Which statement best describes infiltration-excess runoff?

Which statement best describes infiltration-excess runoff?

• A. Rainfall rate exceeds infiltration capacity.
• B. Soil becomes saturated and cannot hold more water.
• C. Runoff is caused by deep groundwater discharge.
• D. It occurs only in arid regions.

Answer: (A)

Infiltration-excess runoff occurs when rainfall arrives faster than the soil can absorb it, meaning the rainfall rate exceeds the soil’s infiltration capacity. When this limit is surpassed, water cannot infiltrate quickly enough and surplus water flows across the surface as runoff. This is also known as Hortonian runoff and depends on factors like soil type, soil moisture before the storm, surface crusts or cover, and rainfall intensity. It differs from saturation-excess runoff, which happens when the soil is already near its full capacity and additional rain cannot be stored in the pores, forcing surface runoff even if the rainfall isn’t exceptionally intense. It’s not driven by deep groundwater discharge, which contributes to baseflow rather than surface runoff, and it isn’t restricted to arid regions—high-intensity rain on any soil can cause infiltration-excess runoff if it overwhelms infiltration capacity.

Infiltration-excess runoff occurs when rainfall arrives faster than the soil can absorb it, meaning the rainfall rate exceeds the soil’s infiltration capacity. When this limit is surpassed, water cannot infiltrate quickly enough and surplus water flows across the surface as runoff. This is also known as Hortonian runoff and depends on factors like soil type, soil moisture before the storm, surface crusts or cover, and rainfall intensity. It differs from saturation-excess runoff, which happens when the soil is already near its full capacity and additional rain cannot be stored in the pores, forcing surface runoff even if the rainfall isn’t exceptionally intense. It’s not driven by deep groundwater discharge, which contributes to baseflow rather than surface runoff, and it isn’t restricted to arid regions—high-intensity rain on any soil can cause infiltration-excess runoff if it overwhelms infiltration capacity.