Name: _______Caleigh Kehoe_______ Learning Unit 8: Coast Review Ques;ons This assignment is designed to assess your understanding of Unit 4 and includes some of the Ques;ons for Review at the end of Chapters 3 and 4 from your text plus a few addi;onal ques;ons. Each ques;on can be answered in one to two sentences. Please limit yourself to a maximum of three sentences. Access the assignment, complete it with ANSWERS IN A DIFFERENT COLOR FONT as a separate file, and send it back for evalua;on and grading through the assignment tab by or before the due date. 1. How can there oVen be big waves at the coast when there is liWle or no wind? The big waves at the coast are due to a storm that is far offshore. 2. What force creates most waves? What factors influence the size of most waves? Most waves are created by the energy of wind. The fric;on of the wind with the surface of the water pushes it to form waves. The size of most waves is influenced by the speed of the wind, how long the wind is blowing for, and how far the wind has traveled across the ocean (this is known as the fetch). 3. Why do waves not break in the open ocean? Most waves are created by the energy of wind. The fric;on of the wind with the surface of the water pushes it to form waves. The size of most waves is influenced by the speed of the wind, how long the wind is blowing for, and how far the wind has traveled across the ocean (this is known as the fetch). 4. Describe what happens to waves as they enter shallow water. As a wave enters shallow water, wave height increases and wavelength decreases. As the ra;o of wave height to wavelength, called wave steepness, increases, the wave becomes less stable. 5. Where does beach sand originate? Beach sand can come from the erosion of beach cliffs, or rivers and streams that were carried to the ocean. 6. Why does sand gradually migrate along the beach? Briefly explain. The sand gradually moves along the beach, because of longshore driVs. This is a gradual migra;on of the sand or gravel along the shoreline resul;ng from waves carrying thesediment grains obliquely up onto the shore and then back down to the water’s edge (from the textbook). This happens in a zig-zag paWern that moves the sand. 7. Why do barrier islands gradually migrate landward with ;me? What evidence is there that a barrier island has migrated landward with ;me? The barrier islands migrate landward as the sea level rises and erodes its base in order to maintain its equilibrium with the wave height. Some evidence is: - A lighthouse that was once on shore is now off shore. - Oyster shells that grew in the bay behind the island are now present on the front beaches - Tree stumps that were once on the lagoon are now on the front beach. 8. Which side of a beach groin collects sand? Up-current side of a beach groin collects sand. 9. List the purpose and effects of seawalls, groins, breakwaters and ar;ficial reefs, an jehes? a) Seawalls; parallel to the land to hold the shoreline in place and protect structures from damage. b)Groins; long and narrow structures that run parallel to the beach to prevent beach erosion and/or trap sand from driVing to help build up the beach. c) Breakwater; parallel to the shoreline, and protect the smaller stretches of the shore from large breaking waves. They can help speed up erosion on the down driV side d)Ar;ficial Reefs; these are built to help support marine life in the area. They can help to control erosion, block the passage of ships, and an added benefit is that they improve the quality of surfing. e)Jehes; these are built perpendicular to the shoreline to prevent an inlet from being blocked or moved by longshore driV. 10.Why is piling riprap boulders or building a seawall to protect a sea cliff or beach houses not a good solu;on to erosion? Explain what happens. These are not good solu;ons, because they actually cause more erosion. By reflec;ng the waves back, the greater erosion causes the water to get deeper, and allows stronger and bigger waves to cause more erosion. Eventually, the boulders/seawalls will just topple into the ocean. 11.Where does the sand go that is eroded from a beach during a storm? The sand is moved offshore to longshore/offshore bars that run parallel with the coastline. 12.Where would a sand spit form on a barrier bar island rela;ve to the direc;on of longshore driV? It would form at the down driV end of the barrier island at the bay13.What is a beWer solu;on than the variety of erosion-preven;on efforts used on most coasts? Aside from replenishing the beaches, which is costly and ;me consuming, it would be beWer to learn to live with and adapt to the changing coastline. Roads, houses, and buildings should be built further back to accommodate future beach erosion. 14.Why is sand from dunes or lagoons not very good to replenish beaches? The sand from dunes or lagoons is much finer, so it is more easily washed away. It would only be a very temporary fix. 15.With large-scale replenishment of sand on beaches by the Corps of Engineers, who generally pays most of the tens of millions of dollars it costs? Unfortunately, the cost of most things falls into the hands off the taxpayers. The government will pay for some, but most of the money is paid by the general
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