Streams and Flooding Chapter 13
Dissolved Load
A kind of stream load AKA Chemical Load NOT IMPORTANT FOR MOVING SEDIMENT it IS important for stream chemistry
Bedload
A kind of stream load Sands, gravels, boulders Carried along the bottom Rolling action known as traction or bouncing (known as saltation)
Q =
Amount of water in the stream
Stream Geometry
Any change in cross section area affects the VELOCITY Q=A x V His example was a garden hose
Q= A x V
Any change in the stream load forces the stream to adjust its cross section, so that it has just enough velocity to carry the new load.
Water flow and transported sediment
As velocity decreases so does the capacity. The river is able to carry less sediment as it slows down.
shallow and and wide represented
BEDLOAD STREAM SHAPE
Kinds of Stream Load (3)
Bedload Suspended Load Dissolved Load
Landforms that form headwaters of water streams
Begin in bedrock dominated areas High elevation the high elevation causes water to gain energy to wear down and sculpt rock
Continental Divide
Best known drainage divide separates flow west to Pacific from those that flow east and south to Gulf of Mexico
Bedload size
CAN BE ANY SIZE OF MATERIAL depends on the stream energy at any one time
Structurally Conrolled Pattern
Can form a trellis pattern if it cuts across a ridge if curbed around they form annular patterns
How do streams start?
Channelized = grows incrementally as surface runoff becomes concentrated into channels
What type of load is important for stream chemistry
Dissolved load
Radial drainage pattern
Drainages flow downhill in all directions from highest area (Volcano or mountain)
Centripidal drainage pattern
Drainages flow inward to a low area from several directions
Annular pattern
Drainages follow curved layers around a central area
Streams and erosion
Erode bedrock and loose material. Transporting material like sediment and chemical components dissolved in the water.
K = 1/2 (2 2 squared) 1/2(2 4) 4 = 1/2 (8) 4 = 4
Example of Kinetic Energy formula
Stream Terraces
Flat benches that are perched above a river or stream Stair step up and outward from active channel Some terraces cut directly into bedrock and formed by erosion.
Intermittent Stream
Flows every year but NOT ENTIRE YEAR flowing only during rainstorms and spring snow melt ex: desert stream
Structurally controlled pattern
Fractures or folded layers that produce drainage that cut across a ridge to follow a different feature
Discharge related to
Gradient = velocity = stream energy = sediment load = stream shape (cross section)
Stream Load is determined by
Gradient Velocity Stream Energy (Discharge)
H T1 T2 T3 D M
Headwaters Tributary 1 Tributary 2 Tributary 3 Delta Mouth
Relationship between Flow and Transported Sediment
High velocity = above 100 cm/s carry clay, silt and sand suspended Moderate Vel = 10 - 100 cm/s silt and clay may remain suspended but the sand and gravel slide roll or bounce Low Vel = below 10 cm/s gravel and sand remain at rest only silt clay and fine sand are transported
Peak Discharge
Highest value Highest during spring when snow and ice melt
Stream Geometry
How create their shapes Why narrow/deep why some wide and shallow?
Deposition of sediment
Influenced by discharge wave erosion and river and ocean ice and vegetation in sediment load PAGE 435
Drainage Network
It is the combination of the tributaries and the main channel
Geomorphology
Landforms created by water wind and ice
River
Large stream of considerable volume with a permanent or seasonal flow
As gradient decreases
Maximum size of sediment that the river carries decreased and abrasion during transport reduces the size of the clasts SO THERE IS MORE COARSE MATERIAL in the headwaters than there is near the mouth
How do river systems change down stream
Most stream systems are steep at the beginning becoming less steep down stream towards the mouth. The steepness is the gradient.
Streams move:
Move eroded rock materials as stream sediment Deposits and RE depostis these sediments along the stream valleys While ALL THIS HAPPENS streams create distinctive landforms
What processes erode material in streams?
Moving water and the sediment it carries can erode bedrock it occurs along the base and sides of the channel
First order stream
No tributaries
Ephemeral streams
Only flow after a storm event not on an annual basis
Low gradient streams PAGE 432
PAGE 432
Meanders PAGE 439
PAGE 439
Floods and causes of FLOOD PAGE 440-441
PAGE 440-441
Devastating flood events PAGE 442-443
PAGE 442-443
How floods are measured PAGE 444
PAGE 444
Pictures of shallow bowl and deep bowl
Picture used to represent shallow and wide vs deeper and narrow streams The shallow and and wide represnet BEDLOAD STREAM The narrow and deeper represented a SUSPENDED LOAD STREAM
Factors that influence and change stream profiles PAGE 425
Rock types Tectonics Sea level Climate Instability of Conditions.
Dendritic Pattern
Rocks have about same resistence streams form a treelike system very common
narrow and deeper represented
SUSPENDED LOAD STREAM SHAPE
Hydrology
Science study water, including stream flow
Competence
Size of the largest particles that can be transported is called the Stream's competence
V =
Speed of water
A =
Stream cross section This is the depth times the width also known as the AREA
stream energy
Stream move materials to create the landscapes we see: Using KINETIC ENERGY KE=1/2 (mv2)
What controls profiles of streams
Streams erode mountains and carry sediment downhill depositing it in a basin along the sea. The lowest level to which a stream can erode is base level. Base level controls how a stream develops and how it responds to change.
Tributaries
Streams have a main channel fed by subsidiary channels. Each tributary drains part the larger drainage basin. The tributary can have a larger flow The combo of the main stream and the tributaries form a drainage network.
What gives stream it's color
Suspended load
Critical factor for stream energy
VELOCITY
Kind of stream determined by
Velocity and discharge and Type of sediment that is available to the stream
How does turbulence in flowing water effect erosion?
Viscosity resistence to flow as the water's velocity increases the flow becomes more turbulent and water can pick up more materials in the channel.
Stream's life can begin or end
Water and sediment supply at the source Slopes across which the streams flow OR elevation of it's base level.
Laminar Flow
Water moving smoothly in parallel layers smooth appearing water
Dendritic Drainage Pattern Page 419
Where rocks add about the same resistence to erosion or the drainage network has operated for a long time.
What influences the SHAPE (Geometry) of a real world stream channel
Why is it narrow/deep vs wide/shallow
Lowest discharge
Winter
Suspended Load
a kind of stream load Silts and clays It is in suspension above the stream bed GIVE STREAM IT'S COLOR
Discharge
amount of water flowing in a given amount of time units of Cubic Meters per second m3/s
mud
collective term for silt and clay
Where does it get its water
drainage basin basin slope basin size and shape influence it's flow response to rainfall a lareger or more complex basin will be higher and more spread out
Radial Pattern
fairly symetrical mountain or volcano or a pluton the flow is down and outward in all directions If it flows INWARD they call it CENTRIPTEL PATTERN
Turbulent Flow
fast and rough obstruction filled stream bottom promote turbulance
Perennial Stream
flows all year MISSISSIPPI RIVER no place has rain fall all of the time must be supplied by subsurface flows ex: lake, melting snowpack,
If a network as fewer tributaries
it responds more quickly to an event
Streams +
most important factor sculpting the earth's surface.
Gradient
most streams are steep in headwaters gradually becoming less steep down toward mouth steepness is gradient Def: change in elevation for a given horizontal distance
Streams
no accepted definition of the difference between stream and river stream = as any body of water that has a current and flows downhill within a channel and driven by the influence of gravity Each stream (ex Yukon River) has its own characteristics an history.
traction
rolling and sliding process moving only during times of high flow
Tributaries
small subsid channels each one drains part of the larger drainage basin but it CAN have more flow than the main channel
Q = Discharge
stream depth x stream width x average stream velocity
Up current EDDIES
swirls in current near bottom of stream
What controls velocity
the gradient = slope of the hill = Rise/Run Larger gradient (slope) the higher the velocity
decreases then
through spring and into early summer can increase with rainfall
Second order stream
two or more tributaries join to produce a second order stream
As velocity increased
viscosity less able to slow it down and it becomes more turbulant swirls in current called EDDIES occur
How is material transported and deposited into stream beds?
water applies force to bottom and sides of channel and can transport particles of various size
Discharge
water in the stream = gradient + velocity + stream energy
Concentrated erosion
when water and sediment swirl in small depressions carve bowl shaped pits called POTHOLES
Shape or geometry depends on......
The kind of LOAD the stream must carry
Stream Load
The materials that are carried by the water in the stream, channel
Basin Slope
The overall slope of drainage basin determines how fast water drains after a heavy rain or snow melt
Shape of streams profile
They are dynamic systems driven by precipitation and gravitational forces
Streams approaching base level
They deposit coarser sediment when the current slows leaving a delta along the shoreline.
Blue Triangles
They represent changes in gradient steeper gradient = bigger drop meters per kilometer, feet per mile or as a percentage 4%
Stream behavior over time
They vary by precipitation, snow melt and influx of ground water.