Which factor affects the intensity of surface runoff?

The slope of the land is a critical factor that affects the intensity of surface runoff. When the slope is steep, gravity acts more forcefully on water, accelerating the runoff as it flows downhill. This leads to higher volumes of water moving quickly over the surface, increasing the potential for erosion and runoff. Additionally, steep slopes can limit the amount of water that infiltrates the soil, as it may not have enough time to percolate down before it runs off. Therefore, in areas with higher slope gradients, you can expect intensified surface runoff due to these gravitational and physical processes.

In contrast, the other factors listed do not have a direct impact on the intensity of surface runoff. The type of microorganisms present, while important for soil health and nutrient cycling, does not influence the movement of water across the surface. The temperature of the water may affect other properties of water bodies but does not significantly change how water runs off surfaces. Lastly, the depth of the riverbed is related to the flow characteristics of the river itself rather than the runoff from surrounding land areas.