Activity 33: Earth Processes and Boomtown’s Coast Challenge - How is a beach part of a coastal system?

Key Vocabulary Breakwaters: structures/walls built out into the sea to protect a harbor or beach from the force of waves; are parallel to the shore Dredging: The process of digging up sand, and moving it to another location Jetty: A rock structure built perpendicular to the shore used to influence the current or tide to determine where deposition occurs

Longshore current: a stream of water in the ocean that runs parallel to the shore and moved sand across the face of the beach; is the result of waves hitting the beach at an angle Seawall: Piles of rock against a cliff or shoreline to reduce wave energy and amount of erosion.

Getting Started Read the introduction on page 44. You will begin to explore the connection between Green Hill, Rolling River and Seaside Cliff as components of the larger coastal system. The diagram on the next slide illustrates the movement of sediment from the Seaside Cliff and Rolling River to the town Beach area.

Sediment moves from the top of Seaside Cliff to the base of the cliff near the beach. Town Beach Green Hill Rolling River Sediment flows down Rolling River and is deposited at the Town Beach area.

Procedure You will be reading pages 45-47. As you read, you need to stop where you see the pencil, and write the main ideas in your notebook. This process will continue for all five reading sections on pages 44-46.

Advantages and Disadvantages of Erosion Mitigation Methods Dredging Jetty Breakwater Seawall (riprap)

Follow-Up TRUE or FALSE . . . Humans can stop earth processes from occurring. FALSE Human activity can upset the balance of a system of processes which may result in the acceleration or slowing down of a given earth process. Human efforts to prevent the effects of nature may work in the short term, but are often ineffective in the long run.

Follow-Up (cont.) What is an advantage and disadvantage of a breakwater? Advantage . . . Reduce the amount of shoreline erosion (i.e., prevent the beach from washing away) Disadvantage . . . Increase the amount of deposition (i.e., cause the water to become more shallow)

Analysis Questions Answer questions #1 and #2 on page 47. Answer #1 as a group. Answer #2 independently. Write all answers in your science journal. All answers must be written in complete sentences. Complete the Advantages & Disadvantages of Erosion Mitigation Methods table.

Analysis Question #1 1A. When erosion moves sediment off of Seaside Cliff, it falls down to the beach area, adding material to the beach. 1B. The Delta Wetlands feeds sediment directly from the Rolling River to the Town beach. 1C. Sediment that is eroded from Green Hill is washed into the Rolling River and then transported to the beach. 1D. The Rolling River transports the sediment from Green Hill and beyond to the ocean, where it then reaches the beach.

Analysis Question #2 2. The constructive force of deposition is greater than the destructive force of erosion. The evidence is that the topographical maps show that the coastline at the Delta Wetlands is moving towards the ocean. This indicates that the sediment from Rolling River is building up faster than the ocean waves can erode it.