GEOLOGY 102
Lecture 31 – Streams
1) Introduction and Definition
a) When more water falls on the land that can ________________ into the ground –
referred to as _________________________
b) _____________________ - water that flows on the land surface
c) Running water transports _____________________ products - eroded from
higher areas to lower areas
d) By far, the most dominant ______________ shaping the Earth’s surface
e) _____________________ - a body of water, confined to a ________________,
which flows under the influence of ________________
i) Regardless of size
2) Forming Streams
a) A stream channel _____________________ by erosion up slope __________________________________________
b) ______________________________ form in the area at the same time
c) Array of _______________ streams evolves – forming a drainage network
3) Parts of a Stream
a) _____________________
- outlet of a stream
b) headwater - source of a
stream
c) ___________ - floor of a
stream
d) _____________________ - flat land on either side of the stream that becomes
covered with water during _____________________
e) _____________________ - smaller streams
f) _____________________________ - larger stream that tributaries flow into
g) _____________________ - specific segment of a stream
i) ____________ reaches – lie near the _____________________
ii) ____________ reaches – lie near the _____________________
4) Stream Flow
a) Laminar flow – water particles travel in
_____________________ line paths that are
________________ to the channel
i) No mixing
ii) _____________ velocity
iii) Occur in smooth channels
b) Turbulent Flow - water moves in a
_______________, erratic fashion
i) Whirlpool eddies
ii) Due to ___________________ of water particles and __________________
of particles by obstacles (rocks)
iii) Turbulent flow common in:
(1) _________________ water
(2) shallow streams
(3) Stream flowing in a _______________, gravelly channel
5) Stream Parameters
a) _____________________ - slope of a stream =
i) Typically decreases downstream
b) _____________________ - rate of flow =
i) Directly related to gradient
c) Discharge (___) – volume of water that passes a ______________ in a given
period of _____________ as it flows through a channel of a certain width and
depth
i) _________________________________
ii) Depends on 2 factors:
(1) _______________________________
(2) _______________________________
Q = AV = w x d x V
iii) Measured by a stream-_______________
station
(1) Well measures the ____________ of
the water
(2) A current meter measures the
____________
iv) Varies along along a stream’s path
v) Can also vary with time
(_____________________)
vi) All water in a stream _____ _______
travel at the same velocity
vii) _____________________ at the channel
surface slows the flow
viii) Water ___________ the channel walls and floor moves more
______________ than water in the ______________ of the flow
ix) _______________ flow lies near the _______________ in the center of the
channel
d) _____________________ - deepest part of a
channel
i) In a _____________ stream, the thalweg
shifts to the _____________ of a curve
ii) Water flows in a ____________ motion
6) Work of Running Water
i) 3 components:
(1) _____________________
load: material carried in
______________
(a) Ions released by
weathering
(b) Nitrates, calcium carbonate
(2) _____________________ load: material being carried in _____________
(a) Bulk of sediment carried by a stream
(b) Intermittent or permanent
(c) ______________ particles _______________ faster
(3) __________ load: material carried along the ____________ by rolling or
sliding
(a) Moved by water ______________ or grain collisions
(b) Material _____________________
(c) Mainly large particles, > sand-sized
ii) any place where a stream’s velocity ____________ down, the stream’s ability
to carry sediment decreases and sediment is _________________
iii) What causes water to slow down?
(1) If water passes from a ___________ part in the stream to a
______________ part
(2) If water _________________ out over a floodplain
(a) In both cases - _______________ between the bed slows water down
(3) If water enters a _____________________ body of water
(4) When the _____________________ of a stream (the downstream slope )
_____________________
7) Changes along a stream’s length
a) _____________________ Profile – a crosssection showing the variation in a stream’s
_____________________ along its length
i) Roughly _____________________ curve
ii) Gradient is _____________________ near the headwaters than the mouth
iii) Near headwaters: flows down deep _____________ and _____________,
over water falls
iv) Near mouth: flows over nearly ____________________ plain
8) Stream Patterns
a) Meandering vs. Braided
i) Function of (amount of _______________ (climate), type of
________________ carried, stream gradient)
b) _____________________ stream – single, sinuous channel with broadly looping
curves, or meanders
i) Common on _________ gradient slopes – coastal areas & midcontinents
ii) Typically form ___________ valleys
iii) _______________________ - sediment deposited on the _____________ of
a meander
(1) Composed of relatively coarse material
(2) Grows by ________________ accretion
iv) _____________________ - erosional bank on the ________________ of a
meander
(1) Energy of the river focused on the outside of the curve
(2) Material eroded and transported ________________
v) A stream gradually works its way across the valley by ________________ on
one side and ________________ on the other side
(1) A stream wants to follow a more _______________ route
(2) Eventually a meander will be ________________ forming an oxbow lake
(3) ________________________________
(4) Later, the lake fills with ________________
vi) __________________________ - part of the stream valley subject to
________________
(1) Grows by ________________ deposition
c) _____________________ Stream – many channels that ___________ apart and
then rejoin
i) Large variations in flow ability to carry sediment, high sediment _________,
and easily ________________ banks
ii) Usually found near _____________________, ________________ areas, or
________________ climates
i) Areas with ________________ discharge
d) ________________ - a wedge of sediment formed where a stream enters
________________ water, the current _____________, the stream loses it’s
ability to carry sediment, and sediment ________________________________
i) River tends to divide into small streams (___________________________)
(1) Mississippi River deltas
(a) Indicate that the main ________________ of the river has
________________ on several occasions
(b) Occur when the ________________ builds so far out into the sea that
the ________________ of the stream becomes to ________________
to allow the river to flow
9) Floods
a) A flood occurs when the ________________ of water flowing down the stream
________________ the volume of the stream ________________
i) Water rises out of the normal channel and ___________________________
over the floodplain
ii) Flooding stream is more ________________, has more ability to carry
sediment, and exerts more ________________ on structures in its path
iii) When do they occur?
(1) During abrupt, heavy rains - ________________ > ________________
(2) After a long period of continuous rain – ground is ________________
(3) When heavy snows melt rapidly
(4) When an artificial or natural ________________ suddenly collapses
iv) Flood stage - water surface in the stream is
________________ than the ___________
of the normal channel
(1) Takes time to develop – hours to days
v) Prediction (and prevention?)
(1) U.S. Army Corp of Engineers
(2) Built 300 + dams along tributaries of the
Mississippi River – store
________________
________________ in reservoirs to be
released ________________
(3) ________________________________ - sand and mud levees and
concrete flood walls to ________________ the channel’s volume
(4) Could not contain the 1993 flood
(a) ________________________________ - increasing water pressure
on the river side ________________ water through the levee to the dry
side
vi) Other ways
(1) Transforming parts of the ________________ back into natural
________________ - wetlands ________________ water like a sponge
(2) ______________________ - regions likely to be flooded – abandon or
move buildings located in these regions
vii) ________________________________ Interval – the average ___________
between successive floods of a given ________________
(1) Depends on ________________ of the flood (______________________)
(2) The ________________ the flood, the ________________ the recurrence
interval, ________________________ the flood with occur in a given year