• in upper reaches ("youthful") of streams
  • straight and incised by downcutting
• in steep mountains with deep canyons, exposed bedrock
  • "V" shaped valley - deep gorges from erosion
  • "U" shaped - like Yosemite from glaciation
    
    
• knickpoints and waterfalls common from resistant bedrock
  
  

• in lower reaches ("mature") streams
  • side to side cutting in broad floodplain
  • meandering stream
    
    • Example: Amazon Basin (Rio Beni, Bolivia)
      
      
• significantly reduced gradient
  • more deposition, limited incising, especially with flat gradient

Characteristics of a Floodplain:

• cut banks - erosion on outside of banks
  • carves away material & widens channel
    
    
• point bars (sand bars) - deposition on inside of banks
  • slower current settles material out of suspension
    
    
• oxbow lakes - abandoned crescent-shaped lake
  • broad loops that eventually reach maximum radius & break through

natural levees - heaviest and densest material drops out first

• back swamps - remaining water stays to create seasonal wetlands
  
  
• bluffs - usually demarcate furthest extent of floodplain
  
  • Mississippi Valley (about 30 miles)
    
    

Delta’s and Rejuvenation Delta - outlet to the sea with flat gradient slow stream velocity reduced load capacity deposition occurs forming triangle shape maze of sediment blocks outlets Nile River (Greek letter) Rejuvenated" and entrenched rivers uplift and downcutting at the same time Goosenecks of the San Juan River in Utah Andecendent rivers - some rivers were there first - before mountains compression, folding, and slow uplift Tiger Leaping Gorge, Yunnan, China