Water Cycle What is it?
Running Surface Water
Main erosional force on earth
Starts as run off (snow or rain)
Stream--> flowing body of water
Possible outcomes for surface water
Run off
Evaporation
Infiltration
Infiltration capacity?
What factors determine how much water soaks into the ground?
Stream Types?
http://www.freefoto.com/pictures/nature/water/index.asp?i=4
http://piru.alexandra.ucsb.edu/~buchel/catalog/show_collection.php/www?record_id=180
Longitudinal profile
change of a streams features from the headwaters to the coast.
How do streams change as they move away from their headwaters?
Types of streams
Mountain streams--> Features?
Braided streams--> Features?
Meandering streams--> Features?
Flood plains--> Features?
Factors affecting Stream flow Characteristics
Turbulent vs. Laminar flow
high frictional forces vs. low frictional forces
Discharge
volume of water flowing past a point at a given time
m3/second Width x Depth x Velocity
Velocity
affected by gradient
channel shape (width to depth ratio)
Which would have a higher velocity flow and why: shallow stream or deep stream
channel roughness
volume If you increase velocity what happens to discharge?
Capacity vs. Competence
Stream capacity:
maximum load of solid particles a stream can carry
Stream competence:
maximum size of particles a stream can carry
Question: which stream would have the highest capacity and competence-->
large stream immediately after a long heavy rain or a large stream in the middle of the summer?
How can a stream carry material?
The amount and types of load is unique to each river
Dependent on location and type of rock in area
Can change depending on discharge
Compare and contrast the load found in the Columbia river and the Mississippi river
Http://webserver.cr.usgs.gov/sediment/conc.frame.html#HDR3
Base Level
What is the base level of a stream?
What is ultimate base level?
What is meant by a temporary base level?
What is a graded stream?
Streams erode their channels to reach an equilibrium
Changes in variables can move streams out of equilibrium
Variables
Independent variables (externally controlled)
discharge
type of sediment load
ultimate base level
Semi-dependent variables (stream’s use of energy)
channel width and depth (velocity)
bed roughness
channel shape (straight, meandering braided etc…)
Changing a base level of a stream changes the characteristics of a stream
alters velocity-->changes load capacity--> changes erosion capabilities
What happens when a dam is installed on a stream
What are some other ways base levels can change?
Features Created by Change
Terraces
incised meanders
pot holes
graded beds (not graded stream)
Deposits and features
In a stream with meanders:
where does deposition occur?
where does erosion occur?
where is velocity the highest/lowest?
Cut off meanders and oxbow lakes
levees
back swamps
Yazoo tributaries
Deltas
Created when a stream enters standing water (ocean or lake)
distributaries (bird foot structure)
http://www.state.me.us/doc/nrimc/mgs/sites-2002/nov02-2.htm
Bottomset, topset and foreset beds
Other features
Head water erosion
Stream Piracy
Drainage basin and divide
Flooding
Why do streams flood?
What is a flash flood?
How can flooding be mitigated?
100 year flood?
R = (n +1) / m
R is recurrence interval
n is number of years
m is magnitude rank
Flood Control
Levees
dams
river channelization
zoning