Streams GLG Physical Geology Bob 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, Dr. Bob if you have any questions about today’s lecture Leave no questions behind! 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 Cycle Streams

Where’s the Water? Streams

 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 Water Streams

 Services over 17 million people in 7 states (Colorado River Compact)Colorado River Compact Colorado River  Arizona portion over 600 miles long  Several hydroelectric dams (& lakes)hydroelectric  Lots of dissolved material (a desalting plant was built in 1993 near Yuma for $484 million) Arizona’s Water Streams

 Averages 80 ft wide & 16 ft deep  7% lost to seepage & evaporation  Built ( ) to provide an alternative water source  336-mile canal system (Colorado River to Tucson) costing $3.6 billion Central Arizona Project (CAP) Arizona’s Water Streams

 7 dams (& lakes) on the Salt River & Verde RiverSalt RiverVerde River Salt River Project (SRP) Arizona’s Water Streams

 Water collects in drainage basinsdrainage basins  Streams = all channelized runoff (any size) Streams How Do Streams Form? Streams  Fluvial = stream-related process

 Highest velocity in upper-center of a straight channel How Do Streams Flow? StreamsVelocity

 At a river bend - highest velocity shifts to outside How Do Streams Flow? StreamsVelocity

 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? StreamsVelocity

 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? StreamsGradient

 Steeper gradients = in upper areas of stream (100’s of ft/mile; rapids & waterfalls) How Do Streams Flow? StreamsGradient

 Gentle gradients = in lower areas (1’s of ft/mile; “old man river”) How Do Streams Flow? StreamsGradient

 Streams cut vertically  Common in areas with high stream gradients  Creates V-shaped valleys, waterfalls, rapids How Do Streams Erode? StreamsDowncutting

 Slot canyons result from extreme downcutting How Do Streams Erode? StreamsDowncutting

 Stream cuts sideways  Creates meanders, flood plains, wider valleys  Common in areas with low stream gradients How Do Streams Erode? Streams Lateral Erosion

Lateral erosion at a meander bend How Do Streams Erode? Streams Lateral 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? Streams

 Alluvium = material deposited by stream Alluvium  Sediment is deposited if stream velocity decreases How Do Streams Deposit Sediment? Streams

 Channel - Higher velocity water; sand & gravel Channel Fluvial Features Streams

 Floodplain – Flat area with lower velocity water; mud & silt Floodplain Fluvial Features Streams

 Terrace - Remnant of a former floodplain Terrace Fluvial Features Streams

 Delta – Sediment accumulates as streams enter a lake or ocean, because of the reduction in water velocity Delta Fluvial Features Streams

The Mississippi Delta in the last 6,000 years Fluvial Features Streams

 Alluvial fan - Similar to a delta “on dry land” Alluvial fan Fluvial Features Streams

 Entrenched meanders – Regional uplift or a drop in base level causes streams to downcut Entrenched meanders Fluvial Features Streams

 Slot canyons – Regional uplift or a drop in base level causes streams to downcut Slot canyons Fluvial Features Streams

WWW Links in this Lecture > Hydrologic cycle - > Colorado River - > Colorado River Compact - > Hydroelectricity - > Central Arizona Project - > Salt River Project - > Salt River - > Verde River - > Drainage basin - > Stream - > Alluvium - > Channel - > Floodplain - > Stream terrace - > River delta - > Alluvial fan - > Entrenched meanders - > Slot canyon -