Ch 13.1 Streams & Rivers
pg 280 – 282
Almost half of the water that falls to the Earth’s surface
eventually ends up in a stream or river (runoff), where it
travels overland to the oceans. Streams and Rivers are an
essential part in the water cycle and account for most of
the erosion of Earth’s surface.
A tributary is a stream that runs into a larger stream. The
main river will eventually drain into the ocean. A river
and all of its tributaries is called a river system.
The drainage basin, or watershed, of a
river includes all the land that drains into
the river either directly or through its
tributaries. The largest drainage basin in
the U.S. is the Mississippi River system.
The Continental Divide
The high land that separates one
drainage basin from another is called a
divide. The major divide in the U.S. is
called the Continental Divide. Rain
falling east of the divide will flow into
the Atlantic Ocean and rain falling west
of the divide will flow into the Pacific
Ocean.
Characteristics of Streams & Rivers
pg 281-282
Describe the following:
Velocity – the distance water travels in a certain amount of time; related
to the amount of energy the water has; fast moving rivers erode material
more quickly and can carry larger particles
Gradient – the slope or incline of a stream; sources of rivers tend to
have large gradient whereas mouths of rivers have small gradients.
Discharge – the volume of water a river or stream passes in a certain
amount of time; becomes larger as tributaries add water; seasonal
changes
Channel – the path through which water flows; size and shape effect
velocity
13.2 Stream Erosion & Deposition
pg 283-286
Running water is the most effective agent of erosion.
Gravity pulls water downhill eroding soil and rock
materials along the way. The soil and rock materials are
called sediments. Sediments that are transported by a
river are called its load. A river carries its load in three
different ways: in solution, in suspension and in its bed
load.
Rock materials or sediments that are transported by rivers
or streams are eventually deposited or dropped out. A
river will deposit some of its load when either its velocity
or discharge decreases.
Depositional Features
The beginning of a river is known as the source. The end
of the river is known as the mouth. As a river reaches its
mouth it slows down and deposits its load in a fan shape
called a delta.
An alluvial fan is similar to a delta, but forms on land
where a river emerges from a mountainous area and flows
out onto a more gently sloping plain.
3.4 Floodplains and Floods
pg 290 – 292
Rivers may overflow its banks as a flood. The floodwater
may cover part or the entire valley floor where the river
runs eroding and depositing sediments. This part of the
valley floor is called the floodplain.
Features of a Floodplain
– created by erosion & deposition
A river flowing through a floodplain typically winds back
and forth in broad curves called meanders.
A river wants to find the shortest, straightest way to the
ocean, so it will change paths along the floodplain cutting
off wide loops (or meanders) leaving behind a curved body
of water called an oxbow lake.
Elevated ridges along stream banks are called natural
levees.
River Development
The three stages in the development of a river are
described as youthful, mature, and old. Most rivers begin
in the highlands or mountains. There water sources such
as melting snow and ice feed fast-moving young rivers.
As the young rivers feed into larger rivers over flatter land
they may take on characteristics of mature rivers. As the
river approaches the ocean it slows down and becomes
wider & flatter taking on the characteristics of an old river.
1. A youthful river has a
steep slope, fast-moving
water, V-shaped valleys,
and many rapids and
waterfalls.
 Rapids & Waterfalls caused by steep
slopes and differential
erosion.
2. A mature river has a
shallower slope, is slow
moving, and forms
meanders.
3. An old river moves very slowly, has a nearly flat slope,
and has oxbow lakes.