Printable Copy of the Field Study Guide (PDF)

Station #1: Gradient vs. Velocity
Elevation: _200.6 meters Latitude: _42 o 34’29” N_ Longitude: _73 o 57’50” W_
Factors Affecting Transportation of Sediments
Running water is the primary agent of erosion on Earth. Most running water is found in
streams and rivers. There are many factors that affect the movement of sediments in a
stream. Gradient (slope), discharge, and channel shape influence a stream’s velocity.
Sediments carried by a stream become rounded due to the grinding action of the water on
the rocks, a process called abrasion. The average velocity (speed) of a stream depends
on its slope and discharge, which in turn help to explain the carrying power of a stream.
As the velocity of the stream water increases, the size of the particles carried in the
stream also increases, a direct relationship.
Streams carry materials in 4 distinct ways:
Floatation - floating of particles less dense than water
Solution - dissolved particles
Suspension - tiny particles can travel within the water without touching the stream bed
Bed Load - bouncing (saltation) and dragging (traction) of sediments along the stream
bed
View the following:
Powerpoint of Jake stick Use
Video of Eye Level
Station 1 Photos from the Field Trip
Activities
1) In this activity students measure the velocity and gradient of the stream at two
different locations. Location A is the upstream location. The table on the next page must
be completed in its entirety using the steps in this process and the data given.
Each student is assigned to either the Location A team or the Location B team.
You are assigned to the Location A team.
(a) Determine the gradient of the stream for location A – Students will determine the
gradient using jake sticks, sight levels, and a tape measure.
1. Using the tape measure the students assigned to Location A determine the
horizontal distance between the two canisters representing the start and finish points to
be 25.8 meters. Enter this data in the table below in the appropriate space.
2. The student with the sight level determines their eye height to be 155 cm for the
Location A team. Enter this data as the starting elevations in the appropriate space.
3. The student with the sight level stands at the starting point while the student with
the jake stick stands at the finish point. The person with the sight level determines the
new jake stick reading to be 209 cm. Enter this data as the finish elevation in the table.
4. Complete the calculation for change in elevation and stream gradient (use the
formula found on the front cover of the Earth Science Reference Tables) and enter them
into the table. The first four columns of line one in the table should now be complete.