Activity #33 Reflection Questions

Question #1 Describe how each of the landforms below contribute sediments to the Town Beach in Boomtown. Seaside Cliff – Seaside cliff is located above and just to the north of the Town Beach. When erosion moves sediments off of the cliff, they fall down to the beach area, adding material to the beach.

Delta Wetlands – The Delta Wetlands feeds sediments directly from the Rolling River to the Town Beach. Since the beach is north of the mouth of the river, it is likely that the shoreline cureent runs south to north. Green Hill – Sediments that are eroded from Green Hill are washed into the Rolling River and then transported to the beach.

Rolling River – The Rolling River transports the sand and sediments from Green Hill and beyond to the ocean, where they make up the beach.

Question #2 The constructive force of deposition is greater than the destructive force of erosion. The evidence for this is that the topographical maps show that the coastline at the Delta Wetlands is moving towards the ocean, indicating that the sediments from the Rolling River are building up faster than the ocean waves can erode them.

Question #4 Deposition can be controlled by jetties. A jetty has the advantage of holding back the sand being transported in a longshore current and preventing it from being deposited in and undesirable location, such as a harbor. A disadvantae, however, is that the other side of the jetty tends to erode more than if the jetty were not there.

Erosion can be controlled by breakwaters Erosion can be controlled by breakwaters. A breakwater has the advantage of reducing erosion on the shoreline. It has the disadvantage of increasing the amount of deposition between the breakwater and the shoreline.

Method Advantages Disadvantages Dredging Removes unwanted sand Opens up silted areas, such as channels and harbors Hard work, expensive Deposition can return Sediments can be contaminated Can destabilize the land Jetty Easy to build Keeps harbors from filling in Accelerates erosion on the other side of it Eventually sand may have to be moved if too much builds up Breakwater Slows down erosion of cliffs and beaches Increases deposition of sand between breakwaters and shore Seawall (riprap) Can be easy to build Reduces rate of erosion More erosion around the sides of the wall.