FLOODS

 

Choose the best word from the box to complete the following sentences.

o  combine o  dams

o human-made o pieces

o   potential o   widespread

o   devastating o   flooding

o   prevent o   snow

CAUSES OF FLOODS

Floods cause ___________    damage. Unfortunately, there is little we can do to _____ flooding in some situations. There are several causes for _________   including deep ______ melt, icy rivers, and broken __________.  First, when deep snow melts it creates large amounts of water. When heavy rain and sudden warm temperatures ___________with the deep snow, floods can occur. Second, rivers that are covered in ice can cause floods when the ice melts. The ice ____________ form dams which break and cause flooding. Third, ________ dams can break and  cause _______  damage. The water from these dams can be as powerful as a tidal wave. Our best plan of attack against flooding is to recognize the _________ for flooding in certain conditions.

Read the  text and choose  the  best  answer(s) for each question.

THE CAUSES OF FLOODS

Floods are second only to fire as the most common of all natural disasters. They occur almost everywhere in the world, resulting in widespread damage and even death. Consequently, scientists have long tried to perfect their ability to predict floods. So far, the best that scientists can do is to recognize the potential for flooding in certain conditions. There are a number of conditions, from deep snow on the ground to human error, that cause flooding.

When deep snow melts it creates a large amount of water. Although deep snow alone rarely causes floods, when it occurs together with heavy rain and sudden warmer weather it can lead to serious flooding. If there is a fast snow melt on top of frozen or very wet ground, flooding is more likely to occur than when the ground is not frozen. Frozen ground or ground that is very wet and already saturated with water cannot absorb the additional water created by the melting snow. Melting snow also contributes to high water levels in rivers and streams. Whenever rivers are already at their full capacity of water, heavy rains will result in the rivers overflowing and flooding the surrounding land.

Rivers that are covered in ice can also lead to flooding. When ice begins to melt, the surface of the ice cracks and breaks into large pieces. These pieces of ice move and float down the river. They can form a dam in the river, causing the water behind the dam to rise and flood the land upstream. If the dam breaks suddenly, then the large amount of water held behind the dam can flood the areas downstream too.

Broken ice dams are not the only dam problems that can cause flooding. When a large human-made dam breaks or fails to hold the water collected behind it, the results can be devastating. Dams contain such huge amounts of water behind them that when sudden breaks occur, the destructive force of the water is like a great tidal wave. Unleashed dam waters can travel tens of kilometres, cover the ground in metres of mud and debris, and drown and crush every thing and creature in their path.

Although scientists cannot always predict exactly when floods will occur, they do know  a great deal  about when  floods are  likely, or probably, going to occur. Deep snow, ice-covered rivers, and weak dams are all strong conditions for potential flooding. Hopefully, this knowledge of why floods happen can help us reduce the damage they cause.

1)      Which of the following words are natural disasters? (More than one answer may be correct).

a) flood                b) earthquake        c) airplane crash               d) typhoon

2)      Which of the following are included as causes for floods in the  reading passage?

a) droughts          b) large lakes       c) poorly built roads          d) melting snow

3)      How does deep snow cause flooding?

a)    melting snow causes flooding

b)   too much rain causes flooding

c)    sudden warm temperatures combined with  heavy rains  causes flooding

d)   freezing water causes flooding

4)      A broken human-made dam is compared to what?

a) a tsunami         b) a tidal wave       c) a broken ice dam         d) overflowing

5)      Which of the following best describes how  a frozen river can  cause a flood.

a)    The ice in the river melts too quickly and causes a flood.

b)   The ice in the river cracks causing the water to overflow.

c) The ice in the river cracks into pieces that eventually create a dam causing the water to overflow.

d) The water behind the ice dam collects and when  the  dam  breaks, it causes flooding upstream.

6)      How far can  dam  water travel when  it is  unleashed from a  broken dam?

a) less than 10 kilometres

b) tens of kilometers

c) thousands of kilometers

d) tens of thousands of kilometres downstream

7)      Why does saturated ground contribute to flooding problems?

a) the ground cannot absorb more  moisture

b) the ground is too hard, so the  water runs off

c) the ground forms a kind of dam

d) it remains frozen

8)      What kinds of problems can floods cause?

a) death

b) widespread damage

c) destruction of plants and animals

d) all of the  above

9)      What is the most common natural disaster?

 a) flood               b) fire               c) wind  damage            d) rain

10)   How does melting snow cause problems related to flooding?

a) it makes the  rivers run too fast

b) it makes the  water too cold

c) it causes pieces  of ice to block the  river

d) it makes the  level of the  river rise

Key: 1 a, b, d; 2 d; 3 c; 4 b; 5 c; 6 b; 7 a; 8 d; 9 b; 10 d.

HOMEWORK

p.163, Ex. 4