Module 3 Summative Assessment Worksheet
Note: Because this exercise has so many steps, we wanted to make it easy for you to print off the entire exercise to have available as you follow the directions. As a result, this worksheet is a little different than the others. You only need to turn in the last page of this worksheet. You can just copy and paste the questions into another Word document once you have answered them.
Beach Profiling Exercise
Beaches evolve or change over time due to both natural forces and man-made engineering. Coastal geologists and engineers evaluate how sediment is deposited, eroded, and transported along coastal beaches and barrier islands to better understand the processes that drive these kinds of changes. One method that is commonly used to evaluate and understand beach evolution and sediment transferal is to repeatedly measure the elevation of the beach. This can be done a number of different ways but one of the quickest and cheapest methods is to use the Emery beach profiling technique, which was developed by K.O. Emery in 1961.
This YouTube video provides a good explanation of the procedure that is used to obtain data for the elevation of a beach.
Here is another link describing Emery (1961) method of beach profiling:
Collected data can be plotted to show a cross sectional profile of the beach at the time of surveying. If the beach is surveyed multiple times at different time periods, a record of the changes in the cross sectional picture of the beach emerges. Comparing the cross sections for different survey dates enables one to determine whether the elevation of the beach has been locally reduced because of erosion or if the elevation of the beach has locally increased, implying deposition at this location. Take a look at this enlarged plot from the previous link to fully understand the type of cross sectional plot that can be created with the beach profiling technique
Here is another link to a plot of beach elevation profiles with a discussion of what the changes in elevation for successive seasons indicates about sediment transport in the area.
Be certain to look at the links provided above before attempting this assessment.
When multiple profile transects are set up and surveyed repeatedly along the length of a beach then it is possible to determine how different sections of the beach evolved. For example, suppose you have two different profiles set up along a beach with 1 kilometer spacing between them. At the first profile location, repeat surveys show that there is net erosion on the beach face, whereas at the second profile location, a kilometer away, there was deposition. One mightinterpret the increase of sediment volume at the second profile a result of sediment being erodedfrom the first location and transported to the second location.
In this exercise you are given beach profile survey data for three different transects along
Integrate Island. The three transects are 500 m apart from one another and each transect wassurveyed three times (Fig. 1). The first survey was completed on February 1, 2008 to establish a baseline elevation dataset for each profile location. The second survey was completed on
September 9, 2008. Although the second survey was only 6 months after the first survey there was a category 3 hurricane late in the summer of 2008. Hurricane Alberto made landfall just 100 km away from Integrate Island and caused significant changes to the elevation of the island due to large waves and a 2 meter storm surge. The final survey was completed on November 1, 2009.
Figure 1. Location of the three elevation transects surveyed on Integrate Island. The image was taken the day of initial survey on February 1, 2008.
Your goal for this exercise is to take the raw survey data for the island and plot it in Excel. When finished you will have three different plots, one for each beach profile transect, and each plot will have three different elevation profiles overlain upon one another so that you compare the changes in elevation for the three time periods (one for 02/01/2008, one for 9/9/2008, and one for 11/01/2009). Once you have all three plots constructed you can answer the questions that are at the end of this assignment.
Steps to Complete the Exercise
An instructional video is included here to show you how to plot the data in Excel so that you make the final interpretations but here is also a step by step write up of how to plot the data.
Preparing the Data for Plotting
1)Open up the attached Excel file and save it locally to your desktop or relevant folder with the naming convention: yourname_IntegateIsland_BeachProfiles (e.g. mkulp_IntegateIsland_BeachProfiles)
2)Now click on the Profile Data tab at the bottom of the page to open up the worksheet with all of the raw data.
3)On this sheet you will see boxes containing all of the profile data for each transect across all of the survey dates
4)For each survey date there are the following columns:
Each pair of readings for the horizontal distance and elevation change represents the amount of horizontal distance moved and the elevation change represents the amount of elevation change that was observed with the survey rods across this horizontal distance. Notice that the first measurements in all cases are 0,0 and that the next measurement is thus relative to those initial starting values of distance and elevation. The column for Back Stake Height represents the measured elevation between the top of your back survey stake to the ground, in this case there was 0.98 distance between the top of the stake and the top of the island surface.
5)The next step is to calculate the cumulative changes that were observed. These values will be placed in the rows directly below cumulative distance of transect and cumulative change in elevation for transect.
6)First put 0’s in the first row below the headings cumulative distance of transect and cumulative change in elevation for transect (these will be cells D4 and E4, respectively). This represents the starting point of your profile.
7)Now you will have to determine the cumulative distance and cumulative elevation changes indicated by the first set of distance and elevation readings during the survey.
8)Next, you will need a formula for D5 that will add the value of the first horizontal offset to the starting point of 0. In Excel this can be calculated in cell D5 using the following formula: =B5+D4
9)Hit enter and if done correctly the value in D5 should now be 3 because 0+3= 3
10)Now in D6 you will be adding the value of D5 to the measured horizontal distance of cell B6. So in D6 input the formula: = B6+D5 and the result should be 6.
11)You can continue this for the rest of the cells in the cumulative distance of transect column for the first survey date To save time you can simply copy the formula from cell D5 and paste it in the rest of the cells for the remaining cumulative distance of transect (be sure to stop at D34 in that column otherwise you will overwrite the first value of the next survey).
12)In order to determine the cumulative change in elevation for transect along the profile, you will need to enter the following formula: =E4+C5 in cell E5
13)Continue this process for all of the rows below cumulative change in elevation (be sure to stop at E34 in that column otherwise you will overwrite the first value of the next survey).
14)If you have done everything correctly your cumulative columns should be populated with the following values in the first six rows.
15)Now we need to do this for the other survey dates of 09/09/2008 and 11/01/2009. Look at the table below and you will notice that in your spreadsheet the back stake height measured on 09/09/2008 was only 0.70 m compared to the first survey date when it was 0.98. This means that between the two surveys the distance between the top of the survey stake and the island surface decreased by 0.28 m because of deposition of 28 cm (equivalent to 0.28 m) of sand
16)This change in elevation at the starting point of the back stake needs to be accounted for by putting the following formula in cell E35: =(F4-F35)*100
17)This formula subtracts the value of the measured stake height on 09/09/2009 (0.7 m) from the value on the first survey date (0.98 m) and yields a total reduction of 0.28 m in elevation due to deposition. Notice that in the formula for E35 the value of subtraction is multiplied by 100 to convert the values of stake heights that are in meters to centimeters, which is the unit used for the measurements of elevation change made in the field with the Emery rods.
18)Now complete the rest of the cumulative change rows for the 09/09/2008 survey date just as you did for the 02/01/2008 survey date.
19)If you have done everything correctly your spreadsheet for transect 1 should like the table below.
20)Using these steps fill in all of the cumulative change rows for all of the profile survey dates of the three profile transects and you are now ready to begin plotting the data.
21)One thing to keep in mind is that the first value of cumulative change in elevation for the second and third surveys of a transect is actually the difference in height between the back stake height during the first survey and the second and third surveys. This value is already placed in the spreadsheets and all you will have to do is determine the rest of the cumulative values.
Preparing the Data for Plotting
1)Click on the tab profile plot sheet.
2)At the top of the page click on the tab INSERT and select “Scatter Plot with Straight Lines” option from the dropdown list.
3)A blank plot should appear on your worksheet
4)Now click on the chart and then right click your mouse. A window will pop up that has a line “Select Data”. Click this and a new box will appear that allows you to specify which data you want to plot.
5)On the left hand side of the “Select Data Source” box, click on the “add” button and a new box entitled “Edit Series” will appear. Place your cursor in the line for “Series name”. Now click on the Profile Data Tab and find the cell with the first survey date (cell A4). Click on this cell and the “Series name” line will be populated.
6)Next click in the area for “Series X values”. Then click on the Profile Data tab and move your cursor to cell D4, which is the first value of the cumulative horizontal distances. Hold your mouse button down and drag all the way to the end of the cumulative horizontal distance column for that survey date.
7)Now click in the “Series Y values”. Delete anything that is in that box and replace it with an equals sign. Now click on the Profile Data tab, click in cell E4 of the cumulative change in elevation column and again while holding your mouse button down drag to the end of the column for that survey date.
8)Now hit “ok” and the Select Data Source box should still be open. Click "Add“ to add the next survey date and repeat the above process for the September 09, 1008 dataset. Repeat this procedure to include the third survey data. The final plot should look similar to the one shown in figure 1.
9)You will have to add axes titles, as well as, a title at the top of the chart. This can be achieved by clicking on the “Chart Tools Layout” tab where additional buttons will appear for “Chart Title” and “Axis Titles”.
10)If you right click on the chart, a dropdown list will appear. Choose “Format Chart Area” to set the size of the chart to be 5” height and 9” width. All of your charts should be the same size and the axis lengths should all be the same as well. Axis lengths can be adjusted by right clicking on each individual axis to highlight it, and then choose “format axis” option where you can set the range of values for that axis. The horizontal axis should span 0 to 100 and the vertical axis should range from 180 to -200. You also need to make sure that the X axis of the plot (horizontal distance) crosses the Y axis (relative elevation) at the -200 value of the Y axis. To do this go to format the Y axis and you will see an axis value setting where you can change it from “fixed” to “axis crosses at”, type in -200.
11)Follow these steps for all three transects and then answer the questions at the end of this assignment.
Figure 1. Plot of the first transect for three different survey dates that is properly adjusted for colors, labels, main and axes titles, as well as horizontal and vertical scales.
Summative Assessment Questions:
Assessment Questions: Be sure to include the three transect plots that you created when you hand in the answers to these questions.
- During which of the time periods are the sand dunes of the island most evident in the profile data?
- Which of the profile transects had the highest sand dunes during this time period?
- Which had the lowest sand dune during this time period?
- Which of the profiles had the widest horizontal extent of sand dunes? Approximately how wide were they?
- During which of the time periods were the sand dunes the most reduced in elevation?
- Why were the dunes reduced? Provide some explanation about where this sediment may have gone.
- During which time period did the greatest amount of erosion take place on the island relative to the baseline survey date of February 1, 2008. Explain why you think that this erosion took place.
- For each survey transect location (1-3) indicate where along the transect the most significant erosion take place during the three survey dates. For example did the most amount of erosion on transect 1 take place at the beach face or in the dunes between the first and third survey?
- Which of the 3 transects shows the greatest amount of net deposition in the dunes during the post-Hurricane Alberto recovery time period?
- Which of the profiles shows the greatest amount of net deposition in the intertidal zone during the post-Hurricane Alberto recovery time period?