1 Name Date Controlling Processes That Change Land People try to control some of the processes that change land. To do this, people apply technology- the use of science to solve problems in everyday life. Technology does solve many problems. But sometimes it creates others.
Controlling Floods 2 A flood is an overflow of water onto land that is usually dry. Damage buildings, roads, people and farmers fields. Dams control floods built across rivers to control its flow. It can be opened to let water through. Many dams hold back floodwaters at times of heavy rainfall, but also hold back sediments that rivers carry. Then these sediments cannot form floodplains and beaches. To maintain a beach, deposition of sand and erosion of sand must be in balance. Where water washes sand away, new sand must take its place. Dams that hold back sediments upset the balance. Levees also hold back floodwaters. a raised bank of Earth built along the edges of a river to prevent flooding. Difference between a dam and a levee is that a levee holds back water only at times of high water levels. Sometimes levees break. They need to be maintained to keep people and property safe.
Storm Drain Management 3 The use of drains to prevent flooding during heavy rainstorms. Water runs off roads and other land into the drains. Rain can wash harmful materials into the drains and can end up in rivers and other waters. Controlling Erosion Ocean waves and currents cause erosion on coasts. Ocean water carries sand away from beaches. Coastal erosion makes beaches smaller. It also destroy things built on beaches. People build structures to keep beaches from eroding. These structures include groins and seawalls. They can prevent erosion in some places. But they may make erosion worse in others.
Groins are built at right angles to the beach. 4 They protect the beach by trapping sand that currents carry along the shore. Trap sand on their upstream sides But they block sand from reaching their downstream sides. In those areas, eroded sand is not replaced. Seawall is built along the shore Absorbs the pounding of waves and protects the land and buildings behind it. But any beach on the ocean side of a seawall can still erode. They can increase erosion of nearby beaches. Beach nourishment Eroded beaches are reclaimed, or restored. Workers dig up sand from the ocean bottom or from a riverbed and add this sand to an eroded beach to rebuild it. Very expensive but temporary. It can harm plants and animals living in the coastal area. Beaches erode again, and then the process must be repeated. Ex. Tybee Island in Georgia. Scientist worry about harm to sea Created turtles by: and Cammie s other Corner animals.
Plant roots help hold soil in place so wind and water cannot erode it. In some coastal areas, vegetation is planted on sand dunes to stop them from eroding. Dunes protect coastal islands from erosion. People have found ways to prevent erosion in areas away from the shore. Farmers use several methods to prevent the loss of soil. Contour plowing- farmers plow across the sides of hills instead of down their slopes. 5 Terracing farmers plant crops on flat terraces cut into hillsides. Both prevent soil from washing downhill. Windbreaks are rows of plants or fences. They slow down wind and limit the distance it can carry soil.
Vocabulary Words to Know 6 1. Technology- the use of science to solve problems in life. 2. Flood- over flow of water onto dry land. 3. Dam- structure built across a river to control its flow. 4. Levee- a raised bank of earth built along the edges of a river to prevent flooding. 5. Storm drain management- the use of drains to prevent flooding during heavy rainstorms. 6. Beach nourishment- the process of adding sand to an eroded beach to rebuild it. 7. Contour plowing-a method of reducing erosion in which farmers plow across the sides of hills. 8. Terracing- a method of reducing erosion in which farmers plant crops on flat terraces cut into hillsides.
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