How long did the carlisle floods last? What are the social impacts of floods? How did the floods in Mumbai take place? What happens when you take responsibility for your actions? What is upstream flooding? Are floods cyclical phenomenon? How long did the Brisbane floods last? What part of the United States do floods mostly take place at?
Types of floods? What are the problems of floods? What are the effects of floods with the oceans? Why and when floods take place? Where do floods take place? When did the Madeira floods take place? What is the difference between flash floods and floods?
How long did it take for pioneers to complete the Oregon trail? What does Golf irrigation design mean? How do floods affect the spheres of the earth? Each year, flooding causes more deaths than any other hazard related to thunderstorms. The most common flood deaths occur when a vehicle is driven into hazardous flood waters. Use extreme caution when returning to your home after a flood.
Appliances that may have been flooded pose a risk of shock or fire when turned on. Do not use any appliances, heating, pressure, or sewage system until electrical components have been thoroughly cleaned, dried, and inspected by a qualified electrician. Several factors contribute to flooding. Two key elements are rainfall intensity and duration. Intensity is the rate of rainfall, and duration is how long the rain lasts.
Topography, soil conditions, and ground cover also play important roles. In other words, the chances that a river will flow as high as the year flood stage this year is 1 in Statistically, each year begins with the same 1-percent chance that a year event will occur. Flooding can occur slowly as rain continues to fall for many days. This type of flooding, sometimes called a slow-onset flood, can take a week to develop and can last for months before floodwaters recede.
Rapid-onset floods occur more quickly, typically developing within hours or days. Some methods of flood control have been practiced since ancient times. These methods include planting vegetation to retain extra water, terracing hillsides to slow flow downhill, and the construction of floodways man-made channels to divert floodwater. An arroyo is a water-carved gully or norma lly dry creek bed. Arroyos can fill with fast-moving water very quickly. Flash flooding at this arroyo in Arizona took only 58 seconds to develop.
Floating ice can accumulate at a natural or man-made obstruction and stop the flow of water. When a vehicle stalls in the water, the water's momentum is transferred to the car. For each foot the water rises, lbs. Average range is 40 miles, depending on topography. Your National Weather Service recommends purchasing a radio that has both a battery backup and a tone-alert feature which automatically alerts you when a watch or warning is issued.
Families should be prepared for all hazards that affect their area. Where will your family be when disaster strikes? They could be anywhere at work, at school, or in the car. How will you find each other? Will you know if your children are safe? Disasters may force you to evacuate your neighborhood or confine you to your home.
What would you do if basic services water, gas, electricity or telephones were cut off? Follow these basic steps to develop a family disaster plan Practice and maintain your plan. Ask questions to make sure your family remembers meeting places, phone numbers, and safety rules. Conduct drills. Test your smoke detectors monthly and change the batteries at least once a year.
Test and recharge your fire extinguisher s according to manufacturer's instructions. This monsoon wind system can cause a period of intense rain that is completely out of step with the climate the rest of the year. In some areas, this flooding may be exacerbated by excess water from melting snow. Perhaps the best known example of seasonal flooding is the annual expansion of the Nile River in Egypt. In Ancient Egypt, monsoon rains at the source of the river would cause the waterway to extend out a good distance during the summer.
In this case, the flooding was not a disaster, but a godsend. This is one of the main factors that allowed civilization to thrive in the Egyptian desert. These days, the river is blocked off by a dam upstream, which collects the summer rain and doles it out throughout the year. This has extended the planting season so that Egyptian farms can grow crops year-round.
Another common source of flooding is unusual tidal activity that extends the reach of the ocean farther inland than normal. This might be caused by particular wind patterns that push the ocean water in an unusual direction. It can also be caused by tsunamis , large waves in the ocean triggered by a shift in the Earth's crust. Floods may also occur when a man-made dam breaks. We build dams to modify the flow of rivers to suit our own purposes.
Basically, the dam collects the river water in a large reservoir so that we can decide when to increase or decrease the river's flow, rather than letting nature decide. Engineers build dams that will stand up to any amount of water that is likely to accumulate. Occasionally, however, more water accumulates than the engineers predicted, and the dam structure breaks under pressure.
When this happens, a massive amount of water is released all at once, causing a violent "wall" of water to push across the land.
In , such a flood occurred in Johnstown, Pennsylvania. The townspeople were warned that the flood was coming, but many dismissed the alert as unfounded panic. When the rushing wall of water did hit, more than 2, people were killed in only a few minutes.
The severity of a flood depends not only on the amount of water that accumulates in a period of time, but also on the land's ability to deal with this water. As we've seen, one element of this is the size of rivers and streams in an area. But an equally important factor is the land's absorbency. When it rains, soil acts as a sort of sponge. When the land is saturated -- that is, has soaked up all the water it can -- any more water that accumulates must flow as runoff.
Some materials become saturated much more quickly than others. To see how this works, just take a bucket of water outside and try wetting various surfaces. Soil in the middle of the forest is an excellent sponge. You could dump several buckets of water on it and it would soak the water right up. Rock is not so absorbent -- it doesn't seem to soak up any water at all. Hard clay falls somewhere in between. Generally, soil that has been tilled for crops is less absorbent than uncultivated land, so farm areas may be more likely to experience flooding than natural areas.
One of the least absorbent surfaces around is concrete. In the next section, we'll see how concrete, asphalt and other human construction can affect flooding. In the last section, we saw that the degree of flooding is determined by the amount of water that accumulates in an area, as well as the nature of the land surface.
As civilization has expanded, human beings have altered the landscape in a number of ways. In the Western World, one of the most significant changes has been covering the ground in asphalt and concrete. Obviously, these surfaces are not the best sponges around: Almost all rain that accumulates becomes runoff. In an industrialized area without a good drainage system, it may not take much rain to cause significant flooding.
Some cities, such as Los Angeles, have constructed concrete flood-relief channels to prevent this problem. When it rains a lot, the water flows into these channels, which meander out of the city where the water can be better absorbed. These sorts of systems may cause flooding farther down the line, however.
When you cover an area in concrete and asphalt, you are essentially cutting off part of the Earth's natural sponge, so the rest of the sponge has a lot more water to deal with. A similar problem can arise with levees , large walls built along rivers to keep them from overflowing.
These structures extend the natural banks of the river so that much more water can flow through it. But while they may be effective at keeping water out of one area, they usually make problems worse for an area down the line, where there are no levees. That area gets all the flood waters that would have spread out farther up river. Another danger of levees is that, like dams, they can break.
When this happens, a large amount of water flows out onto the land in a short period of time. This can cause some of the most dangerous flood conditions. People haven't had much success with controlling flooding along coastlines. Excessive water in these areas is particularly destructive to man-made structures because of the erosion it causes.
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