Why Study A Stream’s Velocity?. Because the speed of stream can be used to predict and assess future events and give us valuable information. http://www.youtube.com/watch?v=TDtBby7lJX0 Flash floods amateur footage, arid climate
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Because the speed of stream can be used to predict and assess future events and give us valuable information
A stream’s velocity (or speed) effects the rate of erosion. Predicting erosion can predict floods and future changes in the stream channel.
A stream’s velocity effects the type of debris and material that it carries down the stream.
Damming and deposits of woody debris can have serious consequences.
The velocity of streams and rivers will also determine the type of sediment that is transported, called the stream load. This can be valuable info
for fisheries and the study
of spawning channels
Turbidity= cloudiness or particles in water
As turbidity rises, so does the risk of gastrointestinal illness .
While this might not be of great concern to most of us, the risk for the very young, the very old, and people with weakened immune systems can be higher.
Question: Is velocity the main cause of turbidity?
Turbidity= Boil Water Advisory
The velocity of streams and rivers gives data about what kind of changes might have to be made to the banks to prevent erosion and flooding
High Velocity kind of changes might have to be made to the banks to prevent erosion and flooding
Low VelocityWhat Effects Velocity?
TheStream Gradient or Slope Does!
The slope/gradient of the stream channel = the vertical drop over a certain distance.
Question: Do mountain streams tend to have a high or low gradient?
Slopes change, THEREFORE a stream’s gradient also varies.
The steeper the gradient, the greater the energy.
The greater the velocityThe greater the effects
Shape, Size, and Roughness of the Channel Does!
The channel controls the flow of a stream and river.
Water experiences friction at the base and this will effect the velocity of the stream.
Large channels have more efficient flow because less water is in contact with the channel.
QUESTION: What else do you think can slow flow down?
Large boulders in a channel tend to slow water flow.
Velocity is less near the banks too!
Velocity varies around bends as well!
Stream Discharge or Volume of Flow
Discharge = Volume of water flowing past a certain point at a given time.
Crawford Ck. Discharge Rates
Discharge from streams is not constant and is controlled by other factors.
What increases discharge?
Rainfall and its runoff
Logging and land clearing.
How Will We Measure Velocity? kind of changes might have to be made to the banks to prevent erosion and flooding
There are 7 important Do’s and Don’ts. What are they? kind of changes might have to be made to the banks to prevent erosion and flooding
Divide the meters by the seconds (10 / 5) = 2 kind of changes might have to be made to the banks to prevent erosion and flooding
10 / 6.1 = 1.64, etc.
Bob (thrower), Emily (Shouter at A), Dave (StopWatch at B), Steve (Time recorder and Calculator)
Find the average by summing the m/sec
(eg 2 + 1.64 + 1.51 + 1.4)
then divide by 4. In this case it equals
200 kind of changes might have to be made to the banks to prevent erosion and flooding
5 min 26 secs
Multiply the 200 m. by 1.63 seconds (the average calculated last day).
200 x 1.63 = 326 seconds
or 5 minutes and 26 secs.