Shoreline Position: Learn More About It

Students will gain experience in determining temporal and spatial changes in nature and identify forces that are directly or indirectly responsible.

Example of Pathway to Exploration of Shoreline Change

  1. Question “What is a shoreline?” (Answer: The place on the beach where the water and beach meet at a particular time. The location of the “line between the water and land” is dependent upon water level which is a function of the tide and wind forcing).
  2. Demonstrate how to select the earliest shoreline measured (August 2001).
  3. Demonstrate how to select each successive year measured one at a time.
  4. Question “Is the shoreline shifting toward the land or bay? (Answer: Depends upon where you are on the beach. The beach is shifting offshore on the western side and onshore in the center of the beach).
  5. Question “Is the dry beach (subaerial) getting wider or narrow in width? (Answer: Depends upon where you are on the beach. Narrower in the central region where sand is moving into the water to build the submerged or wet part of the beach and wider on the west end of the beach where accretion is occurring)
  6. Question “Why do you think that the shoreline is moving? (Answer: Sand is being redistributed between the dry and wet portions of the beach by waves and currents. Erosion or loss of sand in one area is seen as accretion in another area of the beach).
  7. Question “What would it be called if the beach where getting wider, if more sand was gained rather than lost?” (Answer: Accretion).
  8. Question “What forces might cause the sand to be eroded from the beach?” (Answer: wind, waves, currents, storms with higher than average wind, waves, and currents).

TEKS That Apply

  • 3.2, 4.2, 5.2, 6.2, 7.2, 8.2(c,d) Scientific Process/Scientific Inquiry: analyze/interpret evidence, construct reasonable explanations from direct and indirect evidence and draw conclusions
  • 4.10 (a,b) and 5.11 (a,b) Science Concepts: I.D. and Observe effects of events that require time for changes to be noticeable.
  • 5.12 Science Concepts: Interpret how land forms are the result of combination of constructive and destructive forces (deposition/erosion).
  • 6.6(c) Science Concepts: Identify forces that shape features of the earth.
  • 7.14 and 8.14 Natural events and human activities can alter earth systems: Predict land features resulting form gradual changes such as beach erosion. How humans initiate such changes or accentuate.

Shoreline Shape: Learn More About It

Students will learn to recognize temporal and spatial change as they compare aerial photographs. Students will identify change in beach shape and the development of new features. In addition, wave refraction can be identified in the aerial photographs allowing students to see the force driving the changes in the shape of the beach. Finally, students can see how building coastal structures can stabilize a beach and change how wave energy impacts a beach.

Example of Pathway to Exploration of Shoreline Shape and Feature Change as Identified in Aerial Photographs

  1. Demonstrate how to select the first aerial photograph (In CHRGIS select August 26, 2001 from the menu on the left and Refresh or select Compare Aerial Shoreline).
  2. Demonstrate how to select each successive aerial image one at a time (images can not be overlain only viewed sequentially or look at the link in # 1).
  3. Question “How would you describe the shape of the shoreline in the first photograph? (Answer: bumpy straight line).
  4. Question “How is the shoreline changing, how would you describe the shape of the shoreline in the later photographs?(Answer: snake like, wavy. The term for this type of shape is sinusoidal).
  5. Question “Is the beach curving out (toward the water) behind the detached breakwaters or curving inward (toward the land)? (Answer: The shoreline is curving outward behind the breakwaters and toward the land in between the breakwaters).
  6. The curved or bowed out part of the beach is called a salient.
  7. If the salient grew to touch the breakwater it would be called a tombolo.
  8. Ask the students to select the October 16, 2001 aerial photograph from the CHRGIS menu on the left and ask them to zoom into the region around two of the breakwaters by drawing a box around the area with the tool on the right. Note the red curves in the above link image showing the curvature of the diffracted waves.
  9. Ask the students to look at other aerials and see if they can find evidence of diffraction. Also see if they can see evidence of deposition in the nearshore behind the breakwaters. This could be evidence of a tombolo developing in the future. Sediment deposition can be seen in some of the aerials. Look for brownish haze in the water near the curved shore and behind the breakwaters (subaqeous or submerged deposition).
  10. Question “What is making the design in the water near the breakwaters and the shore? (Answer: Waves hitting the breakwaters and bouncing off. This is called wave diffraction. The students can see the waves curving and working to reshape the beach.
  11. Question “What do you think is causing the shoreline to curve this way? (Answer: waves interacting with the breakwaters and then acting on the beach).
  12. Question “Looking at the shoreline where do you think the most wave energy hits the beach? What is protecting the beach and how? (Answer: the curved inward areas. More wave energy is impacting the regions without a breakwater in front. The breakwaters “break” wave energy before it reaches the beach and disperses the energy).
  13. Question “Can you find other evidence of wave diffraction in other aerial photographs?” (Hint: see March 24, 2005 image)

TEKS That Apply

  • 3.2, 4.2, 5.2, 6.2, 7.2, 8.2(c,d) Scientific Process/Scientific Inquiry: analyze/interpret evidence, construct reasonable explanations from direct and indirect evidence and draw conclusions
  • 4.10 (a,b) and 5.11 (a,b) Science Concepts: I.D. and Observe effects of events that require time for changes to be noticeable.
  • 5.12 Science Concepts: Interpret how land forms are the result of a combination of constructive and destructive forces (deposition/erosion).
  • 6.6(c) Science Concepts: Identify forces that shape features of the earth.
  • 7.14 and 8.14 Natural Events and human activities can alter earth systems: Predict land features resulting form gradual changes such as beach erosion. How humans initiate such changes or accentuate.