Garrapata Beach Profile Lab Oceanography Spring 2012 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 length
3
, 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 length 3 ?
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?
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 “GarrapataProfilesS12.xls”.
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 08, 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 45.
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 100 meters long
(probably an inaccurate assumption), by multiplying the sum by 100 meters.
In the cell BA49, just below the expression “X100”, enter the expression
“=BA45*100”, 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
100 meters, to the amount of sand that would fit in this class room. 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?