Garrapata Beach Profile Lab
Oceanography Spring name_______________
Goal:
-The main goal of this lab is to calculate how much sand is transported to and from
Garrapata Beach annually. It is well documented that big winter storm waves transport
sand off the beach, whereas smaller summer waves transport sand back onto the beach.
But how much sand is actually transported seasonally by the waves at Garrapata Beach?
Logisitics:
-We will accomplish this goal by comparing Garrapata Beach profiles collected by this
semester’s class with those collected by Oceanography students in previous semesters.
-Remember, an amount of sand is measured as a volume of sand. The units of volume are
length3, or (width X height X length).
As shown in the image at left,
Length= the distance
from the seacliff to the
water’s edge. This could
be calculated by
multiplying the length of
the MPC high-technology
beach profilers (1.6
meters) by the number of
stations you recorded (1.6
X number of stations).
Height= this is the
difference in elevation
between your
measurements and those
of the previous semester.
To calculte this amount you will plot your
measurements on a graph and compare them
to previous semesters’ results. Note that in
Fall 2005, we could not even see the rock on
the beach seen above.
The profile to the right shows the relationship
between the sea cliff, the benchmark, and the
sand.
Width= we will assume this width is 100 meters for the purposes of this project. So, we
are calculating the amount of sand transported to and from the beach per 100 meters of
beach.
Questions:
1. In what kind of units is volume measured? Why is it often in units of length3?
2. In your own words, what is the main goal of this project?
3. What time of year should there be the most sand on the beach? Why does this
occur?
4. What time of year should there be the least amount of sand on the beach? Why
does this occur?
5. Why is the height of the benchmark so important for this project? Please draw a
picture of the relationship between the benchmark and the beach to help you
explain
6. Which profile do you have data from, the northern, “new” northern, central,
stairs, or southern profile?
Step-by-Step Instructions.
1. Open the Excel Spreadsheet called “GarrapataProfilesXXX.xls”, where XXX is the
semester you’re taking the class.
2. Go to the worksheet for which you have data—either the northern, New Northern,
Central, Stairs, or southern profiles—by clicking on the appropriate worksheet name at
the bottom left of the spreadsheet.
Click the curser on
the profile for which
you have data. There
are now the “new
northern” and “stairs”
profiles as well.
3. Enter your data in the appropriate columns. The A data goes in column D, and the B
data goes in column I. Remember that station 0 is the vertical distance from the
benchmark to the sand. In the example from Fall 2005 below, I’ve written in some
fictional A data in the appropriate spot.
A Data
B Data
4. Note that the numbers in columns C and H change automatically as you enter the data
into columns D and I, respectively.
5. Fill in all of your data. From the examples of data that I have seen, I think your data
should correspond to the amount of shaded cells in the spreadsheet.
6. After filling in all the data, scroll to the right until you find the graph. The graph
should look something like this example from Fall 13, except that the blue data points
should represent the data from your beach profile:
7. Draw a quick sketch here of what YOUR data plot looks like. Include the data
from the last two semesters and label each line. Label both your A data and your B
data.
8. How do your “A” and “B” data compare? Do you think the data collection
technique is reproducible?
9. How does your data differ from previous years’ Spring data? A lot? A little?
How?
10. How does your data differ from previous years’ Fall data? A lot? A little? How?
11. Describe in your own words how you could quantitatively figure out how much
sand was added or removed from the beach since last semester from the plot you
drew above.
10. Scroll to the right until you see the
columns labeled “Difference in the amount of
sand on the beach.”
In the cell AW7, enter the expression “=m7c7”, (without the quotation marks), and press
Enter.
A number should appear that represents the
difference in height of the beach in cm,
between this semester and last semester.
11. You want to now make this calculation for
each one of your data points.
Use the power of Excel by copying your
equation down to the row indicated in the
spreadsheet.
Start by highlighting the cell AW7 with the curser so it
looks like this:
12. Copy it by pressing Edit > Copy (or control-C). The solid highlighting boarder will
now be blinking, sort of.
13. Paste the equation to all the other rows by highlighting all
the other rows, so it looks like the image to left. Highlight the
rows down to the row indicated in the spreadsheet.
14. Now press Edit > Paste (or control-V). Immediately upon
pasting you should see numbers appear all the way to the end
of your data. Don’t worry about zeros in the rows below your
data.
15. Do the numbers look right, based upon your inspection
of your graph and the sketch you made on the previous
page? Why? What is it in the numbers that makes you
think the numbers look right or wrong?
16. Now, convert the units from centimeters to meters. Since there are 100 centimeters in
a meter, we will want to divide all the
numbers in the AW column by 100.
In the cell AY7, enter the following
expression: “=AW7/100”, and press
Enter.
17. Calculate an “area” of sand by
multiplying the numbers in the AW
column by the length of our hightechnology-beach-profilers: 1.6 meters.
In the cell BA7, enter the following
expression: “=AY7*1.6”, and press
Enter.
18. Copy these two operations so that
these calculations are done on every data
point for which we have data for both
this semester and last semester.
Highlight the cells AY7 to BA7 by
clicking and dragging the cursor over all
three of these cells. The spreadsheet should
look like the image below left. Press Edit >
Copy.
Paste these values to the cells below by
highlighting all the cells below, as seen in the
image to the right, and pressing Edit > Paste.
Paste the formulas down to row where your
data stops.
After pressing Edit > Paste, the screen should
look something like the one on the next page.
We now have an area of sand calculated
beneath each of the stations where we
collected data.
19. The next step is to add up, or sum, all of
the data.
In the cell BA46, just right of the sum=
phrase, enter the expression
“=sum(BA7:BA45)”, and press Enter. You
may have to scroll down to find this.
Note that instead of physically writing the
BA7:BA45 part, you can just highlight these
cells with your cursor, so it looks like the
image below.
20. Now convert this sum into a volume
by assuming the beach is 10 meters long
(probably an inaccurate assumption), by
multiplying the sum by 10 meters.
In the cell BA49, just below the
expression “X10”, enter the expression
“=BA45*10”, and press Enter.
This is one of your important results. This
is the volume of sand that has been
transported to or from the beach since last
semester based on your beach profile
measurements. On the next page we
convert this amount of sand to a perfect cube and then compare this amount of sand to the
amount of sand that would fit into the classroom.
How much sand did you calculate has been added or removed from the beach since
last semester? What are the units?
21. Now we’ll try to envision this amount of sand by envisioning the size of a cube that
would contain this amount of sand. We will calculate the length of one of the edges of
this cube. We are doing this to help you visualize this amount of sand.
In cell BA53, enter the expression
“=BA49^(⅓)”, and press Enter.
Note that the “^” symbol is Shift-6, and
that it signifies the start of an exponent.
In this case the exponent is ⅓, which is another way of writing a cube root.
How long is the edge of the cube that your calculated amount of sand would fill?
What are the units?
22. Now compare the amount of sand that has been removed or added to the beach per 10
meters, to the amount of sand that would fit under one of the black tables in this
classroom. Measuring tapes are available for use.
How much sand would fit in this room?
What are the units of your
measurement?
How much sand was added or removed
from the beach? What are the units of
your measurement? Ask your instructor
if you have questions about where to find
this value in your spreadsheet.
How does the amount of sand added or removed from the beach compare to the
amount of sand in this room?