World Geography 3202
Understand how
running water
acts as an agent
of erosion and
deposition.
(Chapter 2)
Introductory Terms / Information




Tributaries are branches of a river
that feed water into the larger river
Rivers flow from high elevation to
low elevation
Rivers empty into the sea at sea
level = 0 ft
Look for elevation legend, often
color coded, symbols or contour
lines.
Amazon River
What direction does the river flow? Where is the high elevation?
Where are the tributaries?
Where does the river begin?
Define the term drainage basin. (p. 26)


Drainage Basin = the
area of land drained by
a river and its
tributaries.
Try question #4 p. 26
Drainage Basin-Circled in red
Drainage Basin. (p. 26)
The Amazon Basin is the planet's
largest body of fresh water with 1100
tributaries 17 of which are more than
1000 miles long.
 Many of the tributaries begin in
Colombia and Peru.
 WHY????

Nile River Basin
The Nile river in
Africa is the
longest river in
the world.
 The green area
on the map
marks the Nile
River basin.

1.3.1
Describe the three stages in
the life cycle of a river.
(P. 26)




Rivers change
over time and
seem to go
through three
stages:
1st Youthful rivers
2nd Mature rivers
3rd Old rivers
Young Rivers








Usually found in
highland or mountain
regions
Steep slope (high
gradient)
Small volume of water
Rapid flow of water
Rapid erosion
More vertical erosion
than lateral
Narrow “V” shaped
valley
Water falls & rapids
common
Mature Rivers







Most high relief is
eroded
Gentler slope
Many well
developed
tributaries
Broad flat river
valley
Well developed
flood plain
More lateral (↔)
erosion than vertical
Meandering results
Late River Maturity


Remember the
stages are not
distinct.
These changes
occur over long
periods of time.
Old River






Almost no slope
Very little relief
Elaborate
meandering
Often swampy
areas around river
Very muddy due to
slow speed and
deposition
Most susceptible to
flooding because of
large flood plain.
The Amazon- What stage??
1.3.2
Describe two ways in which
water erosion occurs. (P. 31)


Vertical erosion
makes rivers
deeper as is the
case in young
rivers
Lateral erosion
makes rivers wider
leading to the
meandering of
mature rivers.
Youth Stage
Mature Stage
Old Age Stage
1.3.4
Define the term Delta. (P.32)
Delta =
 low lying area at
mouth of river
 formed by
deposition of silt
 deposition occurs
because river slows
as it enters ocean or
lake
* 1.3.5
Distinguish among the terms arcuate
delta, digitate delta and estuarine
delta. (P. 32)




Arcuate Delta=
Named from Latin
word for curved in
the shape of a bow.
Fan shaped
Example Nile Delta
p. 32
Nile
Delta
Digitate Delta
Digitate Delta =
 From Latin for
finger
 Delta with long
fingers of sediment
reaching into the
sea
 Example
Mississippi
Mississippi
Delta
Estuarine Delta p. 32
Estuarine Delta =
 Formed when river
runs into bay or
estuary
 Tidal mud flats
form which can be
seen at low tide
 Sediment deposited
from river outflow
and from Tidal
inflow
Sacramento River – San Joaquin
San Francisco Bay Delta
Delta Similarities & Differences
Similarities



Arcuate & digitate
both flow into open
ocean
All three allow river
water to flow out
All have channels
or distributaries cut
into them by the
river
Differences


Estuarine empties
into a bay whereas
other 2 empty into
open water
Three different
shapes
1.3.3 Examine evidence to determine the life
cycle stage of a river. (P. 28 questions # 5 & 6)
Evidence to look for!!
1.
2.
3.
4.
5.
6.
Slope of the river
Relief of the
banks
Width of the
valley
Meandering
Size of flood
plain
Rapids or water
falls
What stage is this river in?
Young
 Water falls & rapids
 Steep slope
What stage is this river?
Early maturity
 Some meandering
 However still some
relief
 Associated with
mountain
What river Stage?
Youth
 Rapid water movement
 Rapids & water falls
 High relief on banks