Which of the following terms refers to the steepness or incline of a river?

The term that refers to the steepness or incline of a river is stream gradient. Stream gradient is defined as the vertical drop of the river over a certain horizontal distance, typically expressed as a ratio or percentage. This measurement is crucial in understanding how fast water flows and the energy of the river, as steeper gradients generally result in faster flow velocities and increased erosion potential.

Discharge refers to the volume of water flowing through a river at a given time, which does not specifically indicate the incline or steepness. Flow velocity pertains to how quickly the water is moving along the river, which is influenced by the gradient but is not the measure of steepness itself. Wetted perimeter is the measure of the contact between the water and the riverbed and banks, also unrelated to the incline of the river. Understanding stream gradient is essential for assessing river dynamics, sediment transport, and habitat conditions.