G202 Nehalem River Field Trip
Name __________________
Overview
Today we will be visiting an interesting river in the coast range, the Nehalem River.
You have several objectives:
 Learn how the Nehalem River’s course to the sea is unusual for a coast range river.
 Describe changes in river morphology along the Nehalem from headwaters to the sea.
 Relate stream morphology and river course to stream processes and bedrock geology.
 Gauge the Nehalem to measure its velocity and discharge.
 Measure two beach profiles: one for a sandy beach, the other for a rocky beach.
STOP 1 USGS Gauging Station 142998800 Near Vernonia
LAT: _____________ LONG: ________________
River Mile:
Elev.(feet): ____________
Gradient:
Draw a cross section of the Nehalem River valley at this location:
Describe the Nehalem River at this location:
Measuring Velocity and Discharge
1) Estimate the velocity of the stream in feet per second. ____________________
2) Describe the method used to measure the velocity of the stream.
3) Record data for 4 measurements of stream velocity. Average these to get an average velocity.
If one of your velocity measurements is flawed, repeat that measurement.
Trial Distance (feet)
1
Time (seconds)
2
3
4
AVG
Calculate the average velocity making sure to show your work!
4) The velocity you measured is probably not perfectly accurate. Is it more likely to be slower or
faster than the true velocity? Explain your reasoning!
5) Convert the average velocity you determined to miles per hour. Show work!
6) BONUS: Can you run faster than the water in this stream is flowing? Show work!
DISCHARGE = VELOCITY x CROSS SECTIONAL AREA
You have the velocity, you now need to measure the cross sectional area.
How wide is the stream?
Measure the depth of the stream at six or so evenly spaced intervals noting the water depth and
distance from stream bank.
Draw a sketch of the stream in cross section.
Calculate the average depth of the stream, show work!
Now calculate the cross sectional area and the discharge.
___________ ft X ____________ ft = _____________ ft2
width
avg. depth.
cross sect. area
_____________ ft2 X ____________ ft/sec = _____________ ft3/sec
cross sect. area
velocity
discharge
How does the discharge you measured compare to that measured at the USGS gauging station
14299800( http://waterdata.usgs.gov/or/nwis/nwisman/?site_no=14299800&agency_cd=USGS)?
Should the discharge you measured be the same as that measured at the gauging station? Why or
why not?
STOP 2 Keasy Formation Outcrop Vernonia-Timber Road
LAT: _____________ LONG: ________________
River Mile:
Elev.(feet): ____________
Gradient:
Draw a cross section of the Nehalem River valley at this location:
Describe the Nehalem River at this location:
Describe the Keasy Formation at this locality. Describe any fossils we find. What type of
environment may have the Keasy formation been deposited in? Is the Keasy Formation resistant
to erosion, how can you tell?
STOP 3 Jewel School
LAT: _____________ LONG: ________________
River Mile:
Elev.(feet): ____________
Gradient:
Draw a cross section of the Nehalem River valley at this location:
Describe the Nehalem River at this location:
STOP 4 Spruce Run State Park
LAT: _____________ LONG: ________________
River Mile:
Elev.(feet): ____________
Gradient:
Draw a cross section of the Nehalem River valley at this location:
Describe the Nehalem River at this location:
STOP 5 Nehalem Falls State Park
LAT: _____________ LONG: ________________
River Mile:
Elev.(feet): ____________
Gradient:
Draw a cross section of the Nehalem River valley at this location:
Describe the Nehalem River at this location:
Describe the Tillamook Volcanics at this locality. Find and sketch a dike. What percentage of
the outcrop consists of dikes? Are the Tillamook Volcanics resistant to erosion, how can you
tell?
STOP 6 Nehalem Bay State Park DATE: __________ TIME: _______
TIDE:_________
LAT : ________________ LONG: ______________
A. Profile Sketch a cross sectional view (side view) of this beach. Label the beach face, high tide
line, berms, cliffs, dunes or other features you can identify you can identify. Note any variation in
the material the beach is made of. Provide a scale bar, a key to any symbols used and indicate the
location of the cross section on the sketch map above.
B. Landforms What coastal landforms can you identify here? Is this an erosional or depositional
beach? Describe at least three characteristics of this beach that are consistent with it being
erosional or depositional. Explain your reasoning.
C. Measure a beach profile. For this we will break into two groups, directions will be provided
on site.
STOP 7 Hug Point
DATE: __________ TIME: _______
TIDE:_________
LAT : ________________ LONG: ______________
A. Profile Sketch a cross sectional view (side view) of this beach. Label the beach face, high tide
line, berms, cliffs, dunes or other features you can identify you can identify. Note any variation in
the material the beach is made of. Provide a scale bar, a key to any symbols used and indicate the
location of the cross section on the sketch map above.
B. Landforms What coastal landforms can you identify here? Is this an erosional or depositional
beach? Describe at least three characteristics of this beach that are consistent with it being
erosional or depositional. Explain your reasoning.
C. Measure a beach profile. For this we will break into two groups, directions will be provided
on site.
Reflection/Feedback
Take a minute to reflect on your field trip experience. What was surprising? What did you learn?
What did you especially like about the field trip? What could be done to improve this field trip?