Explain what it is meant by, in a drainage basin, by the terms drainage density and stream order

Authors Avatar

A) Explain what it is meant by, in a drainage basin, by the terms drainage density and stream order.

        The drainage basin is an area of land drained by a river and its tributaries.

        Drainage Density represents an approach to the quantitative analysis of drainage basin. It is the average length of channel per unit area of the drainage basin. It is calculated as shown below. Drainage density is a qualitative analysis of the areal properties of a river basin .

        Drainage density is useful as a measure of frequency and spacing of streams within the drainage basin. It also helps to determine the texture of dissection of a drainage basin- the extent to which the landscape is cut into by river valleys and in turn influence slope development. Generally, there are 4 categories of drainage density and corresponding texture of dissection.

Very low- less than 8km/km sq coarse

Medium low- 8-20 medium

High density- 20- 200 fine

Very high density- more than 200 ultra fines


        Drainage density and texture of dissection varies in response to these factors:

  • Permeability of surface- a highly permeable material such as sand tends to give low drainage density because of high infiltration capacity and little water is available as surface runoff to maintain channels.

  • Rock type
  • Topography

  • Vegetation- dense vegetation helps to intercept rainfall, because of infiltration capacity and prevent overland flow. This will inhibit channel development and thus the reduction of drainage density.
Join now!

  • Rainfall amount, intensity and duration
  • Human activities
  • Time

Stream order refers to stream hierarchy- the way the various stream channels in drainage fit together. Identification of the link in a stream network is by the process of stream ordering. Analysis of the stream order in a drainage basin can help in predicting the shape of hydrograph, and hence flood forecasting. This is a quantitative approach to drainage basin morphology by examining the linear properties of the river basin

The Horton’s law of stream number shows that there is ...

This is a preview of the whole essay