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FLUVIAL LANDFORMS

A. INTRODUCTION

Rivers: agents of change

Available Energy

• flow velocity
  
  
• flow depth
  
  
• gradient (slope)

Work

• degradation (vertical erosion) and lateral erosion
  
  
• aggradation (vertical deposition) and lateral deposition

Base Level

• lowest elevation a stream can attain through erosion
  
  
• vertical erosion is most prominent in rivers high above base level
  
  
• lateral erosion is most prominent in rivers close to base level

B. STREAM CHANNELS

Straight Channels

Braided Channels

 

Meandering Channels Image credit: R. Simmon (1999) NASA Earth Observatory. Mississippi River Meanders. http://earthobservatory.nasa.gov/Newsroom/ NewImages/images.php3?img_id=17383

C. MEANDERING RIVERS  

Meander Details

photo credit: Louis J. Maher, Jr. photo 156-18. Turkey River, Clayton County, IA.

Oxbow Lakes and meander scars  

photo credit: Louis J. Maher, Jr. photo 156-07. Pecatonica River near Mineral Point, WI.

 

D. FLOODS & FLOODPLAINS

Flood Frequency & Magnitude

photo credit: Andrea Booher/FEMA, photo 3438

Floodplains

• land area inundated (covered by water) when rivers overflow their banks

• relatively flat area of land adjacent to river channels

Floodplain Landforms

point bar deposits bar and swale topography incipient oxbow lakes channel cutoffs oxbow lakes meander scars natural levees yazoo streams terraces

photo copyright: Michael Collier, Image courtesy Earth Science World Image Bank, image imuzx5, http://www.earthscienceworld.org/images

E. SUMMARY

• Rivers expend their energy eroding and depositing material on the landscape

• Combination of erosion & deposition results in:

  • different channel forms (straight, braided, meandering)

  • various landforms within and along the channel (e.g. pools, riffles, point bars)

  • creation of V-shaped valleys high above base level due to vertical erosion

  • creation of floodplains at elevations closer to base level in response to lateral erosion & deposition

• Floods are a natural part of all river flow regime