streams glg 101 - physical geology bob leighty. these lecture notes are very similar to the ones i...

StreamsStreams

GLG 101 - Physical GeologyGLG 101 - Physical Geology Bob LeightyBob Leighty

These lecture notes are very similar to the ones I use in my traditional classes. You’ll find they are loaded with imagery and streamlined text that highlight the most essential terms and concepts. The notes provide a framework for learning and, by themselves, are not meant to be a comprehensive source of information.

To take advantage of the global knowledge base known as the Internet, I have included numerous hyperlinks to external web sites (like the Wikipedia, USGS, NASA, etc.). Follow the links and scan them for relevant info. The information from linked web sites is meant to supplement and reinforce the lecture notes – you won’t be responsible for knowing everything contained in them.

As a distance learning student, you need to explore and understand the content more independently than in a traditional class. As always, I will help guide you through this learning adventure. Remember, email Dr. Bob if you have any questions about today’s lecture (rleighty@mail.mc.maricopa.edu).Leave no questions behind!

Explore and have fun!Explore and have fun!

These notes and web links are your primary “lecture” content in this class. Additionally, various articles are assigned each week to supplement this “lecture” information. I believe you’ll have enough information to reference without having to purchase a costly textbook.

Cycling of water due to gravity & solar energy

The Hydrologic CycleThe Hydrologic CycleStreamsStreams

Where’s the Water?Where’s the Water?StreamsStreams

Water flowing in streams, canyons, ravines, etc.

Lakes, ponds, and springs

Intermittent streams = flow only at certain times of the year (e.g., Salt, Gila)

Perennial streams = flow continuously (e.g., Colorado,

Verde)

Arizona’s WaterArizona’s WaterStreamsStreams

Services over 17 million people in 7 states (Colorado River Compact)

Colorado RiverColorado River Arizona portion over 600 miles long

Several hydroelectric dams (& lakes)

Lots of dissolved material (a desalting plant was built in 1993 near Yuma for $484 million)

Arizona’s WaterArizona’s WaterStreamsStreams

Averages 80 ft wide & 16 ft deep

7% lost to seepage & evaporation

Built (1973-1993) to provide an alternative water source 336-mile canal system (Colorado River to Tucson)

costing $3.6 billion

Central Arizona Project (CAP)Central Arizona Project (CAP)

Arizona’s WaterArizona’s WaterStreamsStreams

7 dams (& lakes) on the Salt River & Verde River

Salt River Project (SRP)Salt River Project (SRP)

Arizona’s WaterArizona’s WaterStreamsStreams

Water collects in drainage basins

Streams = all channelized runoff (any size)

How Do Streams Form?How Do Streams Form?StreamsStreams

Fluvial = stream-related process

Highest velocity in upper-center of a straight channel

How Do Streams Flow?How Do Streams Flow?StreamsStreams

VelocityVelocity

At a river bend - highest velocity shifts to outside

How Do Streams Flow?How Do Streams Flow?StreamsStreams

VelocityVelocity

Velocity of stream controls whether it erodes, transports, or deposits material

Most erosion occurs on outside (higher velocity) & most deposition on inside (lower velocity)

How Do Streams Flow?How Do Streams Flow?StreamsStreams

VelocityVelocity

Typically measured in feet per mile

Gradient = the slope of the channel (vertical drop / horizontal distance)

Most streams decrease in gradient (become less steep) downstream (seaward)

How Do Streams Flow?How Do Streams Flow?StreamsStreams

GradientGradient

Steeper gradients = in upper areas of stream (100’s of ft/mile; rapids & waterfalls)

How Do Streams Flow?How Do Streams Flow?StreamsStreams

GradientGradient

Gentle gradients = in lower areas (1’s of ft/mile; “old man river”)

How Do Streams Flow?How Do Streams Flow?StreamsStreams

GradientGradient

Streams cut vertically

Common in areas with high stream gradients

Creates V-shaped valleys, waterfalls, rapids

How Do Streams Erode?How Do Streams Erode?StreamsStreams

DowncuttingDowncutting

Slot canyons result from extreme downcutting

How Do Streams Erode?How Do Streams Erode?StreamsStreams

DowncuttingDowncutting

Stream cuts sideways

Creates meanders, flood plains, wider valleys

Common in areas with low stream gradients

How Do Streams Erode?How Do Streams Erode?StreamsStreams

Lateral ErosionLateral Erosion

Lateral erosion at a meander bend

How Do Streams Erode?How Do Streams Erode?StreamsStreams

Lateral ErosionLateral Erosion

Material moves:

1) along bottom of channel (bed load)

2) by drifting along (suspended load)

3) in solution (dissolved load)

How Do Streams Transport Sediment?How Do Streams Transport Sediment?StreamsStreams

Alluvium = material deposited by stream

Sediment is deposited if stream velocity decreases

How Do Streams Deposit Sediment?How Do Streams Deposit Sediment?StreamsStreams

Channel - Higher velocity water; sand & gravel

Fluvial FeaturesFluvial FeaturesStreamsStreams

Floodplain – Flat area with lower velocity water; mud & silt

Fluvial FeaturesFluvial FeaturesStreamsStreams

Terrace - Remnant of a former floodplain

Fluvial FeaturesFluvial FeaturesStreamsStreams

Delta – Sediment accumulates as streams enter a lake or

ocean,

because of the reduction in water velocity

Fluvial FeaturesFluvial FeaturesStreamsStreams

The Mississippi Delta in the last 6,000 years

Fluvial FeaturesFluvial FeaturesStreamsStreams

Alluvial fan - Similar to a delta “on dry land”

Fluvial FeaturesFluvial FeaturesStreamsStreams

Entrenched meanders – Regional uplift or a drop in base level causes streams to downcut

Fluvial FeaturesFluvial FeaturesStreamsStreams

Slot canyons – Regional uplift or a drop in base level

causes streams to downcut

Fluvial FeaturesFluvial FeaturesStreamsStreams

WWW Links in this LectureWWW Links in this Lecture

> Hydrologic cycle - http://en.wikipedia.org/wiki/Water_cycle

> Colorado River - http://en.wikipedia.org/wiki/Colorado_River

> Colorado River Compact - http://en.wikipedia.org/wiki/Colorado_River_Compact

> Hydroelectricity - http://en.wikipedia.org/wiki/Hydroelectricity

> Central Arizona Project - http://en.wikipedia.org/wiki/Central_Arizona_Project

> Salt River Project - http://en.wikipedia.org/wiki/Salt_River_Project

> Salt River - http://en.wikipedia.org/wiki/Salt_River_%28Arizona%29

> Verde River - http://en.wikipedia.org/wiki/Verde_River

> Drainage basin - http://en.wikipedia.org/wiki/Drainage_basin

> Stream - http://en.wikipedia.org/wiki/Stream

> Alluvium - http://en.wikipedia.org/wiki/Alluvium

> Channel - http://en.wikipedia.org/wiki/Channel_%28geography%29

> Floodplain - http://en.wikipedia.org/wiki/Floodplain

> Stream terrace - http://en.wikipedia.org/wiki/Stream_terrace

> River delta - http://en.wikipedia.org/wiki/River_delta

> Alluvial fan - http://en.wikipedia.org/wiki/Alluvial_fan

> Entrenched meanders - http://en.wikipedia.org/wiki/Entrenched_river

> Slot canyon - http://en.wikipedia.org/wiki/Slot_canyon

StreamsStreams