The hydraulic gradient is an essential concept in fluid mechanics, particularly in the field of hydrology and open channel flow. It represents the slope of the hydraulic head along a flow path and is crucial in understanding the flow of water in rivers, streams, and open conduits. The hydraulic gradient ($i$) is defined as the change in hydraulic head per unit length along the direction of flow. Mathematically, it can be expressed as,

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Where:

• $i$ is the hydraulic gradient, typically measured in meters per meter or in dimensionless form,
• $\Delta h$ is the change in hydraulic head along the flow path,
• $L$ is the length of the flow path.