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• http://www.youtube.com/watch?v=guBo0FQhjaM&feature=related Homes float away• http://www.youtube.com/watch?v=NDr8PQQdXzM Nechako River (During high water)• http://www.youtube.com/watch?v=GHJHDJdoQMQ Sooke River (Spring time)

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

TurbidityTurbidity = 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

High VelocityLow

Velocity

What Effects Velocity?

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?

The Stream Gradient or Slope Does!

Slopes change, THEREFORE a stream’s gradient also varies.

The steeper the gradient, the greater the energy.

The greater the velocityThe greater the effects

What Other Factor Controls Velocity?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 FlowOne More Factor Effecting Velocity

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.

QUESTION: What increases discharge?SnowmeltRainfall and its runoffLogging and land clearing.

How Will We Measure Velocity?

Rules Around The Creek

No running.Do not go into the creek for any reason.No pushing or horseplayPlease do not litter or alter the landscape.Get help right awayStay with the group and the classListen to instructions.

There are 7 important Do’s and Don’ts. What are they?

10

Bob (thrower), Emily (Shouter at A), Dave (StopWatch at B), Steve (Time recorder and Calculator)

5

10 6.120 13.220 14

2

1.64

1.51

1.4

1.63

Divide the meters by the seconds (10 / 5) = 2 10 / 6.1 = 1.64, etc.

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 1.63 m/sec

200

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.

3265 min 26 secs