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

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Devastating flood events PAGE 442-443

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How floods are measured PAGE 444

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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.