Flood

An overflowing of water onto land that is normally dry.

Floods are caused by large amounts of precipitation, by melting of the winter's snow, or both. They happen naturally, recurring often, and are only hazardous when people build on or farm near a flooding location. The extra water from the melting or the rain fills rivers and makes them overflow because they cannot carry all the water. A flood could just make the meadows a little wet, or it could rise high and fast to wash away bridges, roads, cars, and houses. Floods also occur when very high tides, perhaps helped by strong winds, break through or overflow sea walls. A hurricane or thunderstorm often causes a flood because of the unusually large amount of rain that falls in such a short time. A heavy rainfall can be too much for the normal drainage and can cause a flood, as well.

Explanation

Floods can be very devastating. The quick, strong, and plentiful water that rushes into a town has the power to wash away houses, cars, and other possessions, as well as to drown people and animals. Plants suffer from the excess of rain, nutrients are swept away from the river beds, and much more can happen from a flood.

Often times, people who live in a home where it has just flooded have water covering the floor. But that's only if their house survives. Good drainage systems can help, but often times they can't handle all of the water that rushes at them from a flood. The experiment below shows you what happens to the nutrients in the soil when a flood occurs.

What You'll Need:

• 1/4 cup of dirt
• red powdered tempera paint
• water
• teaspoon (5 ml measuring spoon)
• funnel
• coffee filter paper
• wide-mouthed jar (1 liter)
• 1 cup (250 ml measuring cup)
• stirring spoon

Directions:

1. Mix 1/4 teaspoon (1.25 ml) of the red paint with 1/4 cup (75 ml) of dirt.
2. Set the funnel in the jar and put the coffee filter inside the funnel.
3. Pour the colored sand inside the paper filter.
4. Add 1/4 cup (75 ml) of water to the funnel.
5. Watch the water drip into the jar.
6. Pour this water out of the jar and add another 1/4 cup (75 ml) of water to the funnel.

What's Happening?

The water dripping out of the funnel is red. The red paint you added to the dirt is like the nutrients in topsoil that dissolve in rainwater and feed the plants growing in the soil. If there is a hard rain, the water runs across the land, and takes the dissolved nutrients with it. This can leave the topsoil without the necessary nutrients. The same thing can happen when there is a flood because the water levels will rise and the overflow will take the nutrients with it.

There are several different types of floods. Here are a few common types.

• High Flood Waves: These floods are caused from hard rainfalls that make high flood waves. Destroying roads, bridges, homes, and buildings, these floods are short and dangerous. They normally reach a peak quickly, and diminish just as fast. These flows usually contain large quantities of sediments and debris that they collect along the way, which are deposited in streets, cellars, and the first stories of homes and buildings.
• Flash Flood: These are among the most severe floods, occurring after a violent thunderstorm which pours down a lot of rain in a short time. They are especially hazardous when the ground is already wet from previous rains, or the streams are already filled high. When a flash flood hits a town, the water level rises too quickly for the drainage systems to handle it, and water overflows into the streets. A flash flood hit London in 1975, washing away cars and filling subways with water. Another hit Big Thompson Canyon in Colorado in 1976, drowning eighty people, smashing a road, and flattening part of the forest.
• Tidal Floods: These are overflows that occur right along the coast. Most of the severed tidal floods are caused by tidal waves that are made by high winds from a hurricane adding to the regular cycle of tides. They usually last for a short time because they work with the tides, which rise and fall twice each day. The waves are often about three feet or higher than the maximum level of the high tide. These floods can also be caused by the flood runoff and waves that are generated by hurricane winds that come from the heavy rains of hurricanes.

Many cities are next to rivers and oceans because of the need for transportation by water. However, these cities are prone to flooding because they are so close to rivers which can flood with a large amount of rain. In the United States alone, the average annual flood loss is more than three billion dollars. India, China, Italy, Bangladesh, and many more places around the world also suffer greatly from floods. If you live in a flood-prone area, be sure to get insurance on your property and listen after a thunderstorm for warnings of a flood.