RIVERS!!!!!!!!
(and valleys)
Chapter 12 (page 39)
Because Bill Nye always makes things
better…
http://www.youtube.com/watch?
v=Xtk_bqkfeyE
Drainage Basins, Streams, Rivers
 A drainage basin (watershed, catchment) is
a piece of land where water (rain and
melting ice) drains into a larger body of
water. Includes the streams, rivers and
channels  OPEN SYSTEM separated by
divides
 When water accumulates upland, and
flows along a definite course, they are
called streams
 Small streams  tributary streams
 Tributary streams flow down and join
together to connect to a river
Drainage Basin
Types of drainage patterns
 The hardness of the rock layers in the region determines the
formation of certain drainage pattern that results
 There are three types of drainage patterns
Drainage pattern #1: Dendritic
 Most common pattern
 Resembles vein or tree branch pattern
 Forms on flat surfaces where the rock
layers are of uniform hardness
 Form in v-shaped valleys where many
small tributaries join together and then
join onto a main river, giving it the
appearance of a tree
Drainage pattern #2: Trellis
 As a river flows down a valley,
smaller tributaries flow into it from
steep mountain slopes
 Tributaries enter the main river at
approximately 90 degree angles,
causing a trellis-like appearance of
the drainage system
 Trellis drainage is characteristic of
areas with alternating parallel
valleys and ridges, and folded
mountains
Drainage pattern #3: Radial
 The streams radiate equally
outwards from a central high point
 Volcanoes (as well as domes and
laccoliths  Cone-shaped
mountains) usually display excellent
radial drainage
River Valley shapes
 Dry (arid) regions  steep slope  forms canyons
(vertical erosion)
 Wet regions  gentle slope  heavy sediments in water
(vertical erosion)
Four stages of a River development
 Youth stage
 Mature stage
 Old age stage
 Rejuvenated stage
http://www.youtube.co
m/watch?v=AjZLAw_lgZ
4&feature=related
Stage #1: Youth Stage
 River cuts a deep V-shaped valley
(steep gradient)
 Flows in highlands of mountainous
areas with very little shifting of its
channel
 Usually small in size
 Dominated by erosion  fast, violent
water  little deposition
 Little floodplain, but rapids, waterfalls,
and boulders may be found
Stage #2: Mature Stage


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Receives the waters of many tributaries
River increases in size and slows in velocity  more deposition
Eroded the bed downward and gotten closer to the base level
Though it is still eroding downwards, it mainly erodes laterally to
form meanders and eventually flood plains
Stage #3: Old Age stage
 Extensive meandering forms oxbow
lakes
 Its gradient and speed are very slow,
 Because of this it has lost the power
to erode downwards and carry as
much sediment load  deposits rich
alluvium on the floodplain
http://www.igeography.ie/maturestage.html
Stage #4: Rejuvenated stage
 River returns to
the youthful stage
 Vertical erosion
creates v-shaped
valley and process
starts again
The four stages
http://www.slideshare.net/Dannyoc/stages-of-a-river
Erosional action of rivers (4 types)
THIS SHOULD BE FAMILIAR!!! 
 Hydraulic action
 Abrasion
 Attrition
 Corrosion
Ways that rivers transport sediments
THIS SHOULD BE FAMILIAR!!!
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
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Solution
Suspension
Saltation
Traction
http://library.thinkquest.org/28022/transport/index.html
Rivers PART TWO!!
Landforms associated with
upland rivers
 Steep gradient (steep slope)
 Water flows swiftly with
vertical erosion
 Waterfalls occur where rocks
have eroded quickly
 Igneous rock wears out much
slower than others (e.g.
sedimentary rock)
Potholes, Gorges and Canyons
 Potholes develop along
river beds
 Pebbles get trapped
 Water spins and abrasion
deepens the hole
 Eventually a gorge or
even a canyon may result
(narrow slot in
landscape)
Landforms associated with lowland
rivers
 When the river has reached an
elevation close to the sea level, a
flood plain may result
 Lateral erosion and energy
 River can flow overflow and
deposit rich alluvium (ideal for
farming)
Meanders, undercut banks and
slip-off slopes
 Erosion is greatest and fastest
along the outer edge of a
meander (bend)
 Undercut bank (outer edge)
 Point bar/ slip-off slope (inner
bank)
Levees and dikes
 Levees: mounds of sediment
that slowly build up along
the river bank
Hold in flood water
Natural dikes
Common in valleys where
river cannot carry all of its
load
• Dikes: artificial levees
created to minimize flooding
Mississippi River floods of 1993
River terraces
 Lowland regions sometimes uplift and the
meandering river begins vertical erosion again
 Once uplifting stops and a flood plain is formed,
lateral erosion is once again dominant
 The old, uplift flood plain sits high above river banks
These ledges are called river terraces
Let’s draw it out!!! 
Braided river channels
 Sand and gravel “islands”
may break up the water
flow, so rivers take on a
braided appearance
 Transport large volumes of
debris  when deposited,
creates sand bars and
islands
River deltas
 A river carries sediment from its
drainage basin into the ocean
 Current carries them into the
ocean before they are deposited
 Sand (heavy)  silt  clay (light)
 Large rivers have broad deltas
with shallow water extending far
into the sea
Very gentle slope
Waves cannot erode as
effectively
3 main types of delta
 Arcuate delta
 Bird’s foot delta
 Estuarine delta
 LOOK ON PAGE 190 OF BLUE
GEOGRAPHY BOOK FOR
AWESOME ILLUSTRATIONS
FO DELTAS AROUND THE
WORLD!!! 
Arcuate delta
 Carries water and
sediment across a
symmetrical delta in
distributaries
 Inverted cone shape
 EX. Nile River Delta
Bird’s foot delta
 Many distributary channels
branch out from main river
channel
 Bird’s foot shape
 EX. Mississippi River Delta
Estuarine delta
 Forms when river sediment is
deposited in a submerged river
mouth
 Estuary shape