What is surface runoff?

Surface runoff refers to the portion of rainfall or melted snow that flows over the land surface into streams and rivers. It occurs when the rate of rainfall or snowmelt exceeds the capacity of the soil to absorb or infiltrate the water. Several factors influence surface runoff, including:

1. Rainfall Intensity: The higher the rainfall intensity, the greater the chances of surface runoff. Heavy downpours often result in higher volumes of surface runoff because the soil may not be able to absorb the water fast enough.

2. Soil Permeability: The permeability of the soil determines its ability to absorb water. Soils with high permeability, such as sandy soils, allow water to infiltrate quickly, reducing surface runoff. In contrast, soils with low permeability, such as clay soils, have a slower infiltration rate, leading to increased surface runoff.

3. Land Cover: The type of land cover also plays a role in surface runoff. Impervious surfaces like concrete, asphalt, and buildings prevent water infiltration and promote surface runoff. On the other hand, areas with vegetation like forests and grasslands facilitate water absorption, reducing surface runoff.

4. Slope: The slope of the land affects the rate of surface runoff. Water flows faster on steeper slopes, increasing surface runoff. Gentle slopes allow water to infiltrate more readily, reducing surface runoff.

5. Land Use: Land use practices can impact surface runoff. Agricultural activities, construction sites, and poorly managed urban areas can increase impervious surfaces and alter natural drainage patterns, resulting in higher surface runoff.

Surface runoff is an essential component of the water cycle. It transports water from the land to water bodies, contributing to the replenishment of groundwater aquifers, streams, and rivers. However, excessive surface runoff can lead to problems like flooding, erosion, and sedimentation, which can have adverse effects on the environment and infrastructure.