Drainage density refers to the frequency of streams on the land/drainage basin. In technical terms drainage density is the length of all streams divided by the drainage basin area ∑L/A (L= stream length, A= catchment area).It is measured in km/km2.
The drainage density or frequency of streams is influenced by varying factors such as:
Climate Regions with high amounts of rainfall tend to have high drainage densitiies.
Surface nature Permeable surfaces allow water to infiltrate through and result in lower drainage densities.
Vegetation cover Vegetation impedes , intercepts and stores water limiting the contribution to streams. Drainage basins with sparse vegetation cover have relatively high drainage densities.
Relief Steep terrains favor high amounts runoff than gentle undulating terrains which promotes infiltration.