Why Study A Stream’s Velocity?

1. 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=TDtBby7lJX0Flash floods amateur footage, arid climate • http://www.youtube.com/watch?v=guBo0FQhjaM&feature=relatedHomes float away • http://www.youtube.com/watch?v=NDr8PQQdXzM Nechako River (During high water) • http://www.youtube.com/watch?v=GHJHDJdoQMQSooke River (Spring time)

2. A stream’s velocity (or speed) effects the rate of erosion. Predicting erosion can predict floods and future changes in the stream channel.

3. 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.

4. 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

5. Turbidity 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

6. 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

7. High Velocity High Velocity Low Velocity What 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

8. 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!

9. One More Factor Effecting Velocity 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. QUESTION: What increases discharge? Snowmelt Rainfall and its runoff Logging and land clearing.

10. How Will We Measure Velocity?

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

12. Divide the meters by the seconds (10 / 5) = 2 10 / 6.1 = 1.64, etc. Bob (thrower), Emily (Shouter at A), Dave (StopWatch at B), Steve (Time recorder and Calculator) 5 10 2 6.1 10 1.64 20 13.2 1.51 20 14 1.4 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 1.63

13. 200 326 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.