Agricultural Engineering 2025 – 400 Free Practice Questions to Pass the Exam

Manning's coefficient, often denoted as 'n', is a crucial parameter used in open channel flow calculations. It represents the roughness of the channel's surface and varies based on the characteristics of that surface, such as vegetation, soil type, and channel shape.

Channel roughness is the primary factor that affects Manning's coefficient because it directly influences the resistance encountered by water flowing through the channel. A rough channel surface, such as one with vegetation or large stones, increases the coefficient, implying more resistance to flow, whereas a smoother channel will have a lower coefficient, indicating less resistance.

Factors like soil temperature, crop variety, and water depth do not directly affect the channel roughness, which is the primary component here. Soil temperature might influence plant growth or soil characteristics over time, crop variety does not have an impact on flow resistance in the channel context, and while water depth can affect flow velocity and character, it does not influence the roughness of the channel surface in a way that modifies the Manning's coefficient itself. These distinctions clarify why channel roughness is the key factor affecting Manning's coefficient.