nedbørtilafstrømningforhold

Nedbør til afstrømning (rainfall-to-runoff) is the hydrological process by which precipitation is transformed into runoff that contributes to streamflow within a watershed. It integrates rainfall intensity and duration with the soil’s infiltration capacity, storage characteristics, and evapotranspiration, as well as land cover and topography. The resulting runoff is the sum of overland flow, subsurface flow, and baseflow, routed through the drainage network.

Two main mechanisms generate runoff: infiltration-excess runoff, where rainfall rate exceeds the soil’s ability to absorb water, and saturation-excess runoff, where the soil becomes fully saturated and additional rainfall becomes surface flow. The dominant mechanism depends on soil texture, drainage, slope, and antecedent moisture conditions. The interplay of rainfall characteristics, soil properties, and drainage determines the timing and magnitude of the runoff response.

Data for studying nedbør til afstrømning include rainfall records and streamflow (hydrographs). Analyses use event-based and continuous approaches, from simple empirical relationships to physically or structurally based models. Conceptual rainfall-runoff models describe runoff with a small set of storage components; distributed physically based models solve infiltration, runoff generation, and routing with spatial data such as digital elevation models. Units like unit hydrographs or more advanced routing schemes are used for forecasting.

Applications include flood forecasting, urban drainage design, and water resources management. Urban areas exhibit rapid runoff due to impervious surfaces, while forests and soils with high infiltration reduce peak flows. Climate change and land-use change can alter precipitation patterns and runoff response, impacting flood risk and water availability.