Lab9_FollyCaseStudy.F21.ONLINE

1 Environmental Geology 103L Lab 9: COASTAL HAZARDS: Folly Beach Case Study PART 1: Folly Beach Case Study Complete the following questions based on the information provided by your instructor. This video link is also helpful in understanding this information: Animation: Living with the Coast: https://d1lexza0zk46za.cloudfront.net/geology/animations+and+simulations/coast/index.html The direction of wave approach is shown. The zig-zag arrows indicate the transport of sediment along the shoreline. 1. On the sketch below, label the Inlet, Ocean, and beach . * * wave approach direction Use the information from the video and the diagram above to answer the following questions: 2. At Site 1, would sand be ACCRETED or ERODED? 3. At Site 2, would sand be ACCRETED or ERODED? 4. What is the name of the elongate, hooked, feature (indicated with a * ) that is formed from longshore transport of sediment? 5. What region(s) appears to be the most dynamic or changing on the model (whether gain or loss of sediment) – End or Middle of the island? 6. Based on the sketch and animation of longshore drift do you think inlets stay in the same place over time? Why/why not? • You will need: o Internet o Laboratory Manual for Introductory Geology, chapter 13 Shorelines o The PowerPoint slides presentation on OAKS Site 1 Site 2

2 7. Development companies often want to build upon the tip of a barrier island. Knowing what you now know about ebb tidal deltas, do you think this is a good idea? WHY or WHY NOT? The South (west) end of Folly (in the COASTAL IMAGES FOLDER) 8. Slide 5: “ S end 2014 .” a. What is the difference between the 1989 and 2014 vegetation line? b. What sign/feature of erosion do you see? 9. Slide 6: “ S end 1989-2014 .” a. In which year was the beach farthest seaward? b. In what year was the beach farthest landward? c. Is there any year when the beach accreted (accumulation of sand)? The South end of Folly in Google Earth • You will need to download GOOGLE EARTH for this exercise. You will also need to download the CCPRC_Folly_term_groin and the Coastal Lab – Folly KMZ files from OAKS . Once you have the file open in Google Earth, zoomed to Folly Beach, under View , click on Historical Imagery. A timeline will appear in the upper left corner so that you can view various historical images for the location. Answer the following: 10. Zoom in to the south (west) end of Folly Beach. You should see two irregular shapes, one yellow and one green, in the Stono Inlet. The yellow outline is a small island called Bird Key and the green outline is Skimmer Flats. These two small islands have been extremely important biologically and support nesting seabirds http://www.dnr.sc.gov/news/yr2015/oct22/oct22_bird.html a. What happens to Bird Key between 1989 and 1995? b. What happens to Skimmer Flats between 1989 and 1995? c. How do you think these islands formed (look back to Part 2)? d. Which natural process(es) do you think is influencing what is happening to these islands? e. What human influences (which we will explore more next week) do you think could be shaping these islands? Part 5 of this lab will be a virtual field trip on Folly Beach. In preparation for this trip, the following section explores the N end of Folly Beach, and some of the concepts we will cover during the virtual field trip. Part 3: Hard Stabilization: Use the following to answer the questions on hard stabilization: • Jetties and Groins : https://d1lexza0zk46za.cloudfront.net/geology/animations_and_simulations/coast/index.html • Seawalls and Groins : https://www.thestate.com/latest-news/article214678990.html • Seawalls : https://www.youtube.com/watch?v=yWkOtQ1CdJs 1. What are groins? a. Are groins PARALLEL or PERPENDICULAR to shore?

4 b. In the photograph, what effect is this structure having on the south side of it and WHY? c. What does the construction of a groin tell you about Folly Beach? 4. Slide 4 “ Seawall ”. a. What is the purpose of this structure? b. What effect is the seawall having on the beach in front of it? (look carefully at the water level in the image on the lower right). 5. Slide 5 “ Morris Island Lighthouse ” . Built in 1876, the Morris Island Lighthouse was originally built on land. a. What is happening to the island surrounding the Morris Island lighthouse? b. What natural factors may be contributing to this? c. What man-made factors might be contributing to this (hint: think about the location of Morris Island relative the Charleston Harbor)? d. How far (in feet) did the shoreline move inland from the 1890s to the 1990s? e. How fast is this barrier island rolling over (in feet/year)? 6. Slide 6 “ Boneyard Beach ” . These are the remains of live oaks that grew in what was once part of the maritime forest that grows on the landward sides of some barrier islands. This area is now part of the beach. a. What is your hypothesis for why these trees are dead? b. Do you think these trees were originally growing on the beach, or did the position of the beach change over time? c. What does this indicate about Folly Beach? 7. Slide 7 “ Washover Fans ” a. What is a washover fan (refer to your Coastal 1 lab)? b. What do washover fans tell you about what is happening to the barrier island? 8. Slide 8 “ Sand Dunes ” a. How do sand dunes form (refer to your Coastal 1 lab)? b. Notice the roots and layers visible on these dunes. What is a happening to these dunes that makes these visible? Part 4: Summary 9. Based on the features that you examined above, is Folly Beach overall experiencing more erosion or accretion? Describe your evidence. 10. What is the main reason for the changes seen on Folly Beach? Think about the structures built on and around the Charleston area that could be affecting Folly Beach.