billion Km3 of water exists on the Earth
2.1% ice cap and glaciers
0.65% in the freshwater reservoar (atmosphere, lakes,
unending circulation of the Earthís water supply is the so called water cycle.
The cycle itself is powered by the heat of the sun and gravitation
is from http://www.und.nodak.edu/instruct/eng/fkarner/pages/cycle.htm
from the ocean and from the land is continuously evaporating into the
atmosphere, where it is transported by wind. Than clouds
are forming followed by precipitation.
of the water soaks into the ground (infiltration);
other part after big rains runs off (runoff)
evaporates from the surface,
will be adsorbed then released by plants (transpiration)
and 4 together is called Evapotranspiration
of the water can be stored on the surface for a while as snow (in glaciers)
water may have the largest influence on human life.
water is divided into two big group:
SHEETFLOW (water flowing on the surface)
usually depend on the infiltration capacity of the bedrocks.
(after a while sheetflow will distribute into tiny
Confined flow (STREAM)
In Confined flow or
stream water flows in channels, which are long narrow depressions eroded by the
river or flow into the underlying rocks.
the HEADWATER PART of the stream it
has a typical V shape,
where the stream occupy
the bottom of the channel.
There is absolutely no floodplain.
the MOUTH of the stream, it is flowing on
a broad flat-floored valley. Here the
stream channel is surrounded by
stream usually stays in the CHANNEL, where the side of the channel is called
in the channel can be LAMINAR or TURBULENT
flow is usually slow and particles are moving straight, parallel with the
Turbulent flow water flows in erratic fashion that is often characterized
by swirling, whirpool-like eddies.
affecting stream erosion, and deposition:
speed at which water in a stream travels is
called stream velocity. (moderately fast (3 miles/hour) Fast (15 miles/hour)
velocity in a channel usually is close to its middle (Friction is the smallest
here). If there is a curve the centrifugal force pulles the highest velocity to
the outer part of the curve!!!! Changes the channel shape!!!
erode and transport sediment
of a stream IS CONTROLLED BY:
downhill slope of the bed. (Feet/miles; or %)
G=difference in elevation
distance in course (feet)
Ex:. Changing gradient strongly influence wether the river
b. Channel shape and roughness
As the water flows it wets the channel, and between the bank and the
water there is
friction. The larger the channel the larger the bank, the larger
Friction slows down the flow.
Roughness has the same affect. In smooth channel water flows
faster. (Changes shape as it flows on
different rock types.)
discharge of a river is the volume of water that flows through at a certain
point in a unit of time.
(m3/sec)= channel with(m)*channel depth(m)*velocity (m/sec)
10 times more than Mississippi
IS INCREASING DOWNFLOW
Streams usually cut their own valley by deepening and widening it for long time
can happen in three ways.
Hydraulic action (ability of the flowing water to pick up and move sediment
solution (carry chemicals in solution)
abrasion (grading, carving of river bed rocks)
Potholes (abrasive action of sediment load makes these
sediment in a river can be carried as
Large or heavy
sediment particles that traven on or near the stream bed, and move by traction
Movement by rolling, sliding or draging is called TRACTION
Sediment which is carried in the flow all the time
chemicalias in the stream
max. sized sediment in the stream that the river can carry define its COMPETENCE,
a factor related to flow velocity. CAPACITY on the other hand is the
measure of the total load the stream can carry.
Transportation of sediment
IN US. CARRY 250 MILLION TONS of SOLID LOAD
MILLION TONS of DISSOLVED LOAD.
IN A CHANNEL
IN THE MIDDLE OR THE SIDE OF THE RIVER (CAN
OF INTERCONNECTED RIVULETS AROUND
IN HIGHER MOUNTAINS WHEN RIVER ENTERING TO FLAT AREA.
STREAM AND POINT BAR
FLAT, SLOW FLOWING RIVER
EROSION IN THE OUTSIDE CURVE,
ON THE OPPOSITE SIDE.
DELTAS (WITH LOTS OF DISTRIBUTARIES) DELTA SHAPE
STREAM AS A SYSTEM
stream has a drainage basin.
basin is the total area drained by the given stream and its tributary
is a small stream flowing into a larger one.
riverís drainage basin contain 1/3 USA, together with its tributary channels
such as Ohio and Missouri rivers
ridge or strip of high ground dividing one drainage basin from the other.
flowing to the PACIFIC from
flowing to the Atlantic and Gulf of Mexico
POWELL (1875) REALIZED, THAT THERE IS A DOWNWARD LIMIT OF EROSION, WHICH HE
level = ULTIMATE BASE LEVEL
level = TEMPORARY BASE LEVEL
CONCEPT OF GRADED STREAM
A STREAM JUST BEGIN TO DOWNCUT ITS LONGITUDINAL PROFILE IS IRREGULAR, WITH
RAPIDS AND WATERFALLS ALONG ITS COURSE.
OF ITS ENERGY IS USED FOR
THE STREAM SMOOTHES ITS COURSE INTO A CONCAVE UPWARD SHAPE,
IT BECAMES GRADED.
BETWEEN TRANSPORTING CAPACITY AND SEDIMENT LOAD AVAILABLE
WIDENING OF THE CHANNEL BY ABRASION OF BANKS +MASS
MOVEMENT ALONG SIDES
SLOW UPHILL GROWTH OF THE CHANNEL
PENEPLAIN (FLAT ERODED AREA)
EVOLUTION OF A RIVER CAN BE DIVIDED INTO THREE
MATURITY, AND OLD AGE
-LATERAL EROSION MATURE
-PENEPLAIN (FLAT ERODED AREA) OLD
-DENDRITIC PATTERN (IRREGULAR BRANCHING)