Which aspect influences both the volume and velocity of surface runoff?

The influence of slope length and steepness on both the volume and velocity of surface runoff is significant because these factors directly affect how quickly water can travel over the land surface. When the slope is steeper and longer, gravity has a greater impact, causing water to flow more rapidly and at higher volumes than it would on a flatter or shorter slope.

As water flows down a steep slope, it gains momentum and can mobilize more sediment and water, leading to increased surface runoff. This is critical in understanding hydrology and erosion processes, as steep slopes can exacerbate erosion risks during rainfall events, amplifying the potential for sediment transport into nearby waterways.

Other factors, while important in their own right, primarily influence specific aspects of runoff or sedimentation rather than the fundamental dynamics of volume and velocity. For instance, soil texture can affect infiltration rates, the type of vegetation can help with water retention and stabilization of soil, and soil organic matter improves soil structure and water-holding capacity, but none of these directly impact the rapid movement of water across the landscape in the same way that slope characteristics do.