infiltrationsekscess

Infiltration-excess, commonly referred to as Hortonian overland flow or infiltration-excess runoff, is a form of surface runoff that occurs when rainfall intensity exceeds the soil’s infiltration capacity. When water cannot infiltrate quickly enough, the excess rainfall flows over the ground surface rather than entering the soil.

The infiltration capacity is controlled by soil properties such as texture, structure, permeability, and crusting, as well as antecedent moisture, surface roughness, vegetation, and land cover. Rainfall characteristics—especially high intensity and short duration—along with slope and exposure, determine whether infiltration-excess runoff develops. In urban areas with impervious surfaces, infiltration is effectively zero, so rainfall frequently produces infiltration-excess runoff during storms.

Infiltration-excess runoff is distinct from saturation-excess runoff, which occurs when the soil profile becomes saturated and incapable of accepting more water, causing excess rainfall to become runoff even if infiltration capacity is not exceeded. Both forms contribute to total runoff but are driven by different soil moisture and rainfall conditions.

Hydrologically, infiltration-excess is important for understanding flash floods, erosion, and urban flood risk. It is commonly modeled using infiltration concepts (such as the Green–Ampt or Horton infiltration models) and rainfall–runoff simulations that compare rainfall intensity with estimated infiltration capacity. The term infiltrationsekscess is a nonstandard spelling sometimes seen in non-English sources; the standard term remains infiltration-excess runoff.