore, it reviews classical empirically driven approaches, such as Strickler, Cowan, Meyer–Peter and Müller, Limerinos, and Henderson, as well as tabulated, photographic, and storage-based techniques. The latter is a consideration in terms of formulations that factor into vegetation effects, bed material characteristics, bedform-induced resistance, and composite channel roughness. Newer advances in entropy theory, statistical approaches, and data-driven methods are also introduced. The study describes both the advantages and disadvantages of specific methods and shows that no way to predict Manning’s n can be applied universally under different flow conditions and channel types. Instead, the precise estimation has to be based on empirical field observations, analytical construction, and engineering judgment. The observations support the use of an integrated and hybrid approach and can be supplemented with high-resolution measurements and standardized databases for the purpose of minimizing prediction uncertainty for the roughness estimation. This review contributes to enhancing the knowledge and application base of researchers and practitioners in river hydraulics, channel design, and flood modeling.
A. Nama, Sabah Jassim Mohammed, Sura Sabah Rasool et al.· Jurnal Engineering· 0 citations
Riverbank failure offers serious geotechnical and hydraulic dangers to infrastructure, the environment, and the quality of water along fluvial rivers. This study looks at the collapse causes of riverbanks and surrounding embankments over an 8-kilometer stretch of the Euphrates River in Babilon City. An integrated technique integrating field collection, thorough laboratory testing, and the GeoStudio (SEEP/W and SLOPE/W) model was used. Laboratory data demonstrated that high silt and clay concentration (62% silt, 28% clay in embankments; 58% silt, 24% clay in banks) influences soil behavior. Also, the seepage analysis highlighted pore water pressure variations (0.2–1.2 m) and discharge rates (1.76×10⁻⁸ to 1.84×10⁻⁷ m³/sec), which directly influence embankment stability. Slope stability analysis demonstrated a 26% increase in the factor of safety (FS) with higher soil cohesion, emphasizing the importance of cohesive strength in mitigating failure risks. This study bridges the empirical-computational gap by establishing site-specific hydraulic conductivity functions and safety factor sensitivity charts for fine-grained fluvial soils, offering actionable reinforcement strategies (geosynthetic additives and stone riprap). The integration of field data with comprehensive laboratory tests utilizing GeoStudio to determine seepage flow and slope stability under many circumstances is innovative. The work comes to the conclusion that practical insights for riverbank management may be obtained by combining laboratory data with numerical modeling. Periodic monitoring, soil fortification with additives, and stability-enhancing preventive measures like stone rippling or gabions are among the recommendations.
A. Abbas, A. Nama, Zainab Kadhim Jabal· Civil Engineering Journal· 0 citations
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