• in upper reaches (usu. mtns), streams are more straight and incised
  • sometimes referred to as "youthful" streams
    
    
• "downcutting" - creates steep canyon walls, exposed bedrock
  • stream profile of upper reaches is "V" shaped valley or gorges
  • some are "U" shaped like Yosemite from past glaciation
    
    
• knickpoints and waterfalls common from resistant bedrock (basalt)
• headward erosion occurs after millions of years to lengthen valley

• in lower reaches - meandering stream and floodplain
  • sometimes referred to as "mature" streams
  • Sacramento Valley
  • Amazon Basin (Rio Beni, Bolivia)
    
    
• significantly reduced gradient
  • more deposition, limited incising

Characteristics of meandering stream and floodplain:

• cut banks - erosion occurs on outside of banks
  • cork-screw current carves away material
  • widens channel and flood plain
    
    
• sand bars or point bars - deposition occurs on inside of banks
  • slower current settles material out of suspension
    
    
• oxbow lakes - leaves abandoned crescent-shaped lake
  • broad loops that eventually reach maximum radius & break through

flood plain - during periodic high water or flooding, river overflows entire region

• 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
    • can't see opposite side (about 30 miles)

Delta’s and Rejuvenation broad triangular shape, such as Nile River (Greek letter) reduced load capacity and velocity (deposition occurs) outlets become clogged and new channel created maze of outlets richest habitat severely threatened by diversions and pollution some rivers become "rejuvenated" and entrenched uplift and downcutting Goosenecks of the San Juan River in Utah / Arizona Tiger Leaping Gorge, Yunnan, China