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Drainage Patterns
Patterns of Water
• All water will eventually drain to another
water source.
• Most of the time it is to a larger water source,
such as an ocean.
• How different flowing water types drain
creates a pattern.
Drainage System
• In geomorphology (the study of the Earth’s
processes), a drainage system is the pattern
formed by the streams, rivers, and lakes in a
particular drainage basin.
What are some natural processes you
can think of that happen on the Earth?
Why water drains…
• http://www.youtube.co
m/watch?v=DPlkw5L5Yg
8
• Water drains due to the
topography of the land.
• Topography refers to the
shape and features of
the Earth’s surface.
Relief
• These features typically form a pattern
depending on what makes up the topography,
which can be called the ‘relief’ of a region.
• Relief can refer to how flat an area is in
relationship to the area around it.
• Example: Manitoba is mostly flat so would
have less relief, while Alberta would have
more relief closed to the Rocky Mountain
range.
• Topography can also be described as whether a
particular region is dominated by hard or soft
rocks, and the gradient of the land.
• The harder the rocks, the less the water will seep
or absorb into them. Softer rocks work like a
sponge and take in much more water, allowing
for more drainage.
• The gradient refers also to the height of the land
but also how much difference between the
different heights there is.
Drainage Basin
• A drainage basin is the topographic region
from which a stream receives runoff,
throughflow, and groundwater flow.
Runoff
• When the ground (specifically the soil) cannot
absorb any more water from precipitation
sources, it flows over the land until it comes in
contact with a drainage source. This can cause
erosion of the land.
Throughflow
• When water flows in horizontal manner,
mostly below ground. It must emerge onto
land before it enters a larger body of water,
such as a lake. The reason why it flows
underground is that when water enters the
soil, the force of gravity pulls it down below
the soil. This typically happens when the soil
gets super saturated with water and cannot
absorb anymore water.
Groundwater Flow
• Is the movement of water that travels and
seeps through soil and rock underground. It is
stored in cavities and geologic (rock) pores of
the earth's crust and is under a great deal of
pressure. It is different from a throughflow
because it is not just horizontal movement.
Watershed
• Drainage basins are divided from each other
by topographic barriers called a watershed.
• It is represented by tributaries. These are
parts of a steam that will flow into fresh water
sources, such as rivers and not salt water
sources, such as oceans.
• A watershed represents all of the stream
tributaries that flow to some location along
the stream channel.
• The number, size, and shape of the drainage
basins found in an area can vary.
Types of Drainage Systems
• Types of drainage system
• Drainage systems can fall into one of several
categories, depending on the topography and geology
of the land:
• Dendritic drainage pattern.
• Parallel drainage pattern.
• Trellis drainage pattern.
• Rectanglar drainage system
• Radial drainage system
• Deranged drainage system
• Annular drainage pattern
Dendritic drainage system
• Comes from the Greek word meaning tree.
• Most common types
• Many contributing streams (like twigs on a
tree)
• They then join into the main stream or river.
• They form following the slope or gradient of
the terrain they are in.
Parallel drainage system
• Pattern of rivers caused by steep slopes with
some relief (flat parts)
• Due to the steep slopes, the streams are swift
and straight, with very few tributaries
(branches), and all flow in the same direction.
Trellis drainage system
• The geometry of a trellis drainage system is
similar to that of a common garden trellis
used to grow vines.
• As the river flows along a valley, smaller
tributaries feed into it from the steep slopes
on the sides of mountains.
• These tributaries enter the main river at
approximately 90 degree angles, causing a
trellis-like appearance of the drainage system.
Rectangular drainage system
• Develops on rocks that are of approximately
uniform resistance to erosion. This means that
the all the rock types are the same in that
area.
• However, the rocks join at right angles.
• This causes the streams to form along the
joints where the rocks are attached.
• The streams are then mostly straight lines
along the system.
Radial drainage system
• Streams radiate outwards from a central high
point.
• Volcanos usually display excellent radial
drainage.
• Will also form on domes or laccoliths.
• This creates a radial pattern (think of a pizza
or an orange).
Deranged drainage system
• A deranged drainage system is a drainage
system in drainage basins where there is no
set pattern to the rivers and lakes.
• It happens in areas where there has been
much geological disruption, such as
earthquakes and mountains forming.
Annular drainage pattern
• In an annular drainage pattern streams follow
a roughly circular path, creating a ring like
pattern.
• This is because the rock is weak, which means
that it is very porous, allowing a lot fo water to
flow into it.