Deflusso

Deflusso, in hydrology, refers to the portion of precipitation that does not evaporate or infiltrate and therefore flows across the land surface or moves as groundwater to streams and other bodies of water. In common usage it corresponds to the concept of runoff and is composed of surface runoff and subsurface flows that contribute to river discharge.

Key factors influencing deflusso include rainfall intensity and duration, soil permeability, antecedent soil moisture, land cover and land use, topography, and drainage characteristics. Urban areas with impervious surfaces exhibit higher deflusso coefficients, leading to rapid peak flows; vegetated and permeable surfaces reduce deflusso by increasing infiltration and storage.

Processes and modeling: Runoff can be separated into surface runoff (overland flow) and subsurface runoff (infiltration to groundwater and baseflow). Runoff generation mechanisms include infiltration-excess (Horton) and saturation-excess, depending on antecedent conditions. In hydrological models, the water balance is commonly used, with precipitation distributed into runoff, changes in storage, and evapotranspiration.

Applications: Deflusso assessment informs flood risk management, urban drainage design, and water resources planning. Mitigation strategies include green infrastructure such as permeable pavements, bioswales, detention basins, and green roofs to decrease peak deflusso and improve water quality.