Transcript Surface Water - Burlington Area School District

Surface Water
Earth Science- Chapter 13
Mr. Hendricks and Mr. McMahon
Chapter Outline

Streams and River

Erosion and Deposition

River Valleys

Floodplains and Floods
Streams and Rivers
River Systems Vocabulary

- Continental Divide:

- Water Shed aka Drainage Basin:

- River system

- Tributary

River System
River System
• Definition- A river and
all of its tributaries
(feeder river or
connecting rivers)
• Example: Mississippi
River System
Drainage Basin or Watershed
Drainage Basin or
Watershedall is all
the land that drains
into the river directly
or through it’s
tributaries.
Example: green area is
Mississippi R. Basin
Continental Divide
• Defined as the
highland that
separates one
drainage basin from
another.
• Usually a mountain
range
• Sub-Continental
divide in Men. Falls
Tributary
• A tributary is a feeder
river/ creek/ stream
that flows into a large
parent river.
• There are some 250
tributaries of the
Mississippi which drain
a total area of more
than 1,247,000 square
miles--one third of the
nation's landmass!
River Characteristics
Channelized flow- water flows in a chanel

Velocity- how fast a river is flowing

Gradient- how steep a river is

Discharge- how much water is flowing

Velocity
How fast something is
moving

High velocity = high
speed

Low velocity = low
speed

Channelized Flow
Cross section of river
displaying channelized
flow

Rivers are “Confined”
by their channel

Affects Velocity of
water

Gradient
Slope of a stream

Rise over Run

A river may drop 10
feet over a distance of
100 feet

Gradient
is 1/10 or 10%
Discharge
Cross Sectional Area = Width * Depth

5
ft * 100 ft = 500 ft2
Velocity = 1 foot / second

Discharge = 500 ft2 * 1 ft/sec

=
500 ft3 / second
Discharge
Volume of water that
passes a point over an
amount of time

How much water is
flowing in a river

Cross sectional area *
Velocity

Stream Discharge
How to determine discharge
Discharge = Cross sectional area * Velocity

Determine the discharge of a stream with the
following characteristics:

Confined
by two vertical walls.
The
average depth of water is 5 feet.
The
channel is 100 feet wide
Average
velocity = 1 foot per second
Discharge
Discharge is not
constant. Depends on
conditions

Increased down river

Increased during times
of high precipitation or
melt

Spring = High
Discharge

Yearly Discharge
Erosion and Deposition
•
How does it happen?
Mechanical Weathering- Abrasion
Running water
• What does it produce?
Sediment
Rounded rocks
Potholes
Erosion, Transport, and Deposition
• Whether sediment is
being eroded,
transported, or
deposited depends on
the size of the particle
and velocity of water
• Hjulstrom Curve
Color Hjulstrom
Transportation of Sediment
Load: material transported by river

Bedload:
moved along bottom, rocks, gravel, pebbles
Suspension:
Solution:
clay- silt muddy water
material dissolved in water
Capacity:

total amount of sediment a stream can carry

Competence:

Maximize size particles a steram can carry

Stream Load
Stream Load
Deposition
Sediment is deposited when the velocity of the
current can no longer transport material

Examples:
A boulder will not be transported by a trickling
crick

A rapid river will move particles of all sizes
because of the high V

Silt and Clay is deposited in the deep ocean
because there is barely a current (low V)

Color Hjulstrom
Depositional Feautres
Delta

Sandbars

Deposit Bank

Delta
A fan-shaped deposit
that forms when a river
flows into a quiet or
large body of water

Where do you think
clay particles are
deposited on the
diagram?

Sand Bars
Wisconsin River-

How do they form?

-Discuss for 2 mins
Sand Bar Formation
Current carries sediment

Sediment is deposited when current is slowed
down

Sediment begins to pile up and catch more
sediment

Bars constantly move to change in current and
water depth

River Deposit
River Valleys
Toad River, Canada
Why do some rivers grow so big?
All rivers start on a small scale

Rainstorm
forms a valley in loose soils called a gullie
Rainstorm
ends, water evaporates, but depression
remains
Next
rainstorm, erosion continues
As time goes on, a gullie increases length, width,
and depth

Continuous erosion of land

Headward Erosion
The process by which land is worn away at the
head of a stream or gully

Head: An abrupt drop in elevation

Waterfall
Erosion opposite the direction of waterflow

Canyons
• Canyon- river valley
with steep vertical
sides
• Form in areas with low
rainfall
• Factors in formation:
Type of rock, amount
of water, climate
• Colorado R. -Grand
Canyon)
V-Shaped Valleys
• Rain erodes the sides
of a valley which forms
a V shape
• Deeper channel =
greater width
• Ex: Yellowstone River
Base Level
• Streams can’t cut
any deeper than
the body of water
they flow into
• Ultimately, all rivers
only can cut to sea
level
Rapids and Waterfalls
• Water flowing over a cliff or steep, jagged slope
forms rapids and waterfalls
• High rate of erosion at Rapids and WF
• Undermining
• Temporary features
Undermining
1) Waterfall creates pool
2) Undercuts the
waterfall
3) Creates overhang
4) Overhang collapses
5) Recession upstream
Niagara Falls
Dry Niagrara Falls?
Floodsplains and Floods
• Features of a Floodplain:
• Meanders
• Oxbow Lake
• Natural Levees
Floodplain Features
Meander-River winding back and forth with broad curves
Features
• Oxbow Lake- A curved
body of water that
separates a meander
from its river
• Formed due to erosion
of river banks
Oxbow Lake
Floodplain Feature
• Natural Levee- thick
deposits alongside
stream banks
• Elevated ridges
Floods
• Naturally occurring
event after heavy or
long-lasting rains
• Positive and Negative
Effects
• Recent Flooding?
Flood Effects
Positive
• Relieve water and
sediment overload of the
channel
Negative
• Destructive for people near
rivers
• Cause damage to
• Floods deposit minerals on
buildings, farmland, and
floodplains making these
other properties
areas fertile for agriculture
• Dangerous water
levels/velocity
Flood Causes
• For large rivers, like the Mississippi, floods
occur after many days of heavy, steady rainfallNo flash floods
• Spring melt
• Dam failures- Ex: Lake Delton
Lake Delton
Flood Control and Prevention
• People rely on controlling and preventing floods
• Communities built on flood plains are of special
concern
• Any time a flood occurs their property and their life is at
risk
Flood Prevention/Control
Means:
1. Restore natural flood protections
–
Replanting removed vegetation
–
Urbanization = problem
2. Dams
–
Creates reservoir
–
Risk of failure – Lake Delton
–
Eventually fill up with sediment
Flood Prevention Continued
3. Artificial Levees- sandbags
•
•
Deeper river holds more water
May create erosion downstream
4. Spillways
•
Channels parallel to river to collect water
Floodgates
Artificial Levee
Stream Stages
Youthful
________:
Old
_______:


Rapids
Broad
Waterfalls
Fast-moving
Steep
slope
water
floodplain
Meanders
Oxbow lakes
Meander Scars
Meanders – the bends and curves
________
of a stream
Oxbo
w
lake
depositi
on
erosio
n
____________ – deposit formed when a
stream spreads out onto a less steep
area
Delta – where a stream empties
_____
into a larger body of water
Rejuvenation – when an old age stream
____________
downcuts to “make it new again”