Drainagedichtheid

Drainagedichtheid, also known as drainage density, is a parameter used in geomorphology and hydrology that quantifies the extent of a drainage network within a watershed or catchment area. It is expressed as the total length of all streams and rivers in the area divided by the area itself, usually measured in kilometres per square kilometre (km/km²). The formula is: drainage density = total stream length / catchment area.

High drainage densities generally indicate a landscape with many small tributaries, rapid surface runoff, and a highly dissected terrain. Low drainage densities imply fewer streams, slower runoff, and often flatter or tighter erosion-resistant surfaces. The parameter is influenced by several factors: lithology, climatic patterns, vegetation cover, slope steepness, and human activity. Soils with low infiltration capacity and surfaces covered by impervious materials, for instance, tend to enhance drainage density. Conversely, permeable soils and dense vegetation reduce it.

Drainage density is used to assess hydrological response of catchments, to evaluate terrain susceptibility to erosion, and to calibrate computer models for flood forecasting and water resource management. In flood risk studies, high drainage density can signal quicker peak discharges following rainfall. In geomorphic analyses, it helps infer tectonic activity or past climatic conditions. Modelling software often incorporates drainage density values to predict runoff curves and sediment transport.

Although the metric is straightforward to compute if stream networks are mapped, it can be sensitive to data resolution. Small streams may be omitted in coarser maps, biasing the density downward. Modern remote sensing and GIS technology has improved the accuracy of drainage density estimation by allowing finer-scale mapping of channel networks.

In practice, drainage density values range widely: from less than 1 km/km² in arid or mountainous regions with sparse channels, to over 10 km/km² in humid, permeable terrains with abundant small streams. Comparative studies often pair drainage density with other indices such as slope–area ratios or channel width to provide a more comprehensive understanding of watershed behavior.