Question

explain stream drainage patterns with the help of diagram

Answer 1

Development of Streams - Steamflow begins when water is added to the surface from rainfall,
melting snow,and groundwater. Drainage systems develop in such a way as to efficiently move
water off the land. Streamflow begins as moving sheetwash which is a thin surface layer of
water. The water moves down the steepest slope and starts to erode the surface by creating
small rill channels. As the rills coalesce, deepen, and downcut into channels larger channels
form. Rapid erosion lengthens the channel upslope in a process called headward erosion. Over
time, nearby channels merge with smaller tributaries joining a larger trunk stream. (See figure
17.3 in your text). The linked channels become what is known as a drainage network. With
continued erosion of the channels, drainage networks change over time.
Drainage Patterns - Drainages tend to
develop along zones where rock type
and structure are most easily eroded.
Thus various types of drainage patterns
develop in a region and these drainage
patterns reflect the structure of the
rock.
z Dendritic drainage patterns are
most common. They develop on a
land surface where the underlying
rock is of uniform resistance to
erosion.
z Radial drainage patterns develop
surrounding areas of high
topography where elevation drops
from a central high area to
surrounding low areas.
z Rectangular drainage patterns develop where linear zones of weakness, such as joints or
faults cause the streams to cut down along the weak areas in the rock.