Floods, Dams, and Levees

Floods, Dams, and Levees — page 1 — CHAPTER ONE What Is a Flood Water is one of the most powerful forces on Earth When water is controlled it can help people in many ways Water can move machinery and create energy It can move boats and barges carrying people and goods all over the world People could not survive without water to drink and to nourish plants and animals Sometimes however water gets out of control When this happens an area can suffer a flood A flood occurs when water covers an area that is usually dry Most floods happen naturally A river lake or other body of water may overflow because of too much rain or melting snow Or a bad storm can dump several inches of rain on an area filling streets and homes and causing waterways to spill over 4

Floods, Dams, and Levees — page 2

Floods, Dams, and Levees — page 3 — In 1889 Johnstown Pennsylvania New York New Jersey PENNSYLVANIA Johnstown Ohio Maryland Other floods are manmade People might build a dam that is not strong enough to hold back water Or a dam can be damaged and break releasing the water behind it received several inches of rain The rain was too much for the South Fork Dam which stood about 12 miles 19 3 kilometers above Johnstown The dam collapsed sending a wall of water down the river The water reached 75 feet 23 meters high and was powerful enough to wash away train locomotives Johnstown was destroyed by the flood and more than 2,000 people were killed The flood in Johnstown destroyed four square miles 10 kilometers of the city’s downtown and 1,600 houses 6

Floods, Dams, and Levees — page 4 — Some floods take a long time to develop A storm might last for days causing rivers and streams to rise over time After a few days the water rises over the banks of the river and floods the land around it Melting snow can also fill rivers and other bodies of water until they flood Meteorologists can often warn people so they can protect their homes and get to safety if they have to Did You Know Sometimes areas that do not have a history of flooding begin to flood Often this is the result of new land development that changes the natural runoff paths 7

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