streams glg 101 - physical geology bob leighty. these lecture notes are very similar to the ones i...
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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 ([email protected]).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