Transcript Surface Water Movement & Stream Development

Surface Water Movement
&
Stream Development
Chapter 9.1 - 9.2
Surface Water Movement
• Once water reaches the Earth,
what happens to it?
–Runoff – water flowing downslope
along Earth’s surface
• Can reach a stream
• Can evaporate
• Can infiltrate Earth’s surface to
become groundwater
Surface Water Movement
• What conditions determine whether water
will infiltrate the surface?
– Soil composition
• Pore spacing & percentage of particles
– Soils w/ lots of sand, infiltrate; lots of clay – harder to
infiltrate
– Rate of precipitation
• Light, gentle infiltrates more than heavy downpour.
– Vegetation – more is better
– Slope – gentle to no slope is better for
infiltration
Stream Systems
• Streams – surface water channels
• Tributaries – streams that flow into other
streams
• Watersheds – all of the land area whose
water drains into a stream system
Georgia Riverbasins
Stream Load & Carrying Capacity
• Stream Load: the amount of material a stream
carries
• Load is carried in 3 ways
– Materials in suspension
• Particles small enough to be held up by the turbulence of the
moving water
– Bed load
• Sediment too big to be suspended, but is rolled or pushed
along by the moving water
– Materials in solution
• Materials dissolved in the stream’s water
• Expressed in parts per million (ppm)
• Carrying capacity is the stream’s ability to
transport material.
– Depends on velocity and amount of water in stream
– affected by channel’s slope, depth, and width
Stream Development
• Headwaters – region where water first
accumulate to supply a stream
– Usually high in mountains
• Stream channels – the path of a stream,
with water held within its banks
• Meanders – bend or curve in a stream
channel caused by moving water
Visualizing Erosion & Deposition in
a Meander
Click on picture to animate
Visualizing Stream Development
Click on picture to animate
Deposition of Sediment
• The velocity of a stream determines how much
sediment it will transport and subsequently the
loss of velocity dictates how much of that
sediment will deposit out of the stream
• Alluvial fans – in mountainous regions where the
gradient suddenly decreases, the sediment is
dropped quickly at the base of the mountain in a
fan-shaped deposit.
• Deltas - triangular deposit that forms where a
stream enters a larger body of water