Tributary Delta Alluvial Fan Drainage Basin Drainage Basins

Tributary

Delta

Alluvial Fan

Drainage Basin

Drainage Basins or watersheds are separated by high elevations

Mississippi River Drainage Basin

Stream Velocity

Gradient or Slope

Discharge

Channel

River and Glacial Valleys Glaciated Valley River Valley

Floodplain

Stages of River/Stream Development

The Ideal Stream Cycle (W. M. Davis, 1880) Not a Literal Time Sequence • Youth • Maturity • Old Age • Rejuvenation

Youth • • V-Shaped Valley Fast Current Pot holes common Rapids Waterfalls No Flood Plain Drainage Divides Broad and Flat, Undissected by Erosion • Valley Being Deepened • General Agreement on this stage, lots of examples

Maturity (Early) • V-Shaped Valley • Beginnings of Flood Plain • Sand Gravel Bars • Sharp Divides • Relief Reaches Maximum • Valleys stop deepening • General Agreement on this stage, lots of examples

Maturity (Late) • Valley has flat bottom • Narrow Flood Plain • Divides begin to round off • Relief diminishes • Sediment builds up, flood plain widens • River begins to meander • Many geologists believe slopes stay steep but simply retreat.

Old Age • Land worn to nearly flat surface (peneplain) • Resistant rocks remain as erosional remnants (monadnocks) • Shallow gradient • Slow current • Rivers meander across extremely wide, flood plains • Ox bow lakes • Levees • Deltas

Rejuvenation • Some change causes stream to speed up and cut deeper. – Uplift of Land – Lowering of Sea Level – Greater stream flow • Stream valley takes on youthful characteristics but retains features of older stages as well. • Can happen at any point in the cycle.